biology

1

Chapter

The Living World What is living Taxonomy & Systematics

The Living World

Taxonomic Categories Taxonomic Aids

LIVING Living Characteristics Non Define (with exception)

Growth

Define (without any exception)

(Not a characteristic feature of living) Reproduction Consciousness Metabolism

Increase in Mass

Increase in Cell Number

Cellular Organization

Asexual Reproduction (Uniparental)

Sexual Reproduction (Biparental) e.g., mostly multicellular and unicellular organisms

By Budding (Yeast, Hydra) e.g.,

Regeneration (Planaria) Fragmentation – Fungi and Filamentous algae and protonema of mosses

Non Defining Characteristics Growth + Reproduction → Mutually Inclusive Event → Unicellular z Growth + Reproduction → Mutually Exclusive event → Multicellular Note: z Growth in plant is localised & indefinite (throughout life) z Growth in animal is diffused and definite (up to a limit) Important: z Reproduction is not a characteristic feature of living e.g., mules, worker bees and infertile human.

Irreversible change z In living — Growth Intrinsic (occurs due to increase protoplasm) z

Defining Characteristics (a) Metabolism → Catabolism + Anabolism. It mean some of all catabolic and anabolic reactions in our body.

In vitro → Not a living thing but is a living reaction.

Metabolism is a characteristic feature of living things inside a cell. (b) Cellular Organisation → Metabolic reaction inside the cell, it mean cellular organization strictly require for metabolism to define the feature. (c) Consciousness → The state of being aware of what is around you and able to sense environment. Consciousness therefore, become the defining property of living organism.

TAXONOMY AND SYSTEMATICS Identification: Correct description of organism. z Nomenclature: Scientific naming → Binomial nomenclature given by Linnaeus. z Classification: Give a particular position of an organism in a particular taxa.

ICBN → International Code for Botanical Nomenclature. z

ICZN → International Code for Zoological Nomenclature.

Binomial nomenclature given by Carolus Linnaeus.

Name with two components

Generic name

Specific epithet

System Naturae – written by Linnaeus.

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TAXONOMIC CATAGORIES Taxonomic Arrangement All categories together constitute the taxonomic hierarchy.

Each category referred to as a unit of classification, infact, represent a rank and as commonly called as taxon (Pl. Taxa): (i) Species: Group of individual with fundamental similarities e.g., nigrum, tigris. (ii) Genus: Group of closely related species e.g., Mangifera (iii) Family: Group of less related genus e.g., Solanaceac (iv) Order: The similar characteristics are less in number as compaired to different genera. Assemblage of families which exhibit a few similar characteristics e.g., Polymoniale. (v) Class: Group of related orders e.g., Primata. (vi) Phylum/Division: In division, related plant classes come in group but in case of animal, related classes became a part of phylum e.g., Chordata. (vii) Kingdom: Group of similar phylum or division e.g., Animalia and Plantae.

Kingdom ↑ Division/Phylum ↑ Class ↑ Order Taxonomic hierarchy ↑ Family ↑ Genus ↑ Species

TAXONOMICAL AIDS Collection of samples or preserved organisms which help in extensive research for the identification of various taxonomic hierarchy e.g., (i) Herbarium: It is a store house of collected plant specimens that are dried, pressed and preserved on sheets (42 × 29 cm).

3

The Living World

(ii) Botanical Gardens: Collection of living plant for reference in a specialised gardens e.g., Kew (England), Indian Botanical Garden, Kolkata (W.B.). (iii) Museum: Collection of preserved plants and animal specimens in colleges for study purpose and reference. (iv) Zoological Parks: A place where wild animal kept under human care for learn about food habits and behaviour. (v) Key: Keys are generally analytical in nature. Keys are based on contrasting characters generally in a pair called couplet. Each statement in the key is called lead. qqq

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2

Chapter

Biological Classification ROBERT H. WHITTAKER (1969) Two Kingdom Classification

Organisms Prokaryotic

z

Eukaryotic

z

Monera Unicellular

Multicellular

Protista

Three Domain of Life (Six Kingdom)

Without cell wall z

With cell wall Phototrophic

Heterotrophic

Plantae

Fungi

Given by Linnaeus Divided into Plantae & Animalia

z

This system divide the Kingdom Monera into two domain.

Remaining Kingdom in 3rd domain.

Characteristics of Five Kingdoms Five Kingdoms

Characters

Monera

Protista

Plantae

Animalia

Cell type

Prokaryotic

Eukaryotic

Eukaryotic

Fungi

Eukaryotic

Eukaryotic

Cell wall

Noncellulosic (Polysaccharide + amino acid)

Present in some

Present with chitin

Present (cellulose)

Absent

Nuclear membrane

Absent

Present

Present

Present

Present

Body organisation

Cellular

Cellular

Multicellular/ loose tissue

Tissue/organ

Tissue/organ/ organ system

Mode of nutrition

Autotrophic (Chemosynthetic and photosynthetic) and Heterotrophic (saprophytic/parasitic)

Autotrophic (Photosynthetic) and Heterotrophic

Heterotrophic (Saprophytic/ Parasitic)

Autotrophic (Photosynthetic)

Heterotrophic (Holozoic/ Saprophytic etc.)

MONERA Kingdom Monera

Archaebacteria (primitive bacteria)

Methanogens (methane producing bacteria)

Halophiles (salty/marine bacteria)

On the basis of staining behaviour

Thermoacidophiles (present in acidic sulphur springs)

On the basis of structure

Gram-Negative Bacteria

Gram-Positive Bacteria Cocci (rounded)

Eubacteria (true bacteria)

Bacilli (capsule)

Spirillum (Spiral)

Vibrio (comma-like)

On the basis of nutrition Autotrophic ○ Photosynthetic bacteria ○ Purple-sulphur bacteria Heterotrophic ○ Saprophytic ○ Symbiotic ○ Parasitic

PROTISTA Single celled eukaryotes

• True nucleus (membrane bound) • Membrane bound organelles

The boundaries of protistia are not well defined

Photosynthetic protista

Plants

Chrysophytes This group includes diatoms and golden algae (desmids). Diatoms have left behind large amount of cell wall deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’. Being gritty, this soil is used in polishing, filtration of oils and syrups. Diatoms are the chief ‘producers’ in the oceans.

6 Hand Book (Biology)

Dinoflagellates Most of them have two flagella; one lies longitudinally and the other transversely in a furrow between the wall plates. Very often, red dinoflagellates (Example: Gonyaulax) undergo such rapid multiplication that they make the sea appear red (red tides).

Euglenoids Though they are photosynthetic in the presence of sunlight, when deprived of sunlight, they behave like heterotrophs by predating on other smaller organisms.

Slime Moulds Slime moulds are saprophytic protists. During unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips. The spores possess true walls.

Protozoans

Amoeboid: They move and capture their prey by putting out pseudopodia (false feet) as in Amoeba. Marine forms have silica shells on their surface.

Some of them such as Entamoeba are parasites.

Flagellated: Free-living or parasitic in nature. The parasitic forms cause disease such as sleeping sickness. Example: Trypanosoma.

Ciliated: These are aquatic, actively moving organisms because of the presence of thousands of cilia.

Sporozoans: The most notorious is Plasmodium (malarial parasite) which causes malaria, a disease which has a staggering effect on human population.

FUNGI Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes. Those that depend on living plants and animals are called parasites. They can also live as symbionts— in association with algae as lichens and with roots of higher plants as mycorrhiza.

Phycomycetes Asexual reproduction takes place by zoospores (motile) or by aplanospores (non-motile). Some common examples are Mucor, Rhizopus and Albugo.

Ascomycetes Commonly known as sac-fungi, the ascomycetes are mostly multicellular, e.g., Penicillium, or rarely unicellular, e.g., yeast (Saccharomyces). The asexual spores are conidia produced exogenously on the special mycelium called conidiophores. Sexual spores are called ascospores.e.g., Aspergillus, Claviceps and Neurospora.

7 Biological Classification

Basidiomycetes Commonly known forms of basidiomycetes are mushrooms, bracket fungi or puffballs. The sex organs are absent, but plasmogamy is brought about by fusion of two vegetative or somatic cells of different strains or genotypes. e.g., Rusts and Smuts.

Deuteromycetes Commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known. Some examples are Alternaria, Colletotrichum and Trichoderma.

KINGDOM PLANTAE Kingdom Plantae includes all eukaryotic chlorophyll-containing organisms commonly called plants.

KINGDOM ANIMALIA This kingdom is characterised by heterotrophic eukaryotic organisms that are multicellular and their cells lack cell walls.

Virus The viruses are non-cellular organisms that are characterised by having an inert crystalline structure outside the living cell. Viruses contain protein and genetic material, that could be either RNA or DNA.

Viroids In 1971, T.O. Diener discovered a new infectious agent that was viroids and they contain only RNA and strictly found in plants.

Prions It is a types of infectious protein aggregates that can cause different types of disease. The most notable diseases caused by prions are bovine spongiform encephalopathy (BSE) commonly called mad cow disease in cattle and its analogous variant Cr–Jacob disease (CJD) in humans.

Lichens A symbiotic form of algae and fungi, in which algae provide food and fungi provide shelter as well as nutrition to algae.

Lichens are very good pollution indicators—they do not grow in polluted areas. qqq

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3

Chapter

Plant Kingdom CLASSIFICATION OF PLANT KINGDOM Plant Kingdom Algae Embryo Stage Absent Green Algae

Brown Algae

Embryophytes Embryo Stage Present

Red Algae

Bryophytes Vascular Tissues Absent

Liverworts

Mosses

Tracheophytes Vascular Tissues Present

Pteridophytes Seed Absent

Spermatophytes Seed Present

Including Ferns Angiosperms Seed Inside Fruit

Gymnosperms Seed Naked Cycads

Conifers

Gingkoales Living fossils

Dicots Two cotyledons in seeds

Monocots One cotyledons in seeds

ALGAE Classification of Algae Item

Chlorophyceae

Phaeophyceae

Rhodophyceae

Common name

Green algae

Brown algae

Red algae

Habitat

Fresh water

Marine water

Marine water

Pigment

Chl a, b, Xanthophyll and Carotene

Fucoxanthin Chl a, c and carotenoids

Chl a & d r-phycoerythrin

Reserve food

Starch

Laminarin, Manitol

Floridean Starch

Flagella

Equal flagella

Unequal flagella

Flagella absent

Sexual reproduction

Present

Present

Present

z

z z z z z

z z z

z

Green Algae h Microscopic, eukaryotic, unicellular green algae. h Generally found in ammonium salt rich habitat. h Reproduce by both sexual and asexual means. h Asexual reproduction through Zoospores, Palusetta stage, Aplanospores and Hyponospores. h Sexual reproduction through isogamy, anisogamy or oogamy. h The holdfast cell is non-photosynthetic and lost the ability to divide.

Brown algae, Sargassum, is a menace to shipping.

No unicellular brown algae is known.

Laminaria and Nereocystes (20–30 m) due to their giant size are called as giant kelps.

Alginic acid is obtained from phycocolloids from kelps.

In deeper oceans, Red algae acquire deeper colour. The pigment r-phycoerythrin in red algae can do this job of capturing light of available wavelength for red algae.

The common name for brown and red algae is sea weed.

Polysiphonia, a red algae, has anti-bacterial property.

Life cycle in green algae is of three types: h Haplontic: Zygotic meiosis e.g., Ulothrix, Spirogyra. h Diplontic: Gametic meiosis e.g., Caulerpa. h Diplohaplontic: Haploid and diploid phases are well developed and multicellular.

Economic Importance of Algae:

Cattle food

Sargassum, Fucus, Macrocystis (rich in Vit. A & E).

Human food

Laminaria, Spirulina (richest in protein), Chlorella (rich in protein & carbohydrates).

Algenic acid

Laminaria, Ascophyllum, Macrocystic.

Carrageenin

Chondrus crispus (Irish moss)

Agar

Gelidium and Gracilaria.

Iodine

Laminaria digetata

Nitrogen fixation

Anabaena, Nostoc

Space algae

Chlorella

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BRYOPHYTES z

Commonly called as plant amphibian.

z

Alternation of generation is observed.

z

Vascular tissues are absent.

z

They lack true stem, leaves and roots.

z

Gametophyte is enchored (attached) by rhizoids.

z

Sporophyte (sporogonium) is dependent on gametophyte for nutrition.

z

Spores are produced by the sporophyte in a spore capsule.

z

Water is essential for fertilization.

z

Sex organs are multicellular and jacketed. Male-antheridium, femalearchegonium.

z

Fertilization produced an embryo inside the archegonium. Embryo grow into a sporophyte.

z

Protonema is the juvenile gametophyte.

z

Zygote and spores are the first cell of sporophytic and gametophytic generation respectively.

z

Life cycle of Moss Plant—Funaria. h Commonly called as cord moss or fire moss. h Vegetative reproduction by fragmentation and gemmae. h Sexual reproduction by syngamy. h Archegonium attract sperm by sucrose present in their mucilage. h Sporophyte consists of three parts-foot, seta and capsule. h The capsule is further differentiated into 3 parts: apophysis, theca and operculum. h Theca contain sterile columella. h Funaria is monoecious and autocecious (male & female sex organs on different branches). h Fossilised Sphagnum produces peat which is used as fuel as well as manure.

PTERIDOPHYTES OR FERNS z

Commonly called snakes of plant kingdom.

First vascular plants without seeds.

z

Main plant body is sporophyte and distinguishes into root, stem and leaves.

z

11

Plant Kingdom

z z z z z z z z z z

The stem is underground rhizome.

Alternation of generation between spore producing diploid sporophyte and gamete forming haploid gametophyte.

Ornamental leaves are called frongs.

Reproduction is of vegetative, asexual and sexual type.

Sperms are flagellated.

Sporangia occurs on leaves in clusture called sori. Fertile leaves are called sporophylls.

A sorus is covered by a flap like outgrowth from its surface (true indusium) or turned margin of the sporophyll (false indusium).

Selaginella is heterosporous i.e., small male and large female spores.

Smallest pteridophyte—Azolla (a bio-fertilizer).

Apogamy—Development of sporophyte (n) from gametophyte without fertilization.

Apospory—Development of gametophyte (2n) from sporophyte without meiosis.

(a) Selaginella

(b) Equisetum

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z z z

Selaginella is popularly known as club moss or spike moss.

Dryopteris is commonly called as male shield fern. Adiantum is commonly called as walking fern, maiden hair fern.

Pteridophytes formed dominant flora in carboniferous period, palaezoic era. Most part of coal is formed from pteridophytes plants.

GYMNOSPERMS z

Vascular plants with naked seeds.

z

Perennial plant of colder region. Annual and herbaceous forms absent.

z

Leaves dimorphic—foliage & scale leaves.

z

Sporophyll produces stobili or cones. Flowers are absent.

z

Integument is three layered. Each one has a mass of tissue called nucellus (equivalent to megasporangia).

z

Female gametophyte develops archegonia. Neck canal cell absent.

z

Endosperm (2n) gametophytic.

z

Gingko and Cycas are called as the living fossils.

z

Sequoia gigantica—Tallest gymnosperm Red wood tree—Father of the forest Cycas—Sagopalm Chilgoza from Pinus girardiana

Dwarf Shoot

Long Shoot

Seeds Ginkgo z

Meroblastic development i.e., only a part of zygote forms embryo.

z

Holoblastic development—when complete zygote form embryo.

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Plant Kingdom

z

The three generations which are represented by seed are: 1. Testa, tegmen and perisperm represent parental sporophyte; 2. Endosperm represent female gametophyte; 3. Plumule, radicle, suspensor & cotyledons (embryo) represent future sporophyte.

z

Polyembryony: It is the formation of more than one embryo inside a single seed. It was reported by Leeuwenhoek in oranges.

Simple Polymbryony is due to fertilization of many eggs e.g., Pinus ovule has 2-8 archegonia.

Cleavage polyembryony is true polymbryony and very common. It is due to splitting of embryo tissue.

Adventive Polymbryony is the formation of extra embryos directly from diploid cells.

z

Male cones are homologous to dwarf branches wherever females cones are homologous to long branches.

z

4-cells in male gametophyte of Pinus are two prothallial cells, one antheridial cell & one small generative cell.

z

The number of archegonia in Pinus ovule is 2-8.

z

Gnetum, Ephedra & Welwitschia are exceptional gymnosperms having primitive vessels in xylem.

z

The wood in Pinus is Pycnoxylic (hard & compact wood) & monoxylic (having only one ring of xylem).

z

Development of sporangium in Pinus is eusporangiate i.e., a group of sporangial initial gives rise to a sporangium. Leptosporangiate is the condition when only one sporangial cell give rise to sporangia.

z

The fertilization in Pinus is Siphonogamous i.e., by pollen tube.

ANGIOSPERM z

In angiosperms, the seeds are enclosed in fruits, the pollen grains and ovules are developed in specialized structures called flowers.

z

Highly evolved plants group.

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z

Sporophylls are aggregated to form flowers. Therefore, angiosperms are also called flowering plants.

z

Both microsporophylls and megasporophylls are specialised.

A microsporophyll or stamen consists of a filament and an anther.

A megasporophyll or carpel consists of a stigma, style and ovary containing ovules.

z

Female gametophyte or embryo sac develops, upto 8-nucleate state prior to fertilization.

z

Archegonia are absent. Instead, there is one oosphere surrounded by two specialised synergid cells that attract the pollen tube. The latter brings two naked non-flagellate male gametes.

Life cycle of an angiosperm

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Plant Kingdom

Life cycle patterns (a) Haplontic, (b) Diplontic and (c) Haplo-diplontic z z z

z z z z

There is double fertlization in angiosperm. One produces embryo or new sporophyte. The other forms primary endosperm cell.

Endosperm is formed through triple fusion and is generally triploid (3n).

Fertilized ovules ripen into seeds, the seeds are covered by fruits. A fruit is technically a ripened ovary. Fruits not only protect the seeds but also help in their dispersal.

Xylem contains vessels.

Phloem possesses sieve tube and companion cells.

A gametophyte can be haploid or diploid but always produces gametes.

Monocots do not grow in girth though they grow in length and produce new leaves and flowers. Dicots have indefinite growth and new roots, shoots, leaves, bark and wood are formed year after year.

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Difference between Dicots and Monocots S.N.

Dictos

Monocots

1. There are usually two cotyledons.

The seeds contain one cotyledon.

2. Flowers are generally pentamerous or tetramerous (floral parts in sets of 5 and 4 or their multiples).

Flowers are usually trimerous (floral parts in sets of three or its multiples).

3. Pollen grains commonly have three germ pores.

Pollon grains generally possess a single germinal furrow.

4. Leaves possess reticulate venation.

The leaves possess parallel venation with a few exceptions.

5. Primary root often long lived forming Primary root is short-lived. Tap root is tap root system. Adventitious roots occur absent. Instead, adventitious roots are in some cases. found.

6. Stem possesses concentric arrangement of tissue systems—epidermis, cortex, endodermis, pericycle, pith etc.

Tissue systems are not differentiated in the stem. Ground tissues are present

7. Vascular bundles of the stem are arranged in a ring.

Vascular bundles are scattered.

8. Vascular bundles of the stem possess cambium (vascular bundles open), so that secondary growth is possible.

A cambium is absent (vascular bundle closed).

9. In root, a pith is absent or small. The vascular bundles are few (8 or less).

In root, a pith is always present. Vascular bundles are many (more than 8).

10. Vessels are polygonal in outline.

Vessels are rounded in outline.

qqq

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Plant Kingdom

4

Chapter

Animal Kingdom INTRODUCTION ♦ Need to classify animals ♦ Classification helps in assigning a systematic position to newly described species. ♦ Characteristics: □ Eukaryotic organisms □ Division of labour □ Definite growth pattern □ Multicellular and their cells lack cell wall □ Heterotrophic with holozoic mode of nutrition □ Capable of locomotion With some exceptions □ Sensory and neuromotor mechanism (Poriferans)

BASIS OF ANIMAL CLASSIFICATION Levels of Organisation Cell Tissue Organ Organ system

Symmetry

Germ layer Organisation

Radial Bilateral Asymmetric

Diploblastic Triploblastic

Coelom

Segmentation

Notochord

Chordates Acoelomates Segmented Pseudocoelo- Unsegmented Nonmates chordates Coelomates

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Animal Kingdom

Complex

Radial Any longitudinal plane passing through the central axis of the body divides the organism into 2 identical halves

Asymmetrical Any plane passing through the centre does not divide the organism into 2 equal halves

Types of Symmetry

Germ Layers

Mesodermally derived rod like structure formed on the dorsal side during embryonic development in some animals.

Non-chordates (Porifera to echinoderms) Chordates

Yes Yes No No No Yes

• Animals without notochord • Animals with notochord

Annelida Arthropoda Mollusca Echinodermata Hemichordata Chordata

Roundworms

Aschelminthes

No

No

Platyhelminthes Flatworms

No

Coelentarata Ctenophora

No

No

Metamerism/ Segmentation

• Notochord

Endoderm

Ectoderm

Ectoderm

Porifera

Phylum(s)

Body is externally and internally divided into segments with a serial repetition of at least some organs.

True coelomates Body cavity lined by mesoderm

Mesoderm

Pseudocoelomate Scattered pouches of mesoderm between Coelom ecto and endoderm

Mesodermal pouches

Acoelomates (No body cavity)

Endoderm

Mesoglea

Acoelomates (No body cavity)

Body Cavity/Coelom (mesodermal lining)

• Metameric Segmentation

Triploblastic Bilateral Ectoderm Only one longitudinal Mesoderm plane passing through the Endoderm centre of the body divides the organism into identical right and left halves

Cellular

Simple

Organ

Level of Organisation

Hierarchy

Present

Absent

Notochord

COMPARATIVE ACCOUNT FROM PORIFERA TO ASCHELMINTHES Parameters Habitat/Habit

Porifera (Sponges) Mostly marine, some are fresh water (Spongilla)

Exoskeleton Endoskeleton Digestive system

Coelenterata (Cnidaria)

No

Mostly marine, some are fresh water (Hydra), sessile or free swimming Coral forms have skeleton of CaCO3

Spicules/spongin fibres

No • Digestive system incomplete • Mouth on hypostome leading to body cavity gastro-vascular cavity • Intra and extracellular digestion

• Digestive system absent • Intracellular digestion

Respiratory structure

Cell surface

Body wall

Circulatory system

Circulating fluid (water)

Circulating fluid (water)

Excretory system

Through body surface

Through body surface

No

Neurons appear

Nervous system Asexual reproduction

Fragmentation, gemmule formation

Budding

Sexual reproduction

• Present • Hermaphrodites

Present

Fertilization

Internal

Development

Indirect, larva (motile) morphologically distinct from adult

Unique features and examples

• Water canal system • Name derived from cnidoblasts/ Food gathering ↓ cnidocytes containg mematocysts, Functions Respiratory exchange present on body and tentacles.

Removal of wastes Anchorage, Defense Functions Parameters Ostia Osculum Capture of prey • Number Many Usually • Obelia exhibits 2 basic forms: • Location Body One surface

• Size • Water flow

Minute Entry

External

body surface Large Exit

• Choanocytes/collar cells line the spongocoel (central cavity).

Examples:

Euspongia (Bath sponge)

Spongilla (Fresh water sponge)

Indirect/direct

Asexually

Polyp Alternation of Medusa Sessile generation/ Free swimming Cylindrical Metagenesis Umbrella like Sexually

Examples: Physalia (Portuguese man-of-war), Pennatula (Sea-pen), Gorgonia (Sea-fan), Meandrina (Brain coral)

Sycon (Scypha)

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Adamsia (Sea anemone)

Aurella (Jelly fish)

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Parameters Habitat/ Habit

Ctenophora Platyhelminthes (Sea walnuts) (Flatworms) Exclusively marine Free living or parasitic

Exoskeleton No Endoskeleton No Digestive • Extracellular system and intracellular digestion Respiratory structure Circulatory system Excretory system

Body wall

No No • Digestive system incomplete with single opening • Extracellular digestion • Some forms absorb food directly from body surface Free living-body surface

No

No

Body surface

Nervous Yes system Asexual No reproduction Sexual • Present reproduction • Hermaphrodites Fertilization External Development Indirect Unique • 8 external rows features and of comb plates examples for locomotion, hence, called comb jellies • Exhibit Bioluminescence i.e., property to emit light Examples: Ctenoplana

Flame cells (Protonephridia) for excretion and osmoregulation Yes High regeneration-Planaria capacity • Present • Hermaphrodites Internal Indirect through many larval stages • Dorsoventrally flattened body • Hooks and suckers present in parasitic forms • First ones with bilateral sysmmetry, organ level of organisation and Tribloblastic Examples:

Aschelminthes (Round worms) Aquatic, terrestrial, parasitic in plants and animals No No • Complete alimen tary canal with muscular pharynx • Extracellular digestion Free living-body surface No Excretory tube opens out through excretory pore Yes No Distinctly dioecious Internal Indirect/direct (young one resembles adult) • Circular in crosssection • First ones with organ system level of organisation • Females longer than male • Posterior end curved in males Examples: Wuchereria (Filaria worm) Ancylostoma (Hookworm) Ascaris (Round worm)

Teenia (Tapeworm)

Male

Pleurobrachia

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Fasciola (Live fluke)

Animal Kingdom

Female

COMPARATIVE ACCOUNT FROM ANNELIDA TO HEMICHORDATA  All have complete alimentary canal with extracellular digestion  All can reproduce sexually and are usually oviparous Parameters

Annelida (Segmented worms)

Arthropoda (Arthos-Joint; Pod- Leg) (Joint appendages) Largest Phylum

Habitat

Aquatic and Terrestrial

Aquatic and Terrestrial

Body divisions/ appearance Locomotory structure Exoskeleton Digestive system Respiratory system/surface Circulatory system Excretory system Nervous system

Distinct segments metameres/annuli ○ Longitudinal and circular muscles ○ Parapodia/lateral appendages in some No Yes Body surface Closed Nephridia

Sense organs

Paired ganglia with double ventral nerve cord Eyes, Tentacles

Mono/ Dioecious Development

Monoecios – Earthworm, Leech Dioecious – Nereis (aquatic form) Direct/Indirect

Unique features and Examples

○ First ones with metameric segmentation and true coelom Examples: Pheretima (Earthworm- Decomposer)

Nereis

Head, thorax, abdomen Jointed appendages Chitinous/Cuticle Yes Gills, book gilis, tracheal system, book lungs (Scorpion) Open Malpighian tubules Paired ganglia with double ventral nerve cord Eyes (simple, compound), Antennae, Statocyst (balancing) Mostly dioecious Direct/Indirect Examples: ○ Economically important insects - Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect) ○ Vectors - Anopheles, Culex, Aedes (Mosquitoes) ○ Living fossil - Limulus (King crab) ○ Gregarious pest-Locusta

Hirudinaria (Blood sucking leech)

Locusta (Locust)

Prawn Scorpion

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Parameters

Mollusca/Soft bodied Second Largest Phylum

Echinodermata (Spiny skinned)

Hemichordata (Half chordates)

Habitat

Aquatic and Terrestrial

Exclusively marine

Exclusively marine

Body divisions/ appearance

Head, muscular foot visceral hump

Star like

Proboscis, collar, trunk (worm like)

Locomotory structure

Muscular Foot

Water vascular system

No

Exoskeleton

Calcareous shells

Spines

No

Digestive system

Mouth with file like rasping organ, radula for feeding

Mouth-lower side(ventral) Anus-upper side(dorsal)

Yes

Water vascular system

Pharyngeal gill slits

Respiratory system/surface

Feather like gills in mantle cavity

Circulatory system

Open

Open

Open

Excretory system

Gills

No

Proboscis gland

Nervous system

Yes

Yes

Yes

Sense organs

Tentacles

Yes

Yes

Mono/ Dioecious

Usually dioecious

Dioecious

Dioecious

Development

Indirect (Trochophore larva)

Indirect with free swimming larva

Indirect

Unique features and Examples

○ Soft and spongy layer of skin forms a mantle over the visceral hump. ○ Space between hump and mantle is mantle cavity.

Examples: Sepia (Cuttlefish), Loligo (Squid), Pinctada (Pearl oyster), Dentalium (Tusk shell), Chaetopleura (Chiton), Aplysia (Seahare)

Blue blood due to haemocyanin pigment

○ Water vascular system that

○ Presence of rudimentary Locomotion stomochord helps in Capture and transport of food ○ Earlier Respiration considered as subphylum under ○ Presence of phylum chordata Calcareous ossicles but now placed as Examples: separate phylum Cucumaria (Sea under noncucumber) chordata Echinus (Sea urchin) Examples: Antedon (Sea lily) Saccoglossus Balanoglossus Proboscis

Collar

Ophiura (Brittle star)

Pila (Apple snail)

Trunk

Balanoglossus

23

Animal Kingdom

General Features: Triploblastic organisms Bilaterally symmetrical Coelomates Organ-system level of organisation Closed circulatory system

Basic Plan of a Chordate Salient features

Chordates Yes Notochord Central nervous system Dorsal, hollow and single Paired pharyngeal gill slits Yes Post anal tail Position of heart

Non-chordates No Ventral, solid and double

Yes Ventral

No No Dorsal (if present)

Sub-phyla Parameters Urochordata/

Cephalochordata

Vertebrata

Protochordates Habitat

Exclusively marine

Notochord

Only in larval tail

Examples

Salpa, Doliolum

Polar ice caps, deserts, mountains, forests, grasslands and dark caves Extends from Present in head to tail and embryonic stage and is replaced by persists cartilaginous or throughout bony vertebral their life column in the adult Branchiostoma Scoliodon (Dog sh), Amphioxus or Rana (Frog), Crocodilus (Crocodile), (Lancelet) Pavo (Peacock), Canis (Dog)

Ascidia

Pavo (Peacock)

Neophron (Vulture)

Chelone (Turtle)

Chameleon (Tree lizard)

All vertebrates are chordates but all chordates are not vertebrates

Hand Book (Biology)

24

Parameters Habitat

Marine

Habit No (Poikilothermous) Exoskeleton

Scales are absent

Endoskeleton

Cartilaginous cranium and vertebral column

Appendages

Unpaired fins

Digestive system

Circular and sucking mouth without jaws

Respiratory system

6-15 pairs of gill slits

Circulatory system

Closed type

Excretory system

Kidneys

Reproductive system

○ Migrate to fresh water for spawning ○ After spawning, the adult dies within few days

Development

○ Indirect: Larvae return to ocean after metamorphosis

Examples

Petromyzon (Lamprey)

25

Animal Kingdom

COMPARATIVE ACCOUNT OF GNATHOSTOMATES Characteristics

Chondrichthyes

Osteichthyes

Habitat

Marine

Habit Temperature regulation Exoskeleton

Respiratory system Circulatory system

Predaceous Poikilothermous (Cold blooded) Placoid scales for tough skin Cartilaginous ○ Ventral mouth ○ Teeth are modified scales & backwardly directed ○ Powerful jaws Gill slits without operculum 2 chambered heart with 1 auricle and 1 ventricle

Excretory system Eye

Kidneys (Excretion and Osmoregulation) Eyes present

4 pairs of gill slits with operculum 2 chambered heart with 1 auricle and 1 ventricle Kidneys (Excretion and Osmoregulation) Eyes present

Ear

Tympanum absent

Tympanum absent

Fertilisation

Internal as pelvic fins of males bear claspers Many are viviparous

Usually external

Direct

Direct

○ Streamilined body ○ Notochord persists throughout life ○ Absence of air bladder, hence, swim continuously to avoid sinking Examples: Carcharodon (Great white shark), Trygon (Poisonous sting ray), Torpedo (Electric ray)

○ Streamlined body ○ They have air bladder/swim bladder that regulated buoyancy Examples: Marine – Exocoetus (Flying fish), Fresh water – Labeo (Rohu), Clarias (Magur); Aquarium – Betta (Fighting fish), Pterophyllum (Angle fish)

Endoskeleton Digestive system

Oviparous/ Viviparous Development Unique features

Marine and fresh water – Poikilothermous (Cold blooded) Cycloid and ctenoid scales Bony Terminal mouth

Mostly oviparous

Scoliodon (Dog sh)

Pristis (Saw sh)

Hippocampus (Sea horse)

Catla (Katia)

Hand Book (Biology)

Amphibia Carboniferous period (Age of Amphibians) Both on land and in water Dual life Poikilothermous (Cold blooded) ○ Scales are absent ○ Skin is moist Bony Cloaca present

Gills, skin and lungs 3 chambered heart with 2 auricles and 1 ventricle Kidneys (Excretion and Osmoregulation) Eyes with eyelids and a nictiating membrane Tympanum represents ear External; Internal-Salamandra, Ichthyophis Oviparous Salamandra-Viviparous Indirect ○ Body divided into head and trunk, tail in some e.g., Salamander ○ Alimentary canal, urinary tract and reproductive tracts open into a common chamber known as the cloaca Examples: Bufo (Toad), Hyla (Tree frog), Ichthyophis (Limbless amphibia)

Rana (Frog)

Salamandra (Salamander)

26

Characteristics Habitat Habit Temperature regulation Exoskeleton Endoskeleton Digestive system

Respiratory system Circulatory system Excretory system Sense organs

Fertilisation Oviparous/ Viviparous Development Unique features

Reptilia Mostly terrestrial Creeping and crawling

Aves Mostly terrestrial Most of them can fly except flightless birds Poikilothermous Homeothermous (Cold blooded) (Warm blooded) Epidermal scales or ○ Scales on hindlimbs scutes with dry cornified ○ Body covered by skin feathers and skin is dry Bony Bony (Fully ossified) Pneumatic bones ○ Additional gizzard No

Mammalia Terrestrial, aquatic Limbs adapted to fly and live in water Homeothermous (Warm blooded) Skin may possess hair Bony Different types of teeth in

and crop the jaws ○ Beak (modified jaws) present

Lungs

○ Lungs Lungs ○ Air sacs supplement respiration 3 chambered heart with 4 chambered heart with 4 chambered heart with 2 auricles and 1 ventricle 2 auricles and 2 ventricles 2 auricles and 2 except crocodile ventricles (4 chambered heart) Kidneys (Excretion and Kidneys (Excretion and Kidneys (Excretion and Osmoregulation) Osmoregulation) Osmoregulation) Eyes with eyelids Eyes with eyelids Eyes with eyelids Tympanum represents ear Tympanum represents ear, External ear/pinna & many reptiles do not many birds have external ear present have external ear opening opening Sexual dimorphism Oviparous Direct Snakes and lizards shed their scales as skin cast Examples: Chelone (Turtle), Testudo (Tortoise), Calotes (Garden lizard), Aligator (Aligator), Hemidactylus (Wall lizard), Poisonous snakes – Bangarus (Krait), Vipera (Viper) - Turtle & alligator → Ureotelic - Crocodiles -Ammonotelic -Lizards & SnakesUricotelic

Internal Oviparous Direct ○ Forelimbs modified into wings ○ Hindilimbs of birds are modified for walking, swimming or clasping the tree branches ○ Skin is dry without glands except oil gland at the base of tail Examples: Flying birds Corvus (Crow), Columba (Pigeon) Flightless birds – Aptenodytes (Penguin)

Psittacula (Parrot)

Struthio (Ostrich)

Internal Viviparous except egg laying Platypus Direct ○ Presence of mammary glands to feed young ones Examples: OviparousPlatypus Viviparous Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Panthera tigris (Tiger), Panthera leo (Lion) Bats are the only mammals capable of flight.

Omithorhynchus (Platypus)

Crocodilus (Crocodile)

Naja (Cobra) Balaenoptera (Blue whale)

27

Animal Kingdom

5

Chapter

Morphology of Flowering Plant INTRODUCTION z

Angiosperms show a large diversity in morphology.

z

A plant has root system and shoot system.

ROOT z

Elongation of radicle form primary root.

z

Primary root bears lateral roots of several orders that are referred to as secondary, tertiary etc. roots.

TYPES OF ROOTS z

Tap root system: • Includes primary root and its branches • Seen mainly in dicots eg. Mustard

z

Fibrous root system : In monocots, primary root is short lived and replaced by a large number of roots originate from the base of the stem.

z

Adventitious roots : Roots that arise from parts of plants other than radicle eg. grass, Monstera and banyan tree.

z

Functions : h Absorption of water and minerals from soil. h Provide anchorage to plant parts. h Storage of reserve food materials. h Synthesis of plant growth regulators (PGRs)

REGIONS OF ROOT

Region of maturaton Root hair

Thimble like structure covering root apex

Root cap

Region of elongation

Some epidermal cells of this region form root hairs

Cells of this region gradually differentiate and mature

Region of meristematic activity

Small, thin walled cells with dense protoplasm

MODIFICATIONS OF ROOT Storage of food z z

Tap root - Carrot, turnip Adventitious root - Sweet potato

Prop root z z

Arise from branches to support them eg. Banyan

Stilt root z z

Supporting root coming out from lower nodes eg. Maize, sugarcane

Pneumatophore z z

Root growing vertically upward for oxygen in plants of swampy area eg. Rhizophora

STEM z z z

Develops from plumule.

Bears nodes, internodes, buds (terminal or axillary).

Functions: h Spread out branches bearing leaves, flowers, fruits h Conducts water, minerals and photosynthates

29 M orphology of Flowering Plant

Modifications of Stem z

z z z

Underground stem: For storage of food, also act as organ of perennation to tide over conditions unfavourable for growth. eg. Potato, ginger, turmeric, Colocasia, Zaminkand Tendrils: Axillary bud may modify into tendril, help plants to climb. eg. Grapevines and Gourds (Cucumber, Pumpkin, Watermelon).

Thorn: Axillary buds modify into woody pointed thorn eg. Bougainvillea, Citrus Flat or cylindrical photosynthetic stem: eg. Opuntia (flattened), Euphorbia (cylindrical)

SOME OTHER MODIFICATIONS OF STEM z z z

z

In mint and jasmine, a slender lateral branch arise from base of the main axis and after growing aerially arch downward and touch the ground.

Aquatic plants like Pistia and Eichhornia have lateral branch with short internodes and each node bear rosette of leaves and tuft of roots.

In banana, pineapple and Chrysanthemum, lateral branches arise from basal and underground stem, grow horizontally and then come out obliquely upward to form leafy shoots.

Underground stem of grass and strawberry spread to new niches and when older part dies, new plants are formed. Underground storage stem also acts as organ of perrenation.

LEAF z z z z z

Lateral generally flat structure, develops at node and bear a bud in its axil.

Arise from shoot apical meristem and arranged in acropetal order.

Consist of 3 parts: Leaf base, Petiole and Lamina.

Stripules: Two lateral small leaf like structures at leaf base.

Pulvinus: Leaf base may become swollen in leguminous plants.

Types of Leaves z z

Simple Leaf: Lamina is entire or when incised, incision do not reach midrib.

Compound Leaf: Incision of lamina reaches up to the midrib breaking it into leaflets. It is of two types (i) Pinnately compound–Leaflets are present on a common axis, the rachis. eg. Neem (ii) Palmately compound–Leaflets are attached at a common point i.e at the tip of petiole. eg. Silk cotton 30 Hand Book (Biology)

Venation Reticulate z Veinlets form network z eg. generally in dicots Parallel z Veins run parallel to each other z eg. most monocots

LEAF Modifications of leaves z Tendril eg. Pea z In Australian Acacia, petiole expands and become photosynthetic z Spines eg. Cactus (for defense) z Fleshy leaves for storage e.g. Onion, Garlic z For traping insect eg. venus-fly trap, pitcher plant (insectivorous plant)

Phyllotaxy Alternate : Single leaf at each node arranged in alternate manner eg. china rose, mustard, sunflower Opposite : Pair of leaves arise at each node eg. Guava, Calotropis Whorled: More than two leaves arise at each node eg. Alstonia

INFLORESCENCE z z

z z

Flower is a modified shoot During flowering h Shoot apical meristem modifies into floral meristem h Internode do not elongate and axis gets condensed Solitary flower: Shoot tip transforms into a flower Inflorescence: Arrangement of flowers on floral axis

Two major types Racemose z Main axis continues to grow z Flowers borne laterally in acropetal succession Cymose z Main axis terminates into a flower (limited growth) z Flowers borne in basipetal succession 31 M orphology of Flowering Plant

Hypogynous

Bisexual

Unisexual

Perigynous

TYPES

FLOWER

Symmetry

TYPES

h A flower is asymmetric (irregular) if it cannot be divided into similar halves by any vertical plane passing through the centre. eg.-Canna

z Margin of thalamus grows upward enclosing ovary completely and get fused with it, other parts arise above the ovary. z Eg. Guava, cucumber and ray florest of sunflower

Epigynous

Pentamerous – Floral appendages are multiple of 5

Tetramerous – Floral appendages are multiple of 4

Trimerous – Floral appendages are multiple of 3

Zygomorphic (Bilateral symmetry)

Flower can be divided into two similar halves only in one particular vertical plane eg. Pea. Pea, bean, cassia, gulmohur

z Gynoecium situated in centre, other parts located at the rim of thalamus z Ovary half inferior z Eg. 2PR→ Rose ↓ Peach Plum

TYPES

z Gynoecium occupies highest position, other parts are situated below it. z Superior ovary Eg. BMC → China rose ↓ Mustard Brinjal

Flower have both stamens and carpels

Flower either have androecium or carpels

Actinomorphic (Radial symmetry)

↓

Hand Book (Biology) ↓

Flwer can divided into two equal halves in any plane passing through centre eg. Chilli, mustard, datura

THE FLOWER (REPRODUCTIVE UNIT)

32

PARTS OF A FLOWER Calyx z z z z

z z

Outermost whorl Members called sepal Protect flower in bud stage Generally green May be Gamosepalous (sepals united) Polysepalous (sepals free)

Corolla z z

z z

Members called petals Brightly coloured May Be Gamopetalous (petal united) Polypetalous (petals free)

Androecium z z z z z

Composed of stamens Stamens consist of filament + anther Each anther is bilobed and each lobe has two chambers Sterile stamen - Staminode Male reproductive part

Gynoecium z z z z

Made of one or more carpels Consist of stigma, style and ovary Each ovary bears one or more ovules attached to a flat cushion like placenta.

Carpels may be free, apocarpous (eg. lotus, rose) or united, syncarpous (tomato, mustard)

When calyx and corolla are not distinct termed as perianth (unit tepal) eg. lily.

Aestivation: Made of arrangement of sepals or petals in floral bud w.r.t. other members of the same whorl.

33 M orphology of Flowering Plant

TYPES Valvate z

Sepale/petals in a whorl just touch one another at the margin without overlapping eg. Calotropis.

Twisted z z

One margin of the appendage overlaps the next one and so on. eg. China rose, lady's finger, cotton.

Imbricate z z

Margins of sepals of petals overlap one another but not in any particular direction. eg. Cassia, gulmohur.

Vexillary z z

Five petals, one largest (standard) overlaps two lateral petals (wings) which in turn overlap two smallest anterior petals (keel) eg. Pea, bean

STAMEN Attachment with other floral whorl z z

Epipetalous : Attachment with petals (brinjal) Epiphyllous : Attachment with perianth (lily)

Attachment with each other Free z Free : Polyandrous z Monoadelphous : United with each other in one bundle e.g., China rose z Diadelphous : United in two bundles e.g., Pea z Polyadelphous : United in more than two bundles There may be a variation in the length of filaments within a flower as in Salvia and mustard. 

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34

PLACENTATION Arrangement of ovules within the ovary

Types Marginal Placenta forms a ridge along ventral suture of ovary and ovules are borne on if forming two rows e.g., pea (

)a

(

)a

Axile ( )a Placenta axial ovules attracted on it in a multiocular ovary. e.g., China rose tomato, lemon (

)a

Parietal Ovules develop on inner wall of ovary or on peripheral part Ovary is one chambered but become two charmbered due to false septum e.g., Mustard, Argemone

Free Central Ovules are borne on central axis and septa are absent e.g., Primrose, Dianthus

35 M orphology of Flowering Plant

Basal Placenta develops at the base of ovary and a single ovule is attached to it e.g., Sunflower, marigold

FRUIT AND SEED Ovule Turns into seed

SEED COAT (TESTA, TEGMEN) Embryo Dicot Seed z Contains two cotyledons z Usually lack endosperm except castor z Embryo consists of embryonal axis (radicle + plumule) and 2 cotyledons z Hilum is a scar on the seed coat. z Above hilum is a small pore called micropyle E.g., Bean, gram, pea Seed coat

Cotyledon Plumule

Hilum Radicle Micropyle

MONOCOT SEED z z z z

Single large shield shaped cotyledon called scutellum Endospermous in orchid non-endospermic In cereals, seed coat is membranous and generally fused with fruit wall In maize, endosperm is bulky and stores food. The outer covering of endosperm separates the embryo by a proteinaceous layer called aleurone layer.

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Seed coat & fruit-wall

Endosperm

Aleurone layer Scutellum Coleoptile Endosperm

Embryo

Plumule

Radicle Coleorhiza

OVARY z z

Ripens into fruit Fruit

SEEDS Pericarp z z

May be dry or fleshy Divide into ♦ Epicarp ♦ Mesocarp ♦ Endocarp Parthenocarpic fruit : Fruit formed without fertilization.

Mango and coconut are drupe type of fruits, develop from monocarpellary, superior ovaries and one seeded, In mango, mesocarp is fleshy edible and in coconut, it is fibrous. Both have hard stony endocarp 

DESCRIPTION OF SOME IMPORTANT FAMILIES Fabaceae z z z z

Earlier called Papillionoideaea, subfamily of Leguminosae Stem : Erect or climber Leaves : Alternate, pinnately compound pulvinate, stipulate, reticulate venation Inflorescence : Racemose

37 M orphology of Flowering Plant

z

Flower : Bisexual, zygomorphic

z

Calyx : 5, gamosepalous, valvate/imbricate aestivation

z

Corolla : 5, polypetalous, papilionaceous corolla, vexillary aestivation

z

Androecium : 10. diadelphous, anther dithecus

z

Gynoecium : Superior ovary, monocarpellary, unilocular, many ovules, marginal placentation

z

Fruit and seed : Legume, non-endospermic seed ♂K C %♀ A G (5)

1+2 + (2)

(B) + 1

Solanaceae z

Commonly called potato family

z

Stem : Herbaceous, rarely woody solid/hollow, hairy, underground as in potato

z

Leaves : Alternate, simple, rarely pinnate, reticulate venation

z

Inflorescence : Solitary, axillary or cymose as in Solanum

z

Flower : Bisexual, actinomorphic

z

Calyx : 5, gamosepalous, persistent, valvate aestivation

z

Corolla : 5, gamopetalous, valvate aestivation

z

Androecium : 5, epipetalous

z

Gynoecium : Bicarpellary, obliquely placed, syncarpous. superior, bilocular, placenta swollen, axile placentation, many ovules

z

Fruit and seed : Berry/capsule, endospermous seed

♂ K (5) C ⊕♀ (5) A3 G(2)

Hand Book (Biology)

38

Liliaceae z

A monocotyledonous family also called lily family

z

Stem : Underground bulbs/corms/rhizome

z

Leaves : Mostly basal, alternate, linear, exstipulate, parallel venation

z

Inflorescence : Solitary/cymose, often umbellate clusters

z

Flower : Bisexual, actinomorphic

z

Perianth: Tepal 6(3 + 3), often united in tube, valvate aestivation

z

Androecium : 6(3 + 3). epitepalous

z

Gynoecium : Tricarpellary, syncarpous, superior ovary, trilocular, axile placentation, many ovules

z

Fruit and seed : Capsule rarely berry, endospermous seeds ♂ P

Br⊕♀ (3 + 3) A 3 + 3 G (3)

39 M orphology of Flowering Plant

ECONOMIC IMPORTANCES Fabaceae z z z z z z z

Pulses : (Gram, arhar, sem, moong, soyabean) Edible oil : (Soyabean, Groundnut) Dye : (Indigofera) Fibres : (Sunhemp) Fodder : (Sesbania Trifolium) Omamental : (Lupin, sweat pea) Medicine : (Muliathi)

Solanaceae z z z z z

Food : (Tomato, potato, brinjal) Spice : (Chilli) Medicine : (Belladonna, Ashwagandha) Fumigatory : (Tabacoo) Ornamental : (Petunia)

Liliaceae z z z z

Vegetable : (Asparagus) Medicine : (Aloe) Ornamental : (Tulip, Gloriosa) Colchicine : (Calchicum autumnale) Floral formula of mustard ♂K C A G ⊕♀ 2+2 4 2+4 (2) Floral diagram of mustard

qqq Hand Book (Biology)

40

Chapter

6 Anatomy of Flowering Plants

INTRODUCTION Anatomy: Study of internal structure of plants.

TISSUES Group of cells having a common origin and usually performing a common function.

TYPES Meristematic Tissues z z

Actively dividing cells.

Two types according to appearance in life Primary meristem (Appear early in life) Apical Meristem h Found at tips of roots and shoots. h Some shoot apical meristem cells that are left behind during stem elongation and leaf formation constitute axillary buds. h Axillary buds are capable of forming a branch or a flower.

Intercalary Meristem h Occurs between mature tissues. h Occurs in grasses regenerate parts removed by razing herbivores. h Secondary meristem (appear later than primary meristem) h Also called Lateral meristem. h Cylindrical meristem found in mature regions of roots and shoots.

TYPES Intrafascicular Meristem

Found between xylem and phloem in a conjoint vascular bundle.

Interfascicular Meristem

Found between two vascular bundles.

Cork Cambium

Extrastelar cambium formed in cortical region.

Permanent Tissues z z z

Newly formed structurally and functionally specialised cells.

Do not divide further.

Simple Two types Complex

SIMPLE PERMANENT TISSUES (MADE OF ONLY ONE TYPE OF CELLS) Parenchyma z z z z z

Forms major component within organs.

Spherical, oval, round, polygonal or elongated in shape.

Thin walled, living.

Cellulosic cell wall.

May have small intercellular spaces.

Functions 1. Storage 2. Secretion 3. Photosynthesis (if have chlorophyll)

Intercelluar space

Collenchyma z z z z z

Occurs in layers below epidermis.

Cells may be oval, spherical or polygonal in shape.

Thick walled, living.

Corners of cell deposited with cellulose, hemicellulose and pectin.

Intercellular space absent.

Thickened corners Protoplasm Vacuole Cell wall

Functions 1. Provide mechanical support to growing parts of plants.

2. May perform photosynthesis (if cells contain chloroplast).

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Sclerenchyma z z z z

Long, narrow cells with thick lignified wall.

Dead.

May be elongated and pointed-Sclerenchyma fibre.

May be spherical, oval or cylndrical-sclereid (Common in fruits, nuts, pulp of guava, pear, etc.).

Lumen Thick cell wall

Pits Lumen

A bre

Thick A sclereid cell wall

Function Mechanical support

COMPLEX PERMANENT TISSUES (MADE OF MORE THAN ONE TYPE OF CELLS) Types Xylem (Four components) Tracheid: h Elongated, tube like with tapering ends, lignified, dead and without protoplasm. h Water transporting element.

Vessel: h Long cylindrical tube, absent in gymnosperm. h Multicelled, dead, devoid of protoplasm, lignified with large central cavity. h Main water conducting element in angiosperms.

Xylem Parenchyma: h Living, thin walled. h Involved in radial conduction of water, may store food.

Sclerenchyma Fibres h Dead, lignified wall with obliterated lumen.

43

Anatomy of Flowering Plants

Phloem (Four components) Sieve tube elements (Gymnosperms have sieve cells): h Long, tube like, perforated end walls, lack nucleus at maturity. h Peripheral cytoplasm with large central vacuole. h Transport of food material.

Companion cell (Gymnosperms have albuminous cells): h Specialised parenchyma cell, connected to sieve tubes by pit fields. h Helps to maintain pressure gradient in sieve tubes. h The functions of sieve tubes are controlled by the nucleus of companion cells.

Phloem parenchyma: h Elongated, tapering cylindrical cells. h Stores food material, resin, mucilage, latex etc. h Absent in most of the monocots.

Bast fibres (Phloem fibres): h Elongated, sclerenchymatous, unbranched, pointed needle like apices. h Jute, flax and hemp produce commercial bast fibres. h Generally absent in primary phloem but found in secondary phloem.

XYLEM TYPES Primary Xylem z z

Protoxylem (First formed with narrow vessel).

Metaxylem (Later formed with broader vessel).

Secondary Xylem Formed during secondary growth.

PHOLEM TYPES Primary Phloem z

Protophloem (First formed and have narrow sieve tube).

z

Metaphloem (Later formed and have broad sieve tube).

Secondary Phloem z z

Formed during secondary growth.

Endarch - Protoxylem lies towards pith/centre and metaxylem towards periphery e.g., Stems.

44 Hand Book (Biology)

z

Exarch - Protoxylem lies towards periphery and metaxylem towards pith e.g., Roots.

TISSUE SYSTEM Epidermal Tissue System Forms outermost covering of plant body.

Epidermis h Parenchymatous, usually single layered, outermost covering. h Often covered by waxy cuticle (absent in roots).

Stomata h Consist of guard cells and subsidiary cells. h Bean/kidney shaped guard cells - Dicot and Dumbell shaped - Monocot. h Stomatal aperture + guard cells + subsidiary cells = Stomatal apparatus.

Root hairs h Unicellular elongation of epidermal cells. h Absorb water and mineral from soil.

Trichomes h In shoot system, usually multicellular. h Branched/unbranched, soft or stiff. h Can be secretory, prevent water loss.

Ground Tissue System In leaves h Ground tissue consists of thin walled chloroplast containing cells called mesophyll.

In stem and root h Made up of all the tissues except epidermis and vascular bundles. h Consist of parenchymatous cortex, pericycle, pith, medullary rays and conjunctive tissue (between xylem and phloem in roots). h Hypodermis - Found in stem absent in roots.

Vascular Tissue System Types Consists of xylem and phloem.

Presence/absence of cambium h Open - Cambium present e.g. Dicot stem. h Closed - Cambium absent e.g., Monocot stem.

45

Anatomy of Flowering Plants

According to arrangement of xylem and phloem h Conjoint - Xylem and phloem on same radius e.g., Stem, leaves h Radial - Xylem and pholem are on different raddi in alternate manner e.g., Root.

COMPARISON BETWEEN DICOT AND MONOCOT ROOT Features

Dicot root

Monocot root

Epiblema

With root hairs

Cortex

Thin walled parenchymatous Thin walled parenchymatous with with intercellular space intercellular space

With root hairs

Endodermis Barrel shaped cells with casparian Barrel shaped cells with casparian strip strip Pericycle

Thick walled parenchymatous, Thick walled parenchymatous, form lateral roots and vascular form lateral roots cambium

Vascular bundle

Radial, exarch, 2-4 xylem and Radial, exarch, usually more than phloem patches 6 xylem bundles (polyarch)

Pith

Poorely developed or absent

Well developed

COMPARISON BETWEEN DICOT AND MONOCOT STEM

Cortex

Features

Dicot stem

Monocot stem

Epidermis

With cuticle and stomata With cuticle and stomata

Hypodermis

Collenchymatous

Sclerenchymatous

Cortical layer

Parenchymatous

Large parenchymatous

Endodermis

Starch ich referred to as Absent starch sheath

Pericycle

Semi-lunar patches of Absent sclerenchyma

Vascular bundle

Conjoint, open, endarch Conjoint, closed, scattered and each and arranged in a ring surrounded by sclerenchymatous sheath, smaller peripheral ones, larger central ones, water containing cavity in vascular bundle

Pith

Parenchymatous with Absent intercellular spaces

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COMPARISON BETWEEN DICOT AND MONOCOT LEAF Features Stomata

Dicotyledonous leaf

Monocotyledonous leaf

More on lower (abaxial) surface Equally distributed on both adaxial as compared to upper (adaxial) and abaxial epidermis, isobilateral one. It is called dorsiventral leaf. leaf.

Covered by cuticle.

Epidermis

Covered by cuticle, may have large, empty, colourless bulliform cells on upper epidermis, to minimise water loss.

Two types - Adaxially placed Only spongy parenchyma is found, palisade parenchyma (elongated palisade parenchyma absent. cells, vertically and parallely Mesophyll arranged to each other), spongy parenchyma - loosely arranged with air cavities, below the palisade cells.

Vascular bundle

Conjoint, size vary according Conjoint, nearly similar sized due to thickness of veins, has thick to parallel venation. walled bundle sheath.

SECONDARY GROWTH z z

Occur in most dicots to increase girth.

Tissue involved are lateral meristem - Vascular cambium and cork cambium.

Vascular cambium z z z

z z z

47

Form secondary vascular tissues.

In dicot stem formed by Intrafascicular cambium and Interfascicular cambium (formed by dedifferentiation of cells of medullary rays).

Vascular cambium cuts off cells Towards pith

Towards periphery I

Form secondary xylem

Form secondary phloem

Since cambium is more active towards innerside, thus amount of secondary xylem produced will be more than secondary phloem.

Primary and secondary phloem gradually get crushed while primary xylem remains more or less intact.

Vascular cambium also produces secondary medullary rays in radial direction.

Anatomy of Flowering Plants

Cork cambium z z z z

Replaces outer broken cortex and epidermis.

In dicot stem formed by dedifferentiation of cortex cells.

Couple of layer thick and composed of narrow thin walled nearly rectangular cells.

Phellogen or cork cambium cuts off cells Towards outer side

Towards inner side

Form suberin deposited impervious cells, cork/phellem

Form parenchymatous secondary cortex, phelloderm

Phellem + Phellogen + Phelloderm → Periderm. z

Bark: Non technical term referring all tissues exterior to vascular cambium, it can be early bark (produced early in the season) or late bark (produced in the end of season).

Lenticels: z z z

Lense shaped opening formed by rupturing of epidermis.

At certain region, phellogen produces closely arranged parenchymatous cells instead of cork cells.

Permit gaseous exchanges in woody parts.

DIFFERENT TYPES OF WOODS Spring wood

Autumn wood

z Form in spring season

z Form in autumn season

z Also called early wood

z Also called late wood

z Cambium usually more active in

z Cambium is less active in autumn

spring

z Contains more xylary elements z Vessels have wider cavities z Lighter in colour, lower density

z Contains fewer xylary elements z Vessel have narrow cavities z Darker in colour, higher density

Spring wood + Autumn wood ⇒ One annual ring (in temperate region plants) (used to estimate age of tree)

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Heart wood

Sapwood

z Secondary xylem of center most

z Formed by secondary xylem of

z Dead with lignified wall

z Living

z Dark in colour, hard, durable

z Lighter in colour

z Deposited with tannin, resin etc.

z Involved in conduction of water and

region

z Do not conduct water but provide

peripheral region

minerals

mechanical support

SECONDARY GROWTH IN ROOTS Occurs Through Vascular cambium z Completely secondary in origin z Formation:

Cork cambium z Formed by cells of pericycle, rest

activity is similar to dicot stem

(i) A portion of pericycle (ii) Tissues just below phloem z Similar to dicot stem z In roots, cambium do not show

seasonal activity

z z z z

Endodermis is innermost layer of cortex in roots and dicot stem.

Primary meristem contributes to the formation of primary plant body.

Secondary meristem are responsible for producing secondary tissue.

Stele: All tissues on the innerside of endodermis such as pericycle, vascular bundles and pith.  qqq

49

Anatomy of Flowering Plants

7

Chapter

Structural Organisation in Animals TISSUE ♦ Human body is composed of billions of cells to perform various function. ♦ Division of labour contributes to survival of multicellular organisms e.g., Hydra. ♦ No division of labour in unicellular organism. ♦ A group of similar cells along with intercellular substances which perform a specific function. ♦ Organs such as stomach, lungs, heart and kidney comprise a specific proportion and pattern of all basic types of tissues. ♦ Organ system: Two or more organ perform a common function by physical/chemical interaction e.g., Digestive system.

Different types of cells ♦ Hydra Number of cells in thousands ♦ The skin is the largest organ in the body.

TYPES OF TISSUES Based on: Structure of cells vary according to their function Epithelial tissue

Connective tissue

Muscular tissue

Neural tissue

CELL JUNCTIONS Tight Junctions Prevent leakage of substance across a tissue

Gap Junctions Adhering Junctions Perform cementing Facilitate the cells to communicate to keep neighbouring with each other by connecting the cells together cytoplasm of adjoining cells, for rapid transfer of ions, small molecules and sometimes big molecules.

Simple epithelium (single-layered) Example: Cavities, Duct, Tubules

Structural Organisation in Animals

Location

Function

Air sacs of Tubular parts of lungs, walls nephron (PCT), of blood vessels ducts of glands

Location

faces body fluid or outsides environment

Central or at base

Central or at base

Inner surface of inner organs, bronchioles and fallopian tubes

Salivary glands

Move particles Specialised or mucus in a for secretion specific direction

Cuboidal or columnar

II.**

I.*

Glandular

Cuboidal or columnar

Ciliated

covering of a lining for some part of the body

Epithelial tissue provides a

packed with little intercellular matrix

Its cells are compactly

nephron and small intestine increase surface area for absorption

Microvilli present in PCT of

Dry surface of skin, buccal cavity, pharynx, inner lining of ducts of salivary glands and pancreatic ducts

Protection against mechanical and chemical stresses Limited role in secretion and absorption

2 or more cell layers

Stomach and intestine

Secretion and absorption

Secretion and absorption

Diffusion boundary

Function

At base

Tall and slender

Columnar

Central

Central

Nucleus

Cuboidal

Single layer of Single thin layer of flattened, cube-like irregular boundaries

Squamous

Cells

Figure

Characteristics

Free surface of epithelial tissue

Compound epithelium (multi-layered) Example: Skin

51

EPITHELIAL TISSUE (Avascular)

Transitional Epithelium Stratified Epithelium Thinner and more elastic Type of compound epithelium Lines the inner surface Found in dry surface of skin of the urinary bladder and moist surface of buccal and ureter cavity and pharynx Glands

(Glandular epithelium)

I.* Based on the number of cells • Number of cells Unicellular Multi-cellular • Example

Salivary glands (secrete saliva)

Goblet cells (Secrete mucus)

II.** Based on the mode of pouring their secretions

Exocrine glands Ducts Present Secretions Mucus, saliva, earwax, oil, milk, digestive enzymes and other cell products

Endocrine glands Absent Hormones

Endocrine glands directly release their secretions into the fluid bathing the gland

CONNECTIVE TISSUE (VASCULAR) Most abundant and widely distributed tissue Linking and supporting other tissues and organs Range from soft connective tissues to specialised types Components of Connective tissue: Matrix/ground substance: Modified polysaccharides or intercellular material Cells: Fibroblasts, macrophages, adipocytes etc.

Fibres: Fibroblasts secrete collagen or elastin fibres In all connective tissues except blood have fibroblast cells to produce fibre of structure of proteins called collagen or elastin Fibres provide strength, elasticity and flexibility to the tissue

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THREE TYPES OF CONNECTIVE TISSUE I. LOOSE CONNECTIVE TISSUE Cells and fibres are loosely packed in semi-solid ground substance Types Areolar tissue

Adipose tissue

Major cells

Fibroblasts, macrophages, mast cells

Adipocytes

Function(s)

Serve as support framework for epithelium

Reservoir of stored fats

Beneath skin

Mainly beneath skin

Location Macrophage

Fat storage area Nucleus

Fibroblast Collagen fibres

Plasma membrane

Mast cell

Excess of nutrients not meant for immediate use are converted to fats and are stored in adipose tissue 

II. DENSE CONNECTIVE TISSUE Fibroblasts and fibres are compactly packed in matrix Types Dense regular

Dense irregular

Cells and fibres

Parallel bundles of collagen fibres

Fibroblasts and fibres are oriented differently

Function(s)

Tendons (attach skeletal muscles to bone) Ligaments (attach bone to bone)

Skin

Arrangement

53

Collagen fibre

Collagen fibre

Structural Organisation in Animals

III. SPECIALISED CONNECTIVE TISSUE 1. Skeletal Connective Tissues

Cartilage

Bones

Matrix

Solid, pliable

Hard and non-pliable

Cells in lacuna

Chondrocytes

Osteocytes

Location/ Functions

Tip of nose, outer ear joints, between vertebrae, limbs and hands in adults Most of the cartilages in vertebrate embryos are replaced by bones in adults

Constitutes main structural framework Interact with skeletal muscles to bring movements Bone marrow in some bones is the site of production of blood cells Support & protect softer tissues & organs

Diagram

Collagen fibers Collagen fibers Cartilage cell (chondrocyte)

• Cartilage resists compression.

• Calcium salts and collagen fibres in ground substance provide strength to the bones.

• Lacunae are small cavities enclosing bone cells within matrix secreted by them.

2. Fluid Connective Tissues Blood – main circulating fluid that helps in the transport of various substances Composed of plasma, RBC, WBC, platelets Fibroblasts and fibres are absent in blood

RBC

Platelets

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WBC

54

MUSCULAR TISSUE

nMyofibrils nMuscle fibres Muscle Show contractility and return to their uncontracted state in a coordinated fashion Play an active role in all movements Parameters Shape

Skeletal muscle fibres Cylindrical

Smooth/Visceral muscle fibres Spindle/fusiform

Cardiac muscle fibres Cylindrical

No. of nuclei

Multi-nucleated

Uninucleated

Uninucleated

Location of nuclei Peripheral nuclei Striations Branching Under control of will Junctions Location

Central

Central

Striated

Non striated

Faint striations

Unbranched

Unbranched

Branched

Yes (Voluntary)

No (Involuntary)

No (Involuntary)

Present Absent Attached to bones Blood vessels, e.g., Biceps stomach, intestine

Present Heart wall

Communication junctions (intercalated discs) at some fusion points allow the cells of cardiac muscles to contract as a unit



NEURAL TISSUE

Exerts the greatest control over the body’s responsiveness to changing conditions.

Neural Tissue

Neurons

Neuroglial cells

Composition

Unit of neural system

More than one half the volume of neural tissue

Excitability

Yes

No

Function

Respond to changing conditions through various stimuli

Protect and support neurons

Axon Cell body with nucleus Dendrite Neuroglea Upon suitable stimulation, the electrical disturbance generated travels swiftly along the plasma membrane of neuron. 

Our heart consists of all four types of tissues.

Complexity in organ and organ systems display certain discernable trend called evolutionary trend.

55

Structural Organisation in Animals

INTRODUCTION (Cockroach) Classification Kingdom : Animalia Phylum : Arthropoda Class : Insecta Genus : Periplaneta Species : americana Size Colour Habitat Habit

Characteristics 0.6-7.6 cm (1/4 inches to 3 inches) Brown or black colour; Bright yellow, red and green coloured reported in tropical regions Damp places throughout world Omnivorous, Nocturnal

Economic Residents of human homes and are importance serious pests & vectors of several diseases and spoil food & contaminate it with their smelly excreta MORPHOLOGY

Exoskeleton: Head, brown chitinous plates called sclerites

34-53 mm long with wings extend

Dorsal plates – Tergites Ventral plates – Sternites Plates connected by a thin, flexible articular/ arthrodial membrane.

beyond the tip of abdomen in males. Pronotum

Body Division: Compound eye

Head (6 segments)

• Triangular, right angle to longitudinal body axis

Appendages:

Filiform antennae

• Long, sensory thread like • Segmented arise from membranous socket • Present in front of eyes • Help in monitoring environment

Mesothoracic wings/

Thorax (3 segments) • Prothorax • Mesothorax • Metathorax

Abdomen

(10 segments) Broader in females than males

Neck:

Anal cerci (1 pair)

Forewings/Tegmina (1 pair) • Opaque, dark and leathery • Cover hindwings at rest • Do not help in flight Metathoracic wings/ Hindwings (1 pair) • Transparent and membranous • Meant for flight Legs (3 pairs) • 1 pair of walking legs on each thoracic segment

Head connected to thorax by short extension of prothorax.

It provide great mobility of head in all directions.

The sclerite of prothorax is large and is known as a pronotum.

Head capsule bears a pair of compound eyes.

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DIGESTIVE SYSTEM Alimentary canal Well developed with a mouth surrounded by mouth parts Foregut (Lined by cuticle entirely) • Pharynx (shorts tubular) • Oesophagus (Narrow tubular) • Crop (sac like for temporary storage of food) • Gizzard/proventriculus • Outer thick circular muscles and inner six chitinous teeth • Grinding of food particles

Accessory glands

Salivary gland

• 1 pair • Present near crop

Salivary reservoir Hapatic/gastric caecae

• Ring of 6-8 blind tubules • At the junction of foregut and midgut • Secrete digestive joice

Malpighian tubules (part

Mesenteron/Midgut

of excretory system) • 100-150 in number • Yellow coloured, thin filamentous tubules at the junction of midgut and hindgut

(Between foregut and hindgut)

Hindgut (Broader than midgut)

• Ileum • Colon • Rectum (Opens out through anus)

Head bears appendages forming biting and chewing type of mouth parts Ocellus

Maxilla

Mandible

Labrum Upper lip

Compound eye

Grinding region Incising region

Mandidble

Mandible (Grinding of food)

Hypopharynx

Labrum Labium

Maxilla

57

Labium Lower lip

Structural Organisation in Animals

Maxilla

BLOOD VASCULAR SYSTEM Open type Heart

Blood vessels

Elongated muscular tube with 13 chambers

Haemolymph

Poorly developed

Composed of colourless Open into haemocoel plasma and Lying along mid dorsal line of haemocytes thorax and abdomen Visceral organs Funnel shaped chambers with bathed in ostia on either on either side haemolymph Blood flows anteriorly in heart

Anterior Alary muscles aorta

Chambers of heart

Open circulatory system of cockroach

RESPIRATORY SYSTEM Network of trachea (thin, branching tubes) that open through 10 pairs of spiracles present on lateral side of the body.

Opening of spiracles is guarded by sphincters.

Site for exchange of gases: Tracheoles by diffusion.

EXCRETORY SYSTEM Malpighian tubules, lined by glandular and ciliated cells.

They absorb nitrogenous waste products and convert them into uric acid which is excreted out through hindgut.

Excretory product: Uric acid (Uricotelic).

Other excretory structures: Fat body, nephrocytes and uricose glands.

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NERVOUS SYSTEM (Spread Throughout Body) Parameters Head Ventral part of body Proportion Bit of nervous system Most part of nervous system of nervous Supra-oesophageal Paired longitudinal system ganglion (brain) connectives with series of fused segmentally Supply nerves to arranged ganglia Antennae and compound • 3 ganglia in thorax eyes (Each compound • 6 ganglia in abdomen eye consists of 2000 hexagonal ommatidia & situated at dorsal surface of head) • Sense organs: Antennae, Labial palps, Eyes, Maxillary palps, Anal cerci • Cockroach has mosaic vision with more sensitivity and less resolution • If head of cockroach is cut off, it will still live for as long as one week 

REPRODUCTIVE SYSTEM [Dioecious] MALE REPRODUCTIVE SYSTEM Testis 1 pair, lateral side th th 4 -6 abdominal segments

Phallic gland Long tubules

Mushroom gland th th 6 -7 abdominal Seminal vesicle segments Vas deferens Accessory reproductive Ejaculatory duct gland Opens through male genital pore which is ventral to anus Anal cercus Small tubules

External genitalia/gonapophysis Components 1. Chitinous asymmetrical structure 2. Present around male gonopore 3. Three phallomeres: (a) Right phallomere Pseudopenis (b) Ventral phallomere Tibillator (c) Left phallomere

th

Male genital pouch (Lies at the hind end of abdomen)

59

Caudal/anal style 1 pair, only in males

th

Dorsally by 9 and 10 terga th Ventrally by 9 sternum Contains dorsal anus, ventral male genital pore gonapophysis

Structural Organisation in Animals

FEMALE REPRODUCTIVE SYSTEM Ovary 1 pair nd th 2 -6 abdominal segments 1 ovary contains 8 ovarioles • Each ovariole contains chain of developing ova Oviduct

Spermatheca 1 pair th 6 abdominal segment

Common oviduct or vagina Collaterial gland 1 pair Secrete ootheca Genital chamber Genital pouch Vestibulum

Gonapophyses th

th

th

7 sternum (boat shaped) along with 8 and 9 sterna Female gonopore, spermathecal pores and collaterial glands

Anterior part

Path of sperms Testes → Vas deferens → Seminal vesicle → Ejaculatory duct → Male genital pore → Spermatheca of female during copulation Path of ova

Female genital pore Common oviduct/Vagina Oviduct Ovary (Ovarioles)

Sperms Ova

Anal cerci Anal style Paired, long Paired, short Unjointed Jointed Filamentous Thread like Both ♀ & ♂ Only ♂

Sperm

Female genital pouch (brood pouch) Fertilisation Secretion of collaterial glands form ootheca On an average, female produces 9-10 ootheca each containing 14 to 16 fertilised eggs

• Ootheca is a dark reddish to blackish brown capsule about 3/8" (8 mm) long.

• Female deposits ootheca in crack or crevice 13 times moulting (Paurometabolous development indirect) • Nymph Adult • Next to last nymphal stage has wing pads but only adult cockroaches have wings

qqq

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Chapter

8 Cell: The Unit of Life

INTRODUCTION Cell, basic unit of life, makes an organism living. All organisms are composed of cells.

CELL z z

Cell is the fundamental structural and functional unit of all living organisms. Anything less than a cell does not ensure independent living.

Anton Von Leeuwenhoek first saw and described a live cell.

CELL THEORY z

z

z

In 1838, Matthias Schleiden, a German botanist, examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant.

At the same time, Schwann (1839) a British Zoologist, reported that animal cells had a thin layer called plasma membrane. He concluded that plant cells have cell walls. Schleiden and Schwann together formulated that cell theory but this theory did not explain as to how-new cells are formed.

Rudolf Virchow explained that new cells arise from pre-existing cells (Omnis cellula-e cellula) and finally modified the cell theory as: (i) All living organisms are composed of cells and products of cells. (ii) All cells arise from pre-existing cells.

AN OVERVIEW OF CELL z

Cells differ greatly in size, shape and activities for example, Mycoplasma is smallest cell (0.3µm), Egg of an ostrich is the largest isolated single cell. Nerve cells are some of the longest cells. (RBCs- 7µm in diameter, Bacteria – 3-5µm, Virus - 0.02 – 0.2µm).

z

Cytoplasm is main arena of cellular activities in both plant and animal cells.

PROKARYOTIC CELLS z z z

z

Lack membrane bound nucleus and cell organelles.

Represented by bacteria, blue green algae, mycoplasma or PPLO (0.1µm).

In addition to genomic DNA, many bacteria have small circular DNA outside the genomic DNA called plasmids. Plasmid DNA confers certain unique phenotypic characters to such bacteria. One such character is resistance to antibiotics. Plasmid DNA is used to monitor bacterial transformation with foreign DNA. All prokaryotes have a cell wall surrounding the cell membrane (except mycoplasma)

Cell Envelope and its Modifications z z z z z

z z

z z z

Most prokaryotic cells have cell envelope which is tightly bound three layered structure.

The outermost glycocalyx → Cell wall → Plasma membrane Glycocalyx may be a loose sheath called slime layer or thick and tough called capsule.

The cell wall prevents bacteria from bursting or collapsing.

Mesosomes: Extension of plasma membrane into the cell in the form of vesicles, tubules and lamellae. It helps in cell wall formation, DNA replication, distribution of daughter cells, respiration, secretion process and increase the surface area of plasma membrane.

In cyanobacteria, chromatophores contain pigments.

Each layer of the cell envelope performs distinct function, they act together as a single protective unit. The plasma membrane is selectively permeable in nature and interacts with the outside world. It is structurally similar to that of eukaryotes.

Bacteria may be motile or non-motile. If motile they have flagella, composed of three parts: Filament (longest portion), hook and basal body.

Pili and fimbriae do not play role in motility.

Bacteria, on the basis of the staining, can be Gram positive or Gram negative.

Ribosomes and Inclusion Bodies z z

Ribosomes are non-membrane bound organelles.

Found in both eukaryotic and prokaryotic cells.

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z z

z z

Also found in cytoplasm, mitochondria & RER. Ribosomes are 70S, has subunits 50S and 30S, Several ribosomes may attach to a single mRNA and form a chain called polyribosome or polysome.

Ribosomes are associated with plasma membrane.

The ribosomes of a polysome translate the mRNA into proteins.

Inclusion bodies z

z

Reserve material is stored in the form of inclusion bodies in prokaryotic cytoplasm. Eg. phosphate granules, cyanophycean granules and glycogen granules.

Gas vacuoles are found in blue green and purple and green photosynthetic bacteria.

EUKARYOTIC CELLS (10-20µm) z z

z

Besides the nucleus, eukaryotic cells have other membrane bound structure called organelles like ER, Golgi complex etc.

The eukaryotes include all the protists, plants, animals and fungi. Plant cells have large vacuole. Animals cells have centrioles which are almost absent in plant cells.

Cytoplasmic ribosomes are of 80S. Small subunit is 40S and large 80S.

Cell Membrane z z z z z z z z z

63

Chemical studies on the cell membrane, especially in human RBC enabled scientists to deduce the possible structure of plasma membrane.

Cell membrane is mainly composed of proteins and lipids (mainly phospholipids).

Phospholipids consist of polar head (outward) and non-polar tail (hydrophobic) inner side. In human RBC, 52% is proteins and 40% lipids.

Membrane proteins can be integral or peripheral.

Most accepted model for structure of cell membrane is fluid mosaic model given by Singer and Nicolson (1972).

Membrane is selectively permeable.

Passive transport: Many molecules can move across the membrane without any requirement of energy.

Osmosis: Movement of water by diffusion.

Active transport: Many molecules require energy/ATP for their transport e.g. Na+/K+ pump.

Cell: The Unit of Life

z

z

The quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer. This ability to move within the membrane is measured as its fluidity.

Polar molecules cannot move through the non-polar lipid bilayer.

FUNCTIONS z z z

Cell growth Formation of intercellular junctions Secretion, endocytosis, cell division etc.

CELL WALL z z z z z z

Non-living rigid structure forms an outer covering of the plasma membrane in fungi and plants.

Primary wall: Cell wall of a young plant cell is capable of growth which gradually diminishes as the cell matures.

Secondary wall: is formed on inner side (towards membrane) of the cell.

Middle lamella: is a layer mainly of calcium pectate.

Cell wall of Algae: Cellulose, galactans, mannans and calcium carbonate.

Cell wall of plants: Cellulose, hemicellulose, pectin and proteins.

ENDOMEMBRANE SYSTEM z

While each of the membranous organelles is distinct in terms of its structure and function, many of these are considered together as an endomembrane system because their functions are coordinated.

Nucleus Nuclear pore

Rough endoplasmic reticulum

Cisternae

Ribosome

Smooth Endoplasmic reticulum Endoplasmic reticulum

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Golgi apparatus

64

Endoplasmic reticulum (ER)

Golgi apparatus

Reticulum of tiny tubular structures scattered in the cytoplasm.

These were named Golgi bodies after discoverer name Camillo Golgi.

These are membrane bound vesicular structures formed by the process of packaging in the Golgi apparatus.

The vacuole is the membrane bound space found in the cytoplasm, membrane is called tonoplast.

RER: ER which has ribosomes on surface SER: In absence of ribosomes, they appear smooth.

They consist of cisternae, which are concentrically arranged near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face.

They are rich in hydrolytic enzymes (lipases, proteases carbohydrases), optimally active at acidic pH (5.5).

Contain water, sap, excretory product and other materials not useful for the cell. In Amoeba, contractile vacuole is important for excretion.

RER is involved in protein synthesis SER is involved in lipid synthesis.

Principally performs the function of packaging of materials.

It is the important site for formation of glycoproteins and glycolipids.

These enzymes are capable of digesting carbohydrates, proteins, lipids and nucleic acids.

In many cells. as in protists, food vacuoles are formed by engulfing the food particles.

Lysosome

Vacuole

MITOCHONDRIA z

Mitochondria are visible under microscope only after staining.

z

Each mitochondria is a double membrane bound structure with inner compartment called matrix. The two membranes have their own specific enzymes.

z

Outer membrane: Forms the continuous limiting boundary of the organelle.

z

Inner membrane: Forms cristae.

z

Sites of aerobic respiration. They produce cellular energy in the form of ATP, hence called 'power house of the cell'.

z

Matrix has single circular DNA molecule, a few RNA molecules, ribosomes (70S) and the components required for the synthesis of proteins.

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Cell: The Unit of Life

‘S’ (Svedberg's unit) stands for sedimentation coefficient. It is an indirect measure of density and size.

Outer membrane

Inner-membrane space Inner membrane Crista Matrix

Outer membrane Inner membrane Granum Thylakoid Stroma lamella

Structure of mitochondria (Longitudinal section)

Stroma Sectional view of chloroplast

PLASTIDS z

Plastids are found in all plant cells and in euglenoids. Based on the pigments, plastids can be classified into chloroplasts, chromoplasts and leucoplasts.

z

Chloroplast contain chlorophyll and carotenoid pigments.

z

Leucoplast are colourless plastids.

z

Amyloplasts store carbohydrates e.g. Potato, Elaioplasts store oils and fats whereas the aleuroplast store proteins.

z

Chloroplast are also double membrane bound structure which has membranous sac like structure called thylakoids and the matrix is called stroma. It also contains small, ds circular DNA and ribosomes.

z

Carotenoid is fat soluble pigment e.g., Carotene, xanthophyll etc.

z

The ribosomes of the chloroplasts (70S) are smaller than cytoplasmic ribosomes (80S).

z

Thylakoids are arranged in stacks called grana (singular-granum). Flat membranous tubules called the stroma lamellae connecting the thylakoids of the different grana.

z

Stroma contain required enzymes for carbohydrate and protein synthesis.

z

Chlorophyll pigments are present in the thylakoids.

CYTOSKELETON z

An elaborate network of filamentous proteinaceous structures present in the cytoplasm.

FUNCTIONS z

Mechanical support, motility, maintenance of the shape of the cell.

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CILIA AND FLAGELLA z

Hair like outgrowths of the cell membrane. Flagella are comparatively longer and responsible for cell movement.

z

The prokaryotic bacteria also possess flagella but these are structurally different from eukaryotic flagella.

z

The central core- Axoneme.

z

Arrangement of axonemal microtubules is referred to as the 9 + 2 array.

z

Both cilium and flagellum arise from centriole like structure called basal bodies. They are covered will plasma membrane.

Plasma membrane Peripheral microtubules (doublets) Central sheath Interdoublet bridge

Radial spoke

Central microtuble

Structure of cilia/flagella

CENTROSOME AND CENTRIOLES z

A non-membrane bound organelle usually containing two cylindrical structures called centrioles. They are surrounded by amorphous pericentriolar materials and lie perpendicular to each other.

z

The central part of the proximal region of the centriole is proteinaceous called the hub, which is connected with tubules of the peripheral triplets (nine) by radial spokes made of protein.

z

Helps in cell division.

NUCLEUS z

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Nucleus as a cell organelle was first described by Robert Brown as early as 1831. Later, the material of nucleus was given the name chromatin

by Flemming.

Cell: The Unit of Life

z

z z z

z z

Interphase nucleus has chromatin, nuclear matrix and nucleolus. Nucleus has the membranes and the space between two membranes is perinuclear space.

Outer membrane usually remains continuous with the endoplasmic reticulum and also bears ribosomes on it.

The nuclear matrix or the nucleoplasm contains nucleolus and chromatin.

During different stages of cell division, cells show structured chromosomes.

Chromatin contains DNA, some basic histones, some non-histones and some RNA. Every chromosome has primary constriction called centromere on the sides of which disc shaped structures called kinetochores are present.

Based on the position of centromere, the chromosome can be classified into four types.

Secondary constriction

Satellite

Short arm Short arm Centromere Centromere

Long arm Metacentric (V-shaped)

Sub-metacentric Acrocentric (L-shaped) (J-shaped)

Telocentric (Rod-shaped)

z

Satellite: Sometimes, a few chromosomes have non staining secondary constrictions at a constant location. This gives the appearance of a small fragment.

z

Nucleolus: Not a membrane bound structure and site for active ribosomal RNA synthesis.

MICROBODIES z

Membrane bound minute vesicles.

z

Enzymes are present in both plant and animal cells.

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9

Chapter

Biomolecules BIOMOLECULE All the carbon compounds that we get from living tissues can be called ‘biomolecules’.

However, living organisms have also got inorganic elements and compounds in them.

Chemical Analysis Living tissue (Plant tissue/animal tissue/microbial paste)

+

Trichloroacetic acid (Cl3CCOOH)

Thick slurry Cheese cloth

Entire chemical composition of living tissues or organism Filtrate (Acid soluble) Roughly cytoplasmic components

Inorganic

Organic Biomicromolecules

• Water

• M.wt. - 18-800 Da + + 2+ • Ions (e.g., Na , K , Ca , • Monomeric form 2+ 3– 2– E.g., Simple sugars Mg , Po4 , So4 , etc.)

Nucleotides • Gases Amino acids

• Relative abundance of carbon and hydrogen of living organism > Earth crust

Retentate (Acid insoluble) (Macromolecules from cytoplasm and organelles) Organic Biomacromolecules • M.wt. - > 10,000 Da • Polymeric form Polysaccharides Nucleic acids Proteins Lipids (Not a polymer) • Not strictly biomacromolecule • M.wt < 800 Da • Cell membrane fragments form vesicles which are not water soluble.

ELEMENTAL ANALYSIS Elemental analysis gives elemental composition of living tissues in the form of hydrogen, oxygen, chlorine, carbon etc.

Weight

Living tissue

Dry

Dried living tissue

Wet weight Dry weight

Burn All carbon compounds

‘Ash’ (contains only inorganic elements)

oxidise to CO2 and H2O

Comparison of Elements Present in Non-living and Living Matter Element

% Weight of Earth’s crust

Human body

Hydrogen (H) Carbon (C) Oxygen (O) Nitrogen (N) Sulphus (S) Sodium (Na) Calcium (Ca) Magnesium (Mg) Silicon (Si)

0.14 0.03 46.6 very little 0.03 2.8 3.6 2.1 27.7

0.5 18.5 65.0 3.3 0.3 0.2 1.5 0.1 negligible

Order of element in Earth crust > Si > Ca > Na > Mg > H > C > S > N Order of element in Human body > C > N > Ca > H > S > Na > Mg > Si Molecular formula Analytical technique Structure of compound Average Composition of Cells in Descending order Component

% of the total cellular mass

Water Proteins Nucleic acids Carbohydrates Lipids Ions

70-90 10-15 5-7 3 2 1

True Macromolecular fraction = Polysaccharides + Polypeptides + Polynucleotides

Water is the most abundant chemical in living organism Oxygen is the most abundant element in living organism

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METABOLITES

Primary metabolite

Secondary metabolite

Identifiable functions Play known roles in physiological processes E.g., Sugars, amino acids lipids, nitrogen bases, etc.

Not involved in primary metabolism Seems to have no direct function in growth and development of organisms Many of them are useful to human welfare E.g., Rubber, drugs, spices and pigments Some have ecological importance E.g., Flavonoids, antibiotics etc.

Some Secondary Metabolites Pigments Carotenoids, Anthocyanins Alkaloids Morphine, Codeine Terpenoides Monoterpenes, Diterpenes Essential oils Lemon grass oil Toxins Abrin, Ricin Lectins Concanavalin A Drugs Vinblastine, curcumin Polymeric substances Rubber, gums, cellulose CARBOHYDRATES 1. Monosaccharides/sugar No. of Carbon 5C Single unit C5H10O5 Formula Example Ribose HOCH2 O Structure OH OH OH

2. Polysaccharides Acid-insoluble pool Long chains of sugars Linked together by glycosidic bond formed by dehydration

Features Found in Function

Homopolysaccharides Same monomer units Glycogen Starch Animals Plants

Monomer Colour with I2

Storage

Red

OH OH OH OH

Heteropolysaccharides Different monomer units Cellulose Chitin Plants Animals

Inulin Plants

Cell wall Exoskeleton (Structural) of arthropods

Storage Fructose

Glucose

6C C6H12O6 Glucose CH2OH O

Blue

Glucose

N-acetyl glucosamine

No

No

Chitin-Building blocks of Glycosamine and N-acetylgalatcosamine – Complex polysaccharide – Exoskeleton of arthropods – Homopolymers • Glycogen Right end is reducing while left end is non-reducing • Starch hold I2 in helical portion • Cellulose can not hold I2 as no helical portion • Cotton fibre Cellulose • Paper is made from plant pulp

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Biomolecules

NUCLEIC ACIDS (Acid Insoluble Fraction) Polymer of nucleotides Sugar/monosaccharide Heterocyclic Nucleoside Each nucleotide comprises Nucleotide nitrogenous base Phosphate Nitrogenous base Adenine

Nucleoside

Nucleotide

Adenosine

Adenylic

Substituted Purines

Adenine

Substituted Pyrimidine

acid

Guanine

Thymine Cytosine Uracil

Guanosine

Thymidine Cytidine Uridine

Guanylic acid

Thymidylic acid Cytidylic acid Uridylic acid Uracil

Watson-Crick model of B-DNA DNA exists as double helix (secondary structure).

Two polynucleotide strands are helically coiled around a common axis.

The two polynucleotide strands are antiparallel i.e., run in opposite direction and complementary to each other.

Ribose sugar and uracil exist in RNA (Ribonucleic acid) 2 -deoxyribose sugar and thymine exists in DNA [Deoxyribonucleic Acid] DNA and RNA act as genetic material.

Phosphate moiety links 3 -carbon of one sugar of one nucleotide to 5 -carbon of sugar of succeeding nucleotide.

Nitrogen bases are perpendicular to backbone and faces inside.

At each step of ascent, strand turns 36°.

1 turn = 10 base pairs 1 complete turn = 34Å Rise per base pair = 3.4Å 2 hydrogen bonds

Phosphodiester bonds (formed by dehydration) Ester bond 3 hydrogen bonds

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LIPIDS Generally water insoluble Could be simple fatty acids (R – COOH) where R group could be • Methyl (–CH3), ethyl (–C2H5), higher no. of –CH2 (C–1 to 19) Types of fatty acids Parameter

Unsaturated

Saturated

One or more No. of C = C No double bonds Arachidonic acid (20 carbon Example Palmitic acid (16 carbon including carboxyl carbon) including carboxyl carbon) CH3 – (CH2)14 – COOH Many lipids are esters of fatty acids and glycerol Type

No. of fatty acids

Monoglyceride Diglyceride Triglyceride

1 2 3

Glycerol (trihydroxy propane) CH2 – CH – CH2 1 1 | | | 1 OH OH OH

Melting point

State in winters

Examples

Fats

Higher

Solid

Ghee, Butter

Oils

Lower

Liquid

Gingelly oil

Triglyceride (R1, R2 and R3 are fatty acids) Some lipids have phosphorous and phosphorylated organic compound called phospholipids e.g., Lecithin - found in cell membrane Neural tissues structure - More complex lipids

Phospholipid (Lecithin)

Cholesterol have lipid like properties

Cholesterol

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Biomolecules

AMINO ACIDS Organic compounds containing an amino group and an acidic group as substituents on same carbon i.e., -carbon, hence called -amino acids.

Substituted methane, four substituent groups occupying four valency positions.

Chemical and physical properties of amino acids are essentially of amino, carboxyl and R-functional groups.

Types of amino acids I. On the basis of R-group R-group –H –CH3 (methyl) –CH2 – OH (hydroxy methyl)

Amino acids Glycine Alanine Serine

II. On the basis of Nature of amino acids Nature Acidic Basic Neutral Aromatic

Amino acids Glutamic acid Lysine Valine Tyrosine, tryptophan, phenylalanine

III. On the basis of Body’s requirement Non-essential Essential Synthesised Not synthesised by body by body Not required Required in diet in diet 10 in number 10 in number

Mnemonics: VILL PMT THA

Zwitterionic Form A particular property of amino acids is the ionisable nature of –NH2 and –COOH group.

In solutions of different pH, the structure of amino acids changes.

N

N

N

Zwitterionic form (Both positive and negative charge)

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STRUCTURE OF PROTEINS Each protein is a heteropolymer of amino acids linked by peptide bonds (formed by dehydration) and only 20 types of amino acids participate in their formation.

Dietary proteins are the source of essential amino acids.

Biologists describe structure of proteins at four levels: Typical

Level Primary

Positional information of sequence of amino acids Protein thread as extended rigid rod

Secondary

Thread

Tertiary

Quaternary

Structure COOH

NH2 Left end • N-terminal • First amino acid

Right end • C-terminal • Last amino acid

folded in the form of a helix i.e., similar to revolving stair case Only right handed helices observed in proteins 3-dimensional view, like hollow woolen ball This structure is absolutely necessary for many biological activities of proteins

Hydrogen bond Disulphide bond

More than one polypeptide chains are involved e.g., Haemoglobin consists of 4 subunits: 2 and 2 .

It is based on how individual polypeptide are arranged with respect to each other.

SOME PROTEINS AND THEIR FUNCTIONS Protein Collagen

Functions Intercellular ground substance

Trypsin

Enzyme

Insulin Antibody

Hormone Fights infections agents

Receptor

Sensory reception (smell, taste, hormone)

GLUT-4

Enables glucose transport into cells

• Collagen is the most abundant protein in animal world.

• RuBisCO is the most abundant protein in the whole of the biosphere.

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Biomolecules

DYNAMIC STATE OF BODY CONSTITUENTS ATP: Energy Currency Used in anabolic reaction

ATP

Produced during catabolic reactions

Pentose sugar ribose is present in ATP. Living state is a non-equilibrium steady state to be able to perform work.

Living process is a constant effort to prevent falling into equilibrium.

Living state and metabolism are synonymous.

Without metabolism, there can not be a living state.

Metabolism is sum total of all the reactions (do not occur in isolation) within the body.

There is no uncatalysed metabolic conversion in living system.

Metabolic pathways (Series of linked reactions) Catabolic pathways • Degradation pathways • Complex structure converts into simple structure • Energy released (stored in ATP) • Examples: Glucose

Glycolysis 10 steps

Anabolic pathways • Biosynthetic pathways • Formation of complex structure from simple structures • Energy is used • Examples: Amino acids Proteins

Pyruvic acid

CO2 + H2O

Carbonic anhydrase

H2CO3

Carbonic anhydrase is present in cytoplasm With enzyme - 6,00,000 molecules of H2CO3 formed in 1 sec, Rate increase 10 million times Without enzyme - 200 molecules/hr • Rate refers to the amount of product formed per unit time, expressed as rate = P/ t • Rate double or decreases by half for every 10°C change in either direction.

• Flow of metabolites through metabolic pathways has a definite direction, this is called dynamic state of body constituents.

• Biomolecules are constantly being changed into some other biomolecules and also made from some other biomolecules called turnover.

• Glucose concentration in blood: 4.2 - 6.1 mmol/L. • Hormone concentration = nanograms/ml

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ENZYMES (BIOCATALYST) Properties: Tertiary structure.

Unchanged at the end of reaction.

Highly specific.

Not used up in the reaction.

Proteinaceous in nature except ribozymes (nucleic acids).

Increases rate of reaction by lowering activation energy.

Have active site/pockets where substrate binds.

Inorganic catalysis work efficiently at high temperatures and high pressures while enzymes get denatured at high temperature (>40°C) except enzymes of thermophilic organisms (can tolerate 80°-90°C).

For metabolic conversion, substrate ‘S’ has to bind the enzyme at its active site and results in obligatory formation of ‘ES’ complex (Transient phenomenon), essential for catalysis.

Structure of substrate gets transformed into structure of products(s).

E + S ES EP E + P ‘Altered structural states’ (unstable)

• Difference in average energy content of ‘S’ from that of transition state is called ‘Activation energy’.

• Transition state – High energy unstable state.

• ‘P’ is at lower level than ‘S’ – Reaction is exothermic.

• ‘S’ is at lower level than ‘P’ – Reaction is endothermic.

FACTORS AFFECTING ENZYME ACTIVITY Temperature Enzyme shows highest activity at optimum temperature.

Low temperature Enzyme is temporarily inactive.

High temperature Tertiary structure of enzymes destroyed due to denaturation. pH Enzyme shows highest activity at optimum pH. Rate of reaction declines both below and above optimum pH. Substrate concentration Initially rate of reaction increases with increase in substrate concentration but becomes constant when all enzymes get saturated with substrate.

Binding of specific chemicals (Inhibitors) When binding of chemicals shuts off enzyme activity, the process is called inhibition and chemical is called inhibitor.

Vmax = Maximum Michaelis constant [KM] = Concentration at which rate of reaction the reaction velocity reaches half its maximum velocity.

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Biomolecules

Competitive inhibitor: Inhibitor resemble the substrate and compete with substrate for the active site of enzymes.

Closely resembles substrate in molecular structure and inhibits enzyme activity.

Consequently, substrate can not bind and as a result enzyme action declines.

E.g., Malonate closely resembles the substrate succinate in structure.

Inhibition of succinic dehydrogenase by malonate.

Application: Control of bacterial pathogens.

Note: Effect of the competitive inbibitor can be reversed by increasing the concentration of the substrate.

CLASSIFICATION AND NOMENCLATURE OF ENZYMES Most of these enzymes have been classified into different groups based on the type of reactions they catalyse. Enzymes are divided into 6 classes each with 4-13 subclasses and named accordingly by a four-digit number.

Class I

II

Name

Function

Oxidoreductases/ Enzymes which catalyse oxidoreduction between dehydrogenases: two substrates S and S S reduced + S oxidised S oxidised + S reduced Transferases:

Catalyse a transfer of a group, G (other than hydrogen) between a pair of substrates S and S S – G + S S + S – G

III

Hydrolases:

Catalyse hydrolysis of ester, ether, peptide, glycosidic, C – C, C – halide or P-N bonds.

IV

Lyases:

Catalyse removal of groups from sub-strates by mechanisms other than hydrolysis leaving double bonds.

X C | | C–C X–Y+C=C

Isomerases:

Catalyse inter-conversion of optical, geometric or positional isomers.

Ligases:

Catalyse the linking together of two compounds, e.g., enzymes which catalyse joining of C-O, C-S, C-N, P-O etc. bonds.

V VI

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CO-FACTORS Enzymes Simple enzymes Only protein

Conjugated enzymes

Apo-enzyme (inactive) Protein part

Co-factor Non-protein part

Catalytically active enzyme

Co-factor

Prosthetic group Organic, tightly bound to apoenzyme Haem is prosthetic group for catalase and peroxidase Co-enzyme Organic, loosely bound to apo-enzyme for transient period (just during catalysis) e.g., NAD, NADP (Contain niacin vitamin) Metal ions Form coordination bond with active site and one or more coordination bond with substrate

+2

Zn for carboxypeptidase

Catalytic activity is lost if co-factor is removed

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Biomolecules

10

Chapter

Cell Cycle and Cell Division INTRODUCTION z z

All cell reproduce by dividing into two, with each parental cell giving rise to two daughter cells each time they divide.

Growth and reproduction are characteristics of cells, indeed of all living organisms.

CELL CYCLE z

z

z z

It is sequence of events by which a cell duplicates its genome, synthesises the other constituents of the cell and eventually divides into two daughter cells.

Cell growth results in disturbing the ratio between the nucleus (N) and cytoplasm (C). It therefore becomes essential for the cell to divide to restore the nucleo-cytoplasmic ratio (N/C).

Cell growth (in terms of cytoplasmic increase) is a continous process.

Duration of cell cycle can vary from organism to organims and also from cell type to cell type. e.g., Yeast - 90 minutes Human - 24 hours

PHASES OF CELL CYCLE Interphase

M-phase

z Called resting phase.

z Actual cell division phase.

z Cell is preparing for division by

z Starts with nuclear division

undergoing both cell growth and DNA replication in an orderly manner.

z

Lasts more than 95% of the duration of cell cycle.

(karyokinesis) and usually ends with division of cytoplasm (cytokinesis)

INTERPHASE

G0

Divided into three phases (i) G1 phase (Gap 1)

z

(iii) G2 phase (Gap 2)

M phase

(ii) S phase (Synthesis)

Cy tok in Teloph esis ase Anaphase e as taph se Me pha o Pr

G1

S G2

z Some cells do not divide further, exit G1 phase to enter an inactive stage

called quiescent stage (G0) of the cell cycle.

G0 z Cells in this stage remain metabolically active but no longer proliferate unless called on to do so depending on the requirement of the organism. e.g. Heart cells. z Interval between mitosis and initiation of DNA replication.

G1

z Cell is metabolically active and continuously grows but does not replicate

its DNA.

z Most of the cell organelles duplicate. z Marks the phase of DNA replication and chromosome duplication. z Amount of DNA per cell doubles but there is no increase in initial

S

chromosome number.

z In animal cells, centriole duplicates in cytoplasm. z DNA replication begins in nucleus.

G2

z Proteins are synthesised in preparation for mitosis while cell growth

continues.

In animal cells, mitotic division is only seen in diploid somatic cells.

Plant cells show mitotic division in both haploid and diploid cells. 

M PHASE (MITOSIS) z z

81

Most dramatic period of cell cycle.

Chromosome number in parent and progeny cells is the same hence called equational division.

Cell Cycle and Cell Division

DIVIDED INTO Karyokinesis 1. Prophase z First phase, follows the S and G2 phases of interphase. z Marked by the initiation of condensation of chromosomal material which becomes untangled. z Centrosome starts to move towards opposite poles. z The completion of prophase can be marked by:(i) Chromosomes condense to form compact mitotic chromosome. (ii) Each centrosome reach at pole and radiates out microtubules called asters. The two asters together with spindle fibres form mitotic apparatus. z At the end of prophase, cells do not show Golgi complex, ER, nucleolus and nuclear envelope.

Early Prophase

Late Prophase

2. Metaphase z The complete disintegration of the nuclear envelope marks the start of metaphase. z Condensation of chromosomes is completed and can be observed clearly under microscope and morphology of chromosomes is most easily studied. z Each chromosome has two sister chromatids which are held together by the centromere. z All the chromosome coming to lie at equator. z Each chromosome connected by its kinetochore to spindle fibre from one pole and its sister chromatid connected by its kinetochore to spindle fibre from the opposite pole. z The plane of alignment of the chromosomes at metaphase is referred to as metaphase plate.

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(a) Transition to Metaphase

(b) Metaphase

3. Anaphase z

Centromere of each chromosome split simultaneously and chromatids separate.

z

Two daughter chromatids, now referred to as daughter chromosome begin their migration towards the two opposite poles.

z

The centromere of each chromosome remain directed toward the pole and arms trailing behind, (leading to different shapes of chromosomes).

Anaphase

4. Telophase z

Final stage of karyokinesis.

z

Chromosomes that have reached their respective poles decondense and lose their individuality.

z

Nuclear envelope develops around the chromosome cluster at each pole forming two daughter nuclei.

z

Nucleolus, Golgi complex and ER reform.

Cytokinesis

Telophase

z

It is division of cytoplasm at the end of which cell division gets completed.

z

Achieved by the appearance of a furrow in the plasma membrane in animal cell (Centripetal).

z

Cytokinesis is achieved by wall formation in plant cell that starts in the centre of the cell and grows outward to meet the existing lateral wall (Centrifugal).

The formation of new cell wall begins with the formation of a simple precursor, called the cell plate that represents the middle lamella between the wall of two adjacent cells.

Cell Cycle and Cell Division

z

83

z

When karyokinesis is not followed by cytokinesis as a result of which multinucleate condition arises leading to formation of syncytium, e.g., liquid endosperm in coconut.

Kinetochore is a disc shaped structure at the surface of centromere, serves as the site of attachment of spindle fibres. 

SIGNIFICANCE OF MITOSIS z z z z z

Identical genetic complement in daughter cells.

Growth of multicellular organisms.

Cell repair.

Continuous growth of plants throughout their life.

In some lower plants and in some social insects, haploid cells also divide by mitosis.

MEIOSIS z z z z z z

Specialised kind of cell division that reduces the chromosome number by half results in the production of haploid (n) daughter cells.

Ensures the production of haploid phase in the life cycle of sexually reproducing organisms.

Fertilisation restores the diploid phase.

Meiosis involves two sequential cycles of nuclear division i.e. meiosis I and meiosis II but only single cycle of DNA replication.

Meiosis I initiated after parental chromosomes have replicated.

Four haploid cells are formed at the end of meiosis II.

MEIOSIS I (REDUCTIONAL PHASE) Prophase I Typically longer and more complex when compared to prophase of mitosis.

1. Leptotene z Chromosomes become gradually visible under the light microscope. z The compaction of chromosomes continues throughout leptotene.

2. Zygotene z Homologous chromosomes called synapsis. z

Synapsis is accompanied by formation of complex structure called synaptonemal complex.

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The complex formed by a pair of synapsed homologous chromosomes is called bivalent or a tetrad z Leptotene and zygotene are relatively short lived compared to the pachytene.

3. Pachytene z Four chromatids of each bivalent become distinct and clearly appears as tetrads. z Appearance of recombination nodule, the sites at which crossing over occurs between non-sister chromatids of the homologous chromosomes. z Crossing over is exchange of genetic material between two homologous chromosomes. It is an enzyme mediated process, enzyme involved is called recombinase. z Crossing over leads to recombination of genetic material which is completed by the end of pachytene leaving chromosomes linked at the sites of crossing over.

4. Diplotene z Recognised by the dissolution of synaptonemal complex and tendency of the recombined homologous chromosomes of the bivalent to separate from each other except at the site of crossovers. z This X-shaped structures (site of crossing over) are called chiasmata. z In oocytes of some vertebrates, diplotene can last for months or years.

5. Diakinesis z Marked by terminalisation of chiasmata. z Chromosomes are fully condensed and meiotic spindle is assembled to prepare the homologous chromosomes for separation. z By the end of diakinesis, the nucleolus disappears and nuclear envelope also breaks down. z Diakinesis represents transition to metaphase. z

Metaphase I Bivalent chromosomes align on the equatorial plate (Double metaphasic plate).

Microtubules from the opposite poles of the spindle attach to the kinetochore of homologous chromosomes.

Anaphase I Homologous chromosomes separate, while sister chromatids remain associated at their centromere.

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Cell Cycle and Cell Division

Telophase I z z

The nuclear membrane and nucleolus reappear.

Cytokinesis follows and this is called as dyad of cells.

MEIOSIS II (EQUATIONAL PHASE) - RESEMBLES A NORMAL MITOSIS Prophase II z z z

It is initiated immediately after cytokinesis.

The nuclear membrane disappears by the end of prophase II. Chromosomes become compact.

Metaphase II z z

Chromosomes align at the equator.

Microtubules from opposite poles of the spindle get attached to the kinetochore of sister chromatids.

Anaphase II z

Splitting of centomere allowing chromosomes to move towards opposite poles of the cell by shortening of microtubules attached to the kinetochores.

Telophase II z z z

Meiosis ends with telophase II Two groups of chromosomes once again get enclosed by a nuclear envelope.

Cytokinesis follow resulting in the formation of tetrad of cells.

Prophase I

Metaphase I

Anaphase I Telophase I

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Prophase II

Metaphase II

Anaphase II

Telophase II

SIGNIFICANCE OF MEIOSIS z

z

87

Conservation of specific chromosome number of each species in sexually reproducing organisms, results in reduction of chromosome number by half.

Increases genetic variability in the population of organisms which is important for the process of evolution.

Cell Cycle and Cell Division

Chapter

11 Transport in Plants

INTRODUCTION z

z z

z z z

In a flowering plant, the substances that would need to be transported are water, mineral nutrients, organic nutrients and plant growth regulators (PGRs).

Water and mineral nutrients are taken up by roots and food is synthesised in the leaves.

Short-distance movement is through-diffusion, cytoplasmic streaming and active transport and transport through longer distances is through vascular system (xylem and phloem) and is called Translocation.

Transport in xylem is essentially Unidirectional (of water and minerals) from roots to leaves through the stems.

Organic and mineral nutrients undergo multidirectional transport.

From senescent plant parts, nutrients are withdrawn and moved to growing plants. So, the transport is complex but orderly. Each organ is receiving some substances and giving out some other.

SHORT DISTANCE MOVEMENT Property

Simple Facilitated Active Diffusion Diffusion Transport

1.

Need special membrane proteins

No

Yes

Yes

2.

Highly selective

No

Yes

Yes

3.

Transport saturates

No

Yes

Yes

4.

Uphill movement

No

No

Yes

5.

Need ATP

No

No

Yes

1. Diffusion is the only means for gaseous movement within the plant body.

2. Porins are proteins that form large pores in outer membrane of plastids, mitochondria and some bacteria.

3. In facilitated diffusion, extracellular molecule is bound to transport protein which then rotates and releases the molecule inside the cell, e.g., water channels-made of 8 different types of aquaporins.

Transport protein Transported molecule Outer side of cell

Outer side of cell Membrane

Inner side of cell Membrane

Fig. Facilitated diffusion 4. Passive symports and antiports z Symport: Two molecules move together in the same direction and in opposite direction in antiport. z Uniport: A molecule moves across a membrane independent of other molecules in one direction.

Carrier protein Uniport A

Antiport A

B

Symport A B

Membrane

Facilitated diffusion

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Transport in Plants

PLANT-WATER RELATIONS Water is essential for all physiological activities of plant. Because of its high demand, water is often the limiting factor for plant growth and productivity.

Terms: 1. Water Potential: Water molecules possess kinetic energy. The greater the concentration of water in a system, the greater is its kinetic energy or water potential. (i) Pure water have greatest water potential. (ii) Water moves from a system at higher water potential to the one having low water potential. (iii) It is denoted by Psi or Ψ and expressed in pascals. (iv) Water potential of pure water at standard temperature, which is not under any pressure, is taken as zero.

2. Solute Potential: The magnitude of lowering of water potential due to dissolution of solute is called solute potential or ΨS. (i) ΨS is always negative. (ii) More the solute molecules, the lower ts the ΨS. 3. For a solution at atmospheric pressure.

(Water potential) ΨW = ΨS (Solute potential).

4. Osmotic pressure = – Osmotic potential.

5. Pressure Potential: Pressure builds up in a plant system when water enters a plant cell due to diffusion, it makes the cell turgid, this increases the pressure potential. (i) It ts usually positive. (ii) Though negative potential or tension, xylem plays a major role in water transport.

6. Water Potential is affected by both solute and pressure potential. ΨW = ΨS + ΨP

Osmosis 1. Diffusion of water across a differentially or selectively permeable membrane.

2. Net direction and rate of osmosis depends on both pressure gradient and concentration gradient.

3. Water moves from higher chemical potential to region of lower chemical potential until equilibrium is reached.

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Pressure

Sucrose solution Membrane Water (a)

(b)

Demonstration of osmosis - Thistle funnel experiment.

1. Transport proteins of endodermal cells are control points, where a plant adjusts the quantity and types of solutes that reach xylem.

2. Root endodermis because of suberin, actively transports ions in one direction. 

Plasmolysis 1. Occurs when water moves out of the cell and cell membrane of plant cell shrinks away from its cell wall.

2. This happens when a cell or tissue is placed in hypertonic solution.

3. Reversible process if kept in hypotonic solution.

4. When water flow into the cell and out of the cells are in equilibrium, the cells are said to be flaccid.

A H2 O

Plasmolysed

B H2 O

Flaccid

C H2 O

Turgid

Imbibition 1. Special type of diffusion when water is absorbed by solids-colloids causing them to increase in volume.

2. Water potential gradient between the absorbent and the liquid imbibed is essential for imbibition.

91 Transport in Plants

3. For any substance to imbibe any liquid, affinity between the adsorbent and the liquid is also a pre-requisite.

Example: Absorption of water by seeds and dry wood

LONG DISTANCE TRANSPORT 1. Diffusion is a slow process. It can account for only short distance movement.

2. Long distance movement of water and minerals and food generally occur by mass or bulk flow.

3. Mass flow is en masse movement due to pressure differences between the two points.

4. Bulk movement is through vascular tissues called Translocation.

5. Xylem mainly translocates water, mineral salts, some organic nitrogen and hormones.

6. Phloem translocates a variety of organic and inorganic solutes.

7. Water is absorbed by two distinct pathways:

• Apoplast: A system of adjacent cell wall except at casparian strips of endodermis. This movement is dependent on the gradient.

• Symplast: A system of interconnected protoplasts.

Plasmodesmata Plasma membrane

Epidermis

Cortex

Endodermis

Pericycle Xylem

= symplast = apoplast

Casparian strip

8. In some plants, symbiotic mycorrhizal association of fungus with root system help in water and mineral absorption e.g., Pinus seeds.

WATER MOVEMENT UP A PLANT 1. Root Pressure: Only provide a modest push in overall process of water transport. They do not play a major role in water movement up tall plants.

• The

greatest contribution of root pressure is to re-establish the continuous chains of water molecules in xylem.

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• In many herbaceous plants, grass blades, root pressure is the cause

of loss of water in the form of liquid droplets called Guttation.

2. Transpiration Pull: Cohesion-tension-transpiration pull model of water transport accomplishes water movement in tall plants. ↓ Transpiration is the evaporative loss of water by plants through stomata. ↓ The opening of stomata is caused due to change in turgidity of guard cells. ↓ Opening is also aided by radical orientation of cellulose microfibrils in cell wall of guard cell.

Micro brils Guard cell Stomatal aperture

Stomatal aperture with guard cells

Palisade

Xylem Phloem

Diffusion into surrounding air

Stomatal pore

Guard Cell

Water movement in the leaf ↓ Transpiration driven ascent of xylem sap depends mainly on physical properties of water.

TRANSPIRATION & PHOTOSYNTHESIS A COMPROMISE 1. An actively photosynthesising plant has a need for water.

2. Photosynthesis is limited by available water which can be swiftly depleted by transpiration.

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Transport in Plants

3. A C4 plant loses only half as much water as a C3 plant for the same amount of CO2 fixed.

4. Temperature, light, humidity and wind speed affect transpiration.

5. Plant factors like number and distribution of stomata, water status of plants, canopy etc. affect transpiration.

UPTAKE AND TRANSPORT OF MINERAL NUTRIENTS 1. Plants obtain their carbon and most of their oxygen from CO2 in the atmosphere. However, their remaining nutritional requirements are obtained from water and minerals in the soil.

2. Most minerals must enter the root by active absorption into the cytoplasm of epidermal cell.

3. The active uptake of ions is partly responsible for the water potential gradient in roots and therefore for the uptake of water by osmosis.

4. Some ions also move into epidermal cells passively.

5. Mineral ions are frequently remobilised from older, sensescing, dying parts (leaves) to younger leaves.

6. Elements most readily mobilised are phosphorus, nitrogen and potassium. Some elements like calcium are not remobilised.

PHLOEM TRANSPORT: PRESSURE FLOW OR MASS FLOW HYPOTHESIS 1. Food, primarily Sucrose, is transported by vascular tissue phloem from source to sink.

2. Source: Leaf (synthesise food), roots (storage).

3. Sink: Where needed or stored (buds of trees) 4. Since source - sink relation is variable, so direction of movement of phloem can be bi-directional.

5. Phloem sap is mainly water and sucrose but other sugars, hormones and amino-acids are also translocated through phloem.

GIRDLING EXPERIMENT (i) Identifies the tissues through which food is transported. (ii) Shows that phloem is the tissue responsible for food translocation. (iii) Transport takes place in one direction, i.e., towards the roots.

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Sugars leave sieve tubes; water follows by osmosis Tip of stem

Sugar solution ows to regions of ow turgor pressure

Sugars enter sieve tubes; = High water follows by osmosis turgor pressure Phloem Sugars leave sieve tube for metabolism and storage; water follows by osmosis Root

Mass Flow Hypothesis 1. The accepted mechanism used for the translocation of sugars from source to sink is called the pressure flow hypothesis.

↓

2. Glucose → Sucrose → Companion (Prepared (Converted to cell Loading at the source) disaccharide) ↓ (Active transport)

↓

↓

↓

↓

↓

Living phloem sieve Unloading tube cells (Active transport) ↓ ↓ Builds osmotic pressure Water from xylem Sink (used or stored)

3. Loading and unloading are active processes.

95

Transport in Plants

Chapter

12 Mineral Nutrition

INTRODUCTION Macromolecules are required for growth and development.

METHODS TO STUDY THE MINERAL REQUIREMENTS OF PLANTS z

z

In 1860, Julius von Sachs, a prominent German botanist demonstrated for the first time that plants could be grown to maturity in a defined nutrient solution in complete absence of soil.

This technique of growing plants in a nutrient solution is known as hydroponics.

CRITERIA FOR ESSENTIALITY (a) The element must be absolutely necessary for supporting normal growth and reproduction. (b) The requirement must be specific and not replaceable by another element. (c) The element must be directly involved in the metabolism of the plant.

Based on Quantative requirement z

z

Macronutrients The are generally present in plant tissues in large amounts (in excess of 10 mmole kg–1 of dry matter) C, H, O, N, P, S, K, Ca, Mg

z

z

Micronutrients Also called trace elements, are needed in very small amount (less than 10 mmole kg–1 of dry matter).

Fe, Mn, Cu, Mo, Zn, B, Cl, Ni.

Essential elements can also be grouped into four broad categories on the basis of their diverse functions. These categories are:

(i) Components of biomolecules and structural elements of cells (C, H, O and N). (ii) Components of energy related chemical compounds in plants (Mg in chlorophyll and P in ATP). (iii) Activate or inhibit certain enzymes. (Mg2+ activates Rubisco and PEP case. Zn2+ activate alcohol dehydrogenase and Mo activate nitrogenase). (iv) Essential elements which alter osmotic potential (K).

Apart from 17 essential elements, there are 4 beneficial elements - Na, Si, Co, Se required by higher plants. 

ROLE OF MACRO AND MICRONUTRIENTS S.No.

Mineral element

Absorbed as

All parts of the plants, particularly or meristems.

Developing fruits, – H2PO4 or seeds, storage organs, young HPO2– 4 meristems.

Meristems, buds, K+ leaves and root tips.

– NO2 NH+4

1.

Nitrogen

2.

Phosphorus

3.

Potassium

4.

Calcium

Ca2+

5.

Magnesium

Mg2+

6.

Sulphur

SO2– 4

7.

Iron

Fe2+

97

Required in

– NO3,

Functions Major constituents of proteins, nucleic acids, vitamins and hormones.

Constituent of cell membrane, certain proteins, all nucleic acids.

Maintain turgidity of cells, required for opening and closing of stomata.

Required for middle lamella, Meristems and mitotic spindle and for differentiating certain enzymes. tissues Accumulates in older leaves Constituent of ring Seeds, leaves, structure of chlorophyll growing areas of and helps to maintain root and stem. ribosome structure.

Constituent of two amino acids cysteine and Young leaves and methionine and main meristems. constituents of several coenzymes and vitamins.

Main constituents of ferredoxin and All parts of cytochromes. It activates plants. catalase enzyme and is essential for the formation of chlorophyll.

Mineral Nutrition

S.No.

Mineral element

Absorbed as

8.

Manganese

Mn2+

9.

Zinc

Zn2+

10.

Copper

Cu2+

11.

Boron

BO2– 3 or B4O2– 7

12.

Molybdenum

MoO2+ 2

13.

Chlorine

–

Cl

Required in

Functions

The best defined function of manganese is in the Leaves and seeds. splitting of water to liberate oxygen during photosynthesis.

Activates various All parts of the enzymes especially plants. carboxylases, also needed for auxin synthesis.

Associated with certain All parts of the enzymes involved in plants. redox reaction.

Required for uptake and utilisation of Ca2+, membrane functioning, Leaves and seeds. pollen germination, cell elongation and carbohydrate translocation.

All parts of plants Component of nitrogenase and commonly in and nitrate reductase. roots.

Essential for water splitting reaction in All parts of the photosynthesis and for plants. anion and cation balance in cells.

DEFICIENCY SYMPTOMS OF ESSENTIAL ELEMENTS z z

The concentration of the essential element below which plant growth is retarded is termed as critical concentration.

The element is said to be deficient when present below the critical concentration.

DEFICIENCY SYMPTOMS IN PLANTS INCLUDE: (a) (b) (c) (d) (e)

Chlorosis: Due to deficiency of N, K, Mg, S, Fe, Mn, Zn and Mo. Necrosis: Due to deficiency of Ca, Mg, Cu, K. Inhibition of cell division: Due to deficiency of N, K, S, Mo. Delay in flowering: Due to deficiency of N, S, Mo. Stunted plant growth.

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Mobile Elements z

Transported from older leaves to younger leaves.

z

Deficiency symptoms first appear in older/senescent leaves. Example N, K, Mg.

Immobile Elements z

Not transported out of the mature leaves.

z

Deficiency symptoms tend to appear first in the young leaves. Example Ca.

TOXICITY OF MICRONUTRIENTS z

The requirements of micronutrient is always in low amounts while their moderate decrease causes the deficiency symptoms and a moderate increase cause toxicity.

z

Any mineral ion concentration in tissues that reduces the dry weight of tissues by about 10 percent is considered toxic.

z

Many a times, excess of an element may inhibit the uptake of another element.

For example, Manganese competes with iron and Mg for uptake and with Mg for binding with enzymes. Mn also inhibit calcium translocation in shoot apex.

MECHANISM OF ABSORPTION OF ELEMENTS: z

In the first phase, the rapid uptake of ions is into apoplast. It is passive.

z

In the second phase, the ions move into symplast. It requires energy; so it is active.

TRANSLOCATION OF SOLUTES Mineral salts are translocated through xylem along with the ascending stream of water, which is pulled up through plant by transpiration pull.

SOIL AS RESERVOIR OF ESSENTIAL ELEMENTS Soil not only supplies minerals but also harbours nitrogen fixing bacteria.

99

Mineral Nutrition

METABOLISM OF NITROGEN Nitrogen Cycle Atmospheric N2 (Pseudomonas) Biological N2 fixation NH3

Industrial N2 fixation

Electrical Denitrification N2 fixation (Thiobacillus)

Nitrification – NO2 Soil 'N' Pool

Nitrosomonas

– NO3

Nitrosococcus

Nitrobacter

(Ammonification)

(Uptake)

Decaying biomass

Plant biomass

Animal biomass The nitrifying bacteria are chemoautotrophs.



BIOLOGICAL NITROGEN FIXATION Only certain prokaryotic species are capable of fixing nitrogen. Reduction of nitrogen to ammonia by living organisms is called biological nitrogen fixation.

Enzyme nitrogenase is exclusively present in prokaryotes.

N=N

Nitrogenase

NH3

N2 FIXERS Bacteria Azotobacter Beijerinckia Bacillus Clostridium Rhodospirillum

Nitrogen fixation Free living Free living Free living Free living Free living

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Aerobic/anaerobic Aerobic Aerobic Anaerobic Anaerobic Anaerobic

100

Symbiotic or Free living Symbiotic Symbiotic

Anabaena Nostoc Rhizobium Frankia

— — — —

Rhizobium fixes nitrogen in legumes.

Frankia in non-leguminous plants such as Alnus.



NODULE FORMATION Nodule formation involves a sequence of multiple interactions between Rhizobium and roots of host plant. z Rhizobia multiply, colonise the surroundings of the roots and get attached to epidermal and root hair cells. Root hair curls and bacteria invade the root hair. z An infection thread is produced carrying the bacterial into the cortex of the root where they initiate nodule formation in the cortex. z The nodule thus formed, establishes a direct vascular connection with the host for exchange of nutrients.

Soil particles

Hook

Root hair Bacteria

Infection thread containing bacteria Mature nodule Bacteria Inner cortex and pericycle cells under division

Nodule contains nitrogenase and leghaemoglobin.

Nitrogenase is Mo-Fe protein and highly sensitive to the molecular oxygen, thus requires anaerobic conditions.

To protect nitrogenase, nodule contains an oxygen scavenger called laghaemoglobin.

z z z

Rhizobium and Frankia live as aerobes under free living condition but as symbionts during nitrogen fixing events they become anaerobic.  The ammonia synthesis by nitrogenase requires a very high input of energy 8 ATP for each NH3 produced.

N2 + 8e– + 8H+ + 16ATP → 2NH3 + H2 + 16ADP + 16Pi 101

Mineral Nutrition

Product [ammonia (NH3)]

Substrate [nitrogen gas (N2)]

Reduction Reduction

Reduction

Enxyme Brinding +2 H (nitrogenase) of substrate

+2 H

Release of products +2 H Free nitrogenase

can bind another molecule of N2

FATE OF AMMONIA At physiological pH, the ammonia is protonated to form NH+4 ions while most of the plants can assimilate nitrate as well as ammonia ions, the latter is quite toxic to plants and hence cannot accumulate in them. z NH+4 is used to synthesize amino acids in plants by two ways: Reductive Amination In this process, ammonia reacts with a-ketoglutaric acid and forms glutamic acid. a-ketoglutaric acid + NH+4 + NADPH Glutamate Glutamate Dehydrogenase

+ H2O + NADP

Transamination It involves transfer of amino group from one amino acid to the keto group of a keto acid. Glutamic acid is the main amino acid from which the transfer of amino group takes place and other amino acids are formed through transamination.

The enzyme transaminase catalyses this reaction.

The two most important amides - Asparagine and glutamine found in plants, are a structural part of proteins. The are formed from two amino acids namely aspartic and glutamic acid respectively.

Amides contain more nitrogen than amino acids, they are transported to other parts of the plant via xylem vessels. Nodules of some plants like soyabean export fixed nitrogen as ureides (High N : C ratio). 

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Chapter

13 Photosynthesis in Higher Plants

INTRODUCTION z

Photosynthesis is a physico-chemical process by which plants use light energy to drive the synthesis of organic compounds.

z

Photosynthesis is important due to two reasons: (a) Primary source of all food on earth. (b) Responsible for the release of oxygen into the atmosphere.

WHAT DO WE KNOW? z

Experiment for starch formation on variegated leaf or a leaf that was partially covered with black paper & exposed to light showed that photosynthesis occurred only in green part of leaves in the presence of light.

z

Experiment where a part of leaf is enclosed in a test-tube with some KOH soaked cotton (which absorbs CO2). while other half is exposed to air and set-up kept in light proved that CO2 is needed for photosynthesis.

EARLY EXPERIMENTS (1) Joseph Priestley Using a burning candle, a mouse, mint plant and a bell jar for closed space, hypothesised that plants restore to the air whatever burning candles or breathing animals remove.

(2) Jan Ingenhousz In an elegant experiment with an aquatic plant, showed that in bright sunlight, plants produce oxygen.

(3) Julius von Sachs Found that glucose is made in green plant parts and stored as starch.

(4) T.W. Engelmann Using a prism, green alga Cladophora and aerobic bacteria, described the action spectrum of photosynthesis, which roughly resembles the absorption spectrum of chlorophyll- a and b.

(5) Cornelius van Niel (Work on Purple and Green Bacteria) Demonstrated that photosynthesis is essentially a light dependent reaction in which hydrogen from suitable oxidisable compound reduces CO2 to carbohydrates.

H2A + CO2 D 2A + CH2O + H2O H2O, the hydrogen donor in green plants is oxidised to O2.

H2S is hydrogen donor for purple & green sulphur bacteria.

The oxidation product is sulphur or sulphate in purple & green sulphur bacteria and not O2.

6CO2 + 12H2O

Light

C6H12O6 + 6H2O + 6O2 (By using Radio isotopic technique)

WHERE DOES PHOTOSYNTHESIS TAKE PLACE In green parts of the plants, mainly in the mesophyll cells in the leaves, which have large number of chloroplasts.

CHLOROPLAST ALIGNMENT Parallel Perpendicular In low or optimum light intensity to get In extremely high light intensity to avoid maximum incident light photo-oxidation.

There is a clear Division of Labour within the chloroplast.

CHLOROPLAST Membranous System

Stroma

(Grana + Stroma lamellae)

Enzymatic reactions to synthesise sugar, Responsible for trapping light & which in turn forms starch, takes place. synthesis of ATP and NADPH. Dependent on products of light reactions (ATP & NADPH).

Directly light driven, called Light By convention called Dark Reactions Reaction (photochemical reactions) (Carbon reactions).

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HOW MANY TYPES OF PIGMENTS ARE INVOLVED IN PHOTOSYNTHESIS? z z

Leaf-pigments of any green plant can be separated through paper chromatography.

The colour in leaves is due to four pigments, that have the ability to absorb light, at specific wavelengths.

Colour of The Pigments in The Chromatogram (i) Chlorophyll-a

=

Bright or blue green

(ii) Chlorophyll-b

=

Yellow-green

(iii) Xanthophyll

=

Yellow

(iv) Carotenoids

=

Yellow to yellow-orange

Light absortbed

Rate of photosynthesis Absorption

400 500 600 700 Wavelength of light in nanometres (nm) z

z z

The wavelength of light at which there is maximum absorption by chlorophyll-a i.e., in blue and red regions, also shows higher rate of photosynthesis.

Chl-a is the chief pigment associated with photosynthesis.

Chl-b, carotenoids and xanthophyll are accessory pigments. They absorb light and transfer the energy to Chl-a and also protect chlorophyll-a from photo-oxidation.

LIGHT REACTION Light reactions or the photochemical phase include: (a) Light absorption (b) Water splitting (c) Oxygen release (d) ATP and NADPH formation 105 Photosynthesis in Higher Plants

z

PHOTOSYSTEM PS-I

PS-II LHC-I

(Hundred of pigments)

Reaction

One molecule

centre

of Chl-a

LHC-II

Reaction centre

z

Absorption peak at 700 nm (P700)

z

Named in the sequence of their discovery and not in the sequence of their function.

z

Absorption peak at 680 nm (P680)

ELECTRON TRANSPORT z

Z-scheme (due to its characteristic shape): Whole scheme of transfer of electrons starting from PS-II → uphill to the acceptor → down the ETC to PS-I → Excitation of electrons → transfer to another acceptor → finally downhill → NADP+ → reducing to NADPH + H+.

z

This shape is formed when all the carriers are placed in a sequence on a redox potential scale.

SPLITTING OF WATER z

PS-II continuously supplies electrons which becomes available by splitting of water.

z

Water splitting complex is associated with PS-II, which itself is physically located on inner side of membrane of thylakoid.

z

H2O → 2H+ + [O] + 2e–

CYCLIC AND NON-CYLIC PHOTO-PHOSPHORYLATION z

When both PS-I and PS-II are involved, the process is non-cyclic, producing ATP, NADPH + H+ and oxygen.

z

Only PS-I is functional, cyclic flow takes place to produce only ATP.

z

A possible location for cyclic flow is the stroma lamellae membranes which lack PS-II and NADP reductase enzyme. h Cyclic photo-phosphorylation also occurs when only light of wavelengths beyond 680 nm are available for excitation. h The membrane of lamellae of the grana have both PS-I and PS-II.

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CHEMIOSMOTIC HYPOTHESIS ATP synthesis in photosynthesis is linked to the development of a proton gradient across the membranes of thylakoid and protons accumulate in the lumen of thylakoids.

The proton gradient is caused by: (a) Protons or hydrogen ions (H +) produced by splitting of water, accumulate in the lumen of the thylakoids. (b) The primary acceptor of electron located towards outer side of membrane transfers its electron to an H carrier, which removes a proton from stroma while transporting and electron to thylakoid lumen. (c) The NADP reductase enzyme located on stroma side of membrane, removes protons from stroma, while reducing NADP+ to NADPH + H+.

z

z

+

NADP +H+ NADPH +

Stroma (low H ) Light

H

P680 PS II

+

Light

Cytochrome B6f

PQ

FNR Fd

PQH

P700 PS I

PC Plastoquinone H+

Plastocyanin

1 + 2 O2+H

H2O Oxidation of water

H+ H+

+

H

Thylakoid membrane

High Electrochemical potential gradient

Lumen (high H+)

H+ CF0

Stroma Low

ATP Synthase ADP+P1

CF1

H+ ATP

ATP Synthesis Through Chemiosmosis h Within chloroplast, protons decrease in stroma and accumulate in lumen. This creates a proton-gradient across thylakoid membrane as well as a measurable decrease in pH in the lumen. h Breakdown of this gradient leads to synthesis of ATP, when protons move across the membrane to the stroma through transmembrane channel of the F0 of the ATP synthase.

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Photosynthesis in Higher Plants

ATP Synthase (Two parts) F 0 = Embedded in the thylakoid F0 = Protrudes on outer surface of thylakoid membrane. A transmembrane channel membrane on the side that faces stroma. It for facilitated diffusion of protons synthesise ATP.

h Pre-requisite for Chemiosmosis - a membrane, a proton pump,a proton gradient and ATP synthase.

WHERE ARE THE ATP AND NADPH USED? z

O2 diffuses out of chloroplast while ATP and NADPH are used to synthesise sugars in the biosynthetic phase of photosynthesis.

z

Melvin Calvin used radioactive 14C in algal photosynthesis studies to discover the first CO2 fixation product, the 3-C organic acid (3-PGA) (C3-pathway).

z

In another group of plants, the first stable product was 4 carbon, oxaloacetic acid OAA (C4-pathway).

CALVIN CYCLE z

z

Calvin cycle occurs in all photosynthetic plants whether they have C3 or C4 (or any other) pathways.

Calvin cycle can be described under three stages.

(1) Carboxylation: Most crucial step.

RuBP (5C)

RuBisCO

CO2 + H2O

2 × 3 – PGA (3C)

(2) Reduction: A series of reactions that lead to formation of glucose.

Utilises 2 ATP and 2 NADPH per CO2. (The fixation of 6CO2 and 6 turns of the cycle are needed to form one molecule of glucose).

(3) Regeneration: Regeneration of RUBP is crucial for the cycle to continue. This step require one ATP. In

Out

6CO2 18ATP 12 NADPH2

1 Glucose 18 ADP 12 NADP+

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C4-PATHWAY z z

z

z

Plants adapted to dry tropical regions have the C4-pathway.

C4-plants are special; They have special type of leaf anatomy, tolerate higher temperatures, show response to high light intensities, lack photorespiration and have greater biomass productivity.

C4-plants have leaves showing Kranz Anatomy the particularly large cells around the vascular bundles, which may form several layers and are called bundle sheath cells, characterised by having a large number of chloroplasts, thick walls impervious to gaseous exchange and no intercellular spaces.

The pathway is cyclic & called the Hatch and Slack Pathway. It is partly completed in mesophyll & partly in bundle sheath cell.

MESOPHYLL CELL BUNDLE-SHEATH CELLS 1. Primary CO2 acceptor is a 3-C 1. Malic Acid/Aspartic Acid compound PEP. 2.

Enzyme for this fixation is PEPcase.

CO2

3-Carbon molecule

Transported to mesophyll & converted to PEP 4. C4-acid formed is OAA which Enters - Calvin cycle, a pathway forms malic acid or aspartic common to all plants. acid and transported to bundle 2. Rich in RuBisCO but lack PEPcase. sheath cells.

3.

Lacks RuBisCO.

PHOTORESPIRATION z

z z

RuBisCo, the most abundant enzyme in the world, has the active site that can bind to both CO2 and O2. This binding is competitive and depends on the concentration of O2 and CO2.

RuBisCo, has a much greater affinity for CO2, when the CO2: O2 is nearly equal than for O2.

In C3-plants, some O2 does bind to RuBisCO and hence CO2 fixation is decreased, due to the following reaction.

RuBP + O2

RuBisCo

3 PGA (3C) + 2 phosphoglycolate (2C)

This is called photo-respiration.

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Photosynthesis in Higher Plants

z z z

In photo-respiration, there is neither synthesis of sugars nor of ATP. It results in release of CO2 with utilisation of ATP. The biological function of photorespiration is not known yet.

In C4-plants, photo-respiration does not occur as they have a mechanism that increases the concentration of CO2 at the enzyme site.

RuBisCO functions as a carboxylase minimising the oxygenase activty.

FACTORS AFFECTING PHOTOSYNTHESIS Photosynthesis is under the influence of several factors, both internal (plant) & external.

Internal Factors: z

z

The plant factors include the number, size, age & orientation of leaves, mesophyll cells and chloroplasts, internal CO2 concentration & the amount of chlorophyll.

The plant or internal factors are dependent on the genetic predisposition & growth of the plant.

External Factors: Include availability of sunlight, temperature, CO2 concentration and water.

Rate of Photosynthesis

z

B

E

C

A

D Light intensity

z

Blackman’s Law of Limiting Factor: (i) Light: Light saturation occurs at 10% of the full sunlight. Except for plants in shade or in dense forests, light is rarely a limiting factor in nature. h There is a linear relationship between incident light & CO2 fixation rates at low light intensities.

At higher light intensities, gradually the rate does not show further increase as other factors become limiting. (ii) CO2 concentration: Major limiting factor. The concentration of CO2 is very low in the atmosphere (0.03 & 0.04%), so increase in concentration upto 0.05% can cause increase in CO2 fixation rates, beyond this levels, it can become damaging over longer periods.

110 Hand Book (Biology)

h At low light conditions, neither group responds to high CO2 conditions. h C4-plants show saturation at 360µ1L–1. h C3-plants saturation is seen at 450µ1L–1. h Some greenhouse crops like tomatoes and bell pepper show higher yields in CO2 enriched atmosphere. (iii) Temperature: Dark reactions being enzymatic are temperature controlled. Light reactions are also temperature sensitive. h C4-plants show higher yield at high temperature. h C3-plants have a much lower temperature optimum. (iv) Water: Effect of water as a factor is more through its effect on the plant rather than directly on photosynthesis. h Water stress causes the stomata to close hence reducing CO2 availability. h Water stress also makes leaves wilt, thus, reducing the surface area of leaves and their metabolic activity as well.

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Photosynthesis in Higher Plants

Chapter

14 Respiration in Plants

● ● ● ● ●

INTRODUCTION All living organisms need energy for carrying out daily life activities like absorption, transport, movement, reproduction or even breathing.

All the energy required for ‘life’ processes is obtained by oxidation of macromolecules called food.

Cellular respiration: Mechanism of breakdown of food material within the cell to release energy and trapping it for synthesis of ATP. The process takes place in the cytoplasm and in the mitochondria.

Respiratory substrates: Compounds that are oxidised during this process like carbohydrates, proteins, fats and even organic acids.

The process involves a series of slow step-wise reactions controlled by enzymes and the released energy is trapped as chemical energy in the form of ATP which is broken down whenever and wherever energy needs to be utilised.

DO PLANTS BREATHE? Plants have stomata and lenticels to ensure O2 availability.

A very little transport of gases from one plant part to another.

Roots, stems and leaves respire at rates far lower than animals do.

Complete combustion of glucose produces CO2 and H2O as end products and yields energy in the form of heat.

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy ● Plants oxidise glucose in several small steps and energy released is coupled to ATP Synthesis. ● Facultative and obligate anaerobes can respire in absence of O2. ● ● ● ●

● ● ● ●

GLYCOLYSIS Greek-glycos = sugar and lysis = splitting Scheme given by Embden, Meyerhof and Parnas, referred as EMP-pathway In anaerobic organisms, it is the only process in respiration.

Occurs in cytoplasm and present in all living organisms.

● Glucose

Partial oxidation

2 Pyruvic acid

● In plants, glucose comes from Sucrose (the end product of photosynthesis) or from storage carbohydrates. ● Sucrose Invertase Glucose + Fructose (enter the glycolytic pathway readily). ● In glycolysis, a chain of ten reactions produces pyruvate from glucose by the help of different enzymes. ● In glycolysis, 2 ATP are utilised and total 4 ATP, 2 NADH + H+ and 2 molecules of pyruvic acid are produced. ● Pyruvic acid is the key product of glycolysis and its metabolic fate depends on cellular need.

Pyruvic Acid Three major fates

Lactic acid fermentation

Alcoholic fermentation

Under anaerobic conditions

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Respiration in Plants

Kreb’s cycle

Aerobic (Needs O2 supply)

STEPS OF GLYCOLYSIS Glucose (6C) ATP ADP Glucose-6-phosphate (6C) Fructose-6-phosphate (6C) ATP ADP Fructose1, 6-bisphosphate (6C) Triose phosphate (glyceraldehyde-3-phosphate) (3C) NAD+

Triose phosphate (Dihydroxy acetone phosphate) (3C)

NADH+H + 2 × Triose bisphosphate (1,3 bisphosphoglyceric acid) (3C) ADP ATP 2 × Triose phosphate (3-phosphoglyceric acid) (3C)

2 × 2-phosphoglycerate

H2O 2 × phosphoenolpyruvate ADP ATP 2 × Pyruvic acid (3C)

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FERMENTATION ● In fermentation, incomplete oxidation of glucose is achieved by yeast under anaerobic conditions to produce CO2 and ethanol, by the help of enzymes pyruvate decarboxylase and alcohol dehydrogenase. ● Pyruvate is reduced to lactic acid by lactate dehydrogenase in bacteria and in animal cells (muscles during exercise, when oxygen is inadequate for cellular respiration). ● Less than 7% of the energy in glucose is released. ● Yeast poison themselves to death when concentration of alcohol reaches about 13%.

AEROBIC RESPIRATION ● In eukaryotes, it takes place in mitochondria. Leads to complete oxidation of organic substances, in the presence of oxygen and releases CO2, water and a large amount of energy. ● Most common in higher organisms. ● For aerobic respiration to take place within mitochondria, the final product of glycolysis (Pyruvic acid) is transported into mitochondria from cytoplasm. ● Crucial events of aerobic respiration are: Complete oxidation of pyruvic acid – site = Mitochondrial matrix.

ETS and synthesis of ATP – site = Inner mitochondrial membrane.

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Respiration in Plants

TRICARBOXYLIC ACID CYCLE (TCA cycle or Kreb's cycle) (In mitochondrial matrix) ● Acetyl CoA produced by oxidative decarboxylation of pyruvic acid enters the TCA cycle more commonly known as Kreb’s cycle.

(Scientist Hans Kreb) ● During conversion of succinyl CoA to succinic acid, substrate level phosphorylation takes place to produce GTP which in a coupled reaction simultaneously produces ATP. Pyruvate + 4NAD+ + FAD+ + 2H2O + ADP + Pi Mitochondrial Matrix

3CO2 + 4NADH + 4H+ + FADH2 + ATP

● So, per molecule of glucose, 8 NADH+H+, 2 FADH2 and 2 ATP are synthesised from pyruvic acid.

C A CoA

Pyruvate (3C)

NAD +

NADH+H H+ CO 2 Acetyl coenzyme A (2C 2C 2 C C) (2C)

Oxaloacetic acid a d aci ( ) (4C (4 (4C)

+

NADH+H NADH+H H

+

NAD

Malic acid (4C) FADH2 FAD+

Citric acid C) (6C)

CO 2 NAD N AD+ NADH+H NAD H+H H+ c acid acid d α-ketoglutaric (5C) 5 CITRIC ACID CYCLE C 2 CO NAD+ NADH+H NAD N ADH+H H+ Succinic acid (4C)

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GD GDP GTP P GTP

116

AMPHIBOLIC PATHWAY ● Respiratory pathway is involved in both anabolism and catabolism.

Interrelationship among Metabolic pathways Fats

Carbohydrates

Proteins

Fatty acids and glycerol

Simple sugars e.g., Glucose

Amino acids

Glucose 6-phosphate

Fructose 1, 6 bisphosphate Glyceraldehyde 3-phosphate

Dihydroxy Acetone Phosphate

Pyruvic acid Acetyl CoA H2O

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Krebs’ cycle

Respiration in Plants

Co2

ELECTRON TRANSPORT SYSTEM (ETS) AND OXIDATIVE PHOSPHORYLATION ● NADH + H+ and FADH2 are oxisised through ETS and the electrons

are passed on to O2 resulting in formation of H2O through various complexes in the inner-mitochondrial membrane.

● NADH dehydrogenase (Complex-I) and FADH2 (Complex-II) transfers electrons to Ubiquinone

Ubiquinol (reduced ubiquinone)

Complex IV (Cytochrome c oxidase)

cyt bc1 (complex III)

cyt c (Mobile carrier)

● When electrons pass from one carrier to another via complex-I to IV in ETC, they are coupled to ATP synthase (complex-V) for production of ATP from ADP and inorganic phosphate. ● 1 NADH → 3 ATP ● 1 FADH2 → 2 ATP ● Oxygen is the final acceptor of hydrogen. ● Complex-V has two major components ● F1 is peripheral membrane protein complex and contains site for ATP synthesis. ● F0 forms the channel through which protons cross the inner membrane.

● The passage of protons through the channel is coupled to the catalytic site of F1 for production of ATP. For each ATP produced, 2H+ passes through F0 from the intermembrane space to matrix down the electrochemical proton gradient.

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ELECTRON TRANSPORT SYSTEM (ETS) Inter-membrane space

Inter-Mitochondrial membrane

Matrix

NADH + H –

4H + (Fe-S)

2e –

FMN

I

NAD

Complex I (NADH dehydrogenase)

e– UQ e

–

UQH2

e–

Fe-S

Cyt b

III 4H

+

Cyt C1

Cyt c

Complex II (Succinate dehydrogenase)

UQH2 UQ

e

Complex III (Cytochrome bc1)

II FAD

–

(Fe-S)

Succinatc Fumarate

Cyt c e–

Cyta

F0

+ + + +

119

Cyta3

F1 ATP Synthase

Electochemical gradient

2H H2 O Complex IV (Cytochrome oxidase)

CuB

____

2H

1 O + 2H + 2+ 2

IV

Cu

+

ADP + Pi ATP H+ Complex V (ATP Synthase)

Respiration in Plants

RESPIRATORY BALANCE SHEET ● There can be a net gain of 38 ATP molecules during aerobic respiration of one molecule of glucose. ● In fermentation, there is net gain of only 2 ATP for each molecule of glucose degraded. ● NADH is oxidised to NAD+ slowly in fermentation, however the reaction is very vigorous in case of aerobic respiration.

RESPIRATORY QUOTIENT = (RQ) ● The ratio of volume of CO2 evolve of the volume of O2 consumed is RQ. Volume of CO2 evolved RQ = Volume of O2 consumed ● It depends on the type of respiratory substrate, used during respiration. ● For, carbohydrates = 1 Fat = less than 1, (e.g., Tripalmitin = 0.7) Protein = about 0.9

● ● ● ●

NOTE Glucose is the preferred substrate, though fats and protein can also yield energy.

Fermentation takes place in many prokaryotes, unicellular eukaryotes and in germinating seeds.

In aerobic respiration, O2 is ultimate electron acceptor and it gets reduced to water.

Oxidative Phosphorylation : Process of ATP formation when electrons are transferred by electron carriers from NADH2 or FADH2 to oxygen. qqq

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Chapter

15 9 Plant Growth and Development

INTRODUCTION ● Development of a mature plant from a zygote follows a precise and highly ordered succession of events. ● Development is the sum of two processes: Growth and Differentiation.

GROWTH ● Irreversible permanent increase in size of an organ or its parts or even an individual cell. ● Accompanied by metabolic processes and occur at the expense of energy. ● Plants retain the capacity of unlimited growth throughout their life due to presence of meristem at certain locations in their body. ● This form of growth wherein new cells are always being added to the plant body by the activity of meristem is called open form of growth (Indeterminate). ● Primary growth: Root apical meristem and shoot apical meristem are responsible for it i.e., elongation along their axis. ● Secondary growth: In dicotyledonous plants and gymnosperms, the lateral meristems like vascular cambium and cork-cambium, which appear later in life and cause increase in girth of the organs. ● Growth is measurable: At cellular level, it is principally a consequence of increase in amount of protoplasm.

PHASES OF GROWTH The period of growth is generally divided into three phases Meristematic, Elongation & Maturation. (i) The constantly dividing cells at root apex and shoot apex represent meristematic phase of growth. (ii) Cells proximal to the tip represent phase of elongation. (iii) More proximal to the phase of elongation is phase of maturation.

GROWTH RATES Increased growth per unit time is termed as growth rate (Arithmetic or Geometrical). (a) Arithmetic growth: Following mitotic cell division, only one daughter cell continues to divide while the other differentiates and matures.

So, a linear curve is obtained e.g., Root elongating at a constant rate.

Lt = L0 + rt Lt = Length at time ‘t’ L0 = Length at time ‘zero’ r = Growth rate/elongation per unit time.

Linear growth Sigmoid growth (S-shaped curve)

Time

se pha al ent i pon Ex

Size/weight of the organ

Height of the plant

Stationary phase (Growth slow down)

Increase rapidly

Lag phase (initial slow growth) Time

(b) Geometrical growths A sigmoid curve is a characteristic of living organism growing in a natural environment. It is typical for all cells, tissues and organs of a plant.

Wt = W0ert Hand Book (Biology)

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W1 = Final size (weight, height, number etc.)

W0 = Initial size at the beginning of period. r = growth rate; t = Time of growth. e = Base of natural logarithms. r = Relative growth rate and measure of ability of plant to produce new material called efficiency index.

QUANTITATIVE COMPARISONS BETWEEN GROWTH OF LIVING SYSTEM CAN BE MADE BY (i) Measurement and comparison of total growth per unit time called Absolute Growth Rate. (ii) The growth of given system per unit time expressed on a common basis, e g., per unit initial parameter is called Relative Growth Rate.

Absolute and Relative Growth Rates

B1 A1

● ● ● ● ● 123

CONDITIONS FOR GROWTH Water: For cell enlargement, i.e., extension growth by turgidity.

Water also provides medium for enzymatic activities.

Oxygen: For aerobic respiration to get metabolic energy.

Macro and Micro nutrients: For synthesis of protoplasm.

Temperature: Optimum range for best growth.

Light and Gravity: Also affect certain stages of growth.

Plant Growth and Development

Differentiation The cells derived from root apical and shoot apical meristems and cambium differentiate and mature to perform specific functions, this act leading to maturation e.g., Tracheary element.

De-Differentiation Living differentiated cells that have lost the capacity to divide can regain capacity of division under certain conditions e.g., Formation of interfascicular and cork-cambium from parenchyma cells.

Re-Differentiation De-differentiated meristems are able to divide and produce cells that once again lose capacity to divide but mature to perform specific functions e.g., Secondary xylem, secondary cortex, cork, etc.

DEVELOPMENT ● Development includes all changes that an organism goes through during its life cycle from germination of seed to senescence.

Sequence of developmental process in a plant cell Cell Division

Death

Senescence

Meristematic Cell

Plasmatic growth

Differentiation

Expansion (Elongation)

Maturation

Mature Cell

PLASTICITY ● Plants follow different pathways in response to environment or phases of life to form different kinds of structures. ● Heterophylly in cotton, coriander and larkspur leaves of the juvenile plant are different in shape from those in mature plants. ● Environmental heterophylly in buttercup is also an example of plasticity which shows difference in shape of leaves produced in air and water.

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PLANT GROWTH REGULATORS (PGRs) Broadly divided into two groups based on their functions in a living plant body.

Involved in Growth Involved in Growth promoting activities inhibiting activities (Like-cell division, cell enlargement, (Like-Response to wounds pattern formation, tropic growth, and stresses of biotic and flowering, fruiting and seed abiotic origin; dormancy and formation) abscission) E.g.; Abscisic acid (derivatives of carotenoids) 1. Auxin (indole compounds) IAA. 2. Gibberellins (GA3, terpenes) 3. Cytokinin (adenine derivatives) The gaseous PGR, Ethylene, could fit either of the groups, but it is largely an inhibitor of growth activities.

PLANT GROWTH REGULATORS Auxin ● Charles Darwin and his son Francis Darwin studied phototropism in canary grass. ● F.W. Went isolated auxin from tips of coleoptiles of oat seedlings. ● First isolated from human urine. ● Produced by growing apices of stems and roots. ● IAA and IBA isolated from plants. ● NAA, 2, 4-D are synthetic.

125

Plant Growth and Development

Physiological effects: ● Initiate rooting in stem cultings. ● Promote flowering in pineapples. ● Help prevent fruit and leaf drop at early stages but promote abscission of older mature leaves and fruits. ● Apical dominance. ● Induce parthenocarpy in tomatoes. ● 2, 4-D kill dicot weeds. Used to prepare weed-free lawns. ● Controls xylem differentiation and helps in cell-division.

Gibberellins ● Bakanae (foolish seedling) disease in rice was caused by fungal pathogen G. fujikuroi. Later, Gibberellic acid was identified. ● GA3 discovered first and remains intensively studied form. ● All GAs are acidic. ● Increase length of grapes stalk. ● Cause fruits like apples to elongate and improve shape. ● Delay senescence ● Used to speed up malting process in brewing industry, increases length of stem and yield by 20 tonnes per hectare in sugarcane. ● Spraying juvenile conifers with GAs to hastens maturity period.

Promotes bolting in beet, cabbages and many plants with rosette habit.

Cytokinin ● Skoog and Miller crystalised cytokinesis promoting active substance and termed it kinetin (a modified form of adenine) from autoclaved herring sperm DNA, Kinetin does not occur naturally in plants. ● Zeatin, the naturally occurring cytokinin, was isolated from cornkernels and coconut milk. ● Synthesised in regions of rapid cell-division like root apices, developing shoot buds, young fruits etc. ● Helps produce new leaves, chloroplasts in leaves, lateral shoot growth and adventitious shoot formation. Overcomes apical dominance ● Promote nutrient mobilisation. ● Helps delay leaf senescence.

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Ethylene ● Synthesised in large amounts by tissues undergoing sencescence and ripening fruits. ● Horizontal growth of seedlings, swelling of axis and apical hook formation in dicot seedlings. ● Promotes senescence and abscission in leaves and flowers. ● Effective in fruit ripening by increasing rate of respiration called climactic. ● Breaks seed and bud dormancy. ● Initiates germination in peanut seeds, sprouting of potato tubers. ● Promotes rapid internode/petiole elongation in deep water rice plants. ● Promotes root growth and root hair formation. ● Initiates flowering and helps in synchronising fruit-set in pineapples. ● Induces flowering in mango. ● Ethephon is source of ethylene. It hastens fruit ripening in tomatoes and apples and accelerates abscission in flowers and fruits (thinning of cotton, cherry, walnut). ● Promotes female flowers in cucumbers, increasing yield.

Abscisic Acid ● ● ● ● ● ●

Regulates abscission and dormancy.

A general plant growth inhibitor and inhibitor of plant metabolism.

Inhibits seed germination.

Stimulates closure of stomata.

Plays important role in seed development, maturation and dormancy.

By inducing dormancy, ABA helps seeds to withstand desiccation and other factors unfavourable for growth. ● AB acts as an antagonist to GAs. PHOTOPERIODISM Some plants require a periodic exposure to light to induce flowering: (a) Long-day plants: Require light period exceeding well-defined critical period. (b) Short-day plants: Require light less than critical period. (c) Day-neutral plants: No such co-relation between exposure to light duration and induction of flowering response.

The site of perception of light/dark duration are the leaves.

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Plant Growth and Development

SEED DORMANCY ● Controlled by endogenous factors, i.e., conditions within the seed itself. ● Impermeable and hard seed coat; presence of chemical inhibitorsABA, phenolic acids, para-ascorbic acid cause seed dormancy. ● Man made measures like mechanical abrasions, using knives, sand paper or vigorous shaking can break dormancy. ● In nature microbial action, passage through digestive tract of animals can break dormancy. ● Chilling condition, use of gibberellic acid and nitrates can remove effect of inhibitory substances. ● Light and temperature can also break dormancy.

VERNALISATION ● Vernalisation is either qualitative or quantitative exposure to low temperature for flowering in some plants. ● It prevents reproductive development late in the growing season and enables the plant to have sufficient time to reach maturity. ● Wheat, barley, rye have winter and spring varieties. ● Biennials like sugarbeet, cabbages, carrots to cold treatment stimulates a subsequent photoperiodic flowering response.

NOTE ● Development in plants can be under intrinsic and extrinsic control, intrinsic can be intra-cellular (Genetic) or inter-cellular (PGR). ● In plants, growth and even differentiation is also open, as cells and tissues of same meristem have different structure at maturity. ● PGRs can be having complimentary or antagonistic role, which can be individualistic or synergistic. qqq

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Chapter

16 Digestion and Absorption

BASIC REQUIREMENTS OF LIVING ORGANISMS Digestion: The process of conversion of complex food substances to simple absorbable forms carried out by mechanical and biochemical methods.

1. Food: ○ Provide energy and organic material for growth and repair of tissues.

Major components (biomacromolecules) ○ Carbohydrates, Proteins, Fats

Minor components (biomicromolecules) ○ Vitamins, Minerals

2. Water: ○ Important for metabolic processes. ○ Prevent dehydration of the body.

HUMAN DIGESTIVE SYSTEM Alimentary canal Human digestive system consists of Digestive glands/Associated glands Oral cavity Teeth ○ Thecodont, Heterodont and Diphyodont Buccal cavity Tongue ○ Muscular organ, attached to the oor of oral cavity by the frenulum. ○ Upper surface of the tongue has small projections called papillae. ○ Some papillae have taste buds.

Pharynx Common passage for food and air and helps in swallowing.

Oesophagus Thin, long tube (25 cm long).

Passes through neck, thorax and diaphragm.

Stomach J-shaped bag in upper left part of abdominal cavity.

Cardiac – Oesophagus opens into ○ 4 regions Fundic – Filled with air and gas Body – Main central region Pyloric – Opens into small intestine Small Duodenum – ‘C’-shaped, shortest and widest Intestine 3 regions Jejunum – Long coiled part, plicae circularies prominent Ileum – Highly coiled, opens into large intestine

Large 3 regions Intestine

Caecum – Blind sac, host symbiotic microbes ○ Vermiform appendix: Vestigial organ, ngerlike tubular projection Colon Ascending Transverse Descending Sigmoid Rectum Internal sphincter (Involuntary) External sphincter (Voluntary)

Human Digestive System • Vestibule – Narrow space in the mouth that is bound by lips, cheeks and teeth.

• Epiglottis (cartilaginous ap) prevents the entry of food into the glottis (opening of trachea/wind pipe) during swallowing.

• Sphincters are muscular structures that regulate the ow of partially digested food in the alimentary canal.

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HISTOLOGY OF GUT Layers

Typical

○ Serosa

○ Outermost layer, made up of thin mesothelium (visceral epithelium of visceral organs) with some connective tissues.

○ Muscularis

○ Inner – Circular muscles ○ Outer – Longitudinal muscles

○ Sub-mucosa

○ Loose connective tissue with nerve, blood and lymph vessels. ○ In duodenum, Brunner’s glands present in sub-mucosa.

○ Mucosa

○ Innermost layer lining the lumen

Modifications ○ Stomach

○ Oblique muscle layer is present. ○ Irregular folds of mucosa called Rugae. ○ Small intestine ○ Finger like foldings of mucosa called villi. ○ Cells lining villi produce microscopic projections called microvilli giving brush border appearance.

• Villi, microvilli, rugae – Increase surface area for absorption.

• Villi are supplied with blood capillaries and lacteals (Lymph vessel).

• Gastric glands, goblet cells and crypts of Lieberkuhn – Present in mucosa.

• The muscular activities of different parts of alimentary canal can be moderated by neural mechanisms, both local and through CNS.

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Digestion and Absorption

TEETH Dentition: ○ Thecodont – Each tooth is embedded in socket of jaw bone. ○ Heterodont – Different types: Incisor (I), Canine (C), Premolar (PM), Molar (M) ○ Diphyodont – 2 sets of teeth during life • A set of temporary/milk/deciduous teeth which are replaced by a set of permanent/adult teeth I CPMM

Teeth in each half of upper jaw 2 1 2 3 Dental formula = Teeth in each half of lower jaw = 2 1 2 3 × 2 = 32 Dentition formula of temporary teeth =

2 1 0 2 2 1 0 2 × 2 = 20

Enamel – Hard chewing surface, helps in mastication of food.

Number of Roots: ○ Incisor = 1 ○ Canine = 1 ○ Premolars = 2 ○ Molars = 3

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133

Digestion and Absorption

Outside buccal cavity Cheek Lower jaw

Location

Liver (Largest gland) 1.2-1.5 kg

○ Parietal/oxyntic cells

○ Peptic/chief cells

○ Mucus neck cells

Gastric glands 1.8

6.8

pH

Upper right side >7 of abdomen below diaphragm

Mucosa of stomach

1 Pair – Parotids largest 1 Pair – Submaxillary/ Submandibular 1 Pair – Sublinguals smallest Below tongue

Salivary Glands

Glands

Bile released into duodenum

Gastric juice in stomach

Active form

Active form

Bile salt Bile pigments Cholesterol Phospholipids

Intrinsic factor

Pepsinogen Prorennin (infants) Lipase HCl

Mucus

Secretion Contents (1–1.5 L) Mucus Saliva/ + + salivary Electrolytes-Na , K , juice into – – Cl , HCO3 oral cavity Lysozymes Salivary amylase or Ptyalin

DIGESTIVE GLANDS

• Bile activates lipases

Emulsi cation of fats Bilirubin and biliverdin

Fat digestion Acidic pH, activation of gastric proenzymes Absorption of vitamin B12 (Cobalamin)

Protein digestion Digestion of milk proteins

Lubrication and protection of mucosal epithelium from excoriation by HCl

Mucus + Pepsinogen + Hydrochloric acid

Antibacterial agent, prevent infections Carbohydrate splitting enzyme

Act as buffering agents

Lubrication and adhering of masticated food into bolus

Function

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Mucosa of small intestine between the bases of villi

○ Crypts of Lieberkuhn

7.8

>7

pH

Amylase Lipases DNAase

Trypsinogen Chymotrypsinogen Procarboxypeptidase

Contents

Enterokinase

Nucleases RNAase Intestinal Mucus juice/ Succus entericus Brush border enzymes ○ Disaccharidases ○ Dipeptidases ○ Lipases ○ Nucleosidases

Pancreatic juice released into duodenum

Secretion Protein digestion

Activates trypsinogen into trypsin which in turn activates other enzymes in the pancreatic juice

Carbohydrate digestion Protein digestion Fat digestion Nucleosides digestion

Nucleic acid digestion Lubricate and protect intestinal mucosa from acid and provide alkaline medium for enzymatic activities

Carbohydrate digestion Fat digestion

Active form

Function

Control of activities of gastro intestinal tract • Saliva secretion – Stimulated by sight, smell and/or presence of food in oral cavity.

• Gastric and intestinal – Local hormones produced by gastric and intestinal mucosa secretion – Neural mechanisms – local and via CNS

Sub mucosa of duodenum

Between limbs of duodenum

Location

○ Brunner’s gland (no enzyme)

Intestinal glands

Pancreas (Heterocrine gland)

Glands

DUCTS ASSOCIATED WITH LIVER AND PANCREAS

Pancreas

Exocrine part (acinar cells) secrete alkaline pancreatic juice containing enzymes.

Endocrine part (islets of langerhans) secrete hormones, insulin and glucagon into blood vessel

Schematic flow of digestive juices Liver

Bile

(hepatic cells)

Duodenum

Hepatic ducts

Common hepatic duct

Pancreatic duct Hepato-pancreatic duct

Cystic duct Common bile duct

Sphincter of Oddi

• Hepatic lobules are structural and functional unit of liver.

• Each lobule is covered by a thin connective tissue sheath called Glisson’s capsule.

• Hepatic cells are arranged as cords in hepatic lobule.

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Digestion and Absorption

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Simple absorbable forms.

DIGESTION OF FOOD

Succus entericus

Intestine

Pancreatic Intestine juice

—

Glucose+Galactose

Sucrose Sucrase Glucose+Fructose

Lactose

Lactase

—

Fats

Dipeptidases

Amino acids

Dipeptides

Trypsin Chymotrypsin Carboxypeptidase

Proteins Peptones Proteoses

○ Trypsinogen Enterokinase ○ Chymotrypsinogen ○ Procarboxypeptidase

—

○ Milk protein Rennin Peptones + proteoses Infants

+ Diglycerides

Monoglycerides

Nucleotides

Nucleases

Nucleic acids

—

—

—

Nucleic Acids

Fatty Nucleotides Nucleotidases Nucleosides acids Nucleosidases + Sugars + Nitrogen bases Glycerol

Lipases

Diglycerides + Monoglycerides

Lipases

Fats

○ Emulsi cation of fats i.e., Fats micelles ○ Activates lipases

Lipase minor role ○ Pepsinogen HCl Pepsin Protein Peptones (peptides) + proteoses

Maltose Maltase Glucose + Glucose ○ Dipeptides

Disaccharides

Pancreatic amylase

Polysaccharides (Starch)

Intestine

Bile

—

Maltose

—

Stomach (stores food for 4-5 hrs.)

Salivary amylase

Buccal cavity (30%) Starch

Proteins

Carbohydrates

Gastric juice

Site of Digestion

Saliva

Juice

Bolus – Mucus in saliva helps in lubricating and adhering the masticated food particles.

Bolus passes down into oesophagus by swallowing/deglutition.

Food in stomach mixes with acidic gastric juice by churning movements and is called chyme.

Breakdown of biomacromolecules into its simplest form occurs in the duodenum region of small intestine.

Various types of movements in alimentary canal (e.g., peristalsis) are generated by muscularis layer that helps in a thorough mixing up of the food with various secretions and thereby facilitate digestion.

Complex food substances

Mechanical process Biochemical process

ABSORPTION OF DIGESTED PRODUCTS Absorption is the process by which the end products of digestion (in the form of small units) pass through intestinal mucosa into the blood or lymph.

The digested food is absorbed into the body through the epithelial lining of the intestinal villi of jejunum and ileum.

Protein

Enterocyte Fatty acid + Glycerol + Triglyceride

Fatty acid + Incorporate into Glycerol Micelles/ + small droplet Bile salts Lumen of small intestine

Lacteals in villi Triglyceride

Indirectly absorted in blood

Chylomicron Blood stream Examples – ○ Glucose, amino acids, Cl ions ○ Glucose, amino acids ○ Water +

○ Glucose, amino acids, Na ions

Directly absorbed into blood

Method Mechanism Simple ○ Passive: diffusion (Along concentration gradient) Facilitated transport ○ No energy required Osmosis ○ Active (uphill transport): (Against concentration gradient) ○ Energy is required

Summary of different substances absorbed in different parts of alimentary canal Mouth and lower side of tongue Stomach Small intestine

Lymph Blood

Large intestine

Certain drugs Simple sugars, alcohol, water Fatty acids, glycerol Glucose, fructose, amino acids Water, drugs, some minerals

Maximum absorbtion occur in the small intestine

The digested end products formed in duodenum are absorbed and nally reach the tissues which utilise them for their activities.

This process is called assimilation.

137

ASSIMILATION Food

Alimentary canal

Digested food Undigested and unabsorbed food Faeces

Digestion and Absorption

Maximum absorption in small intestine

Blood Assimilation

Body cells

ROLE OF LARGE INTESTINE No significant digestive activity occurs here.

Absorption of water, minerals certain drugs.

Site for Secretion of mucus, to adhere waste and for lubrication.

Solid faeces initiate neural re ex, causing urge for its removal.

Undigested, unabsorbed substances enters caecum through ileo-caecal valve and the wastes solidi ed into coherent faeces which is temporarily stored in rectum till defaecation.

Egestion of faeces to outside through anal opening is defaecation. It is a voluntary process and is carried by a mass peristaltic movement.

PROTEIN ENERGY MALNUTRITION (PEM) Dietary de ciencies of proteins and total food calories are widespread in children of underdeveloped countries.

It may affect large sections of the population during drought, famine and political turmoil.

Parameters

Marasmus

Kwashiorkor

Dietary deficiency ○ Proteins

○ Proteins and calories

Age

○ Child more than 1 year

○ Infants less than 1 year

Reason

○ Replacement of mother’s milk by high calorie, low protein diet.

○ Replacement of mother’s milk too early by other foods or mother has second pregnancy when older infant is too young.

Characteristics

○ Extensive oedema i.e., swelling of body parts. ○ Wasting of muscles, thinning of limbs.

○ Extensive emaciation of body, Skin is dry, thin and wrinkled, thinning of limbs.

PEM

Growth rate and body weight decline.

Growth and development of brain are impaired.

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ENERGY VALUES Gross Calorific Value ○ Amount of heat liberated from complete combustion of 1 gm of food in bomb calorimeter (metal chamber led with O2) • Carbohydrates - 4.1 K cal/g • Proteins - 5.65 K cal/g • Fats - 9.45 K cal/g

Physiological Value ○ Actual amount of energy released on combustion of 1 g of food in body.

4.0 K cal/g 4.0 K cal/g 9.0 K cal/g

• 1 kilo calories is the amount of energy required to raise the temperature of 1 kg of water by 1°C. • Energy requirements of animals and the energy content of food expressed in terms of heat energy, [calorie (cal) or joule (J)].

DISORDERS OF DIGESTIVE SYSTEM Disease/Problem

139

Cause and Symptoms

Inflammation of intestinal tract

○ Most commonly due to bacterial and viral infections. ○ Can be due to parasites like roundworm, tapeworm, threadworm, hookworm, pin worm etc.

Jaundice

○ Liver affected. ○ Skin and eyes turn yellow due to deposit of bile pigments.

Vomiting

○ Ejection of stomach content, feeling of nausea precedes vomiting. ○ It is a re ex action controlled by vomit centre, medulla.

Diarrhoea

○ Abnormal frequency of bowel movement and increased liquidity of faecal discharge, reduces food absorption.

Constipation

○ Faeces are retained within the colon as bowel movement occurs irregularly.

Indigestion

○ Food not digested properly, feeling of fullness. ○ Can be due to inadequate enzyme secretion, anxiety, food poisoning, over eating and spicy food.

Digestion and Absorption

17

Chapter

Breathing and Exchange of Gases BREATHING/RESPIRATION Atmospheric oxygen

Exchange

CO2 produced by cells

RESPIRATORY ORGANS Based on

Organism Sponges, coelenterates atworms Earthworm, Frog

Habitats

Insects Levels of organisation Aquatic arthropods, molluscs, sh Amphibians, reptiles, mammals

Mechanism Simple diffusion Moist skin Tracheal tubes Branchial/Gills Pulmonary/lungs

Amphibians show cutaneous respiration all the time.

Nostrils (Elastic cartilage that covers glottis during swallowing)

Nasal chamber

Bronchus Primary bronchi Secondary bronchi Tertiary bronchi Initial bronchioles Terminal bronchioles

Larynx (Voice box) Trachea th

(Divides at 5 thoracic vertebra)

Pleural fluid (reduced friction on lung surface)

Cut end of ribs Outer pleural membrane Inner pleural membrane Diaphragm

Respiratory zone

Epiglottis

Conducting zone

OUTLOOK OF HUMAN RESPIRATORY SYSTEM ( Well developed)

Alveoli (Vascular bags with thin, irregular walls)

Functions Conducting zone Humidi cation of air Transport of air Traps dust present in inhaled air Bring air to body temperature

Respiratory zone Exchange of gases O2 and CO2 between blood and atmospheric air

Thoracic Chamber

IMPORTANT POINT Dorsally by the vertebral column Ventrally by the sternum Laterally by ribs Lower side by dome shaped diaphragm

Any change in the volume of the thoracic cavity will be re ected in the lung (Pulmonary cavity).

MECHANISM OF BREATHING Lungs, enclosed in an anatomically air tight thoracic chamber; essential for breathing as we cannot alter pulmonary volumes directly.

Movement of air follows the pressure gradient.

Specialised set of structures involved in breathing: Air entering lungs Ribs and sternum (ventral) raised

Volume of thorax increase

Ribs cage Diaphragm contracted (Posterior)

Air expelled from lungs Ribs and sternum returned to original position

Volume of thorax decreased Diaphragm relaxed and arched upwards

Vertebrae (Dorsal)

(b) (a) Fig.: Mechanism of breathing showing: (a) Inspiration (b) Expiration

Normal rate of breathing 12-16 times/minute in adult human Involve Inspiration Intrapulmonary pressure Pressure in the lungs w.r.t. atmosphere Shape of diaphragm Forceful expiration achieved

141

Low –ve Flat

Expiration High +ve Dome-shaped

Internal intercostal muscle Abdominal muscle

Breathing and Exchange of Gases

EXCHANGE OF GASES Partial pressure drives respiration Site of exchange: ○ Alveoli (Primary) ○ Between blood and tissues Partial pressure: ○ Pressure contributed by an individual gas in a mixture of gases Respiration steps

Atmosphere

1. Breathing/pulmonary ventilation

Partial pressure of gases (mm Hg) CO2 O2

Alveoli

2. Diffusion of O2 & CO2 across alveolar membrane (less than 1 mm thick)

159

0.3

104

40

95

40

40

45

3. Transportation of gases by blood

4. Diffusion of O2 & CO2 between blood and tissues 5. Cellular respiration Exchange of gases is based on: ○ Concentration gradient ○ Thickness of membrane ○ Solubility of gases - CO2 is 20-25% more soluble than O2 ○ Any factor that affects diffusion rate

The thinner the membrane involved in diffusion, the faster is the diffusion of gases.

Total thickness of the respiratory membrane is less than a millimetre.

Diffusion membrane comprises of 3 layers

Squamous Air epithelium of alveolar wall (one-celled thick) Alveolar cavity Blood capillary

Basement substance Endothelium of blood capillary Red blood cell

Fig.: A Diagram of a section of an alveolus with a pulmonary capillary.

Thin squamous epithelium of alveoli Endothelium of capillaries Basement substance in between

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RESPIRATORY VOLUME AND CAPACITIES

Standard volumes 1. Tidal volume/air inhaled or exhaled per breath.

2. Inspiratory reserve volume/forceful inhalation.

3. Expiratory reserve volume/forceful exhalation.

4. Residual volume/air left in lungs after forceful exhalation.

Value in ml TV - 500

Standard capacities IC = TV + IRV

IRV - 25003000

VC = TV + IRV + ERV

ERV - 10001100

FRC = ERV + RV

RV - 11001200

EC = TV + ERV

TLC = TV + IRV + ERV + RV VC + RV

Instrument - Spirometer Significance - Clinical assessment of pulmonary functions Residual volume cannot be measured by Spirometer.

Minute volume: TV × respiratory rate i.e., 500 × 12 = 6000-8000 ml

TRANSPORT OF GASES O2 Lungs Blood Tissue CO2

Haemoglobin ○ Comprises globin and heme. ○ Globin – Protein molecule ○ Heme – Prosthetic group – Imparts red colour 2+ ○ Fe present in the centre of each Heme.

143

Percentage saturation of haemoglobin with oxygen

Oxygen dissociation curve

Partial pressure of oxygen (mm Hg)

Breathing and Exchange of Gases

Oxygen

Carbon dioxide

5 ml of O2 is delivered to the tissues by 100 ml of oxygenated blood

4 ml of O2 is delivered to alveoli by 100 ml of deoxygenated blood

3% dissolved in plasma

7% dissolved in plasma

97% as oxyhaemoglobin

20-25% as carbamino Hb

Binding of O2 with Hb is primarily related to pO2

Binding of CO2 with Hb is related to pCO2 as well as pO2

Hb + O2 Oxyhaemoglobin HbO2

Hb + CO2 Carbaminohaemoglobin (HbCO2) Association Dissociation

Parameter

Association

Dissociation

High pO2

High pCO2

Lungs (Alveoli)

Tissue

Tissue

Lungs (Alveoli)

+

High H High temperature Location

• Each Hb molecule binds 4 oxygen molecules in a reversible manner.

• Oxygen dissociation curve obtained is sigmoid.

• Maximum (70%) CO2 is transported as bicarbonates facilitated by enzyme carbonic anhydrase, which exists more in RBCs and minute quantities in Carbonic Carbonic plasma CO2 + H2O

anhydrase

H2CO3

anhydrase

–

+

HCO3 + H

Bohr effect: ○ The phenomenon of an increase in CO2 concentration resulting in an increased dissociation of oxyheamoglobin. ○ O2–Hb dissociation curve shift right ( ed dissociation of Hb with O2).

Chloride shift or Hamburger phenomenon: – ○ When HCO3 ions from RBC move into plasma, it changes the ionic balance between RBCs and plasma.

– ○ To restore the ionic balance, Cl ions diffuse from plasma into RBC.

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REGULATION OF RESPIRATION Humans have signi cant ability to maintain and moderate the respiratory rhythm to suit the demands of the body tissues.

Regions Pneumotaxic Chemosensitive Aortic Carotid involved center area receptors receptors Pons Medulla Aortic arch Carotid Location oblongata artery Reduces duration Respiratory adjustments of inspiration + Sensitive to pCO2, H Ventral Dorsal respiratory group respiratory group – control inspiration – control inspiration Medulla oblongata and expiration Primary respiratory rhythm center

The role of oxygen in the regulation of respiratory rhythm is quite insigni cant DISORDERS Diseases

Affected Area

Characteristics

Asthma

In ammation of bronchi, bronchioles

Wheezing sound

Emphysema

Alveolar wall damage in chronic cigarette smokers

Respiratory surface area decreased

Occupational respiratory disorder

Lungs

Fibrosis and lungs damage

Workers should wear protective masks while working in industries that are involved in dust producing grinding and stone breaking.

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Breathing and Exchange of Gases

Chapter

18 Body Fluids and Circulation

BLOOD VASCULAR SYSTEM Constituents: Blood + Blood vessels Functions: + Heart ○ Transport of nutrients, O2, glucose etc.

Blood: ○ Removal of harmful substances ○ Synthesised in Red bone marrow Medium of transport ○ Components: (A) Plasma (matrix, 55%) Water Blood & lymph Water: 90-92% Sponges & coelenterates Humans Proteins: 6-8% ○ Fibrinogens – Clotting ○ Albumins – Osmotic balance ○ Globulins – Defense + 2+ 2+ – – Minerals: Na , Ca , Mg , HCO3 , Cl Nutrients: Glucose, amino acids, lipids (B) Formed Elements (45%) Parameter RBCs/Erythrocytes WBCs/Leucocytes 3 3 Number 5-5.5 million/mm 6000-8000//mm Red due to iron Colourless Colour containing Hb (12-16 gm/100 ml) Nucleus Absent Present Life span 120 days Generally short lived Function Transport of gases Defense

Platelets/Thrombocytes 3 1,500,00-3,500,00/mm Colourless

Absent Short lived Coagulation of blood.

If number drops, can lead to loss of blood from body.

Types of WBCs Granulocytes % of total WBCs

Agranulocytes

Basophils 0.5 - 1%

Eosinophils 2 - 3%

Neutrophils Monocytes 60 - 65% 6 - 8%

Lymphocytes 20 - 25%

Involved in in ammatory reactions

Resist infections, associated with allergic reactions

Phagocytic in action

Involved in immune response of body

Shape of nucleus Function

• RBCs are biconcave and enucleated in most mammals.

• Platelets are cell fragments of megakaryocytes.

• Graveyard of RBCs - spleen.

• Basophils secrete heparin, histamine, serotonin.

BLOOD CLOTTING/COAGULATION In response to injury/trauma, clotting prevents loss of blood from body.

Events: Injured tissue Formation of Thrombokinase Release (Cascade (enzyme complex) chemicals Platelets (Thrombo- process) Prothrombin Fibrinogens plastin) Thrombins 2+ Ca ions play an important role in clotting.

Vitamin K helps in the conversion of inactive clotting factors to active clotting factors.

Clotting factors in blood are in inactive form.

Serum = Plasma – Clotting factors

Fibrins + entangled formed elements (Coagulam/reddish brown clot)

BLOOD VESSELS Layers in wall Name Tunica externa Tunica media Tunica intima

Position Outermost Middle Innermost

Composition Fibrous connective tissue & collagen bres Smooth muscle & elastic bres Squamous endothelium

Artery Vein Thick Thin Tunica media Narrow Wide Lumen Circulation Heart Different part of body Different part of body Heart Oxygenation Oxygenated Deoxygenated Valves Absent Present

BLOOD GROUPS ABO grouping

Based on

Parameter Natural Antigen

Parameter

Definition

Rh factor

Present Type

Natural Antibodies Chemicals Proteins that induce produced immune in response response to antigens

On RBC A, B

Present

Rh grouping Rh

+ve

Rh

–ve

Yes

No

On RBC

No

In plasma Anti-A, B

Blood group and Rh factor compatibility of donor and recipient is done before transfusion to avoid agglutination of RBCs.

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Body Fluids and Circulation

Blood Group Antigens on RBCs A B AB O

Antibodies in Plasma

Donor’s Group

anti-B anti-A nil anti-A, B

A, O B, O AB, A, B, O O

A B A, B nil

Universal Donor – Blood Group ‘O’ Universal Recipient – Blood Group ‘AB’ –ve

Rh

+ve

person upon exposure to Rh

blood will form Rh speci c antibodies

Special case of Rh incompatibility Mother Rh

–ve

+ve

Foetus Rh

st

1 baby normal, as during pregnancy, no mixing of blood due to separation by placenta.

During delivery, there are chances of mixing of blood.

Rh–ve mother makes antibodies against Rh+ve antigen.

Antibodies cross placenta in subsequent pregnancy.

Severe anemia and jaundice in baby.

Erythroblastosis foetalis/Hemolytic disease of the newborn (HDN) Administer anti Rh antibodies to the mother immediately st nd after 1 delivery, save baby during 2 Pregnancy.

CIRCULATORY PATHWAYS Open

Closed Absent

Sinuses

Present

Regulation of blood flow Examples

Improper Arthropods, molluscs

Proper Annelids, chordates

Vertebrates Fishes Amphibians, most reptiles

Auricle 1 2

Ventricle 1 1

Crocodile, Aves, Mammals

2

2

Circulation Single Incomplete Double

Fishes pump deoxygenated blood to gills for oxygenation.

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LYMPH (Tissue Fluid) No colour.

Blood – (Larger proteins + most formed elements).

Rich in lymphocytes.

Carrier for nutrients, hormones and fats.

Lymphatic vessels drain interstitial uid back to major veins.

Lacteals are lymph vessels in intestinal villi to absorb fats.

HUMAN CIRCULATORY SYSTEM

(Oxygenated blood) (Deoxygenated blood) (Deoxygenated blood) (Oxygenated blood)

[Conducts action potential]

Heart Mesodermally derived organ present in between lungs, muscular, chambered, tilted to left.

Protected by double walled, membranous bag–Pericardium with pericardial fluid.

4 chambers

2 upper, smaller–Auricles 2 lower, larger–Ventricles

Septum

Between auricles: Inter-atrial (thin, muscular) Between ventricles: Inter-ventricular (thick walled) Between auricle & ventricle: Auriculo-ventricular (thick brous)

Cardiac valves

Between right auricle & right ventricle – Tricuspid valves Between left auricle & left ventricle – Bicuspid/Mitral valves At base of pulmonary artery Semilunar valves At base of aorta

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Body Fluids and Circulation

Cardiac muscles

Contractile tissue Nodal tissue (Auto excitable)

SAN – Maximum – 70-75 action excitability potentials/min

Sino-auricular nodel/ Right upper (SA node/pacemaker) corner of right atrium Atrioventricular node/ AV node

Left lower corner of right atrium

Inter ventricular septum AV bundle Purkinje bres Divides at apex of ventricle Valves are muscular aps or cusps that allow unidirectional ow of blood and prevent its backward ow.

Double circulation No mixing of deoxygenated and oxygenated blood occurs

TYPES OF CIRCULATION Pulmonary: Right ventricle Pulmonary Lungs artery Systemic: Left ventricle

Aorta

Hepatic portal circulation – Digestive tract

Tissues Hepatic portal vein

Pulmonary veins Vena cava

Left auricle Right auricle

Liver

Coronary circulation – Blood ow to and from the cardiac musculature CARDIAC CYCLE Sequential events in the heart which are cyclically repeated. (1) Joint diastole Heart beat rate = 72 beats/min.

Duration of 1 heart beat = 0.8 sec.

Location/Structure Auricle

Ventricle

Tri & Bicuspid valves Semilunar valves

Atrial systole (2) SAN generates action potentials Ventricular systole (3) AV node, AV bundles, bundle of His transmit the action potentials further

Events of 1 cardiac cycle

Atrial Systole Ventricular Systole Contract, increase Relax ow of blood into ventricles by 30% Relax Relax Contract, throw out 70 ml of blood/ventricleStroke volume Closed, 1st heart Open Open sound Lub Closed Closed, 2nd heart Closed sound Dub Joint Diastole Relax, lling

• Heart sounds (Lub & dub) can be heard by Stethoscope and have clinical diagnostic signi cance.

• Cardiac output = Stroke volume × Heart rate = 70 × 72 = 5040 ~ 5 litres • Cardiac output of athletes is higher than a normal man.

• Stroke volume = EDV – ESV

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ELECTROCARDIOGRAPH (ECG) A graphical representation of electrical activities of heart during a cardiac cycle.

Instrument – Electrocardiograph Graphical print – Electrocardiogram For a standard ECG – 3 leads are connected to monitor heart activity – Right wrist, left wrist and left ankle.

R

P

Graphical standards P wave QRS complex T wave

Q

S

T

Represent Depolarisation of atria Depolarisation of ventricles Repolarisation of ventricles

Event associated Contraction of atria Contraction of ventricles Relaxation of ventricles

• Number of QRS complexes in a given time period, determine the heart beat rate of an individual.

• End of T-wave marks the end of systole.

• Any deviation in ECG indicates a possible abnormality or disease e.g., ECG machine makes sound pip---pip---pee as patient goes into cardiac arrest.

REGULATION OF CARDIAC CYCLE Activities of heart are regulated intrinsically i.e., autoregulated as human heart is myogenic.

Medulla oblongata can moderate Cardiac functions through ANS Autonomic nervous system (ANS) Sympathetic

Parasympathetic

Heart beat rate

Increase

Decrease

Strength of ventricular contraction

Increase

Decrease

Cardiac output

Increase

Decrease

Parameter

Hormones of adrenal medulla increase cardiac output

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Body Fluids and Circulation

DISORDERS OF CIRCULATORY SYSTEM Disease

Effects

Cardiac arrest

Heart stops beating.

Heart failure

Heart is not pumping blood effectively enough to meet needs of body.

Atherosclerosis/(CAD) Deposit of Ca2+, fats, cholesterol in blood vessels Coronary artery disease that makes arterial lumen narrower.

High blood pressure Repeated check of blood pressure of an individual 140/90, leads to heart diseases and also affects vital organs like brain and kidneys.

Angina pectoris/ Not enough oxygen is reaching heart muscles. acute chest pain It affects blood ow. Common in middle aged and elderly.

Heart attack

Heart muscle is suddenly damaged by an inadequate blood supply.

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Chapter

19 Excretory Products and Their Elimination

EXCRETORY WASTE Metabolism Excess ingestion Results in accumulation of Nitrogenous wastes – NH2, urea, uric acid Other contents – CO2, H2O, ions (Na+, K+, Cl–, PO3–4 , SO2–4 ) Removed

Partially/Completely NITROGENOUS WASTES Nature of nitrogenous waste formed and their excretion vary among animals depending on the habitat/availability of water.

Major nitrogenous waste

Nature & Examples

Toxicity and water required

Typical

Ammonia

Ammonotelic ○ Aquatic insects ○ Many bony shes ○ Aquatic amphibians

Maximum

○ Diffusion through gills surface or body surface as + ammoium (NH4 ) ions

Urea

Ureotelic ○ Marine shes ○ Many terrestrial amphibians ○ Mammals Uricotelic ○ Land snails ○ Insects ○ Reptiles ○ Birds

Lesser

○ Kidneys lter urea from blood

Least

○ Pellet/Paste (Semi-solid)

Uric acid

• Ammonia converts into urea in liver.

• Elimination of urea, uric acid is meant for conservation of water i.e., a type of terrestrial adaptation.

• Kidneys do not play a signi cant role in removal of ammonia.

• Some amount of urea may be retained in the kidney matrix of some animals to maintain desired osmolarity.

EXCRETORY STRUCTURES Most invertebrates – Simple tubular forms.

Vertebrates – Complex tubular organs called kidneys.

Structures

Examples

○ Protonephridia/ ame cells (osmoregulation)

○ Platyhelminthes (Planaria) ○ Rotifers ○ Some annelids ○ Cephalochordates (Amphioxus)

○ Nephridia ○ Malpighian tubules ○ Antennal/Green glands

○ Annelids (Earthworms) ○ Insects (Cockroaches) ○ Crustaceans (Prawn)

• Function of excretory structures: – Eliminate nitrogenous wastes.

– Maintain ionic and acid-base balance of body uids, i.e., osmoregulation.

HUMAN EXCRETORY SYSTEM

[1 pair]

1 pair, bean shaped, reddish brown Length 10-12 cm, Width 5-7 cm, Thickness 2-3 cm Weight 120-170 g Between T12 - L3 vertebra, close to dorsal inner wall of abdominal cavity Have stretch receptors Store urine till voluntary signals from CNS carries out its release

Guarded by sphincters Meant for release of urine MICTURITION Process of release of urine Mechanism - Micturition reflex

Stretch receptors

Send motor messages

Urimary bladder Smooth muscles contract Urethral sphincters relax

Urinary bladder (Store urine) Activates

CNS (voluntary signals)

signals

Release

Urine

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Columns of Bertini/ Renal columns ○ Part of cortex which extends between medullary pyramids

KIDNEY Capsule–outer tough covering Cortex (Outer) Malpighian corpuscle, PCT, DCT Medulla (Inner) Loop of Henle Hilum ○ Notch towards concave surface ○ Ureter, blood vessels and nerves enter Renal pelvis ○ Funnel shaped space with projections called calyces

Medullary pyramids are conical masses that project into calyces.

NEPHRON Functional unit of kidney Nearly 1 million complex tubular structure Each nephron has two parts—(i) Glomerulus (ii) Renal tubule Efferent arteriole (Narrow)

Afferent arteriole (Short, wide)

(Carry the blood from glomeruli)

(Carry blood to glomeruli)

Malpighian body/ Renal corpuscle

Glomerulus Bowman’s capsule

Peritubular copillaries Proximal convoluted tubule Distal convoluted tubule

Descending limb Henle’s loop of loop Henle (Hairpin shaped) Ascending limb of loop Henle Vasa recta - Branch of Peritubular capillaries - Parallel to loop of Henle - U-shaped Parameters

Collecting duct

Types of Nephron

Cortical

Juxitamedullary

Number

More

Less

Loop of Henle

Too short

Very long

Extension into medulla

Very little

Deep

Vasa recta

Absent/reduced

Present

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Excretory Products and Their Elimination

Juxtaglomerular apparatus (JGA): Sensitive region formed by cellular modi cations in distal convoluted tubule and afferent arteriole at the location of their contact.

JGA is composed of JG Cells and Macula densa.

Nephrons are dipped in interstitial uid having speci c osmolarity – Cortex - 300 mOsm/L – Medulla - upto 1200 mOsm/L (Gradient)

• Glomerulus is a tuft of capillaries formed by afferent arteriole - a ne branch of renal artery.

• Many DCTs open into straight tube called collecting duct, many of which converge into renal pelvis through medullary pyramids in the calyces.

• Efferent arteriole emerging from glomerulus forms peritubular capillaries around renal tubule.

URINE FORMATION

1.

Non-selective process

Glomerular filtration 180 L ltrate/day

2.

Tubular reabsorption

3.

○ H+, K+ and ammonia secreted into trate ○ Maintains ionic and acid base balance

Nearly 99% of ltrate get reabsorbed by renal tubules Active process

Passive process +

○ Glucose, Na amino acid

Tubular secretion

○ Nitrogenous wastes, H2O

Urine 1-1.5 L/day

Glomerular Filtration/Ultra filtration (Non selective process) th

– 1/5 of cardiac output or 1100-1200 ml blood/min is ltered by kidneys Renal Artery Arterioles

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(i) Endothelium of glomerular blood vessels Filtration membrane

(ii) Basement membrane (iii) Epithelium of Bowman’s capsule Glomerular ltrate (Plasma except proteins)

• Bowman’s capsule have podocytes arranged in intricate manner so as to leave some spaces called slit pores/filtration slits.

• Filtration is due to pressure in the glomerular capillaries.

• Glomerular ltration rate (GFR) = Filtration/min 125 ml/min • Kidney has an ability to regulate GFR.

FUNCTIONS OF THE TUBULES PCT DCT Conditional – Nutrients H2O NaCl H O HCO– Reabsorption HCO3 2 3 NaCl K+ 300 mOsm/L Secretion

H

+

+ K NH3

+ K H

+

H

+

K+

H2O

H2O NaCl Urea

1200 mOsm/L

Parameter Permeable Impermeable Filtrate

Descending limb Water Salt Concentrated

Concentrating limb

Ascending limb Salt Water Diluted

Diluting (Minimum reabsorption) limb

PCT: • Lined by simple cuboidal brush border epithelium.

• Nearly all essential nutrients, 70-80% electrolytes and water are reabsorbed.

• Major site of reabsorption & for selective secretion.

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Excretory Products and Their Elimination

COUNTER CURRENT MECHANISM TO CONCENTRATE FILTRATE Flow of ltrate in different limbs of following structures are opposite direction (Counter current): ○ Loop of Henle ○ Vasa recta Proximity of Henle’s loop and Vasa recta and counter current in them increase osmolarity towards inner medullary interstitium (300 mOsm/L in cortex to 1200 mOsm/L).

Interstitium gradient is caused by NaCl and urea.

NaCl trasported by ascending limb of Henle’s loop exchanged with descending limb of vasa recta and is returned to medullary interstitium by ascending limb of Vasa recta.

Urea which enters in thin part of ascending limb of Henle’s loop is transported back to interstitium by collecting tubule.

This mechanism maintain interstitial concentration gradient that helps in easy passage of water from collecting tubule thereby concentrating ltrate (urine).

VR

HL

300 mOsm/L 600 mOsm/L

Cortex H2O

NaCl

H2O

Urea

900 mOsm/L 1200 mOsm/L

H2O Urea H2O

NaCl

Medulla

• Henle’s loop primarily helps to maintain osmolarity gradient in kidney interstitium.

• Mammals have ability to produce concentrated urine.

REGULATION OF KIDNEY FUNCTION/GLOMERULAR FILTRATION RATE Hypothalamus

JGA

Heart

Low blood volume/ Body fluid volume/ lonic concentration

Low GFR/ Glomerular blood flow/Glomerular blood pressure

Increase blood flow to atria of heart

Activate

Osmoreceptors of hypothalamus to release ADH/Vasopressin from neurohypophysis

JG cells to release renin Angiotensinogen

Work

○ Constrict blood vessels ○ Increase reabsorption of water from DCT (Prevent diuresis) Result

Release of ANF (Atrial natriuretic factor)

Activate

Angiotensin II

Work

Angiotensin I ACE Angiotensionogen converting enzyme

Work

○ Constrict blood vessels ○ Activate adrenal cortex to release aldosterone, that causes reabsorption of + Na and water

Hand Book (Biology)

Vasodilation Result

○ Blood pressure decrease ○ GFR decrease

158

○ Blood volume increases ○ Blood pressure increases ○ GFR increases Increase in blood volume

Result

○ Blood pressure increase ○ GFR increase (Renin-Angiotensin mechanism)

Switch off

Osmoreceptors Suppress

ADH/Vasopressin ANF mechanism acts as a check on Renin-Angiotensin mechanism (RAAS)

CHARACTERISTICS AND COMPOSITION OF URINE Colour - Light yellow pH = 6 Odour - Characteristic Human kidneys can produce urine nearly 4 times concentrated than initial ltrate.

Urea - 25-30 gm/day Various conditions can affect characteristics of urine.

Abnormal constituents of urine

Condition

Indicate

Glucose

Glucosuria

Diabetes mellitus

Ketone bodies

Ketonuria

Diabetes mellitus

Analysis of urine helps in clinical diagnosis of many metabolic disorders as well as malfunctioning of the kidneys.

DISORDERS OF EXCRETORY SYSTEM Disorders

Symptoms or Treatment

Renal calculi

Stone or insoluble mass of crystalised salts (e.g., oxalates)

Glomerulonephritis In ammation of glomeruli of kidney Renal/kidney failure

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Malfunctioning of kidneys lead to accumulation of urea in blood (Uremia), highly harmful, may lead to kidney failure.

Treatment (i) Haemodialysis: Process to remove urea from blood Boon for thousands of uremic patients all over the world.

Blood drained Mix with Heparin Pumped from artery (Anticoagulant) through

Excretory Products and Their Elimination

Anti coagulant

Mix with

Clear blood

Pumped back to body through

Composition of dialysing fluid is same as plasma except the nitrogenous wastes

Accessory structure Lungs

Filtration based on concentration gradient Nitrogenous wastes freely move out

Dialysing unit Artificial kidney Porous cellophane tubes surrounded by dialysing uid

Vein (ii) Kidney transplantation Ultimate method in correction of acute renal failure ○ Functional kidney is taken from donor ○ To minimize rejection, close relatives are preferred as donor ○ Modern clinical problems have increased success rate of such complicated techniques

ROLE OF OTHER ORGANS IN EXCRETION Remove Basic work CO2, water

○ Remove large amount of CO2 approximately 200 mL/min ○ Remove signi cant quantity of water

Liver (Largest gland)

Bilirubin, vitamins biliverdin, drugs cholesterol, degraded steroid hormones

○ Remove large amount of CO2 approximately 200 mL/min ○ Remove signi cant quantity of water

Skin ○ Sweat gland

Sweat contains ○ NaCl ○ Urea ○ Lactic acid

○ Primary function of sweat is to facilitate cooling effect on body surface

○ Sebaceous gland

Sebum contains ○ Sterols ○ Hydrocarbons ○ Waxes

○ Sebum provides a protective oily covering for the skin

Salivary glands

○ Small amount of nitrogenous wastes are eliminated through saliva

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Chapter

20 Locomotion and Movement

LOCOMOTION AND MOVEMENT Locomotion ○ Voluntary movements resulting in change in place/location.

Locomotion is performed by organisms for variable reasons e.g., ○ Habitats ○ Demand of situation like search of food, mate, breeding ground, escape from enemies/predators Movement ○ Signi cant feature of living beings.

Move body parts but do not change in position.

TYPES OF MOVEMENT/LOCOMOTION Type

Structure

Examples and functions

Amoeboid

Pseudopodia involve micro laments and streaming of protoplasm

○ Leucocytes, macrophages, Amoeba

Ciliary

Cilia

○ Removing dust particles from trachea ○ Passage of ova through female reproductive tract

Flagellar

Flagella

○ Maintenance of water current in canal system of sponges ○ Locomotion in Euglena ○ Swimming of spermatozoa

Muscular

Muscles

○ Movement of limbs, jaws, tongue ○ Running, walking, climbing, ying

• All locomotions are movements but all movements are not locomotion.

• Paramoecium - Cilia helps in movement of food through cytopharynx and in locomotion as well.

• Hydra - Tentacles are used for capturing of prey & also for locomotion.

• Locomotion requires a perfect coordinated activity of muscular, skeletal and neural systems.

MUSCLES Muscle tissue: Mesodermal in origin.

40-50% of body weight of a human adult is contributed by muscles.

Properties: ○ Excitability ○ Contractility ○ Extensibility ○ Elasticity Many cardiac muscle cells assemble in branching pattern to form a cardiac muscle.

Basis

Location

1. Skeletal Classification 2. Visceral of muscles 3. Cardiac

Appearance

Regulation

Example

Striated Non-striated/ smooth Striated

Voluntary Involuntary

Muscles of limbs Inner walls of visceral organs Muscles of heart

Involuntary

SKELETAL MUSCLE FIBRES & ITS TYPES Skeletal muscles are closely associated with the skeletal components of the body.

Skeletal muscles are primarily involved in locomotion and body posture.

Sarcolemma Blood capilary

Muscle bre [Anatomically (muscle cell) unit of Muscle]

Fascicle (muscle bundle) Skeletal muscle Many

Muscle bre bundles/ Fascicles Held by

Many muscle bres

Fascia (collagenous connective tissue)

Sarcolemma (Plasma membrane) Sarcoplasm (cytoplasm) Nucleus (syncitium)

Types Red

White

Myoglobin

Mitochondria

SR

Sarcoplasmic Respiration reticulum (store Ca2+)

• Each muscle bre has many parallelly arranged myo brils/myo laments.

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Mainly Mainly aerobic anaerobic

162

MYOFILAMENTS AND STRUCTURE OF CONTRACTILE PROTEINS

Cross arm

Head

○ Thick

M-line (thin brous membrane)

Locomotion and Movement

ATP binding sites

Actin binding sites

F-actin (2 strands)

Troponin

Myosin (contractile)

Troponin

Meromyosin (MM)

3

LMM (Light)

- Tail

HMM - Head (Heavy) - Short arm

Project outward at regular distance and angle from each other from the surface of polymerised myosin lament and is known as cross arm.

○ Tropomyosin run close to F-actin throughout its length ○ Troponin distributed at regular intervals on tropomyosin ○ Mask active binding sites for myosin on actin laments

○ F-actin helically arranged

Filamentous ‘F’-actin —

Globular ‘G’-actin —

Actin (contractile) Tropomyosin

Z-line (bisect I-band)

○ Thin/actin

Tropomyosin (2 strands)

Typical

Polymer

Monomer

Protein

Held by

Filament

Each myo bril has dark and light bands due to actin and myosin distribution that establish striated appearance.

Light/I-band

Dark/A-band

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MECHANISM OF MUSCLE CONTRACTION/ SLIDING FILAMENT THEORY Contraction of muscle bre takes place by the sliding of the thin filaments over the thick filaments.

A motor neuron + Muscle bres = Motor unit CNS

via

Motor neuron

Release

Neurotransmitter Acetylcholine (Ach)

At Neuromuscular Junction/Motor end plate, action potential is generated in sarcolemma that causes release of Ca2+ in sarcoplasm from SER leading to Ca2+ increase in sarcoplasm Ca2+ binds to troponin subunit (Troponin C), change in its con rmation and unmask active site for myosin binding on actin lament Energised myosin (Myosin – ADP + Pi) binds to actin Cross bridge = Actin-myosin-ADP + Pi Result Shortening/ contraction of sarcomere

○ Pull thin laments toward centre ○ Pull Z-line ○ Length of I-band reduced ○ Length of A-band retained ADP + Pi released from myosin head New ATP binds to myosin head Cross bridge broken ATP hydrolysis on myosin head Cycle repeats Process will continue till Ca2+ pumped back to sarcoplasmic cisternae Z-line return to original position

T-tubules extension from sarcolemma conduct electrochemical impulses.

Repeated activity of muscle leads to accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue.

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Globular head is active ATPase enzyme and has binding sites for ATP and active sites for actin.

Arranged alternately throughout Thin laments make I (Isotropic) the length of myo brils parallel band – Actin. to each other and to longitudinal Thick laments make A (Anisotropic) axis of myo brils. band – Actin + Myosin Sarcomere: Functional unit of contraction between 2 ‘Z’ lines (elastic bres) = 1 A-band + 2 half I-band.

H-zone is non-overlapped part of thick lament by thin laments.

Z-line A band

I band

H-zone Sarcomere

SKELETAL SYSTEM Signi cant role in movement shown by the body.

Framework of 206 bones & few cartilages.

Principle division ○ Appendicular skeleton ○ Axial skeleton Axial skeleton (Bones-80) Bones distributed along main axis Structure 1 13 12 11 10

2 3 4 5 6 7 8 9

1. Frontal bone 2. Sphenoid bone 3. Ethmoid bone 4. Lacrimal bone 5. Nasal bone 6. Zygomatic bone 7. Maxilla 8. Mandible 9. Hyoid bone 10. Occipital condyle 11. Occipital bone 12. Temporal bone 13. Parietal bone

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Bones No. Name of bones Typical feature or included basic function 8 1-Frontal 1-Occipital -Protect brain Cranium 2-Parietal 1-Ethmoid -Articulates with 2-Temporal 1-Sphenoid superior region of vertebral column by 2 occipital condyles (Dicondylic skull) Facial

14 2-Nasal 1-Mandible -Form front part 2-Lacrimal 2-Maxilla of skull 2-Zygomatic 5-Others

Hyoid

1 1-U-shaped

Ear ossicles

6 2-Malleus 2-Incus 2-Stapes

Locomotion and Movement

-Present at the base of buccal cavity -Present in the middle ear

Bones No. Name of bones included Vertebral Column Dorsal 26 7-Cervical 12-Thoracic Vertebrae 1 5-Lumbar (serially 1-Sacral-Fused arranged 2 1-Coccygeal-Fused units) Structure

3

6 5 4

Sternum Ribs

1. Cervical vertebra 2. Thoracic vertebra 3. Lumbar vertebra 4. Coccyx 5. Sacrum 6. Intervertebral disc

Chest bone True ribs

1 1-Flat bone 24 14-Vertebrosternal

False ribs

6-Vertebrochondral

Floating ribs

4-Vertebral

Typical feature or basic function -Main framework of trunk -Protects spinal cord -Supports head -Point of attachment of ribs and muscles of back

-On ventral, midline of thorax -Attach dorsally to vertebrae and ventrally to sternum with hyaline cartilage -Not directly attached to sternum but to 7th rib with hyaline cartilage (8th to 10th pair) -Not connected th ventrally (11 and 12th pair) • All ribs are bicephalic thin at bones i.e., they have 2 articulating ends on dorsal side Rib cage = Vertebral column + Sternum + Ribs

• 1st vertebra is atlas that articulates with occipital condyles.

• 7 cervical vertebrae exist in almost all mammals.

• Neural canal of vertebrae - Site from where spinal cord passes.

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APPENDICULAR SKELETON (BONES - 126) Consists of bones of limbs (30 × 4 = 120) and girdles (6) Pectoral girdle & upper arm

Pelvic girdle & lower arm

Half of girdle

Pubus Ischium

Coxal bone

Ilium Clavicle (Collar) bone

Scapula (Between 2nd & 7th ribs)

Humerus

Femur (longest bone)

Patella

Radius

Palm

Knee (Ventral)

Tibia Fibula

Ulna Wrist

Thigh

Carpals (8)

(7) Tarsals

Metacarpals (5)

Metatarsals Ankle

Digits

Phalanges (14)

Fingers

• Girdles helps in the articulation of limbs with axial skeleton.

• Scapula, a dorsal triangular at bone, have elevated ridge/spine, expanded to form acromion process that articulates with clavicle.

• Glenoid cavity in scapula articulates with humerus head to form shoulder joint.

• Acetabulum, formed by fusion of ilium, ischium and pubis, articulates with femur to form hip joint.

• 2 halves of pelvic girdle meet ventrally to form pubic symphysis containing fibrous cartilage.

JOINTS They are essential for all types of movements involving bony parts of the body.

Point of contact between bones or bones and cartilages.

Force generated by muscle is used to carry out movement through joint, where joint acts as fulcrum.

Types of joints:

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Locomotion and Movement

Types

Bones joined by

Movement

Fibrous

Dense brous Do not allow connective tissue any movement

Cartilaginous Fibrous cartilage Limited movement Fluid lled Considerable synovial cavity movement, helps between 2 bones in locomotion and many other movements

Synovial

Examples Flat skull bones fused end to end via sutures to form cranium Adjacent vertebrae Humerus & pectoral girdle (Ball and socket joint) Knee joint (Hinge joint) Atlas & axis (Gliding joint) Between carpals (Gliding joint) Carpal & metacarpal of thumb (Saddle joint)

DISORDERS Disease

Causes

Impact

Myasthenia gravis

Autoimmunity

○ Affect neuromuscular junction ○ Fatigue, weakening and paralysis of skeletal muscles

Muscular dystrophy

Genetic

○ Progressive degeneration of skeletal muscles

Tetany

Low Ca2+ in body uid

○ Rapid spasms in muscle (wild contractions) ○ In ammation of joints

Arthritis Gout

Accumulation of uric acid crystals

○ In ammation of joints

Osteoporosis

Age related decreased levels of estrogen

○ Decreased bone mass, increased chances of fracture

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Chapter

21 Neural Control and Coordination

INTRODUCTION Coordination is the process through which two or more organs interact and complement the functions of one another to maintain homeostasis in our body.

The neural system and the endocrine system jointly coordinate and integrate all the activities of the organs so that they function in a synchronised fashion.

SYSTEMS MAINTAINING HOMEOSTASIS Parameters

Neural System

Endocrine System

Integration

Through neurotransmitters

Through hormones

Coordination

Quicker

Slower

Neural system provides an organised network of point to point connections with target cells.

NEURAL SYSTEM Neurons can detect, receive & transmit stimulus ○ Hydra – Network of neurons ○ Insects – Organised neural system with brain and ganglia ○ Vertebrates – Well developed neural system HUMAN NEURAL SYSTEM CNS ○ Brain & spinal cord

PNS ○ All nerves of body from brain and spinal cord ○ Nerve fibres of PNS

Afferent Send impulses from tissues/organs to CNS

Efferent Transmit impulses from CNS to peripheral tissues/organs

Somatic neural system Autonomic nervous system Relays impulses from CNS to involuntary Transmit impulses from organs and smooth muscles CNS to skeletal muscles Visceral nervous • Part of Peripheral Nervous System (PNS) system (VNS): • Complex of nerves, bres, ganglia and plexuses • CNS Viscera VNS

NEURON

Parts

Neuron is the structural and functional unit of the neural system.

Composed of a cell body, dendrites and axon.

Types

Axon

Multipolar

1

Bipolar

1

Unipolar

No. of Location Dendrites

Dendrite Cell body Nucleus Nissl’s granules

Schwann cell

2 or more Cerebral cortex

1

1

Retina of eye

0

Embryonic stage

• Cell body contains cell organelles.

• Impulse from dendrite moves towards cell body and in axon away from cell body.

Myelin sheath

Axon Neurotransmitters are stored in synaptic vesicles of Synaptic knobs

Node of Ranvier Axon terminal

TYPES OF AXONS (NERVE FIBRES) Parameters Myelin sheath

Non-myelinated

Yes

No

Yes

No

Cranial & spinal nerves

Autonomic and somatic neural system

Node of Ranvier Location

Myelinated

• Schwann cells surround both myelinated and non-myelinated nerve bres.

• Schwann cells form myelin sheath only in myelinated bres.

CONCENTRATION GRADIENT ACROSS AXONAL MEMBRANE Excitability of neurons is attributed to polarised state of neural membranes.

It has selectively permeable ionic channels responsible for differential concentration gradient across the axonal membrane.

More permeable for K+ Axonal membranes Nearly impermeable to Na+ Impermeable to negatively charged proteins Types of fluids

Composition

ECF

K+ , Na+

ICF

K+ , Na+

Ionic gradients across resting membrane are maintained by the active ICF = Intracellular transport of ions by uid the sodium-potassium ECF = Extracellular pump which pumps uid 3Na+ outwards and 2K+ into the cell

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GENERATION OF IMPULSE The electrical potential difference across the resting plasma membrane is called the resting potential.

The electrical potential difference across the axonal membrane after receiving threshold stimulus is called action potential (nerve impulse).

Events: +++ ––– Resting state

Threshold stimulus Change in permeability of axolemma for Na+

(This state is maintained

by Na+/K+ pump)

––– +++

Na+ in ux

Depolarisation Change in permeability of axolemma for K+

+

+++ –––

K ef ux

Repolarisation

CONDUCTION OF IMPULSE Impulse generated at a site arrives at another site and same sequence is repeated along the length of axon.

Current ows in a circuit when it moves from A to B site.

Flow of charge is from A

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Inner membrane

Outer membrane

B

Neural Control and Coordination

TRANSMISSION OF IMPULSE Nerve impulse is transmitted from one neuron to another across a synapse.

Events: Neurotransmitters released in synaptic cleft Bind to receptors on post synaptic neuronal membrane Opening of ion channels in post synaptic membrane Generates a new potential in post synaptic membrane Types of synapse Features

Electrical synapse

Chemical synapse

Pre & post neuron

Close proximity through gap junctions

Separated by uid- lled synaptic cleft

Flow of impulse

Direct Faster Bi-directional

Through neurotransmitters

Rare

Common

Transmission Directionality Existence

Slower Unidirectional

CENTRAL NERVOUS SYSTEM (CNS) Acts as command & control system of the body Protective ○ Skull converings ○ Meninges

Name of meninx In contact with

Outer Duramater Skull

Middle Inner Arachnoid (Thin) Piamater Brain

Major Divisions of Brain: Divisions Forebrain Midbrain Hindbrain

Major parts Cerebrum, thalamus, hypothalamus Corpora quadrigemina Pons, medulla, cerebellum (PCM)

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Neural Control and Coordination

BRAIN

Brain stem - Midbrain - Pons - Medulla

Regions in cerebral Appearance Composition Fig. Sagittal section of human brain hemisphere Hindbrain Concentrated cell bodies Pons Grey ○ Outer/cortex Myelinated nerve bres White ○ Inner ○ Fibrous tract that connects different regions of the brain

Cerebellum (little brain) Midbrain ○ Convoluted surface to provide more space for neurons Corpora Quadrigemian ○ Coordinate and integrates information received from auditory ○ Located between thalamus/hypothalamus and pons system and semicircular canal ○ 4 lobes on dorsal side between forebrain and pons Medulla oblongata ○ Integrates visual, tactile and auditory inputs ○ Connects brain to spinal cord Corebral Aqueduct ○ Has centres for controlling respiration, cardiovascular ○ Canal passes through midbrain re exes and gastric secretions

Cerebrum ○ Major part of brain ○ Cleft divides it longitudinally into right & left cerebral hemispheres, connected by corpus callosum Thalamus ○ Major coordinating centre for sensory & motor signaling Hypothalamus ○ Lies at base of thalamus ○ Has various centres for controlling body temperature, urge for eating and drinking ○ Several groups of neuro secretory cell which secretes hormones

Forebrain

Brain is central information processing organ of the body.

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Communication

Association areas (Neither sensory nor motor)

Memory

Motor areas

Basic Functions of Brain • Controls the voluntary movements • Controls hunger, thirst • Balance of body • Circadian rhythms • Functioning of vital organs (kidneys, • Human behaviour lungs, heart) • Activities of endocrine • Thermoregulation glands

One afferent neuron (receptor) [sensory organ to CNS] One efferent neuron (effector or exciter) [CNS to effector]

(Detect stimuli)

Sensory receptors

Input

(Process & analyses)

CNS

Output

Parts/Organs (Response to stimuli)

SENSORY RECEPTION AND PROCESSING Sensory organs detect all types of changes in the environment

Re ex arc = stimulus and Response

Re ex pathway arranged in series

Limbic system/Limbic lobe ○ Parts included: Inner part of cerebral hemisphere, hippocampus, amygdala and hypothalamus ○ Functions: • Involved in expression of emotional reaction (e.g., excitement, pleasure, rage, fear) • Motivation • Regulation of sexual behaviour Reflex action and Replex arc Entire process of response to a peripheral nervous stimulation that occur involuntarily and require the involvement of a part of the CNC

Inter sensory associations

Sensory areas

Cerebral cortex includes

SENSE ORGANS Sense organ Nose (single)

Sense Features associated Smell ○ Mucus coated olfactory epithelium having three types of cells. ○ Neurons extend directly into bean sized olfactory bulb that are extensions of limbic system.

Tongue (single) Taste ○ Input from taste buds is conveyed to the brain and a complex avour of food or drink is perceived The chemical senses of gustation (taste) and olfactory (smell) are functionally similar and inter related as they detect dissolved chemicals.

The wall of the eyeball is composed of three layers: ○ External ○ Middle ○ Inner

EYE Middle layer (Choroid) Anterior, opaque, pigmented, visible coloured portion of the eye Iris Regulates the diameter of pupil through its muscle fibres Ciliary Thick anteriorly body Holds the lens in place through ligaments rd

Choroid

Thin over posterior 2/3 part Contains many blood vessels and looks bluish Outer

Between cornea and lens (Thin watery uid) Aqueous chamber

External Layer (Sclera)

Pupil

Anterior–Cornea Posterior–Sclera

Vitreous chamber (Lens & Retina) Transparent gel

Lens

• Transparent • Crystalline

Composition Dense connective tissue

Photoreceptor cells Types: Rods & cones Middle Bipolar cells Inner Ganglion cells Fovea Only cones are densely packed Thinned central portion of retina Point with greatest visual acuity or resolution Blind

Retina (Inner most layer)

spot (No photoreceplor cells) Optic nerve (Retinal blood vessel enter it at a point medial to and slightly above the posterior pole of eye ball and leave the eye)

Macula lutea – Yellowish pigmented spot lying at the posterior pole of eye lateral to the blind spot with a central pit called fovea centralis.

Photopigments Photoreceptor Vision (light sensitive proteins) cells Rods Twilight/Scotopic Rhodopsin/Purplish red protein/visual purple vision Cones Types of cones Day light/ Photopic vision ○ Different photopigments and Colour in these cones Red vision ○ Sensation of different colours Green by various combinations Blue ○ Equal stimulation of these gives sensation of white light Photopigments contain an aldehyde of vitamin A/retinal and protein, opsin.

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Neural Control and Coordination

Opsin

MECHANISM OF VISION Focuses light rays

Visible light Enter Cornea rays Change in membrane permeability

Optic nerve

Lens

Generate potential difference in photoreceptor cells Visual cortex

Anatomical Divisions Components: ○ Fine hair and wax glands are present in their skin ○ Pinna gathers/ collects the vibrations in the air External auditory meatus/canal extends inwards upto tympanum • Tympanic membrane is composed of • Ear ossicles – Structural details – Function

(change in structure)

Photo sensitive Contain Rhodopsin cells dissociates into Retinal

transmitted to

Generate action potential sent

Impulse

Bipolar forward to Ganglion cells cells Brain analysed image formed on retina based on earlier memory and experience

EAR Outer Ear Middle Ear Internal Ear Pinna + Ear canal Malleus Incus Stapes Labyrinths Temporal M I S Vestibular Pinna bone apparatus Cochlea Cochlea nerve

Tympanic membrane (eardrum)

Eustachian tube ○ Connects middle ear cavity to the pharynx ○ Equalises pressure on either side of tympanum

Connective tissue covered with skin on the outside Mucus membrane on the inside Arranged in a chain (M I S) Malleus is attached to tympanum Stapes is attached to the oval window Increase efficiency of transmission of sound waves to the inner ear

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INTERNAL EAR It is a fluid filled inner ear, consists of two parts: Bony and Membranous labyrinths Encloses Bony Labyrinth ( lled with perilymph)

Membranous Labyrinth ( lled with endolymph) Receptors

Parts of Membranous labyrinth

Sub-parts

○ Vestibular apparatus (complex system above the cochlea)

(a) Semicircular canals (3)

Crista ampullaris (Hair cells)

Macula is the sensory Utricle Saccule part of utricle and saccule. (b) Otolith organ

○ Cochlea (coiled appearance)

Sensory hair cells in organ of Corti

Basic functions

○ Maintenance of balance of the body and posture ○ In uenced by gravity and movements

○ Hearning

• Semicircular canals (surrounded by perilymph) lie at right angle to each other and the base of each canal is swollen called ampulla.

COCHLEA Membrane Reisnners Basilar

Chambers

Fluid

Final region

Scala vestibuli

Perilymph

Oval window

Scala media Scala tympani

Endolymph Perilymph

Round window

Organ of Corti Reissner’s Located on Basilar membrane membrane Contains sensory hairs present in Scala rows on internal side of organ of media Scala Corti, that act as auditory receptors. vestibuli Sensory hair cells Organ ○ Apical part – Possess stereocilia of Cortil ○ Above them there is thin elastic Tectorial membrane called Tectorial membrane membrane Basilar Scala tympani ○ Basal part – is in close contact membrane with afferent nerve bres Fig.: Sectional view of cochlea forming the auditory nerve

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Neural Control and Coordination

MECHANISM OF HEARING Ear converts sound waves into neural impulses.

The cerebellum integrates information received from the semicircular canals of the ear and the auditory system.

Sound waves Received by extends inwards

External ear Auditory Impulse is analysed and sound is recognised cortex

Ear drum

Vibrations transmitted through

Ear ossicles

Oval window Generate waves in

Transmit impulse to

Perilymph

Auditory nerve transmitted further to

Transmits vibrations to

Induce

Afferent neurons

Generates impulses in

Hair cells of cochlea against tectorial membrane

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Ripples in the basilar membrane

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22

Chapter

Chemical Coordination and Integration INTRODUCTION Significance: As the nerve fibres do not innervate all cells of the body and the cellular functions need to be continuous regulated, hence the role of endocrine system (carried out by hormones) is integrated with neural system.

ENDOCRINE GLANDS AND HORMONES secrete

Endocrine glands (Ductless glands)

Hormones Invertebrates (few hormones) Endocrine system form

Together regulate physiological functions in the body

& Neural system

HORMONES

(Point to point rapid coordination)

Vertebrates (many hormones)

Classical definition of hormone: Chemical produced by endocrine glands and released into the blood and transported to a distinctly located target organ.

Scientific definition of hormone: Non-nutrient chemical Act as inter cellular messenger Produced in a trace amounts

HUMAN ENDOCRINE SYSTEM Hypothalamus Pineal Pituitary Thyroid and Parathyroid Thymus Pancreas Adrenal

Testis (in male) Ovary (in female)

Bio-PC22-1

Fig.: Location of endocrine glands Other organs with diffused tissues and cells secrete hormones: Gastrointestinal tract, heart, liver and kidneys

HYPOTHALAMUS AND PITUITARY GLAND Hypothalamus contains several groups of neurosecretory cells called nuclei which produce hormones that regulate synthesis and secretions from pituitary gland enclosed in bony cavity, Sella tursica.

Types of Hypothalamic Hormones Target Example Released hormone Releasing hormone Pituitary Gonadotrophins GnRH Inhibiting hormone Somatostatin Pituitary Absent

Hypothalamic neurons Connected through stalk but not via portal circulation

Hypothalamus Connected through Portal circulation

Posterior pituitary Anterior pituitary

Stalk Stores and releases hypothalamic hormons

Pars distails

Pars intermedia (Merged in humans)

Adenohypophysis

Pars nervosa

Neurohypophysis

Adenohypophysis Hormones of Pituitary Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH)

Basic Function Growth of body Synthesis and secretion of thyroid hormones by thyroid gland

Follicle stimulating hormone (FSH) Gonadotrophins (stimulate gonadal activity) FSH+LH Luteinising hormone (LH)

Synthesis and secretion of steroid hormones from adrenal cortex Male – Regulates spermatogenesis with androgens Female – Stimulates growth and development of ovarian follicles Male – Stimulates the synthesis and secretion of androgens Female – Induces ovulation of full mature Graafian follicle, maintains corpus luteum

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Prolactin

Regulates the growth of the mammary glands and formation of milk in them

Melanocyte stimulating hormone (MSH) by pars intermedia

Acts on the melanocytes of skin and regulates pigmentation of skin Neurohypophysis ○ Acts on smooth muscles and stimulates their contraction ○ Stimulates vigorous contractions of uterus at the time of child birth ○ Milk ejection from mammary glands

Oxytocin

Vasopressin/ADH/Antidiuretic hormone

○ Acts at kidney and stimulates resorption of water and electrolytes by the distal tubules ○ Reduces loss of water through urine (Diuresis) Disorders

Disease Pituitary dwarfism

Age –

Cause

Symptoms

Hyposecretion of GH

Stunted growth

Gigantism

–

Hypersecretion of GH

Abnormal growth of the body

Acromegaly

Middle age –

Hypersecretion of GH

Severe disfigurement especially of face

Hyposecretion of ADH

Diminished ability of the kidney to conserve water leading to water loss and dehydration

Diabetes insipidus

Acromegaly Serious complications of hypersecretion of GH in middle age can leads to premature death if unchecked. The disease is hard to diagnose in early stages and often goes undetected for many years, until changes in external features become noticeable.

PINEAL GLAND Location: Dorsal side of forebrain Hormone released: Melatonin Basic functions ○ Regulate 24 hours diurnal rhythm of our body (sleep wake cycle) ○ Influence body metabolism, temperature, pigmentation, menstrual cycle and defense capabilities

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Chemical Coordination and Integration

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Trachea

Thymus

Parathyroid glands

Thyroid

Parathyroid

Thyroid

Vocal cord

Thyroid

○ Lobular structure located between lungs behind sternum on ventral side of aorta • Degenerates in old age so immune responses become weak

○ Back side of the thyroid gland • Thyrocalcitonin and parathormone play a significant role in calcium homeostasis

1

4

Thymosins (peptide hormones)

Parathyroid hormone/PTH (peptide hormone)

○ Play a role in differentiation of T-lymphocytes, thus provide cell mediated immunity ○ Promote production of antibodies thereby providing humoral immunity

○ Increase level of Ca2+ (hypercalcemic) ○ Acts on bones and stimulates the process of bone resorption (dissolution/demineralisation) ○ Stimulates the reabsorption of Ca2+ by the renal tubules ○ Increases Ca2+ absorption from digested food

Number Hormones Basic functions Location/Functure ○ Regulate basal metabolic rate (BMR) 1 ○ Side of trachea T4 (thyroxine) or tetraiodothyronin ○ Control metabolism of carbohydrates, ○ Bilobed structure connected T3 (triodothyronine) proteins and fats through a thin ap of connective ○ Maintain water and electrolyte balance tissue called isthmus ○ Regulate development and maturation ○ Consists of follicles made up of of CNS follicular cells enclosing a cavity, ○ Support process of RBC formation in stromal tissue (erythropoiesis) and regulates • Iodine is essential for the normal menstrual cycle rate of hormone synthesis in the 2+ thyroid gland Thyrocalcitonin Regulates blood Ca levels (TCT) (Protein hormone)

GLANDS OF THORACIC REGION

DISORDERS OF THYROID GLAND Hypothyroidism • Iodine deficiency in diet during pregnancy and after birth 1. Goitre: Enlargement of thyroid gland 2. Cretinism: Stunted growth, mental retardation, low intelligence quotient abnormal skin and deaf-mutism 3. In adult women, menstrual cycle can become irregular

Hyperthyroidism • Cancer of the thyroid gland • Development of nodules of the thyroid gland 1. Exopthalmic goitre or Graves’ disease: • Enlargement of thyroid gland • Protrusion of eyeballs • Increase in BMR and weight loss

ADRENAL GLAND One pair located on anterior part of kidney Hormone

Adrenal cortex

Zona glomerulosa Main Glucocorticoid (Outermost layer) is cortisol

Functions ○ Stimulates gluconeogenesis, lipolysis and proteolysis

○ Inhibit cellular uptake and utilisation of amino acids, maintains the cardiovascular system and the kidney functions ○ Produces anti-in ammatory reactions and suppresses immune response ○ Stimulate glomerular ltration rate ○ Stimulate RBC production

Zona fasciculata Major Mineralocorticoid ○ Stimulates reabsorption of + (middle layer) is aldosterone Na and H2O and excretion + – of K and PO4 ions, thus helps in maintenance of electrolytes, body uid volume, osmotic pressure and blood pressure Zona reticularis (inner layer)

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Androgenic steroid

○ Play a role in growth of axial hair, pubic hair and facial hair during puberty

Chemical Coordination and Integration

Adrenal

Disorder Addison’s disease

cortex

Adrenal medulla Adrenal medulla (Centrally located)

Cause Underproduction of hormones of adrenal cortex

Hormone Adrenaline/ epinephrine Nor-adrenaline/norepinephrine Catecholamines or Emergency/ ght/ ight hormones

Characteristic Alters carbohydrate metabolism causing acute weakness and fatigue

Functions ○ Increase alertness, pupilary dilation, piloerection, sweating ○ Increase heart beat, the strength of heart contraction and the rate of respiration ○ Stimulate breakdown of glycogen resulting in an increased concentration of glucose in blood ○ Increase breakdown of lipids and proteins

PANCREAS Pancreas: A composite gland whose main hormones is to maintain glucose homeostasis Endocrine part Exocrine part (1 to 2 million) Islets of Langerhans Major cells (1-2% of pancreatic tissue) -cells

-cells peptide hormones

Target Stimulates Blood glucose level Glucose uptake and utilisation by cells

Glucagon Insulin Hepatocytes Hepatocytes, Adipocytes Glycogenolysis, gluconeogenesis Glycogenesis Hyperglycemic

Hypoglycemic

DISORDER Diabetes mellitus – Caused by prolonged hyperglycemia Characteristics – Loss of glucose in urine, Ketone bodies formation Treatment – Insulin therapy

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Primary sex organs: Form gametes and secrete hormones

GONADS Parameter

Male (Testis)

Location

Scrotal sac (outside abdomen)

Structure responsible

Leydig cells/ interstitial cells

Steroid Androgens mainly hormone testosterone Function • Development and maturation of male accessory sex organs.

• Stimulate spermatogenesis.

• Acts on CNS and in uence male sexual behaviour (libido).

• Stimulate muscular growth, growth of facial and axillary hair, aggressiveness and low pitch of voice.

• Produce anabolic (synthetic) effects on protein and carbohydrate metabolism

Female (ovary) in abdomen Ovarian follicles Corpus luteum

Estrogen

Progesterone

• Growth and activities • Supports of female secondary pregnancy sex organs • Stimulates • Stimulate development formation of of growing follicles alveoli (store • Regulate sexual milk and behaviour secretion of • Appearance of milk) secondary sex characters like mammary gland development, high pitch etc.

HORMONES OF HEART, KIDNEY AND GASTROINTESTINAL TRACT Organ Peptide hormone Heart ANF

Tissue Atrial wall

Juxtaglomerular Kidney Erythropoietin cells (JG cells) Endocrine cells in GIT Gastrin different parts of gastro-intestinal tract GIP/gastric inhibitory peptide Cholecystokinin

Secretin

Non-endocrine tissue

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Growth factors

Basic function When blood pressure increases, it dilates blood vessels to reduce blood pressure Stimulates erythropoiesis Acts on gastric glands and stimulates secretion of HCI and pepsinogen Inhibits gastric secretions and motility Acts on exocrine part of pancreas and gall bladder to stimulate secretion of pancreatic enzymes and bile juice Acts on exocrine part of pancreas and stimulates secretion of water and bicarbonates Essential for normal growth, repair and regeneration of tissues

Chemical Coordination and Integration

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Genome and regulate gene expression and chromosome functions

Hormone receptor complex (HR complex)

Generate

Results in physiological and developmental effects

Cumulative effect

Bind to

2+

Second messengers cAMP, IP3, Ca , etc.

Extracelluar/Membrane bound receptors

• Brings biochemical changes in target tissue

Interact with

Intracellular/Nuclear receptors

Bind to

Fig.: Mechanism of action of a protein hormone

Intercellular receptor

Epinephrine Amino acid derivatives Peptide, Polypeptide, Protein Insulin, glucagon, pituitary and hypothalamic hormones etc.

Based on chemical nature

Classification of Hormones

MECHANISM OF HORMONE ACTION Hormone receptors are located in the target tissue only Each receptor is specific to one hormone only Most intracellular receptors are present in the nucleus Steroid hormones and iodothyronines enter the target cell Hormones acting through extracellular receptors do not enter the target cell

Cortisol, testosterone, estradiol, progesterone Steroids Iodothyronines Thyroid hormones

Fig.: Mechanism of action of a steroid hormone

Intracellular receptor

1

Chapter

Reproduction in Organisms INTRODUCTION

TYPES OF REPRODUCTION Parameters Number of parents

Asexual One (uniparental)

Gamete formation Gamete fusion Type of cell division Conditions for occurrence Nature of offsprings Examples

Yes No Mitotic Mostly favourable Identical to parent Hydra, Planaria Simple process

Advantage

Rapid/faster

Sexual One (Uniparental) - Taenia or Two (Biparental) - Periplaneta Yes Yes Meiotic and mitotic Both favourable and unfavourable Mostly non-identical offsprings Pheretima Contributes to evolution significantly through genetic recombination High adaptability

Parameters Disadvantages

Asexual No contribution to evolution as genetic Complex recombination/crossing over is absent Low adaptability

Sexual Elaborate Expensive

Slower process

Clone: Morphologically and genetically similar individuals produced asexually.

Cell division is in itself a mode of reproduction in unicellular organisms e.g.: Amoeba, Paramecium.

TYPES OF ASEXUAL REPRODUCTION

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Asexual Reproductive structure Zoospores

Fungi and Algae

Conidia

Penicillium

Buds

Hydra

Gemmules

Sponge

Bulbils

Agave

In plants, the term vegetative reproduction is used for asexual reproduction.

Vegetative propagules in Angiosperm 1. Eyes of potato 2. Rhizome of ginger 3. Bulbil of agave 4. Leaf buds of Bryophyllum 5. Offset of Water hyacinth

Water hyacinth is called Terror of Bengal 1. Most invasive weeds fast growing in the standing water 2. Introduced in India due to beautiful flowers and leaves 3. Drains oxygen from the water and leads to the death of fishes 4. Difficult to get rid of them due to the propagation at phenomenal rate

Bamboo species flower only once in their life time after 50-100 years Strobilanthus kunthiana flowers once in 12 years, last during September October 2006.

Parthenogenesis Absence of gamete fusion/syngamy.

Female gamete develops into new organism without fertilisation Examples: Rotifers, honey bees, some lizards, birds (turkey).

Sexual Reproduction Remarkable fundamental similarity occur in process of sexual reproduction among different organisms despite different structures for reproduction.

Reproductive processes and associated behaviours are regulated by hormones and environmental factors.

Events Associated Pre-fertilisation events (a) Gametogenesis (b) Gamete transfer 3

Reproduction in Organisms

Gametogenesis

Formation of gametes Meiocytes: Gamete forming diploid cells/gamete mother cells.

Gametes are haploid in nature i.e. receive only one set of chromosomes at the end of meiosis.

A haploid parent produces gametes by mitotic divisions (Monerans, Fungi, Algae, Bryophytes).

A diploid parent produces haploid gametes by meiosis (Pteridophytes, Gymnosperm and Angiosperm) Name of organism Humans House fly Rat Dog Cat Fruit fly Butterfly

Chromosome number Chromosome number in meiocyte (2n) in gamete (n) 46 23 12 6 42 21 78 39 38 19 8 4 380 190

Types of gametes (Basis: Morphological and physiological difference) Homogametes/Isogametes Same (Cladophora)

Heterogametes Different (Fucus)

Heterogametes Parameters

Female

Male

Size

Big

Small

Motility

No

Yes

Chromosome number

Same

Same

Food storage

Yes

No

Number

Less

More Ovum

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Types of organisms Unisexual Bisexual (Hermaphrodite) Homothallic and monoecious used Heterothallic and dioecious used for plants for plants Leech Cockroach Earthworm Papaya and date palm Sponges Cucurbits, Chara and Coconut Gamete transfer: Enables bringing together of ♂ and ♀ gametes physically leading to fertilisation.

Internal fertilisation External fertilisation Fertilisation occurs inside ♀ Fertilisation occurs in water reproductive tract Mostly terrestrial organisms Mostly aquatic organisms e.g. Reptiles, mammals and majority e.g. Bony fishes, amphibians and of plants majority of Algae Disadvantages Limited number of progeny.

Offsprings are extremely vulnerable to predators threatening their survival to adulthood.

Great synchrony required between ♀ and ♂ during external fertilisation to enhance chances of fertilisation.

Heterogametes are present in majority of sexually reproducing organisms.

Fertilistion Most vital event of sexual reproduction is fusion of gametes called syngamy resulting in formation of diploid, single celled structure In seed pants, pollen grains are the carrier of the male gametes. A specialised events called pollination facilitates the transfer of pollen grains to the stigma.

Successful transfer and coming together of gametes is essential for the most critical event in sexual reproduction, the fertilisation.

ZYGOTE Vital connecting link ensuring continuity of species between generations.

Location of development of zygote Oviparous animals ● Outside the ♀ body ● Protected by calcareous shell ● Lesser parental care 5

Reproduction in Organisms

Viviparous animals ● Inside the ♀ body ● Absent ● Greater parental care The chances of survival of young ones is greater in viviparous organisms.

Post Fertilisation Embryogenesis: Process of development of embryo from the zygote through mitotic cell divisions help increase number of cells and cell differentiation helps in formation of specialised tissues and organs.

In flowering plants, Zygote develops in the embryo, ovule into seed, ovary into fruit which has thick wall called pericarp that is protective in function.

After dispersal, seeds germinate to produce new plants. ● End of reproductive phase is a parameter of senescence ● Slowing of metabolism ● Ultimately leads to death

BREEDING SEASON Time duration when mating occurs Parameters

Continuous breeders

Seasonal breeders

Breeding time

Throughout the year

Specific breeding season

Examples

Primates, Hens Elephant, Birds in wild, (poultry birds in captivity) Horse, Cow, Goat

REPRODUCTIVE CYCLES IN PLACENTAL MAMMALS Cyclical changes during reproduction Parameters

Oestrous cycle

Characteristic of Non-primate mammals Examples

Menstrual cycle Primates

Cows, deer, sheep, rats, Humans, apes, monkeys dogs, tiger qqq

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Chapter

2 Sexual Reproduction in Flowering Plants

INTRODUCTION u

All flowering plants show sexual reproduction.

u

Several hormonal and structural changes differentiate & develop the floral primordium, which form inflorescences, bear floral buds and then the flowers.

PRE-FERTILISATION–STRUCTURES AND EVENTS Stamen, Microsporangium and Pollen Grain ● Androecium, consists of a whorl of stamens, representing the male reproductive organ.

Filament ● It is a long slender stalk. ● The proximal end of the filament is attached to the thalamus or the petal of the flower. ● The number & length of stamens are variable in flowers of different species.

Anther ● Terminal generally bilobed structure. ● Each lobe having two theca i.e, dithecous. ● Often a longitudinal groove runs lengthwise separating the theca.

● The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners two in each lobe. ● The microsporangia develop further & become pollen sacs. They extend longitudinally all through the length of an anther and are packed with pollen grains.

STRUCTURE OF MICROSPORANGIUM ● In a T.S., a typical microsporangium appears near circular, it is generally surrounded by four wall layers.

FOUR ANTHER WALL LAYERS

● The outer 3 wall layers perform the function of protection and help in dehiscence of anther to release the pollen. ● Tapetum: Innermost wall layer. It nourishes the developing pollen grains. Cells of tapetum possess dense cytoplasm & have more than one nucleus. ● Sporogenous tissue: Compactly arranged homogenous cells; occupies the centre of each microsporangium.

MICROSPOROGENESIS ● Microsporogenesis is a process of formation of microspores from PMC (Pollen Mother Cell).

● As the anthers mature and dehydrate, the microspores dissociate from each other & develop into pollen grains.

POLLEN GRAIN ● Represent the male gametophytes. ● It has prominent two layered wall-exine and intine.

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Vegetative Cell

2-called stage

● Bigger, has abundant food reserve & a large irregularly shaped nucleus.

Exine ● Outer hard layer, made of sporopollenin. ● Has germ pores where sporopollenin is absent

Generative Cell ● Small, floats in the cytoplasm of vegetative cell; spindle shaped with dense cytoplasm and a nucleus.

Intine ● Inner wall layer, thin continuous, made of cellulose and pectin. ● Sporopollenin is one of most resistant organic material known. It can withstand high temperature, strong acids & alkali. No enzyme that can degrade it is known. Pollen grains are well preserved as fossil due to it. ● Pollen grains are generally spherical; measuring 25-50 mm in diameter. ● In over 60% of angiosperm, pollen grains are shed at 2-celled stage, in the 40% species, generative cell divides mitotically to give rise to two male gametes before pollen grains are shed (3-celled stage). ● Pollen grains of many species cause severe allergies, chronic respiratory disorders, asthma, bronchitis etc. e.g., Parthenum (carrot grass) came to India as a contaminant with wheat, became ubiquitous in occurrence & causes pollen allergy. ● Pollen grains are rich in nutrients. Pollen tablets and syrups has been claimed to increase performance of athletes & race horses. ● Pollen Viability: Highly variable, Depends on temperature and humidity.

In some cereals like rice and wheat, pollen grains lost viability within 30 minutes.

In some members of Rosaceae, Leguminoseae and Solanaceae, viability can be for month. ● It is possible to store pollen of a large number of species for years in liquid nitrogen (–196°C) in pollen banks for crop breeding programmes.

PISTIL, MEGASPORANGIUM (OVULE) AND EMBRYO SAC ● Gynoecium represents female reproductive part. Gynoecium may consist of single pistil (monocarpellary) or may have more than one pistil (multicarpellary). It may be free (apocarpous) eg. Michelia or fused (syncarpous), e.g. Papaver.

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Sexual Reproduction in Flowering Plants

● Each pistil has three parts Stigma: Landing platform for pollen grains.

Style: Elongated slender part below stigma Ovary: Basal bulged part of pistil, has ovarian cavity (locule).

Placenta is located inside ovarian cavity. Megasporangia called ovules arise from placenta. ● One ovule in ovary e.g., Wheat, paddy, mango. ● Many ovule in ovary e.g., Papaya, watermelon, orchids. ● Pollen germination can be studied by dusting pollen on glass slide with 10% sugar solution.

Stigma

Style

Anatropous ovule Ovary Thalamus

Megasporangium (Ovule) ● In embryo sac, 3 celled egg apparatus, at micropylar end, (1 egg cell & two synergids with filiform apparatus, which guide pollen tube into the synergid), 3 antipodals at chalazal end and a large central cell, with two polar nuclei remain present. ● Embryo sac formation from single megaspore is termed monosporic development.

Megasporogenesis ● Process of formation of megaspores from megaspore mother cells. ● Ovules generally differentiate a single megaspore mother cell (MMC) in micropylar region of nucellus.

Meiosis ● MMC 4 megaspores.

(2n) (n) 10 Hand Book (Biology)

Female Gametophyte/Embryo sac ● In majority of flowering plants, one megaspore remains functional and 3 degenerate. ● The functional megaspore develops to the female gametophyte (embryo sac). ● The nucleus of functional megaspore undergoes free-nuclear mitotic divisions to form two nuclei which move to opposite pole. Two more sequential mitotic divisions result 8-nucleate stage, after that cell walls are laid down to form the typical 7-celled-8 nucleate female gametophyte or embryo sac.

POLLINATION Transfer of pollen shed from anther to sigma of a pistil. Pollination can be divided into three types

Autogamy ● Pollination is achieved within same flower, i.e., transfer of pollen from anther to the stigma of same flower. ● It requires synchrony in pollen release and stigma receptivity. ● Cleistogamous flowers (which do not open) are invariably autogamous, eg. Viola (common pansy), Oxalis & Commalina and provide assured seed set even in absence of pollinators. ● These species also produce chasmogamous flowers (with exposed anther and stigma) for cross-pollination.

Geitonogamy ● Transfer of pollen grams from anther to stigma of another flower of the same plant. ● It is functionally cross pollination involving pollinating agents, genetically it is similar autogamy, since the pollen grains come from the same plant

Xenogamy ● Transfers of pollen grains from anther to the stigma of a different plant. ● This is the only type of pollination which brings genetically different types of pollen grains on the stigma.

AGENTS OF POLLINATION Abiotic Agents

Pollen coming in contact with stigma is a chance factor in both wind and water pollination, flowers produce enormous amount of pollen when compared to number of ovules available for pollination. It is to compensate loss of pollen grains.

11 Sexual Reproduction in Flowering Plants

Wind pollination ● Requires light, non-stickly pollen so that they can be transported by wind currents. Well exposed stamens and large often feathery stigma to trap air borne pollen, single ovule in each ovary and numerous flowers in an inflorescence Tassels in corn to trap pollen. ● Quite common in grasses. ● Pollination by wind is more common among abiotic pollinations.

Water pollination ● Pollination by water is quite rare, limited to 30 genera, of monocotyledons e.g. Vallisneria, Hydrilla, Zostera (sea grass). ● In majority of aquatic plants like water hyacinth and water lily, flowers emerge above water & are pollinated by insects or wind. ● In Vallisneria, pollination takes place on the surface of water (epihydrophily). In sea grasses, it takes place below water (hypohydrophily) ● In most water-pollinated species, pollen grains are protected from wetting by a mucilaginous covering.

Biotic Agents ● Majority of flowering plants use a range of animals as pollinating agents-Bees, butterflies, flies, beetles, wasps, ants, moths, birds (sunbirds & humming birds) & bats. ● Among animals, insects particularly bees are dominant pollinating agents. ● Some primates (lemurs), arboreal (tree dwelling), rodents or even reptiles (gecko lizard & garden lizard) are also pollinators in some species ● Insect-pollinating flowers are large, colourful, fragnant and rich in nectar. Small flowers are clustered in inflorescence to make them conspicuous. ● Flowers pollinated by flies & beetles secrete foul odours to attract these animals. ● Nectar & pollen grains are usual floral rewards. ● In some species, floral rewards are in providing safe places to lay eggs, eg, Amorphophallus. A species of moth and Yucca-cannot complete their life cycles without each other.

OUTBREEDING DEVICES ● Flowering plants have developed many devices to discourage self pollination and to encourage cross pollination. For example: Pollen release and stigma receptivity are not synchronised.

Anther and stigma are placed at different positions so that pollen cannot come in contact with stigma of the same flower.

12 Hand Book (Biology)

Self-incompatibility is a genetic mechanism which prevents self­ pollen from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.

Production of unisexual flowers. ● In castor & maize, (monoecious) autogamy is prevented but not geitonogamy. ● In papaya (Dioecious), both autogamy and geitonogamy are prevented.

POLLEN-PISTIL INTERACTION ● The ability of pistil to recognise the pollen followed by its acceptance or rejection is the result of a continuous dialogue between pollen grain and the pistil. It is a dynamic process. ● Mediated by chemical components of the pollen interacting with those of the pistil. ● Following compatible pollination, pollen tube grows through the tissues of the stigma and style, the contents of pollen grain move into pollen tube. ● The growing pollen tube carrying two non-motile male gametes, reaches the ovary, enters the ovule through micropyle & then enters one of the synergids through the filiform apparatus, which guides the entry of pollen tube. ● All these events - from pollen deposition on the stigma until pollen tubes enter the ovule - are together referred to as pollen - pistil interaction.

ARTIFICIAL HYBRIDISATION ● In such crossing, desired pollen are used for pollination & stigma is protected from contamination from unwanted pollen by emasculation and bagging. ● If female parent bears bisexual flowers, emasculation is followed by bagging & rebagging after dusting mature pollen for fruit development. ● If female flowers are unisexual, there is no need of emasculation.

Continued self-pollination result in inbreeding depressions.

DOUBLE FERTIFISATION ● Pollen tube releases the two male gametes into the cytoplasm of the synergid. ● One of the males gametes fuses with egg to form the diploid zygote (Syngamy). The other male gamete moves towards the polar nuclei of the central cell and fuses with them to produce triploid primary endosperm nucleus (PEN) Triple Fusion.

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Sexual Reproduction in Flowering Plants

● Syngamy & triple fusion are called double fertilisation, an event unique to flowering plants. ● The central cell after triple fusion becomes primary endosperm cell (PEC) and develop into endosperm.

APOMIXIS AND POLYEMBRYONY ● Some species of Asteraceae & grasses have evolved a special mechanism to produce seeds without fertilisation called apomixis. A form of asexual reproduction that mimics sexual reproduction. ● In some species, diploid egg cell formed without reduction division develops into embryo without fertilisation. ● In Citrus and mango, nucellar cells protrude into embryo sac & develops into embryos, so each ovule contains many embryo (polyembryony).

POST-FERTILISATION: STRUCTURE AND EVENTS Endosperm ● Endosperm development precedes embryo development. ● The cells of tripoid endosperm are filled with reserve food materials and used by developing embryo. ● The most common type of endosperm, is nuclear type (PEN undergoes successive nuclear divisions to give free nuclei) eg., Coconut water and surrounding white kernel is cellular endosperm.

Embryo ● Develops at micropylar end of embryo sac where the zygote is situated. ● Most zygotes divide only after certain amount of endosperm is formed.

This adaptation provides assured nutrition to the developing embryo. ● Early stages of embryo development (Embryogeny) are similar in both monocotyledons and dicotyledons. ● In dicots, the zygote forms → proembryo → globular → heart-shaped → mature embryo. ● A typical dicot embryo has embryonal axis & two cotyledons. ● Epicotyl terminates with plumule or stem tip. ● Hypocotyl terminates at its lower tip in radical or root tip, covered by root cap. ● Embryos of monocot has only one cotyledon. In grass family, it is called scutellum towards lateral side of the embryonal axis. Radicle or root cap enclosed with undifferentiated sheath called coleorhiza.

Epicotyl has shoot apex & a few leaf primordia enclosed in foliar structure coleoptile.

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Seed ● In angiosperms, seed (fertilised ovule) is the final product of sexual reproduction, formed inside fruits. A seed typically consists of seed coats, cotyledon(s) & an embryo axis. ● Mature seeds may be non-abuminous or ex-albuminous, having no residual endosperm, which is consumed completely during embryo development (eg. Pea, groundnut). Albuminous seeds retain a part of endosperm (eg. Wheat, maize, barley, castor, coconut). ● In black pepper & beet, remnants of nucellus are also persistent, called perisperm. ● Wall of ovary develops into pericarp. True fruits develop from ovary. ● In apple, strawberry, cashew, etc, thalamus also contributes to form fruit called false fruit. ● Parthenocarpic fruit develop without fertilisation eg. Banana. ● Seeds form the basis of agriculture. ● Lupinus arcticus seed germinated and flowered after estimated record 10,000 years of dormancy. Phoenix dactytifera (date palm) seed remained viable for 2000 years. qqq

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Sexual Reproduction in Flowering Plants

Chapter

32 Human Reproduction

PRIMARY SEX ORGANS Parameters Organ

Male Testis

Female Ovary

Number

2

2

Shape

Oval

Almond

Location

Outside abdominal cavity in a pouch called scrotum

Lower abdomen, one on each side

Dimensions

Length 4-5 cm, Width 2-3 cm

Length 2 to 4 cm

Covering

Dense connective tissue (outermost)

Thin epithelium (outermost)

Functions

Sperm formation, synthesise steroidal testicular hormones like androgens

Ova formation, synthesise steroidal ovarian hormones like estrogen and progesterone

Compartments

250 testicular lobules • 1-3 coiled seminiferous tubules/ lobule

Peripheral cortex and inner medulla zones in ovarian stroma have follicles in various developing stages

Cells lining the seminiferous tubules 1. Male germ cells/spermatogonia 2. Sertoli cells Function 1. Sperm formation 2. Provide nutrition to the germ cells ● Scrotum helps in maintaining the temperature 2 to 2.5°C lower than body temperature, necessary for spermatogenesis.

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Human Reproduction

● Interstitial spaces outside seminiferous tubules immunocompetent cells and Leydig cells. ● Ovary is connected to pelvic wall and uterus by ligaments.

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Human Reproduction

● Secretions of epididymis and vas deferens are essential for maturation and motility of sperms. ● Male ejaculates about 200-300 million sperms during a coitus. ● For normal fertility: – 60% sperms must have normal shape and size – 40% sperms must show vigorous motility

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Human Reproduction

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Sequence of reproductive events oocuring in humans include: Gametogenesis ↓ Insemination ↓ Fertilization ↓ Implantation ↓ Gestation ↓ Parturition/Birth

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Human Reproduction

DEVELOPMENT OF THE ZYGOTE ● Every sexually reproducing organism, including human beings, begin life as a single cell i.e., the zygote. ● The process of development of embryo from zygote is called embryogenesis. ● During embryogenesis, zygote undergo cell divisions and cell differentiation. ● Cleavage starts as zygote moves through isthmus to the uterus. ● Daughters formed after cleavage are called Blastomeres.

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Human Reproduction

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Human Reproduction

Chapter

4 Reproductive Health

INTRODUCTION According to WHO, reproductive health means a total well being in all aspects of reproduction i.e., physical, emotional, social and behavioural.

PROBLEMS AND STRATEGIES

India was amongst first countries in the world to initiate action plans to attain reproductive health such as family planning programmes in 1951.

POPULATION STABILISATION According to 2001 census, our population growth rate was around 1.7 per cent – 17/1000/year.

Year

World Population

Indian Population

1900

2 billion

350 million

2000

6 billion

1 billion

Reasons for Increase in Population Size: ● Decline in death rate ● Rapid decline in maternal mortality rate (MMR) ● Decrease in infant mortality rate (IMR) ● Increase in number of people in reproducible age ● Increase in health facilities Measures Taken by Government to Check Population Growth Rate: ● Motivate smaller families by using various contraceptive methods with slogans “Hum do Hamare do”, advertisements and posters ● Urban couples adopting: “One child norm”. ● Statutory raising of marriageable age: ○ Female–18 years ○ Male–21 years ● Incentives given to couples with small families.

BIRTH CONTROL/CONTRACEPTION Features of an ideal contraceptive: ● User-friendly ● Easily available ● Effective ● Reversible ● No/least side-effects ● No interference with libido or act of coitus Two principle methods of birth control: ● Natural methods ● Artificial methods

NATURAL/TRADITIONAL METHODS ● Principle of avoiding physical meeting of the egg and sperms. ● Chances of failure are high.

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Reproductive Health

Method Periodic abstinence

Mode of Action Couples abstain from coitus from day 10 to 17 of the menstrual cycle i.e., fertile period

Withdrawal method/ Coitus interrupts

Insemination is avoided as the male partner withdraws his penis from the vagina just prior to ejaculation

Lactational amenorrhea

Absence of menstruation upto 6 months during period of intense lactation following parturition

ARTIFICIAL METHODS ● ● ● ● ● ● ●

Barrier methods Spermicidal jellies IUDs Oral pills Injections and implants Emergency contraceptives Surgical methods

I. Barrier methods ● Prevent ovum and sperm from physically meeting. ● Self inserted and offer privacy to user. (a) Condoms & its Types: Made up of rubber and thin latex.

(b) Diaphragms, cervical caps, vaults ● Rubber barriers that cover the cervix during coitus ● Reusable ● Do not protect from STDs ● Used by female only

II. Spermicidal jellies, foams and creams ● Kill the sperms by acidic pH ● Used along with barrier methods to increase their efficiency Hand Book (Biology)

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III. Intra-uterine devices (IUDs) ● Inserted by doctors or expert nurses in uterus ● IUDs are one of the most widely accepted method of contraception in India.

IV. Oral Contraceptive Pills (OCP) or Tablets

V. Implants ● Placed under skin ● Effective periods are much longer ● Composition: Progestogens alone/ Combination of Progestogens and Estrogens ● Mode of Action ○ Inhibit ovulation and implantation. ○ Alter the quality of cervical mucus to retard entry of sperms.

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Reproductive Health

VI. Emergency Contraceptives Types ● Progestogens alone ● Combination of Progestogen + Estrogen ● IUDs Characteristics ● Effective with 72 hrs of coitus. ● Used to prevent conception resulting from rape or unprotected intercourse.

VII. Surgical/Sterilization Methods ● Poor reversibility but highly effective ● Mode of action – Blocks gamete transport Types Tubectomy

Vasectomy

In females

In males

Cut and tie fallopian tubes

Cut and tie vas deferens

Incision in abdomen or through Small incision on the scrotum vagina

MEDICAL TERMINATION OF PREGNANCY (MTP)/ INDUCED ABORTION ● ● ● ●

MTP: Intentional or voluntary termination of pregnancy before full term.

MTP was legalized in India in 1971.

40–50 million MTPs performed.

1/5th of the total number of conceived pregnancies.

When can MTP be Performed? ● Unwanted pregnancy due to rape, failure of contraception, casual unprotected intercourse. ● If continuation of pregnancy could harm the mother or foetus or both. ● Intention behind MTP amendment act 2017, (Government of India) ○ Reducing the incidence of illegal abortion. ○ Decrease consequent maternal mortality and morbidity. ○ MTPs are safe upto 12 weeks but riskier in 2nd trimester yet both are legal. ○ Amniocentesis and MTPs have been misused in context of female foeticide.

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AMNIOCENTESIS ● Analyse foetal cells and dissolved substances from amniotic fluids. ● Technique used to check for genetic disorders such as Down’s syndrome, sickle-cell anemia etc. ● Statutory ban on this technique in India to prevent female foeticide.

SEXUALLY TRANSMITTED DISEASES (STDS) ● Alternately named: Venereal diseases (VD) or reproductive tract infections (RTIs). ● High vulnerability/risk group: 15-24 years. ● Mode of transmission: Sexual intercourse.

Category

Disease

Bacterial

Gonorrhea, Syphilis, Chlamydiasis

Protozoan

Trichomoniasis

Viral

Genital herpes, Hepatitis-B, Genital warts, AIDS

● Bacterial and protozoan diseases are completely curable if detected early and treated properly.

● Mode of Transmission: ○ Sharing of injection needles, surgical instruments with infected persons. ○ Transfusion of blood. ○ F rom infected mother to foetus. ● Preventive measures to avoid STDs: ○ Avoid sex with unknown partners/multiple partners ○ Always try to use condoms during coitus

INFERTILITY Unable to produce children inspite of unprotected sexual co-habitation.

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Reproductive Health

Reasons: ● Physical ● Diseases ● Psychological ● Congenital ● Immunological ● Infertility as a problem could be with either the male or female partner. ● In India, female is blamed often than male for the couple being childless.

ASSISTED REPRODUCTIVE TECHNOLOGIES (ART)

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5

Chapter

Principles of Inheritance and Variation INTRODUCTION ♦ Genetics deals with inheritance and variation of characters from parents to offsprings. ♦ Inheritance is the process by which characters are passed on from parent to progeny. ♦ Variation is the degree by which progeny differ from their parents and causes of variation was hidden in sexual reproduction.

MENDEL'S LAWS OF INHERITANCE z

Gregor Mendel conducted hybridisation experiments on garden peas for seven years (1856-1863) and proposed the laws of inheritance.

z

Mendel selected 14-true breeding pea plant varieties as pairs which were similar except for one character with contrasting traits.

Contrasting traits studied by Mendel in Pea S.No.

Characters

Contrasting Traits

1.

Stem height

Tall/Dwarf

2.

Flower colour

Violet/White

3.

Flower position

Axial/Terminal

4.

Pod shape

Inflated/Constricted

5.

Pod colour

Green/Yellow

6.

Seed shape

Round/Wrinkled

7.

Seed colour

Yellow/Green

INHERITANCE OF ONE GENE z

F1 always resembled either of the parents but in F2 (produced by selfing F1), both traits appeared

z

3/4th-Dominant trait

z

1/4th-Recessive trait

z

Both traits were identical to their parental type and did not show any blending, i.e., none were of intermediate type.

z

Mendel got similar results for all traits.

z

To determine the genotype of dominant trait of F2, Mendel performed test cross.

BASED ON MONOHYBRID CROSS z

Law of dominance: Explains the expression of only one parental character in F1 of monohybrid cross. It also explains the proportion of 3 : 1 obtained at the F2.

z

Law of segregation: The factors or alleles of a pair segregate from each other such that gametes receive only one of the two factors.

INCOMPLETE DOMINANCE z

F1 did not resemble either of the parents and was in between the two.

Dog flower (Snapdragon or Antirrhinum sp.).

RR = Red flowers rr = White flowers Rr Pink flowers. z

Genotypic ratio at F2-1 : 2 : 1

z

Phenotypic ratio changed from 3 : 1 → 1 : 2 : 1.

EXPLANATION OF CONCEPT OF DOMINANCE In diploid organisms, there are two copies of each gene, i.e., a pair of alleles.

One of them may be different, i.e., modified. (i) The normal allele produces normal enzyme needed from transformation of substrate.

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(ii) If the modified allele produces normal/less efficient enzyme, which produces same phenotype/trait, it is dominant but if it produces non-functional or no enzyme, the phenotype will be affected and recessive trait is seen.

FACTORS z

Genes units of inheritance.

z

Contain information required to express a particular trait an organism.

British geneticist R.C Punnett developed a graphical representation call Punnett square to calculate possibility of all possible genotype of offsprings in a genetic cross.

CO-DOMINANCE z

F1 resembles both parents.

z

ABO blood group in human being is controlled by Gene-I, having three alleles IA, IB and i. IA and IB produce slightly different form of sugar, while i does not produce any sugar.

z

IA and IB are completely dominant over i, but when IA and IB are present together, they express their own sugars, because of Co-Dominance hence RBC have both sugars.

z

There are 6 genotypes and 4 phenotypes in human ABO blood types.

PLEIOTROPY A single gene can exhibit multiple phenotypic expression. It is the effect of a gene on metabolic pathways which contribute towards different phenotypes.

Example: (a) Phenylketonuria 1. Mental retardation (Single gene) 2. Reproduction in hair & skin pigmentation (b)

Starch synthesis 1. Seed shape gene in pea (B)

2. Size of strach grain BB = Large grains

Round Bb = Intermediate sized grains bb = Small grains → Wrinkled 37 Principles of Inheritance and Variation

MULTIPLE ALLELES z

More than two alleles governing the same character.

z

ABO blood grouping is a very good example of multiple alleles.

z

Multiple alleles can be found only in population studies.

INHERITANCE OF TWO GENES z

Mendel also worked and crossed pea plants that differed into two characters and got a phenotypic ratio of 9 : 3 : 3 : 1 and genotype ratio 1 : 2 : 2 : 4 : 1 : 2 : 1 : 2 : 1.

z

Based on Dihybrid Cross.

LAW OF INDEPENDENT ASSORTMENT When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters.

CHROMOSOMAL THEORY OF INHERITANCE z

Walter Sutton and Theodore Boveri noted that the behaviour of chromosomes was parallel to behaviour of genes and they used chromosome movement to explain Mendel's Laws.

z

Sutton united the knowledge of chromosomal segregation with Mendelian principles and called it chromosomal theory of inheritance.

z

Experimental verification was done by T.H. Morgan, who worked with fruit flies Drosophila melanogaster.

DROSOPHILA MELANOGASTER WERE SUITABLE FOR GENETIC STUIDES z

Grown on simple synthetic medium in laboratory.

z

Complete their life cycle in about two weeks.

z

A single mating could produce a large number of progeny flies.

z

Clear differentiation of sexes.

z

Many types of hereditary variations that can be seen with low power microscopes.

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38

LINKAGE AND RECOMBINATION z

Morgan carried out several dihybrid crosses in Drosophila to study genes that were sex-linked, similar to the dihybrid crosses of Mendel in peas.

z

F2 ratios deviated significantly from 9 : 3 : 3 : 1 (expected when the two genes are independent).

z

When two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than non-parental type.

z

Morgan attributes it to physical association or linkage of two genes and used term recombination to describe non-parental gene combinations.

z

Some genes were very-tightly linked (showed very low recombinations)

z

Others were loosely linked (Showed higher recombinations).

z

Morgan's student Alfred Sturtevant used frequency of recombination between genes on same chromosome as a measure of distance between genes and mapped their position on chromosomes.

POLYGENIC INHERITANCE z

Traits controlled by three or more genes are polygenic traits. It also takes into account influence of enviornment.

z

The phenotype reflects the contribution of each allele, i.e., the effect of each allele is additive.

E.g. Human Skin Colour z

AABBCC has darkest skin colour; aabbcc has lightest

z

AaBbCc has intermediate colour.

SEX-DETERMINATION Genetic/Chromosomal Basis Initial clue came from insects. The X-body of Henking was X-chromosome.

— XO-Type = Male heterogamete

e.g. = Grasshopper — XY-Type = Male heterogamete

e.g. = Insects, Man — ZW-Type = Female heterogamete

e.g. = Birds z

39

Principles of Inheritance and Variation

SEX-DETERMINATION IN HUMANS z

Genetic make-up of sperm determines sex of the child and in each pregnancy, there is always 50% probability of a male or female child.

z

In our society, females are blamed for giving birth to female children.

SEX-DETERMINATION IN HONEY BEE z

Haplo-diploid sex-determination.

z

Unfertilised egg develops as male (drone) i.e. haploid.

z

Queen and worker bees (females) are diploid.

MUTATION z

Alteration in chromosomes result in abnormailities or aberrations.

Chromosomal aberrations are commonly observed in cancer cells.

z

Point Mutation: Mutations also arise due to change in a single base pair of DNA, eg: Sickle-cell anemia.

z

Frame shift mutation: Deletions and insertions of base pairs of DNA.

z

Mutagens: Chemical and physical factors that induce mutations.

E.g. UV radiations can cause mutations in organisms.

GENETIC DISORDERS PEDIGREE ANALYSIS z

Study of family history about inheritance of a particular trait provides an alternative.

Hand Book (Biology)

40

41

Principles of Inheritance and Variation

5

Five unaffected offspring

Parents with male child affected with diseases

Parents above and children below

Mating between relatives (consanguineous mating)

Mating

Affected individuals

Sex unspecified

Female

Symbols used in the Huamn Pedigree Analysis Male • Caused due to absence or excess or abnormal arrangement of one or more chromosomes.

• Failure of segregation of chromatids during cell-division cycle resulting in gain or loss of a chromosome(s), is called Aneuploidy.

• Failure of Cytokinesis after telophase stage of cell division results in an increase in a whole set of chromosomes in an organism, this is called Polyploidy, often seen in plants.

• Trisomy or Monosomy leads to very serious consequences in the individual (i) Down's Syndrome: Trisomy of 21; was first described by Langdon Down (1866).

Symptoms: (i) Short Statured (ii) Small round head. (iii) Furrowed tongue (iv) Partially open mouth. (v) Palm is broad with palm crease (vi) Physical, psychomotor & mental development is retarded. (ii) Klinefelter's Syndrome: Karyotype = 47 xxy, overall masculine development, however Gynaecomastia is also expressed. Such individuals are sterile. (iii) Turner's Syndrome: Due to absence of one of the X-chromosomes, i.e., 45 with XO Such females are sterile as ovaries are rudimentary besides lack of other secondary sexual characters.

• Mainly determined by alternation or mutation in a single gene.

• It may be dominant or recessive Autosomal or Sexlinked.

Examples: 1. Colour-blindness • Sex-linked recessive.

• Due to defect in either red or green cone of eye due to mutation in certain genes present on X-Chromosome.

• 8% of males and only about 0.4% of females affected.

2. Haemophilia • X-linked recessive • A single protein that is part of cascade of proteins involved in blood clotting is affected.

3. Sickle-Cell anaemia • Autosome linked recessive • Controlled by single pair of allele HBA and HbB. 4. Phenylketonuria (Autosomal recessive) • Inborn error in metabolism. Affected individual lack enzyme which converts phenylalaine to tyrosine.

Results in mental retardation.

5. Thalassemia • Autosomal recessive, could be due to mutation or deletion.

• a-thalassemia: Controlled by two closely linked genes HBA1 and HBA2 on Chr-16.

• b-Thalassemia: Controlled by single gene HBB

on Chr-11.

Chromosomal Disorders

Mendelian Disorders

Pedigree analysis of (a) Autosomal dominant trait (e.g., Muscular dystrophy) (b) Autosomal recessive trait (e.g., Sickle-cell anaemia) (a)

(b)

z

TH. Morgan found that in Drosophila, the genes for yellow body and white eye were very tightly linked and showed only 1.3% recombination

z

White eye and miniature wing showed 37.2% recombination.

z

Cystic fibrosis is autosomal recessive disorder.

z

Chromosomal disorders can be easily studied by the analysis of Karyotypes

z

The family pedigree of Queen Victoria shows a number of haemophilic descendents as she was a earner of the disease.

z

Thalassemia: Quantitative problem of synthesising too few globin molecules

z

Sicke cell anaemia: A qualitative problem of synthesising an incorrectly functioning globin. qqq

Hand Book (Biology)

42

Chapter

6 Molecular Basis of Inheritance

DNA (GENETIC MATERIAL OF MOST OF THE ORGANISM) DNA is a long polymer of deoxyribonucleotides. The length of DNA usually defined as number of nucleotides is also characteristic of an organism.

ORGANISM 1. Bacteriophage × 174 2. Bacteriophage lambda 3. Escherichia coli 4. Haploid content of human DNA

DNA CONTENT 5386 Nucleotides 48502 base pairs 4.6 × 106 base pairs 3.3 × 109 base pairs

Structure of Polynucleotide Chain • Nucleotide (Basic unit of Polynucleotide chain) PURINES = A (Adenine) and G (Guanine) (i)

A Nitrogenous base

(ii)

5C-Sugar

(iii)

Phosphate group

PYRIMIDINES = C (Cytosine), T (Thymine) and U (Uracil) RIBOSE (In RNA) 2-DEOXYRIBOSE (in DNA)

• Uracil is present in RNA; Thymine (5-methyl uracil) in DNA • N-glycosidic linkage: A nitrogenous base is linked to the OH of 1'C pentose sugar form Nucleoside • Phosphoester linkage: A phosphate group is linked to OH of 5'C of a nucleoside, a nucleotide is formed.

• Phosphodiester linkage: Two nucleotides are linked to form a Dinucleotide.

• A polymer has at one end a free phosphate moiety at -5¢- end of sugar (5¢P) and at the other end of polymer, the sugar has a free OH of 3¢C group (3¢OH)

DNA-DOUBLE HELIX • DNA as an acidic substance present in nucleus was first identified by Friedrich Miescher in 1969, named it as "Nuclein".

• Based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin, James Watson and Francis Crick proposed a very simple but famous double helix model of DNA in 1953.

• One hallmark of the helix is base pairing between the two strands.

Observation of Erwin Chargaff for a double stranded DNA, the Ratios between A and T and G and C are constant and equals one.

The base-pairing confers complementarity, a unique property to the polynucleotide chain.

• So, if each strand of parental DNA acts as a template for synthesis of a new strand, the two double stranded daughter DNA produced would be identical to the parental DNA molecule.

Salient Features of Double-helix of DNA • Made of two polypeptide chains, where the backbone is constituted by sugarphosphate and bases project inside.

• Two chains have anti-parallel polarity, one chain 5' → 3' and the other 3' → 5' • A = T (2H – Bond); C ≡ G (3H – Bond).

This generates approximately uniform distance between the two strands.

Base Pairs • The two chains are coiled in a right handed Sugar fashion. phosphate backbone • Pitch of the helix = 3.4 nm. Roughly 10 bp in each turn.

• Distance between a bp in a helix is approx.

Fig. DNA double helix.

0.34 nm. (0.34 × 10–9 m) • The plane of one base pair stacks over the other in double-helix. This in addition to H-bonds, confers stability to the helical structure.

CENTRAL DOGMA OF MOLECULAR BIOLOGY: Proposed by FRANCIS CRICK. • Only applicable to dsDNA. Hand Book (Biology)

44

DNA

Transcription

mRNA

Translation

Protein

Replication

In some viruses, the flow of information is in reverse direction, i.e. from RNA to DNA. It is called reverse of central dogma.

PACKAGING OF DNA HELIX • DNA double helix in a typical mammalian cell is 6.6 × 109 bp

DNA

• Length is approx 2.2 m (6.6 × 109 bp × 0.34 × 10–9 m/bp)

H1 histone

Histone octamer

• Dimension of a typical nucleus is 10–6 m • In prokaryote (E.coli), the DNA Core of histone molecules (negatively charged) is held with Fig. Nucleosome some proteins (positive charges) in the “Nucleoid”. The DNA in nucleoid is organised in large loops held by proteins.

• In eukaryotes, it is much more complex.

Histone Octamer: Positively charged set of basic proteins, Histone (rich in lysine and arginine) are organised to form a unit of eight molecules, called Histone octamer.

Nucleosome: Negatively charged DNA is wrapped around positively charged histone octamer. A typical nucleosome contains 200 bp of DNA helix.

• Nucleosomes constitute the repeating unit of a structure in nucleus called chromatin, thread like stained bodies seen in nucleus.

• Nucleosomes in chromatin are seen as beads-on-string structure under electron microscope. Packaged to form chromatin fibers that are further coiled and condensed at metaphase stage to form chromosomes.

• Packaging of chromatin at higher level needs non-histone chromosomal (NHC) proteins.

In a typical NUCLEUS (regions of chromatin) Euchromatin 1. Loosely packed.

2. Stains light 3. Transcriptionally active 45

Heterochromatin 1. More densely packed 2. Stains dark 3. Transcriptionally inactive

Molecular Basis of Inheritance

RNA WORLD (GENETIC MATERIAL OF SOME VIRUSES LIKE TMV) • RNA was the first genetic material.

• The essential life processes like metabolism, translation, splicing evolved around RNA. • RNA used to act as a genetic material as well as a catalyst, so was reactive and hence unstable. (DNA has evolved from RNA with chemical modifications that make it more stable.)

REPLICATION • Watson and Crick had immediately proposed a scheme for replication of DNA while proposing the double helix structure of DNA. • Semi conservative DNA replication: Two strands would separate and act as a template for the synthesis of new complementary strands.

After completion of replication, each DNA molecule would have one parental and one newly synthesised strand.

SEARCH FOR GENETIC MATERIAL Transforming Principle • In 1928, Frederick Griffith, in a series of experiments with Streptococcus pneumoniae, witnessed a miraculous transformation in Bacteria.

• Bacteria → Rough Colonies → non-virulent → do not kill mice • Bacteria → Smooth shiny colonies → Virulent → Kill mice • Bacteria → Killed S-stain → non-virulent → do not kill mice • Heat killed + live R bacteria → Mice died [S-stain living bacteria found.]

Griffith concluded that R-strain was somehow transformed by heat-killed Sstrain. It must be due to the transfer of genetic material (transforming principle).

Biochemical Nature of Transforming Principle • Oswald Avery, Colin MacLeod and Maclyn McCarty (1933-44) discovered.

• DNA of S bacteria caused R bacteria to become transformed.

• As proteases and RNAse did not affect transformation but DNAase inhibit transformation. (They concluded that DNA is the hereditary material but not all biologists were convinced).

Genetic Material is DNA The Unequivocal proof that DNA is the genetic material came from the experiments of Alfred Hershey and Martha Chase (1952), on bacteriophages, using radioactive phosphorus 32P and sulphur 35S in separation medium with E. coll.

46 Hand Book (Biology)

PROPERTIES OF GENETIC MATERIAL (DNA VERSUS RNA) (i) Able to generate its replica (Replication) (ii) Stable chemically and structurally (iii) Scope for slow mutation required for evolution. (iv) Able to express in the form of Mendelian characters.

• 2'-OH group present at every nucleotide, in RNA, is reactive and makes it easily degradable.

• RNA is also catalytic, hence reactive. Among the two nucleic acids, DNA is a better genetic material.

• Presence of thymine at the place of uracil in RNA also confers additional stability to DNA • Being unstable, RNA mutate at a faster rate.

• RNA can directly code for the synthesis of proteins and can easily express the characters. DNA, however is dependent on RNA for synthesis of proteins.

• DNA being more stable is preferred for storage of genetic information.

• For transmission of genetic information, RNA is better.

EXPERIMENTAL PROOF • Semi-conservative DNA replication was shown first in Escherichia coli, then in higher organisms like plants and human cells.

• Matthew Meselson and Franklin Stahl, performed the experiment (1958) using normal 14N and non-radioactive 15N isotope of Nitrogen as source of NH4Cl and centrifugation in a cesium chloride (CsCl) density gradient. The various samples were separated independently on CsCl gradients to measure the densities of DNA. (E. coli divides every 20 minutes) Generation II

Generation I 14 N-DNA N-DNA

15

15

14

N-DNA

15

20 min

40 min

Gravitational force

15

Heavy

N 15 N

14

N 15 N

14

N 14 N

Hybrid

(Separation of DNA by Centrifugation)

47

Molecular Basis of Inheritance

Light

14

N 15 N Hybrid

N-DNA

N-DNA

14

N-DNA

14

N-DNA

• Taylor and colleagues (1958) used radioactive thymidine and Vicia faba (Faba beans) to prove that DNA in chromosomes also replicate semi-conservatively

MACHINERY AND THE ENZYMES • Energetically replication is a very expensive process.

Deoxyribo (1) Act as substrate Serve nucleoside Dual (2) Provide energy triphosphates Purpose for Polymerisation Replication Fork: Replication occur within a small opening of DNA helix.

• DNA-dependent DNA polymerase (main 5¢ 3¢ enzyme) catalyses the polymerisation Template DNA process in 5¢ → 3¢ direction, so on one (Parental strands) 5¢ strand (template with polarity 3¢ → 5¢) 3¢ replication is continuous, while on other (template with polarity 5¢ → 3¢) it is 3¢ 5¢ 3¢ 5¢ dis-continuous.

Newly Ori (origin of replication): A definite synthesised strands region in E. coli DNA where replication Fig: Replicating Fork originates.

• In eukaryotes, replication of DNA takes place at S-phase of the cell-cycle.

A failure in cell-division after DNA replication results in Polyploidy.

TRANSCRIPTION • Process of copying genetic information from one strand of DNA into RNA. • Principle of complementarity governs transcription (except, adenine forms pair with uracil instead of thymine). In transcription, only a segment of DNA and only one of the two strands is copied into RNA.

TRANSCRIPTION UNIT : (i) Promoter (ii) Structural gene (iii) Terminator • DNA-dependent RNA polymerase catalyses polymerisation in only one direction 5¢ → 3¢.

Hand Book (Biology)

48

Template strand: The strand Polarity 3¢ → 5¢.

Coding strand: The other strand Polarity 5¢ → 3¢ and the sequence same as RNA (except thymine at place of uracil).

Transcription start site PROMOTER 3¢ 5¢

TERMINATOR Structure gene Template strand Coding Strand

5¢ 3¢

A transcription Unit

TRANSCRIPTION UNIT AND GENE • Genes are located on the DNA which is functional unit of inheritance.

• Cistron is defined as a segment of DNA coding for polypeptide.

• The structural gene is monocistronic (mostly in eukaryotes) or polycistronic (mostly in bacteria or prokaryotes).

• In eukaryote, genes are split between coding sequences or Exons, which appear in mature RNA and Introns or intervening sequence.

• Regulatory sequences are defined as regulatory genes, even though they do not code for any RNA or protein.

TYPES OF RNA AND THE PROCESS OF TRANSCRIPTION • A single DNA dependent RNA polymerase catalyses transcription of all three types of RNA (mRNA, RNA, rRNA) in bacteria.

• RNA polymerase binds to promoter and initiates transcription. It uses nucleoside triphosphates (NTPs) as substrate and polymerises in a template depended fashion following the rule of complementarity and also facilitates opening of the helix and continues elongation.

• Only a short stretch of RNA remains bound to the enzyme. Once the polymerase reaches the terminator region, the nascent RNA and RNA polymerase falls off. This results in termination of transcription.

• RNA polymerase is only capable of catalysing the elongation process.

It associates transiently with initiation factor and termination factor to initiate and terminate the transcription respectively.

• In bacteria, mRNA does not require any processing, so transcription and translation are coupled.

• In eukaryotes, there are two additional complexities.

49 Molecular Basis of Inheritance

5′

5′

3′

3′

Capping

3′

mRNA

Intron Gppp

m

5′

Exon Gppp

m

5′

Polyadenylation

RNA splicing

3′ Poly A tail Gppp

m

5′

3′

Gppp

m

Messenger RNA

5′

Fig : Transcription in Eukaryotos

ENZYME 1. RNA pol-I

FUNCTIONS Tanscribes 28S, 5.8S and 18S RNA 2. RNA pol-II Tanscribes mRNA precursor i.e. hnRNA 3. RNA pol-III Tanscribes 5S rRNA, tRNA and SnRNAs • The primary transcript (hnRNA) is subjected to splicing, where introns are removed and Exons are joined in a defined order. hnRNA undergoes additional processing called capping and tailing to form mRNA. • In capping, an unusual nucleotide (methyl guanosine triphosphate) is added to 5' end of hnRNA. • In tailing, adenylate residues (200-300) are added to 3'-end in a template independent manner.

• Fully processed hnRNA is called mRNA that is transported out of the nucleus for translation.

GENETIC CODE (GEORGE GAMOW) • Genetic code should be triplet.

• Chemical method developed by Har Gobind Khorana.

RNA molecules with defined combinations of basés. Marshall Nirenberg’s cell-free system for protein synthesis finally helped the code to be deciphered.

50 Hand Book (Biology)

Salient Features of Genetic Code: • The codon is Triplet. 61 codons code for amino acids and 3 codons are stop codons.

• The code is degenerate.

• The codon is read on mRNA in contiguous fashion i.e., there are no punctuations.

• The code is nearly universal. (eg: UUU codes for phenylalanine from bacteria to humans).

• AUG has dual function. It codes for methionine and act as initiator codon.

• UAA, UAG and UGA- Stop terminator codons.

MUTATIONS AND GENETIC CODE • Insertion or deletion of one or two bases changes the reading frame from the point of insertion or deletion and called frame shift mutations.

tRNA-Adapter Molecule • Francis Crick postulated the presence of an adapter molecule that would read the code and bind to specific amino acid.

• tRNA has an anti-codon loop that has bases complementary to the code and it also has an amino acid acceptor end to which it binds to amino acids, tRNAs are specific for each amino acid.

• For initiation, there is another specific tRNA that is called initiator tRNA. There are no tRNAs for stop codons.

• Secondary structure of tRNA looks like a cloverleaf, though the actual structure is a compact molecule which looks like inverted L.

TRANSLATION • Translation refers to the process of polymerisation of amino acids to form a polypeptide. The order and sequence of amino acids are defined by the sequence of bases in the mRNA. • In the first phase, amino acids are activated in the presence of ATP and linked to their cognate tRNA by a process called charging of tRNA, or aminoacylation of tRNA. Protein synthesis takes place on the ribosomes.

• Ribosomes consist of structural RNAs and about 80 different proteins.

It has two sub units. When the small sub unit encounters an mRNA, the process of translation begins.

• Two sites in the large subunit, for subsequent amino acids to bind and thus, be close enough to each other for the formation of a peptide bond by the catalyst (23 S rRNA in bacteria is the enzyme- ribozyme). (enhance the rate of peptide bond formation.)

51 Molecular Basis of Inheritance

• A translational unit in mRNA is flanked by a start condon (AUG) and the stop codon.

• The untranslated additional sequence on mRNA are called untranslated regions, (UTRs) present at both 5'-end (before start codon)and at 3'-end (after stop codons). UTRs are required for efficient translation.

• The ribosome moves from codon to codon along the mRNA. Amino acids are added one by one and translated into polypeptide sequences.

• At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome.

REGULATION OF GENE EXPRESSION Gene expression results in formation of a polypeptide. It can be regulated at several levels. In eukaryotes, the regulation could be exerted at (i) Transcriptional level (Formation of primary transcript) (ii) Processing level (Regulation of splicing) (iii) Transport of mRNA from nucleus to cytoplasm. (iv) Translational level • In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression

LAC OPERON • Francois Jacob and Jacque Monod were the first to elucidate a transcriptionally regulated system, the lac operon (lac refers to lactose), a polycistronic structural gene regulated by a common promoter and regulatory gene called operon.

Lac operon consists of • • • • •

One regulatroy gene Three structural genes (z, y and a) i gene (i refers inhibitor) codes for repressor z-for β-galactosidase (β-gal). y-for permease and gene a codes for transacetylase. (All three gene products in lac operon are needed for metabolism of lactose.)

• Lactose is the substrate of β-galactosidase and it regulates switching on/ off of operon, so called inducer. Regulation of lac operon is regulation of enzyme synthesis by its substrate.

• Regulation of lac operon by repressor is negative regulation however lac operon is under control of positive regulation as well.

• Regulatory proteins can act both positively (activators) and negatively (repressors). Each operon has its specific operator and specific repressor.

52 Hand Book (Biology)

HUMAN GENOME PROJECT - (HGP) • Launched in 1990, a 13 year project was co-ordinated by U.S. department of energy and National Institute of Health, Wellcome trust (UK), Japan, France, Germany, China participated. It was completed in 2003.

• Human genome has approximately 3 × 109 bp and the cost of sequencing in the beginning was US$3 per bp, i.e. 9 billion US dollars. HGP lead to the rapid development of a new area in biology called bioinformatics.

• Many non-human model organisms like bacteria, Yeast, Caerorhabditis elegans, Drosophila, plant (rice and Arabidopsis) have also been sequenced.

METHODOLOGIES • Expressed sequence tags (ESTs): Focussed on identifying all genes that expressed as RNA. • Sequence annotation: Blind approach of sequencing the whole genome containing coding and non coding sequences, needing vectors like BAC (Bacterial artificial chromosomes) and YAC (Yeast Artificial Chromosomes).

SALIENT FEATURES OF HUMAN GENOME • Human genome contains 3164.7 million bp. Average gene consist of 3000 bases.

• Largest gene dystrophin of 2.4 million bases. Total genes estimated at 30,000.

• Almost 99.9% nucleotide bases exactly same in all people. Less than 2% genome codes for protein. Chromosome 1 has most genes (2968) and Y-chromosome has the fewest (231).

53 Molecular Basis of Inheritance

• At 1.4 million locations, single base DNA differences (SNPs - single nucleotide polymorphism, snips) occur.

• The fragments were sequenced using automated DNA sequencer that worked on the principle of a method developed by Frederick Sanger.

DNA FINGERPRINTING • 99.9% base sequence among humans is same. 0.1% differences in sequence of DNA make every individual unique in their phenotype.

• Involves identifying difference in repetitive DNA, a small stretch of DNA repeated many times, called satellite DNA. • Depending on base composition (A:Tor G:C rich), length of segment and number of repetitive units, the satellite DNA is classified into micro-statellites and mini satellites. They do not code for any proteins.

They form large portion of human genome and show high degree of polymorphism and form the basis of DNA fingerprinting.

• Polymorphisms are inheritable from parent to child so DNA finger printing solves paternity disputes.

• The technique of DNA finger printing was initially developed by Alec Jeffreys.

Steps = Isolation of DNA(I)

Detection of hybridised DNA Fragments by autoradiography (VI)

Digestion by restriction endonuclease (II) Hybridisation Using labelled VNTR probe (V)

Separation of DNA fragments by Electrophoresis (III) Blotting on nitrocellulose or Nylon membrane (IV)

Significance • VNTR are called mini-satellite, a small DNA sequence arranged tandomly in many copies. The size of VNTR varies from 0.1 to 20 kb. So after hybridisation with VNTR probe, the autoradiogram gives many bands of differing sizes. These bands give a characteristic pattern for an individual DNA. It differs from individual to individual in a population except in monozygotic twins.

• The sensitivity of the technique has been increased by use of polymerase chain reaction (PCR).

• DNA fingerprinting has much wider application in determining population and genetic diversities. Currently, many different probes are used to generate DNA fingerprints. qqq 54 Hand Book (Biology)

Chapter

7 Evolution

EVOLUTION Evolutionary biology is the study of history of life forms on earth Stellar distances are measured in light years Big band explosion (Singular huge explosion) Resulted in

Parameters Time scale Feature

leading to

Origin of Earth Origin of Universe 4.5 billion years ago 20 billion years ago Comprises cluster of galaxies Occurred in solar system of Milkyway galaxy (stars, clouds of gas, dust)

Events after expansion of universe: Temperature declined H2 + He formed Gases condensed Galaxies formed Hypothesis for Origin of life on early earth: No atmosphere existed on early earth.

Water vapours, methane, carbon dioxide and ammonia released from molten mass covered the surface.

NH3 U.V. rays H2 O H 2 + O2 + O2 CO2 + H2O + other contents CH4

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56

Louis Pasteur

Theory of Biogenesis

Closed flask

CH4 NH3 H2O H2

Boiling water

Vacuum Simulate reducing atmosphere

Oparin-Haldane hypothesis or Chemical Evolution

–

Killed yeast

Electrodes

Life

800°C

Spark discharge Simulate lightening (energy sources)

Amino acids

Gases

No life

Pre-stenlised asks

Air

Early Greek thinkers, Astronomers

Cosmozoic/ Panspermia

Spontaneous generation

Proponents Conventional religious literature

Theory Special creation

Formation of life was precede by chemical evolution i.e., formation of diverse organic molecules from inorganic constituents.

First from of life could have come from pre-existing non-living organic molecules (e.g. RNA, proteins, etc.)

This hypothesis was proved by Miller's experiment, 1953, S.L. Miller (American scientist) In similar experiments, other observed formation of sugars, nitrogen bases, pigments and fats.

Life comes only from pre-existing life He showed that in pre-sterlised flasks, life did not come from “killed yeast”

Life came out from decaying and rotting matter like straw, mud etc.

Disapproved by Louis Pasteur

Life came from outerspace Units of life called spores were transferred to different planets including earth

Signi cance All living organisms that we see today were created Diversity was always the same since creation and will be the same in future also Earth is 4000 years old

THEORIES FOR ORIGIN OF LIFE

57

Evolution Similar Convergent

Similar but developed along different directions due to adaptations to different needs.

Different

Divergent

Anatomical structures

Function performed

Type of evolution

Not similar but resulted in selection of similar adaptive features in different groups of organisms, thus, evolving for the same function.

No

Yes

Common ancestory

Analogous organs

Homologous organs

Parameters

3. Morphological and anatomical evidences

2. Embryological evidences: Proposed by Ernst Heckel.

Based upon the observations of certain features during embryonic stage common to all vertebrates that are absent in adults e.g., embryos of all vertebrates develop a row of vestigial gill slits functional only fish and not found in another adult vertebrates.

It was disproved by Karl Ernst von Baer. He noted that embryos never pass through the adult stages of other animals.

1. Palaeontological evidences (Evidences from fossils): Fossils are remains of hard parts of life forms found in rocks.

Age of fossils is determined by radioactive-dating method.

Fossils of different life forms in different sedimentary layers indicates the geological period in which they existed (epochs, periods, eras).

EVIDENCES OF EVOLUTION

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ADAPTIVE RADIATION The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats).

Examples Darwin’s nches • Small black birds • Evolved from seed eating birds in Galapagos island • Altered beaks arose, enabling them to become insectivorous and vegetarian finches.

Australian marsupials Sugar Tasmanian wolf glider Tiger cat Marsupial mole Banded Marsupial anteater radiation Koala Marsupial rat Bandicoot Kangaroo Wombat

Variety of beaks of nches that Darwin found in Galapagos island

Adaptive radiation of marsupials of Australia

When more than on adaptive radiation appeared to have occurred in an isolated geographical area (representing different habitats), we call their convergent evolution.

Examples

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Placental mammals

Australian marsupials

Mole

Marsupial mole

Anteater

Numbat (banded anteater)

Mouse

Marsupial mouse

Lemur

Spotted cuscus

Flying squirrel

Flying phalanger (Sugar glider)

Bobcat

Tasmanian tiger cat

Wolf

Tasmanian wolf

Evolution

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– Branching descent and natural selection are the two key concepts of Darwinian theory of evolution.

– Habitat fragmentation and genetic drift may accentuate variations leading to speciation.

– Weaknesses: (i) Unable to explain the origin of variations (ii) Could not explain speciation (iii) Ignored work done by Mendel.

Mutation theory th

– Given by Hugo de Vries in first decade of 20 century.

– Worked on evening primrose.

– New species originate as a result of mutations which are single step (saltation) large, random and directionless variations arising suddenly in a population.

• Alfred Wallace, a naturalist who worked in Malay Archipelago has also come to similar conclusions as Charles Darwin around the same time.

• Evolution is not a directed process in the sense of determinism. It is a stochastic process based on chance events in nature and chance mutations in the organisms.

• Arti cial selection: By intensive breeding programme, man has created breeds that differ from other breeds (e.g., dogs).

EXAMPLES OF EVOLUTION BY ANTHROPOGENIC ACTION 1. Antibiotic resistant microbes 4. Herbicides resistant varieties 2. Pesticides resistant varieties 3. The case of Industrial melanism: Classical example of natural selection among variants in moth population observed in England.

Parameters

Before industrialization (1850s)

After industrialization (1920s)

White, covered by lichens

Became dark due to deposition of soot and smoke Less More White winged moths

Figure

Tree trunks

More White moths Melanised moths Less Predators feed on Melanised moths

• Lichens do not grow in polluted area (pollution indicator).

• Agent of natural selection: Predator/birds.

• Moths that were able to camouflage themselves (i.e., hide in the background) survived but no variant is completely wiped out

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Evolution

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HARDY-WEINBERG PRINCIPLE Allele frequencies in a population are stable and is constant from generation to generation. This is called genetic equilibrium.

The gene pool (total genes and their alleles in a population) remains a constant.

Sum total of all the allelic frequencies is 1 and represented as: p + q = 1 [p = Frequency of recessive allele (a); q = Frequency of dominant allele (A)] p2 + q2 + 2pq = 1 [p2 = Frequency of homozygous dominant (AA); q2 = Frequency of homozygous recessive (aa); 2pq = Frequency of heterozygotes (Aa)]

When frequency measured, differs from expected values, the difference indicates the extent of evolutionary change or disturbance in genetic equilibrium.

Factors affecting Hardy-Weinberg equilibrium: 1. Gene migration: When migration of a section of population to another place or population occurs, gene frequencies change in the original as well as in the new population.

When gene migration occurs multiple times, it is called gene flow.

Emigration (–) Immigration (+) Some genes/alleles lost New genes/alleles added 2. Genetic recombination: Variations due to recombination during gametogenesis.

3. Mutation: Microbial experiments show that pre-existing advantageous mutations when selected will result in observation of new phenotypes.

Over few generations, this would result in speciation.

4. Genetic drift: Change in gene frequencies in a small population by chance.

Sometimes, the change in allele frequency is so different in the new sample of population that they become a different species. The original drifted population becomes founders and effect is called founders effect.

5. Natural selection: A process is which heritable variations enabling better survival are enabled to reproduce and leave greater number of progeny.

Types Stabilising selection More individuals acquire mean character value

Directional selection More individuals acquire value other than the mean character value

Number of individuals with phenotype

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Evolution

Disruptive selection More individuals acquire peripheral character value to both ends at the distribution curve

A BRIEF ACCOUTN OF EVOLUTION OF PLANTS

Different types of plants

evolved in different periods of time Palaeozoic, Mesozoic and Coenozoic.

Chlorophyte ancestors: Bryophytes: Tracheophyte ancestors: Lycopods.

Psilophytons were common ancestors for gymnosperms, Ferns, Ginkgo’s, Genetales, Sphenopsids.

Origin of monocotyledons is more recent than that of dioctyledons.

Giant ferns (pteridophytes) were present (200 mya) but they all fell to form coal deposits slowly.

A sketch of the evolution of plant forms through geological periods

A BRIEF ACCOUNT OF EVOLUTION HISTORY OF VERTEBRATES

Turtles, Lizards, Snakes and

Tuatara arose from common ancestor sauropsids.

Thecodont ancestors gave

way to existing crocodiles and birds and extinct dinosaurs.

Origin of mammals:

Extinct Synapsids Pelycosaurs Therapsids Mammals Representative evolutionary history of vertebrates through geological periods

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AN EVOLUTION HISTORY DINOSAURS Triceratops – Three horned

A family tree of dinosaurs and their living modern day counterpart organisms like crocodiles and birds.

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dinosaur with bony frill around back of its head.

Stegosaurus – Large triangular bony plates along the back and spiked tail.

Tyrannosaurus rex – 20 feet in height had dagger like teeth.

Branchio Saurus – Long giraffe like neck, long forelimbs.

Pteranodon were possibly flying reptiles.

Archaeopteryx is a transitional fossil between non avian dinosaurs and birds.

Brachiosaurus and Tyrannosaurus arose separately, mostly likely, from a common ancestor.

Evolution

Human ancestors Homo erectus

Years back

Neanderthal man

1,00,000– 40,000 years back

1400 cc

Homo sapiens

75,000– 10,000 years ago (ice age)

–

1.5 mya

Cranial capacity 900 cc

Specific features

Fossils discovered in Java in 1891 Probably ate meat Lived in near East and Central Asia Used hides to protect their body and buried their dead Arose in Africa and moved across continents and developed into distinct races

The skull of baby chimpanzee is more like adult human skull than adult chimpanzee skull.

A comparison of the skulls of adult modern human being baby chimpanzee and adult chimpanzee.

Pre historic cave art-18,000 years ago. One such cave paintings by prehistoric humans can be seen at Bhimbetka rock shelter, Madhya Pradesh.

Agriculture came around 10,000 years back and human settlements started.

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Chapter

8 Human Health and Disease

HEALTH As per ‘Good humor’ hypothesis arrived at by reflective thought and asserted by Hippocrates along with Indian Ayurveda System.

Health is a state of body and mind where there was a balance of certain certain ‘humors’ e.g., Persons with black bile belonged to hot personality and had fevers.

William Harvey (discovered blood circulation experimentally) disproved this ‘good humor’ hypothesis of health by demonstrating normal body temperature in persons with black bile using thermometer.

Mind influences our immune system through neural and endocrine systems, and that our immune system maintains our health i.e., state of complete physical, mental and social and psychological well being.

Health is not simply ‘absence of disease’ or ‘physical fitness’.

Factors affecting health: Mental state, genetic disorders, infections and life style (habits, rest and exercise) Productivity, longevity Increase Bring economic prosperity Condition of health Decrease Infant and maternal mortality

DISEASE It is state of the body when functioning of one or more organ systems is adversely affected, characterized by various signs and symptoms.

Parameters Transmission from one person to another Example

Types of diseases Non-infectious Infectious Yes No Cancer AIDS

Pathogens: Disease causing organisms: Most parasites are pathogens living in (or on) the host multiply and interfere with normal vital activities resulting in morphological and functional damage.

Gut pathogens can survive harsh pH & digestive enzymes.

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Tetanus Typhoid, dysentery Plague Syphilis

Direct contact Contaminated food and water Insect vector/vector borne Body fluids

Viral Common cold, Smallpox Smallpox Polio Chikungunya, Dengue AIDS Helminthic – – Ascariasis Filariasis –

Protozoan – – Amoebiasis Malaria Trichomoniasis

• Balanced diet, yoga and regular exercise, personal hygiene, awareness about diseases and vaccination are very important to maintain good health.

• Use of vaccines and immunization programmes have enabled us to completely eradicate a deadly disease like smallpox. Large number of infectious diseases like polio, diphtheria, pneumonia and tetanus have been controlled to a large extent by the use of vaccines.

• Biotechnology is at the verge of making available newer and safer vaccines.

• Discovery of antibiotics and various drugs have enabled us to effectively treat infections.

Measures Keeping the body clean Consumption of clean drinking water, food, vegetables, fruits etc.

Periodic cleaning and disinfection of water reservoins, pools tanks Proper disposal of waste and excreta Decontamination of drinking water Contact with infected persons and belongings should be avoided.

Avoid close contact Control vectors and Use of mosquito nets Avoid stagnation of water in and around residential areas, their breeding places Regular cleaning of house old coolers Doors and windows should be provided with wire mesh Introducing larvicidal fishes like Gambusia in ponds that feed on mosquito larvae Spraying of insecticides in ditches, drainage areas and swamps

Parameters Personal Hygiene Public Hygiene

MEASURES FOR PREVENTING SPREAD OF INFECTIOUS DISEASES

Vector: Transmits disease from one organism to another e.g., female Aedes mosquito is the vector for dengue and chikungunya while, Anopheles spreads malaria.

Bacterial Pneumonia, diphtheria

Mode of transmission Air (droplet/aerosol) or object borne (pens, knobs etc.)

CLASSIFICATION OF DISEASES ON THE BASIS OF TRANSMISSION

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Typhoid

Problem in respiration due to fluid filled alveoli Fever, chills, cough, headache In severe cases, lips and finger nails turn gray to bluish

Nasal congestion and discharge Sore throat Hoarseness, cough Headache, tiredness

Symptoms

Common cold does not infect lungs and its symptoms usually lasts for 3-7 days.

Nose and respiratory passage

Rhino virus

Common cold

VIRAL DISEASES Organ affected

Pathogen

Disease

Sustained high fever (39–40°C) Stomach pain Weakness Constipation Headache Loss of appetite In severe cases, intestinal perforation and death may occur.

Common symptoms

Typhoid Mary (Mary Mallon), a cook by profession was a typhoid carrier who spread typhoid through the food she prepared.

Pneumonia Streptococcus pneumoniae, Alveoli of lungs Haemophilus in uenzae

Diagnostic test: Widal test

Small intestine and other organs by migrating through blood

Salmonella typhi

Disease

BACTERIAL DISEASES Organ affected

Pathogen

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Intestine

Lymphatic vessels

Ascaris (Roundworm)

Wuchereria bancrofti/ W. malayi (Filarial worm)

Ascariasis

Elephantiasis/ Filariasis

Skin, nails, scalp

Microsporum, Trichophyton, Epidermophyton

Ringworm

Dry, scaly lesions Intense itching

Symptoms

Chronic inflammation of organs in which they live for many years resulting in gross deformities e.g., limbs, genital organs etc.

Internal bleeding, fever, muscular pain, anemia, blockage of intestinal passage

Symptoms

• Heat and moisture makes the fungi thrive in skin folds such as in groin and between toes.

• Acquired from soil or belongings of infected individuals such as towels, combs, clothes etc.

Body parts affected

Pathogen

Disease

FUNGAL DISEASE

Organ/structure affected

Pathogen

Disease

HELMINTHIC DISEASES

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Rupturing of RBCs releases the toxic substance, haemozoin responsible for symptoms of disease

Constipation Abdominal pain Cramps Stool with excess mucous and blood clots Chills High fever recurring 3-4 days If not treated, can prove to be fatal

Symptoms

• House flies act as mechanical carrier for amoebiasis.

• P. falciparum causes malignant malaria (most serious form).

Plasmodium RBCs • P. vivax • P. malariae • P. falciparum • P. ovale

Large Intestine

Amoebiasis/ Entamoeba Amoebic histolytica dysentery

Malaria

Area affected

Pathogen

Disease

PROTOZOAN DISEASES

Salivary glands

Male

Female

Gametocytes

Human Host

Parasite (sporozoites) reach the liver through blood

Sexual stages–gametocytes (infective stage for female Anopheles) develop in red blood cells.

Stages in the life cycle of Plasmodium

Female mosquito takes up gametocytes with blood meal.

Mosquito Host

Sporozoites

Fertilization and development take place in the mosquito's gut

Mature infective stages (sporozoites) escape from gut and migrate to the mosquito salivary glands.

When the infected mosquito bites another human, sporozoites (infective stage for humans) are injected with the bite

LIFE CYCLE OF

Parasites reproduce asexually in red blood cells, bursting the red blood cells and causing cycles of fever and other symptoms. Released parasites infect new red blood cells

The parasite reproduces asexually in liver cells, bursting the cell and releasing into the blood

Female Anopheles Acts as both host and vector

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Diagnostic Test: ELISA (Enzyme Linked Immuno Sorbent Assay) Treatment: Anti-retroviral drugs, can only prolong life but cannot prevent death Prevention Different agencies like NGOs, NACO, WHO started number of programmes to educate/make people aware of AIDS (Don’t die of ignorance) and some of the measures preventing spreading of HIV infection.

Making blood banks safe from HIV Use of only disposable needles and syringes in public and private hospitals and clinics Free distribution of condoms, advocating safe sex Controlling drug abuse

CANCER A dreaded non-infectious disease; major cause of death all across the globe.

Parameters Cell growth and differentiation

Cancerous cells/Neoplastic cells Uncontrolled & non-regulated

Normal cells Highly controlled and regulated

Contact inhibition Present, virtue of which Lost, so these cells keep on contact with other cells dividing and form mass of inhibits their growth cells called Tumor/Neoplasm Types of Tumor Malignant tumor/cancer Parameters Benign Confined to original place Grow rapidly and spread to other parts Location Damage Invade and damage other cells Little damage starving normal cells by competing for vital nutrients.

Yes, cells sloughed from such tumors Metastasis No reach distant sites through blood and start new tumor called Metastasis (Most feared property).

Cause: Normal cell Proto/cellular Neoplastic transformation oncogene (c-onc) causative agents called carcinogens Ionising radiations– X-rays, -rays

Non-ionising radiations– UV rays

Chemical agents in tobacco smoke

Biological agents–Oncogenic viruses (carry viral oncogenes)

Cancerous cell Oncogene Physical agents

Diagnosis/Detection: Early detection allows the disease to be treated successfully in many cases.

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Technique

Basis Histopathological studies

Detect Changes in tissue

Blood and bone marrow test

Cell counts

Leukemias

Radiography

X-rays

Internal organ cancers

Computed tomography (CT)

X-rays

Internal organ cancers (3D image)

Magnetic resonance Imaging (MRI)

Strong magnetic fields and non-ionising radiations

Accurately detect pathological and physiological changes in living tissue

Molecular techniques

Identification of genes responsible for susceptibility to certain cancers

Antibodies based

Against cancer specific antigens

Biopsy

Certain cancers

Tumor cells have ability to avoid detection and destruction by immune system.

Approaches for treatment: ○ Surgery ○ Radiotherapy: Tumor cells irradiated lethally ○ Chemotherapy: Side effects like hair loss, anemia ○ Immunotherapy: -interferons (Biological response modifiers) activate immune system and helps in destroying the tumor.

IMMUNITY Bio12-P09-8a The ability of the host to fight the disease causing organisms, conferred by the immune system is called immunity.

Types Parameters Observed Exposure to infection Defense Memory record

Acquired

Innate Time of birth Not required Non specific

After birth Required Specific

No

Yes

Memory based immunity evolved in higher vertebrates

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INNATE IMMUNITY Accomplished by providing different types of barriers to the entry of the foreign agents.

Types of Barrier Structures involved/Barrier Basic function Physical

Physiological

Skin Mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts

Prevent entry of microbes Trap microbes entering our body

Saliva in the mouth Acid in stomach Tears from eyes

Prevent microbial growth

Neutrophils/PMNL Monocytes Macrophages Natural killer cells (type of lymphocytes)

Phagocytose microbes Destroy microbes

Cellular

Cytokine

Interferons

Produced by virus infected cells that protect non-infected cells from further infection

ACQUIRED IMMUNITY The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies. This response is carried out by two special types of lymphocytes present in our blood i.e., B and T-lymphocytes.

Thymus

Primary lymphoid organs Lymph nodes

T-cells Secondary lymphoid organs

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Matured lymphocytes migrate

B-cells

Spleen, lymph nodes, tonsils, appendix, MALT, Peyer's patches T-cells mediated response

Thymus

Lymphatic vessels

Bone marrow

Help

Cell-mediated immune response/CMI

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B-cells produce antibodies/Army of proteins in blood Humoral immune response/Antibody mediated immune response

Origin and/or maturation of lymphocytes Lymphocytes become antigen sensitive Provide micro-environments for development and maturation of lymphocytes Provide sites for interaction of lymphocytes with antigen which proliferate to become effector cells.

IMMUNE RESPONSE Type

Primary

Secondary/Anamnestic

Exposure to pathogens

First time

Subsequent times

Low

High

Intensity

Based on memory of first encounter

Responses are carried out by B and T lymphocytes.

Each antibody has 4 peptide chains (H2L2) 2 long heavy chains 2 short light chains Called immunoglobulins (lg) Types – lgA, lgM, lgE, lgG • T-lymphocytes are responsible for graft rejection. Tissue and blood Structure of an antibody molecule group matching are essential before undertaking any graft/transplant and even after this patient has to take immunosuppressants throughout life.

• If the pathogens succeed in gaining entry to our body, specific antibodies and T-cells serve to kill these pathogens.

LYMPHOID STRUCTURES/ORGANS Structure

Typical

Bone marrow Thymus

Main lymphoid organ where all blood cells are produced including lymphocytes.

Spleen

Lymph nodes

MALT

Lobed organ located near the heart and beneath the breast bone. Quite large at the time of birth, keeps reducing in size with age and by the time puberty is attained, it is reduced to a very small size.

Large bean shaped organ, mainly contains lymphocytes and phagocytes Acts as a filter of the blood by trapping blood borne micro-organisms.

Large reservoir of erythrocytes.

Small solid structures located at different points along the lymphatic system Serve to trap the microbes/antigens which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response.

Mucosa-associated lymphoid tissue is located within the lining of major tracts like respiratory, digestive and urinogenital tracts.

Constitutes about 50% of lymphoid tissue in human body.

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VACCINATION AND IMMUNISATION Types of immunity Passive Ready-made/preformed antibodies are directly given

Antibodies

Active Produced within the host body Time taken for full/ Longer effective response Memory cells Examples

Shorter

Yes No Antibody Natural infection production Mother Vaccination in host Deliberate injection of Mother living/dead microbes/proteins

Placenta (lgG)

Foetus

Colostrum (lgA)

Infant

Immunisation (Property of ‘Memory’ of Immune System) Active Passive Preparation of antigenic proteins Direct performed antibodies/antitoxin of pathogen/inactivated/weakened is injected such as antitoxin against pathogen introduced into body snake bites • The antibodies produced in the host body against antigens would neutralize the pathogenic agents during actual infection.

• The vaccines also generate memory B-cells and memory T-cells that recognize the pathogen quickly on subsequent exposure and overwhelm the invaders with a massive production of antibodies.

• Recombinant DNA technology has allowed the large scale production of antigenic polypeptides of pathogen in bacteria/yeast. Hence, greater availability for immunization, e.g., hepatitis B vaccine produced from yeast.

ALLERGIES Exaggerated response of immune system to certain antigens present in the environment.

Allergens Antibodies Symptoms

Substances to which exaggerated immune response is produced e.g., pollens, mites in dust, animal dander, etc. lgE type Sneezing, watery eyes, running nose, difficulty in breathing

Chemical released Histamine and serotonin from mast cells Diagnosis Patient is exposed to or injected with very small doses of possible allergens and reactions studied.

Treatment Anti-histamine, adrenaline and steroids quickly reduce the symptoms of allergy Effects of modern-day life style • Protected environment provided early in life has resulted in lowering of immunity and person is more sensitive to allergens • More and more children in metro cities of India suffer from allergies and asthma due to more sensitivity to the environment.

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DRUG ABUSE

N

Leaves of Cannabis sativa

Synthetic

Other drugs

Coca plant Erythroxylum coca (Native of South America)

Atropa belladonna, Datura

CNS

CH3

Chemical structure of Morphine

HO

H

O

Charas Hashish Ganja Marijuana

(Diacetylmorphine)

Flowering branch of Datura

Snorting

Barbiturates, Benzodiazepines, Amphetamines

alkaloid Commonly called (coke/crack)

Cocaine/coka

dopamine

depression insomnia

Help patients cope with mental illness like

medicine, religious ceremonies and rituals all over the globe

Have been used for hundreds of years in folk-

Excessive dosage causes hallucinations

sense of euphoria and increased energy

Potent stimulating action on CNS, producing

Interferes with transport of neurotransmitter

Effects on cardiovascular system of the body Also being abused by some sport spersons

Effective sedative and pain killer Useful in patients undergone surgery Depressant and slows down body functions Odourless, white, bitter crystalline compound

Morphine Heroin/Smack

Action and anything specific

Examples

Skeletal structure of cannabinoid molecule

Principally Inflorescence, flower Inhalation, oral in brain tops, leaves and resin ingestion of cannabis plant, Cannabis sativa

Opium poppy

Hallucinogens

Stimulants

Cannabinoids

CNS, GIT

Opioids

Intake

Latex of poppy plant, Snorting, injection HO Papaver somniferum

Receptors Source

Drug

Chemical when taken for a purpose other than medicinal use or in amounts frequency impairs one's physical, physiological or psychological functions and constitutes drug abuse. Source-Majorly from flowering plants and some from fungi.

DRUGS AND SPORTSPERSON Why to use?

Increase muscle strength Promote aggressiveness Enhance athletic performance

Commonly abused drugs Narcotic analgesics Diuretics Anabolic steroids Certain hormones

Common side effects Increased aggressiveness Mood swings Depression Stunted growth because of premature closure of growth centres of long bones Severe facial and body acne

Typical side effects Male Breast enlargement Decreased sperm production Reduction in size of testicles Acne, premature baldness, enlargement of prostate gland

Female Masculinisation (features like males) Abnormal menstrual cycles Enlargement hair growth on face & body Deepening of voice

AUTOIMMUNITY Memory based acquired immunity evolved in higher vertebrates can distinguish foreign molecules as well as foreign organisms (pathogens) form self-cells.

Results – Self destruction/body attack self cells Reason – Genetic/unknown Example – Rheumatoid arthritis

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TABACCO/SMOKING-PAVES THE WAY TO HARD DRUGS Intake Chemical substance Action of nicotine Effects Respiratory system

Circulatory system Common diseases

Risk of cancers

Smoked Chewed Snuff Nicotine, an alkaloid Stimulates adrenal gland to release adrenaline and non-adrenaline into blood circulation.

Increases carbon monoxide (CO) in blood and reduces concentration of haembound oxygen, causes oxygen deficiency in the body Increase heart rate and blood pressure Bronchitis Emphysema Coronary heart disease Gastric ulcer Oral cavity Throat Lungs Urinary bladder

• Tobacco has been used by humans for more than 400 years.

ADOLESCENCE AND DRUG/ALCOHOL ABUSE Adolescence means both “a period” and “a process” during which a child mature in terms of his/her attitudes and beliefs for effective participation in society.

Adolescence is a bridge linking childhood and adulthood.

It is a period between 12-18 years of age, a vulnerable phase of mental and psychological development of an individual.

It is accompanied by several biological and behavioural changes.

Curiosity, need for adventure and excitement, and experimentation, motivate youngsters towards drug and alcohol use.

First use may be out of curiosity but later used to escape from stress, pressures to excel in academics, perception that it is cool.

Television, movies, newspapers, internet, promote this perception.

Unstable or unsupportive family structures and peer pressure also promote drug and alcohol abuse.

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ADDICTION AND DEPENDENCE Addiction Because of perceived benefits, drugs are frequently used repeatedly that leads to psychological attachment to certain effects like euphoria and temporary felling of well being.

Dependence It is the tendency of the body to manifest a characteristic and unpleasant “withdrawal syndrome” if regular dose of drugs/alcohol is abruptly discontinues.

Addiction drive people to take drug even when its use become self-destructive.

With repeated use of drug, tolerance level of receptors increases.

Receptors respond only to higher doses of drugs leading to greater intake.

Effects of drug/alcohol abuse Reckless behavior Vandalism Violence Depression Fatigue Drop in academic performance Warning signs: Unexplained absence from school/college Poor personal hygiene, withdrawal, isolation Aggressive and rebellious behavior Loss of interest in hobbies Change in sleeping and eating habits Fluctuations in weight and appetite Deteriorating relationships with family and friends High doses lead to coma and death due to respiratory failure, heart failure or cerebral hemorrhage.

Chronic use of drugs/alcohol damage nervous system and liver (cirrhosis).

Use of drugs during pregnancy adversely affect foetus.

Some far-reaching implications Abuser may turn to stealing.

Addict becomes the cause of mental and financial distress to entire family and friends.

Withdrawl syndrome If drug is abruptly discontinued, symptoms include: Anxiety Nausea Shakiness Sweating In severe cases, can be life threatening, person needs a medical supervision.

Prevention and control “Prevention is better than cure” Avoid undue peer pressure on child related to studies, sports or other activities.

Education and counselling: Channelise energy of child into healthy pursuits like sports, yoga, reading, music, etc.

Sort out problems by seeking help from parents and peers.

Looking for danger signs Alert parents, teachers and close friends need to look for and identify the danger signs of substance (drug/alcohol) abuse and appropriate measures would then be required to diagnose the malady and underlying cause.

Proper remedial steps or treatment should be taken by seeking professional and medical help in the form of highly qualified psychologists, psychiatrists, and de-addiction and rehabilitation programmes, This will totally relieve the individual from these evils.

Use of durgs even once can be “fore-runner to addiction” and pull the user into a vicious circle leading to their regular use/abuse.

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9A

Chapter

Strategies for Enhancement in Food Production ANIMAL HUSBANDRY Agricultural practice of breeding and raising livestock useful to humans.

Animal husbandary deals with the care and breeding of livestock like buffaloes, cows, pigs, goats etc.

Animal husbandary = Poultry farming + Fisheries Some of the products and the animals involved are: Useful product Milk Eggs Meat Wool Honey

Source Cows, buffaloes, Goats Poultry birds, Chicken, Ducks, Turkey, Geese Cattle, Sheep, Pigs Sheep Bees

More than 70% population of livestock is in India and China but contribution to world's farm produce is 25% Due to the low productivity per unit Insuf cient food supply due to ever increasing population size.

Improvement in conventional practices of animal breeding by applying newer technologies to improve the quality and productivity.

FISHERIES Rearing, Fish Catching, Molluscs (shell- sh) Industry devoted Processing Crustaceans (prawns, crabs) & Selling Aquatic animals Aquaculture: Enhancement in aquatic yield including plants and animals Pisciculture: Products from shery Increase in total Food: lobster, prawn, sh, edible oyster sh yield Marine (M) Fresh water (FW) Hilsa, Sardines, Mackerel, Pomfrets Catla, Rohu, Common carp To meet the increasing demand on sheries, different techniques have been employed that led to Blue revolution.

MANAGEMENT OF FARM AND FARM ANIMALS A professional approach is needed to boost our food production.

Some of the management procedures employed in animal farm system are management: 1. Diary farm management/Dairying: Management of animals for milk and its products for human consumption e.g., Cows, buffaloes Aimed at

Increasing yield Depends on Quality of breed

Jersey

Improving quality of milk High yielding potential Resistance under given climatic to diseases conditions of the area ○ Practices involved Stringent cleanliness of – Effective housing – Adequate water Cattle Handlers – Maintain disease free conditions Regular inspection by – Cattle diet (fooder) veterinary doctor Quality Quantity balanced

Increased mechanization in dairy farming particularly milking, storage and transport of milk, reduces chances of direct contact of the produce with the handler 2. Poultry farm management ○ Involves use of birds for food • Birds: Fowl, chicken, ducks, turkey, geese

Eggs Meat

○ Requirement: • Selection of disease free and suitable breeds • Proper and safe farm conditions • Proper feed and water • Maintaining proper health care and hygiene Disease Cause Symptoms People at risk

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Leghorn

Bird y H5N1 virus Respiratory dif culty, fever, malaise – Poultry farmers exposed to infected birds – People who eats under cooked eggs/poultry

Strategies for Enhancement in Food Production

BEE-KEEPING (Apiculture) It is the maintenance of hives of honeybees for the production of honey Age old, high income yield cottage industry and is not labour intensive Most common bee in India: Apis indica Advantages a. Increases product yield b. Enhances crop yield

Products obtained from honey bee

Salient points for successful bee keeping (i) Knowledge of the nature and habits of bees (ii) Selection of suitable location for keeping the beehives (iii) Catching and hiving of swarms (group of bees) (iv) Management of beehives during different seasons (v) Handling and collection of honey and beeswax

Honey • Food: High nutritive value • Used in Indigenous medicine Bees are effective pollinators

Bees wax • Preparation of cosmetics and polishes

Areas for practice Pastures for shrubs Brassica Pear

Crop elds

Fruit orchards Sun ower Apple

Keeping beehives in crop elds during owering period increases pollination ef ciency and improve the yield.

ANIMAL BREEDING Breed: A group of animals related by descent and similar in most characters like general appearance, features, size, con guration etc.

Aims of animal breeding: ○ Increase the product yield (Quantity ) ○ Improving desirable qualities in produce High yielding variety Disease resistant High reproductive rate Longer productivity span

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84

SELECTIVE BREEDING OR HYBRIDISATION Types of selective breeding Outbreeding Inbreeding ○ Mating between male and female ○ Mating of more closely related of same breed (no recent common individuals within the same ancestor) or different breeds or breed for 4-6 generations different species ○ Inbreeding increases homozygosity and is useful to evolve purelines Advantage Disadvantages ○ Increases the productivity of ○ Inbreeding depression Fertility population as superior genes due to continued close are accumulated and harmful inbreeding Productivity recessive genes are eliminated 1. Outcrossing Mating of animals within the same breed but having no common ancestors upto 4-6 generations Advantage A single out cross helps increase productivity of animals below average Growth rate in beef cattle Milk production 2. Cross breeding ○ Mating between superior male of one breed and superior female of another breed ○ This method allows combination of superior qualities of two different breeds on a commercial scale.

Advantage ○ Stable new breeds superior to existing breeds can be developed ○ Example: A new breed of sheep ♀/Female × Bikaneri ewe

Hisardale Location: Punjab

♂/Male Merino ram

3. Interspeci c hybridization ○ Male and female of two different related species are mated Advantage ○ Progeny may combine desirable features of both the parents and may be of considerable economic value

85

Strategies for Enhancement in Food Production

○ Example:

♂/Male Donkey

♀/Female × Horse (Mare)

Mule (Sterile)

Inbreeding depression can be overcome by out crossing i.e., method to restore fertility and yield

CONTROLLED BREEDING EXPERIMENTS Arti cial Insemination (AI) Identify elite bull

Extract semen

Either used immediately of Cryopreservation (cold storage)

Inject into reproductive tract of superior cow Advantages

Multiple Ovulation Embryo Transfer (MOET) Identify superior cow

Inject with FSH-like hormone

Super ovulation (6-8 ova/cycle)

AI or natural insemination

Non surgical extraction of embryo

Gestation in surrogate cow

○ Greater chances of fertilization ○ Increase herd size and quality in less time ○ Economically relevant as all sperms can be used since semen ○ Genetic mother available for from 1 bull can fertilise more than another round of super 1 cow, if needed ovulation ○ Helps to overcome several problems of normal mating Disadvantages ○ The success rate of crossing mature and is fairly low

○ Not applicable to shes and birds

• MOET is demonstrated on mammals such as cattle, mares, sheep, rabbits • Superior cow: High yield of milk/lactation Have been bred successfully to • Superior bull: Lean meat with less lipid increase herd size in a short time

qqq

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86

9B

Chapter

Strategies for Enhancement in Food Production INTRODUCTION ♦ Biological principles as applied to animal husbandry and plant breeding have a major role in our efforts to increase food production.

Plant Breeding • Green revolution was dependent to a large extent on plant breeding techniques for development of high yielding and disease resistant varieties in wheat, rice, maize etc.

• Purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation, give better yields and are disease resistant.

• Classical plant breeding involves crossing or hybridization of pure lines, followed by artificial selection to produce plants with desirable traits of higher yields, nutrition and resistant to diseases.

Characters that breeders want to incorporate into the crops plants are increased crop yield, improved quality, increased tolerance to environmental stresses like salinity, drought, extreme temperature, resistance to pathogens and increased tolerance to insect pest.

The main steps of plant breeding: (i) Collection of variability: Genetic variability is the root of breeding programme (ii) Evaluation and selection of parents: Germplasm is evaluated, selected plants are multiplied and used for hybridisation. Purelines are created wherever desirable and possible. (iii) Cross hybridization among the selected parents: Very time consuming and tedious process, it is not necessary that the hybrids do combine the desirable characters.

(iv) Selection and testing of superior recombinants: This step is crucial to the success of the breeding objective and requires careful scientific evaluation of progeny. This step yields plants that are superior to both the parents. (v) Testing, release and commercialisation of new cultivars: The entire collection of plants/seeds having all the diverse alleles for all genes in a given crops is called germplasm collection.

Agriculture accounts for approximately 33 percent of India's GDP. The development of several high yielding varieties of wheat and rice in the mid 1960s, as result of various plant breeding techniques led to dramatic increase in food production in our country. This phase is often referred to as the Green Revolution.

Wheat and Rice: • During the period 1960 to 2000, wheat production increased from 11 million tonnes to 75 million tonnes. Rice production went up from 35 million tonnes to 89.5 million tonnes. This was due to the development of semi-dwarf varieties of wheat and rice.

• Nobel laureate Norman E. Borlaug, at International Centre for Wheat and Maize improvement in Mexico, developed semi-dwarf wheat.

• In 1963, several varieties such as Sonalika and Kalyan Sona, which were high yielding and disease resistant were introduced all over the wheat-growing belt of India.

• Semi-dwarf rice varieties were derived from IR-8, (developed at International Rice Research Institute (IRRI), Philippines) and Taichung Native-1 (from Taiwan). The derivatives were introduced in 1966. Later, better-yielding semi-dwarf rice varieties Jaya and Ratna were developed in India.

Sugarcane: • Saccharum barberi was originally grown in north India, but had poor sugar content and yield, Tropical canes grown in south India • Saccharum officinarum had thicker stems and higher sugar content but did not grow well in north India. These two species were successfully crossed to get sugar cane varieties combining the desirable qualities of high yield, thick stems, high sugar content and ability to grow in the sugar cane areas of north India.

Millets: • Hybrid maize, jower and bajra have been successfully developed in India.

88 Ha n d Book (Biolog y )

Plant Breeding for disease resistance • Method of breeding for disease resistance: Conventional breeding techniques or by Mutation breeding.

Crop

Variety

Resistance to Disease

Wheat

Himgiri

Leaf and stripe rust, hill bunt

Brassica

Pusa Swarnim (Karan rai)

White rust

Cauliflower

Pusa Shubhra, Pusa Snowball K-1

Black rot and Curl blight black rot

Cowpea

Pusa Komal

Bacterial blight

Chili

Pusa Sadabahar

Chilly mosaic virus, Tobacco mosaic virus and Leaf curl

Resistance of the host plant is the ability to prevent the pathogen form causing disease and is determined by the genetic constitution of the host plant • Mutation breeding: Induce mutations through use of chemicals or radiations and selecting and using the plants that have the desirable character.

In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations.

In Bhindi (Abelmoschus esculantus), resistance to yellow mosaic virus was transferred from a wild species and resulted in a new variety of Abelmoschus esculentus callled Parbhani Kranti.

PLANT BREEDING FOR DEVELOPING RESISTANCE TO INSECT PESTS • It may be due to morphological, biochemical or physiological characteristics.

• Source of resistance genes: Cultivate varieties, germplasm collections of the crop or wild relatives.

Crop

89

Resistance to insect/ pest

Reason of resistance

Type of resistance

Wheat

Stem saw fly

Solid stem

Morphological

Wheat

Leaf beetle

Hairly leaves

Morphological

Cotton

Jassids

Hairly leavs

Morphological

Cotton

Bollworms

Smooth leaves and absence of nectar

Morphological and Biochemical

Maize

Stem borers

Low nitrogen, sugar and high aspartic acid

Biochemical

Strate g ie s

for En h a n c e m e n t in

Food Prod u c tion

Some released crop varieties bred by hybridisation and selection for insect pest resistance are given Crop

Variety

Insect Pestst

Brassica (rapeseed mustard)

Pusa Gaurav

Aphids

Flat bean

Pusa Sem2 Pusa Sem3

Jassids, aphids and fruit borer

Okra (Bhindi)

Pusa Sawani Pusa A-A

Shoot and Fruit borer

Plant Breeding for Improved Food Quality • More than 840 million people in the world do not have adequate food to meet their daily food and nutritional requirements. They suffer from hidden hunger.

Biofortification: Breeding crops with higher levels of vitamins and minerals or higher protein and healthier fats – Most practical means to improved public health.

Objectives of improving 1. Proteins content and quality 2. Oil content and quality 3. Vitamin content 4. Micronutrient and mineral content • In 2000, maize hybrids that had twice the amount of the amino acids, lysine and tryptophan were developed. Wheat variety, Atlas 66 having a high protein content (donor for improving cultivated wheat).

• IARI (India Agricultural Research Institue, New Delhi) has developed several vegetable crops that are rich in vitamins and minerals and proteins e.g.

Vitamin A enriched carrots, spinach, pumpkin.

Vitamin C enriched bitter gourd, bathua, mustard, tomato.

Iron and calcium enriched spinach and bathua and protein enriched beans (Broad, lablab and french) and garden peas.

SINGLE CELL PROTEINS (SCP) • More than 25 per cent of human population is suffering from hunger and malnutrition.

• Source of good protein are Spirulina, Methylophilus methylotrophus, mushrooms and some fungi.

• Microbes like Spirulina can be grown easily on waste water from potato processing plants, such utilisation reduces environmental pollution.

Ha n d Book (Biolog y )

90

• 250 kg cow produced 200 g of protein per day.

• 250g of micro organism like Methylophilus methylotrophus (due to high rate of biomass production & growth) produces 25 tonnes of protein.

TISSUE CULTURE • To provide sufficiently fast and efficient systems for crop improvement.

• Explant: Any plant part taken out and grown in a test tube under sterile conditions in special nutrient media.

• The capacity to generate whole plant from ex-plant is called totipotency.

• Micropropagation: Propagation of a large number of plants through tissue culture.

• They are somaclones.

• Tomato, banana, apple etc. have been produced.

• Another important application of the method is the recovery of healthy plants from diseased plant. Even if the plants is infected with the virus, the meristem is free of virus.

• Somatic hybridisation: Isolated protoplasts from two different varieties of plants can be fused to get hybrid protoplasts which can be further grown to from a new plant. These hybirds are called Somatic hybrids.

• Protoplast hybrid of potato and tomato called pomato was created but unfortunately, this plant did not have all the desired combination of characteristics for its commercial utilization. qqq

91

Strate g ie s

for En h a n c e m e n t in

Food Prod u c tion

10

Chapter

Microbes in Human Welfare INTRODUCTION ♦ Microbes are diverse-protozoa, bacteria, fungi and microscopic animal & plant viruses, viroids and also prions and present everywhere even at thermalvents, snow layer and highly acidic environment. ♦ Grown on nutritive media to form colonies that can be seen with naked eyes. Such cultures are useful in studies on micro-organisms.

MICROBES IN HOUSEHOLD PRODUCTS • Lactobacillus & others (LAB) grow in milk & convert it to curd. LAB produce acids that coagulate & partially digest milk proteins at suitable temperatures. It also improves its nutritional quality by increasing Vit-B12.

• LAB play beneficial role in checking pathogenic microbes in our stomach.

• The dough used for dosa, idli is fermented by bacteria.

• Microbes are used to ferment fish, soyabean & bamboo shoots to make foods.

• The characteristic texture, flavour, taste and specificity of cheese is due to the microbes: Swiss cheese: Large holes are due to large amount of CO2 produced by the bacterium, Propionibacterium sharmanii.

Roquefort cheese: Ripened by a specific fungi which gives the specific flavour. ♦ Dough: Used for making bread, fermented using baker’s yeast Saccharomyces cerevisiae.

• Toddy is fermented sap from palms.

MICROBES IN INDUSTRIAL PRODUCTS Fermented Beverages • Saccharomyces cerevisiae, is used for beverages production and called brewer's yeast. It is also used for fermenting malted cereals & fruit juices to produce ethanol.

• Wine & beer are produced without distillation. Whisky, brandy & rum are produced by distillation of fermented broth.

Antibiotics (Anti = against, bio = life) • Penicillin-First antibiotic was a chance discovery, by Alexander Fleming, while working on staphylococci bacteria, when he observed that they did not grow due to the growth of mould Penicillium notatum.

Its full potential was discovered by Chain & Florey. Fleming, Chain & Florey were awarded Nobel prize 1945.

Chemicals, Enzymes & other Bioactive Molecules • Aspergillus niger (a fungus) – Citric acid • Acetobacter aceti (a bacterium) – Acetic acid • Clostridium butylicum (a bacterium) – Butyric acid • Lactobacillus (a bacterium) – Lactic acid • Saccharomyces cerevisiae – Ethanol • Lipases – Used in detergent formulations.

• Streptokinase produced by bacterium Streptococcus & modified by genetic engineering is used as a ‘clot buster’ for removing clots from blood vessels of myocardial infarction [MI] patients.

• Cyclosporin-A, used as immunosuppressive agent in organ-transplant patients, is produced from Trichoderma polysporum (a fungus).

• Statins produced by yeast Monascus purpureus is a blood-cholesterol lowering agent.

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Microbes in Human Welfare

MICROBES IN SEWAGE TREATMENT z

z

The municipal waste water is called sewage. A major component of this waste water is human excreta. It contains large amounts of organic matter & microbes.

Treated in sewage treatment plants (STPs) by heterotrophic microbes to make it less polluting.

Primary Treatment (Physical treatment) Involves physical removal of particles large & small from the sewage through filtration and sedmentation Floating debris is removed by sequential filtration Grit (soil & small pebbles removed by sedimentation)

Secondary Treatment (Biological treatment) Primary effluent is passed into large aeration tanks

Constantly agitated and air is pumped into it Allows vigorous growth of useful aerobia microbes into flocs.

(Bacteria + fungal filaments to form mesh like structures) Solids that settle form Microbes grow & consume the the primary sludge & the major part of organic matter, supernatant forms the effluent. significantly reducing the BOD. The effluent is taken for Effluent passed into setting tank, secondary treatment. where bacterial ‘flocs’ sediment, called Activated sludge and then effluent from secondary treatment plant can be released into natural water bodies.

A small part of the activated sludge is pumped back into aeration tank to serve as inoculum. Rest is pumped into anaerobic sludge digesters.

In anaerobic sludge digester, aerobic bacteria digest bacteria & fungi in the sludge. Produce a Mixture of CH4, H2S, CO2 (Biogas)

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94

MICROBES IN PRODUCTION OF BIOGAS • Mixture of gases (predominantly methane) produced by microbial activity.

• Methanogens, like Methanobacterium, grow anaerobically on cellulosic material to produce large amount of CH4 along with CO2 and H2.

• These bacteria are commonly found in anaerobic sludge during sewage treatment, rumen of cattle.

• In rumen, these bacteria help in the breakdown of cellulose & play an important role in nutrition of cattle. The excreta of cattle (dung), commonly called Gobar is rich in these bacteria.

• Dung can be used for generation of biogas, so commonly called Gobar gas.

BIOGAS PLANT • Consist of a concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of dung is fed.

• A floating cover is placed over the slurry which rises when gas is produced due to microbial activity.

• It has outlet to transfer biogas.

• Slurry is removed and may be used as fertiliser.

• Biogas can be used for cooking and lighting.

• The technology of biogas production was developed in India mamly due to the efforts of Indian Agricultural Research Institute (IARI) & Khadi & Village Industries Commission (KVIC).

95

Microbes in Human Welfare

MICROBES AS BIOCONTROL AGENTS • Refers to the use of biological methods for controlling plant diseases and pests.

Biological control of pests & diseases • Relies on natural predation.

• Chemical methods: Kill both useful and harmful life forms indiscriminately.

Beetle with red & black markings: Ladybird & dragon­flies are useful to get rid of aphids and mosquitoes respectively.

Butterfly caterpillars are controlled by bacteria Bacillus thuringiensis (Bt) on plants such as brassicas & fruit trees.

Bt toxin genes is introduced to produce Bt-cotton.

Fungus Trichoderma, common in the root ecosystems, effective against several plant pathogens.

Baculoviruses attack insects and other arthropods. Majority of Baculoviruses are in the genus Nucleopolyhedrovirus, they are species-specific, narrow spectrum insecticidal applications.

MICROBES AS BIOFERTILISERS • Organisms that enrich the nutrient quality of the soil.

• Main sources: Bacteria, fungi and cyanobacteria.

• Root nodules in leguminous plants are formed by symbiotic association of Rhizobium to fix atmospheric nitrogen into organic forms.

• Free-living N2-fixers like Azospirillum and Azotobacter enrich the soil.

• Fungi-plant root symbiotic association is called mycorrhiza (Glomus form mycorrhiza). Fungi absorb phosphorus from soil & passes to the plant. Plants also show resistance to root-borne pathogens, tolerance to salinity and drought and overall increase in growth and development.

• Cyanobacteria like Anabaena, Nostoc, Oscillatoria etc. fix atmospheric N2 in paddy fields.

• BGA (blue green algae) also add organic matter to the soil and increase its fertility

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96

NOTES

• The puffed-up appearance of dough is due to CO2 gas.

• Toddy is a traditional drink of some parts of Southern India.

• Antibiotics mean against life, in the context of disease causing organisms but in context to human life they are ‘pro life’.

• Bottled juices are clarified by use of pectinases and proteases.

• Statins act by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

• BOD (Biochemical Oxygen Demand) is the amount of oxygen consumed if all the organic matter in one liter of water were oxidised by bacteria.

• BOD test measures the rate of uptake of oxygen by micro­organisms m a sample of water. BOD is a measure of the organic matter present in the water.

• Microbes play a major rote in treating millions of gallons of waste water everyday across the globe. Till date, no man­-made technology has been able to rival the microbial treatment of sewage.

• The ministry of Environment and Forests has initiated Ganga Action Plan & Yamuna Action Plan to save these major rivers of our country from pollution.

• The biocontrol measures help us to avoid heavy use of toxic pesticides for controlling pests. qqq

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Microbes in Human Welfare

Chapter

11 Biotechnology: Principles and Processes

INTRODUCTION ♦ Biotechnology deals with techniques of using live organisms or enzymes from organisms to produce products and processes useful to humans.

Parameters

Traditional biotechnology

Modern biotechnology

Organisms involved Microbes

Genetically modified organisms

Production

Small scale

Large scale

Examples

Curd, bread or wine In vitro fertilisation making leading to a ‘test-tube’ baby

z

z

EFB (European Federation of Biotechnology)

Synthesising a gene and using it

The integration of natural science and organisms, cells, parts thereof and molecular analogues for products and services.

It encompasses both traditional view and modern molecular biotechnology.

Developing a DNA vaccine Correcting a defective gene

Principles of Biotechnology/Core Techniques Involved in Modern Biotechnology Parameters

Genetic engineering

Bioprocess engineering

Definition

Techniques to alter the chemistry of genetic material to introduce these into host organisms and thus change the phenotype of host organism

Maintenance of sterile ambience in chemical engineering processes to enable growth of only the desired microbe/ eukaryotic cell in large quantities

Include

Creation of rDNA Gene cloning Gene transfer

Manufacture of biotechnological products like antibiotics, vaccines, enzymes etc.

The ability to multiply copies of antibiotic resistance gene in E.coli was called cloning of antibiotic resistance gene in E.coli.

Advantages of Biotechnology over other Techniques Methods

Advantage

Disadvantage

Asexual reproduction

Preserves genetic information

Sexual reproduction

Provides opportunities for Some of which may be variations and formulation harmful to the organism or unique combinations of as well as the population genetic setup

Traditional hybridisation

Used in plant and animal breeding.

Genetic engineering

Allows us to isolate and introduce only one or a set of desirable genes without introducing undesirable genes into target organism.

99

No variations

Very often lead to inclusion and multiplication of undesirable genes along with desirable genes.

—

Biotechnology: Principles and Processes

Three Basis Steps in Genetically Modifying Organisms (GMO) z

Identification of DNA with desirable genes

z

Introduction of the identified DNA into the host

z

Maintenance of introduced DNA in the host and transfer of the DNA to its progeny

KEY TOOLS OF RECOMBINANT DNA TECHNOLOGY (1) Enzymes (2) Vectors (3) Competent host cells Enzymes

Most commonly used Nucleases enzymes in genetic DNA polymerase engineering are Ligases Nucleases ↓

Catalyse the cleavage of nucleic acids ↓ Type Exonucleases

Endonucleases

Remove nucleotides from the ends of the DNA

Make cuts at specific positions within the DNA i.e. at recognition/palindromic sequence ↓ In the year 1963, the two enzymes responsible for restricting the growth of bacteriophage in Escherichia coli were isolated ↓

Methylase

Restriction endonuclease/Molecular scissors

Add methyl group to Cut the DNA of bacteriophage bacterial DNA Palindromic sequence reads same on the two strands (from 5′ → 3′ and 3′ → 5′ direction) when orientation of reading is kept same

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ENZYMES Restriction endonuclease More than 900 restriction enzymes have been isolated from over 230 strains of bacteria (prokaryotic cell) each of which recognise different recognition sequences.

Nomenclature of enzyme: Eco RI

Genus Species Strain Order of Escherichia coli RY13 isolation

First restriction endonuclease-Hindi II: Isolated and characterised five years later, recognises sequence of 6 bp.

Stanley Cohen and Herbert Boyer, 1972.

Functions: • Inspecting the length of DNA sequence • Binds to the specific recognition sequence • Cuts the two strands of dsDNA at specific points in their sugarphosphate backbones and leaves single stranded portions at the ends.

• These overhanging stretches called sticky ends.

Ligase • When source DNA and vector DNA are cut by the same restriction enzyme, the resultant DNA fragments have the same kind of sticky-ends .

• Sticky ends are named so because they form hydrogen bonds with their complementary cut counterparts.

• Stickiness facilitates the action of the enzyme DNA ligase.

101 Biotechnology: Principles and Processes

CLONING VECTORS Vectors are vehicles for delivering foreign DNA into recipient cells.

Vectors used at present are engineered in such a way that they help easy linking of foreign DNA and selection of recombinants from non recombinants.

Features of cloning vectors: • Origin of Replication (ori): Sequence from where replication starts Responsible for controlling copy number of the linked DNA Those vectors are preferred which support high copy number • Selectable Marker: Helps in selection of transformants Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E.coli The normal E.coli cells do not carry resistance against any of these antibiotics • Cloning Sites/Restriction Sites: Single recognition site for a restriction enzyme within the vector is a preferable feature.

Presence of more than one recognition sites within the vector will generate several fragments which will complicate the gene cloning.

The ligation of alien DNA/gene of interest (GOI) is carried out at a restriction site present in one of the antibiotic resistant genes.

Transformation: Procedure through which piece of foreign DNA is introduced in a host bacterium.

• Insertional inactivation: Insertion of gene of interest within antibiotic resistance gene/selectable marker results in inactivation.

• Hypothesis: Insertion of GOI at Bam HI site in tetR. If transformation fails: Non transformants are obtained in antibiotic lacking agar medium but they do not grow on antibiotic rich medium.

• If transformation is successful: Transformants obtained are of two types:

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Non Recombinants EcoR I Cla I

Hind III

Pvu I Pst I E. coli cloning vector pBR322

Recombinants Insertional inactivation BamH I

ampR

Ligate

tetR

pBR322 ori

Sal I

rop

Foreign DNA at Bam HI site

ampR

tetR

Pvu II Gene of interest cloned

No

Yes

Resistance to ampicillin

Yes

Yes

Resistance to tetracycline

Yes

No

All transformants are not recombinants but all recombinants are transformants.

• Non-Transformants: Hosts that do not take up the vector DNA (Recombinant or Non-recombinant).

• Transformants: Hosts that take up the vector DNA (Recombinant or Non-recombinant).

• Recombinants: Transformant hosts that take up the recombinant DNA (Vector DNA with desired DNA).

• Non-Recombinants: Transformant hosts that take nonrecombinant DNA (Vector DNA without desired DNA)

up

the

• rop → Codes for the proteins involved in the replication of the plasmid.

Plasmids as vectors: • Extra chromosomal, circular, double stranded DNA. • Replicate independent of the control of chromosomal DNA (autonomously).

• They may have 1 or 2 copies per cell or even 15-100 copies per cell.

OTHER CLONING VECTORS Selection of recombinants due to inactivation of antibiotic resistant gene as in pBR322 is a cumbersome procedure because it requires simultaneous plating of two plates having different antibiotics.

To overcome the disadvantage of pBR322, alternative selectable markers (lac Z) acting as reporter enzyme have been developed which differentiate recombinants from non- recombinants on the basis of their ability to produce colour in the presence of chromogenic substrate.

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Biotechnology: Principles and Processes

• lac Z gene coding for b-galactosidase acts as selectable marker in the plasmid.

Experiment: Insert foreign DNA at lac Z gene + transformation in E.coli Chromogenic substrate

Fails

Succeeds

Blue coloured colonies

White coloured colonies

Non-recombinants

Recombinants

Ti-plasmid of Agrobacterium tumefaciens • Agrobacterium tumefaciens, a pathogen of several dicot plants is able to deliver a piece of DNA known as ‘T-DNA’ to transform normal plant cells into a tumor and direct the tumor cells to produce the chemicals required by the pathogen.

• Disarmed tumour inducing (Ti) plasmid is used which is no more pathogenic to the plants but is still able to use the mechanism to deliver the genes of our interest into varieties of plants.

Bacteriophages • High copy number than plasmid

Retroviruses • Retroviruses in animals have the ability to transform normal cells into cancerous cells.

Disarmed retroviruses are used to deliver desirable genes into animal cells.

Methods of Transformation 1. Micro-injection Recombinant DNA is directly injected into the nucleus of an animal cell.

2. Biolistic/Gene gun Plant cells are bombarded with high velocity microparticles of gold or tungsten coated with DNA. 3. Heat shock method 4. Disarmed pathogen vector 104 Hand Book (Biology)

Competent Host for Transformation with recombinant DNA • DNA is hydrophilic, so it can not pass through cell membranes • In order to force cell to take up alien DNA/rDNA, it must first be made ‘competent’ by treating with ice cold calcium chloride (CaCl2).

• Entry of rDNA in host cell is due to transient pores created by heat shock (42°C) and not due to Ca2+ ions.

• Divalent cations increases the efficiency with which DNA enters the bacterium through pores in its cell wall.

Process of Recombinant DNA Technology Isolation of DNA Fragmentation of DNA by restriction endonucleases Isolation of desired DNA fragment (electrophoresis) Amplification of gene of interest (PCR) Ligation of the DNA fragment into a vector Transferring the alien DNA/recombinant DNA into the host Culturing the host cells in a medium at large scale (Bioreactors) Extraction and purification of the desired product 1. Isolation of the Genetic Material (DNA) In majority of organisms, DNA is the genetic material.

Since DNA is enclosed within the membranes, we have to break the cell open to release DNA along with other macromolecules

105

 Bacteria

→

Lysozyme

 Fungi

→

Chitinase

 Plant cell

→

Cellulase

Biotechnology: Principles and Processes

Pure DNA

Centrifuge

Chilled ethanol to precipitate DNA

Process

In order to get DNA in pure form (free from other macromolecules), it is treated with different enzymes like RNase, protease etc.

Spooling

2. Fragmentation by restriction endonucleases 3. Separation and isolation of DNA fragments • Gel electrophoresis: Separation of negatively charged DNA molecules under an electric field through a medium/matrix.

Most commonly used matrix for DNA separation is Agarose

Natural polymer, obtained from sea weeds Wells filled with DNA fragments Largest

DNA bands

Separation on the basis of size (Smaller the DNA fragment farther it moves) Smallest

3 4

+ electrode/ anode

Gel

Elution

Stained with

Process

Ethidium Bromide

Exposed to

Removal of DNA fragment from gel

U.V rays

Appears

1

2

–electrode/ cathode

Separate DNA fragments through seiving effect

Bright orange bands

Purified DNA fragments are generally amplified (PCR) before constructing rDNA by joining with cloning vector.

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4. PCR-Polymerase Chain Reaction In vitro amplification of DNA (gene of interest) Reaction mixture

Work/Function

Nucleotides

Formation of DNA

Primers

2 sets of chemically synthesised oligonucleotides, complementary to the regions of DNA

Taq Polymerase

Thermostable DNA polymerase, isolated from bacterium, Thermus aquaticus, remains active during high temperature induced denaturation of dsDNA. It extends the primers i.e., meant for chain elongation.

Genome DNA

Template DNA for gene of interest

Sequence of events

• The amplified fragment if desired can now be used to ligate with a vector for further cloning.

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Biotechnology: Principles and Processes

5. Ligation of the DNA fragment into a vector by DNA ligase 6. Insertion of recombinant DNA into the host cell Transformed host cells are selected with the help of selectable marker genes.

7. Culturing of recombinant host cells (Biosynthetic stage) The cells harbouring cloned genes of interest may be grown in Laboratory/ Bioreactors Bioreactors: Vessels in which raw materials are biologically converted into specific products using microbial plant, animal human cells and provide optimal growth conditions (temperature, pH, substrate, salts, vitamins, oxygen) Parameters

Laboratory

Bioreactors

Culture

Small volume

Large volumes (100-1000 L)

Maintaining optimal conditions

Not possible

No

Growth rate of cell

Never optimal

Optimum

Production

Small scale

Large scale

Cylindrical or with curved base Stirrer Agitator system Commonly used Bioreactors are stirred

Facilitate mixing of reactor contents Facilitate even mixing and oxygen availability throughout the bioreactor

Oxygen delivery system pH control system Foam control system Sampling ports

Hand Book (Biology)

To withdraw small volumes of culture periodically

108

8. Downstream processing Separation and purification of the desired product/recombinant protein from heterologous host (non native host).

Product has to be formulated with suitable preservatives.

Strict quality control testing is done for each product.

The downstream processing and quality control testing vary from product to product.

9. Product is subjected for marketing as a finished product

In Open culture system/Continuous Culture System • Used medium is drained out from one side.

• Fresh medium is added from the other to maintain the cells in their physiologically most active log/exponential phase.

• Larger biomass → Higher yields of desired protein. qqq

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Biotechnology: Principles and Processes

Chapter

12 Biotechnology and Its Applications

INTRODUCTION Biotechnology: Deals with industrial scale production of biopharmaceuticals and biologicals using GM microbes, fungi, plants and animals.

Applications of biotechnology include: Therapeutics

Processed food

Diagnostics

Bioremediation

Genetically modified

Waste treatment

crops for agriculture

Energy production

Three critical research areas of biotechnology: Providing best catalyst in the form of improved microbes or pure enzymes Creating optimal conditions through genetic engineering Downstream processing technologies for purification

BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE Food production could possibly be increased by three ways: (i) Agrochemical based agriculture (ii) Organic agriculture (iii) Genetically engineered crop-based Green revolution resulted in tripling of food production: Reasons for success of green revolution: Improved crop varieties Agrochemicals (Fertilisers + Pesticides) Better management practices Problem: Enhancement in food production by green revolution was still not enough to feed growing population Agrochemicals are often too expensive for farmers of developing world Increase in yield with existing varieties is not possible using conventional breeding

Organisms including plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO) Applications of genetic modification: (i) Made crops more tolerant to abiotic stresses (cold, drought, salt, heat). (ii) Reduced reliance on chemical pesticides (pest-resistant crops). (iii) Helped to reduce post harvest losses. (iv) Increased efficiency of mineral usage by plants (prevents early exhaustion of fertility of soil). (v) Enhanced nutritional value of food, e.g., golden rice, i.e., Vitamin 'A' enriched rice.

Tailor Made Plants: Plants have been developed to supply alternative resources to industries in the form of starches, fuels and pharmaceuticals.

INSECT RESISTANT PLANTS Provides resistance to insects without the need for insecticides (bio-pesticide) Examples of biopesticides are Bt cotton, Bt corn, rice, tomato, potato and soyabean etc.

Bt cotton Bacillus thuringiensis (A bacterium) Source of the cry gene Codes for Bt toxin Produced during a particular phase of their growth) Inactive protoxins (Protein crystals) Endotoxin

Sequence of events cry gene from Bacillus thuringiensis Br cotton (Cells express inactive protoxins) Ingested by cotton bollworms

Alkaline pH in the midgut of insects solubilises protein crystals Active toxin Create pores in midgut epithelial cells Swelling of midgut epithelial cells and thereby lysis Death of insect

Choice of gene depends on (i) Target pest (ii) Crop cry/Ac and cry ll Ab Cotton bollworm cry/Ab Corn borer Bt toxins are insect group specific: Lepidoptera: Tobacco budworm, armyworm, cotton bollworm Coleoptera: Beetles Diptera: Flies and mosquitoes

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PEST RESISTANT PLANTS Method of cellular defense seen in all eukaryotes against pest infestation.

Technique: RNA interference (RNAi) Based on post transcriptional silencing of mRNA Translation of mRNA coded from pest specific genes is silenced/prevented due to formation of complementary dsRNA source Mobile genetic elements Transposons replicating via an RNA intermediate The case of nematode resistant transgenic tobacco: Pest causing roots knot disease in tobacco plant: Meloidogyne incognita (Nematode/helminth) Nematode specific gene is introduced in host plant (tobacco), by using Ti plasmid (vector) of Agrobacterium tumefaciens, in such a manner that it produces both sense and antisense RNA in the host cells.

Viruses with RNA genome

Sense RNA and antisense RNA being complementary form dsRNA that initiates RNAi.

Parasite could not survive in a transgenic host expressing specific interfering RNA Host plant – generated dsRNA triggers protection against nematode infestation

BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE Advantages of Recombinant Therapeutics: 30 recombinant therapeutics have been approve for human use the world over. In India, 12 of these are presently being markted.

Mass production of safe and effective drugs.

Do not induce unwanted immunological responses.

Genetically Engineered Human Insulin Insulin extracted from slaughtered cattle and pigs could cause allergy.

Production of humulin: Recombiant insulin manufactured by Eli Lilly, an American company in 1983 The main challenge for production of insulin Maturation of using rDNA techniques was getting insulin proinsulin to insulin assembled into a mature form

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Artificially synthesised DNA sequence for A-chain

Plasmid

E.coli

Chain A

DNA sequence for B-chain

Plasmid

E.coli

Chain B Produced separately extracted and combined by creating disulphide bonds

Human insulin Insulin is a peptide hormone and can be degraded by proteases in our gut

GENE THERAPY

Insertion of genes into an individual's cells to treat diseases by (i) Replacing a defective mutant allele with a functional one (ii) Gene targeting which involves gene amplification.

First clinical gene therapy was conducted in 1990 in a 4 year old girl to treat adenosine deaminase (ADA) deficiency, ADA enzyme is crucial for immune system to function Treatment for ADA Deficiency (1) Enzyme replacement therapy • Functional ADA is given by injection Not completely curative (2) Bone marrow transplantation in children (3) Gene therapy-Could be a permanent cure if bone marrow transplantion is done at early embryonic stages.

Steps in gene therapy Lymphocytes of patient ADA cDNA Retrovirus mediated transformation

Genetically engineered lymphocytes (not immortal) Infused in patient

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Biotechnology and Its Applications

MOLECULAR DIAGNOSIS METHODS Conventional Parameters Modern Early detection Not possible Possible Examples Serum and urine analysis RDT, PCR, ELISA PCR (Polymerase chain Reaction): Nucleic acid amplification Detection of very low concentration of a bacteria or virus Detection of HIV infection, mutations in genes in cancer patients, genetic disorders ELISA (Enzyme Linked Immuno-Sorbent Assay) Antigen-antibody interaction Detect the presence of antigens or antibodies synthesised against pathogens Autoradiography Radioactive ssDNA or ssRNA that hybridizes with complementary DNA Probe will not hybridise mutated gene, hence mutated gene will not appear on the photographic film due to lack of complementarity

TRANSGENIC ANIMALS Possess manipulated DNA and express foreign gene Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced 95% of transgenic animals are mice.

Uses of Transgenic Animals To study how genes are regulated and how they affect the normal functions of body, e.g., Study of insulin -like growth factors Transgenic models exist for study of diseases like cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's Biological products -1 antitrypsin - Treat emphysema.

Similar attempts are made for treatment of PKU (Phenylketonuria) and cystic fibrosis.

First transgenic cow: Rosie developed in 1997 producing human protein enriched milk (2.4 grams per litre) The milk contained alpha-lactalbumin: More balanced product for human babies than natural cow milk Vaccine Safety Transgenic mice are being used to test the safety of polio vaccine to replace the use of monkeys.

Chemical safety testing Transgenic animals are made more sensitive to toxic substances to obtain results in less time.

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ETHICAL ISSUES Genetic modification of organisms (GMO) can have unpredictable results when such organisms are introduced into the ecosystem.

Genetic manipulation of living organisms by humans has to regulated for moral and biological significance.

GEAC (Genetic Engineering Approval Committee): Makes decisions regarding the validity of introducing GMO for public services.

Developing countries are rich in biodiversity and traditional knowledge related to bioresources.

Biopiracy: Refers to the use of bio-resources by multinational companies and other organisations without proper authorization from the countries and people concerned without compensatory payment.

Controversies regarding patents and biopiracy: (i) Basmatic rice: 2,00,000 varieties of rice in India, 27 documented varieties of Basmati rice in India.

In 1997, an American company got patent rights on Basmatic rice through the US patent Trademark office.

Basmati rice × Semi-dwarf variety of rice

New variety of Basmati rice (ii) Turmeric (iii) Neem The Indian Parliament has recently cleared the second amendment of the Indian Patents Bill.

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Biotechnology and Its Applications

qqq

13

Chapter

Organisms and Populations INTRODUCTION ♦ Ecology (at organismic and population level) studies interactions among organisms and between organism and its physical (abiotic) environment. ♦ Ecology is basically concerned with four levels of biological organisation-organisms, populations, communities and biomes.

ORGANISMS AND ITS ENVIRONMENT • Ecology, at the organismic level, is essentially physiological ecology (different organisms are adapted to their environments in terms of survival and reproduction).

• The rotation of our planet around the sun and the tilt of its axis cause annual variations in the intensity and duration of temperature, resulting in distinct seasons. These variations together with annual variation is precipitation (both rain and snow) account for formation of major biomes such as desert, rain forest and tundra.

• Regional and local variations within each biome lead to the formation of a wide variety of habitats, temperature, water, light and soil affect the habitat.

• Habitat of an organism is characterised by physico-chemical (abiotic) components and biotic components like-pathogens, parasites, predators and competitors- of the organism with which they interact constantly • Our intestine is a unique habitat for hundred of species of microbes.

MAJOR ABIOTIC FACTORS Temperature • • • • •

Ecologically most important factor Affects enzyme kinetics, metabolic activity & physiology Eurythermals tolerate wide temperature fluctuations Stenothermals restricted to narrow range.

Thermal tolerance determines geographical distribution.

Water • Life originated in water • Productivity and distribution of plants is dependent on water • Salinity measured in ppt is: 1. < 5 in inland water 2. 30-35 in sea 3. >100 in some hypersaline lagoons

Light • • • •

Plants need light for photo-synthesis and photoperiod for flowering.

Animals also need light for foraging, reproduction & migration.

UV light is harmful.

Red algae are found in deepest water.

Soil • Nature and properties of soil depends on climate, weathering and transportation.

• Composition, grain size, pH, minerals and topography determine vegetation which dictates the type of animals supported.

117 Organisms and Populations

RESPONSE TO ABIOTIC FACTORS Abiotic conditions of many habitats vary drastically in time and organisms living in such habitats need to evolve strategies to survive or manage with the stressful conditions.

ORGANISMIC RESPONSE TO ABIOTIC STRESS Regulate • Maintain homeostasis by physiological (or behavioural) means.

• Ensures constant body temperature and osmotic concentration.

• All birds, mammals and very few lower vertebrates and invertebrates are capable of this.

Conform • 99% animals & nearly all plants.

• Body temperature changes with the ambient temperature.

Suspend • • • • •

Thick walled spore in bacteria, fungi & lower plants.

Dormancy in higher plants.

Hibernation in bears Aestivation in snails and fish Diapause or suspended development in zooplanktons.

Success of mammals is largely due to their ability to maintain constant body temperature and thrive in antarctica or in Sahara desert  Hand Book (Biology)

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ADAPTATIONS- TO COPE WITH EXTREME ENVIRONMENT Genetically Fixed • Kangaroo rat in North American deserts.

Internal fat-oxidation for water Ability to concentrate urine • CAM plants like Opuntia.

• Allen’s Rule: Shorter extremities of mammals in cold dimate to reduce heat loss. (Thick blubber in seal).

Physiological • Altitude sickness. Symptoms-Nausea, fatigue & heart palpitations.

• Gradually, the body compensates low oxygen by increasing RBC production, decreasing the binding affinity of haemoglobin and increasing the breathing rate.

Behavioural • Desert lizards-bask in the sun & absorb heat when their body temperature drops below comfort zone, but move away into shade when ambient temperature starts increasing • Some species hide in burrow to escape from the above-ground heat.

Biochemical/Adaptation: Organisms living in extreme environments like hot springs, deep sea hydrothermal vents, antarctic fishes in freezing conditions or at > 100 times normal atmospheric pressure. 

POPULATION Population Attributes: • Birth rates and Death Rates: Refer to per capita births and deaths.

• Sex-ratio: e.g. 60 percent of the population are females & 40 percent males.

• Age-pyramids: Shows percent individuals of a given age or age group. For the shape of the pyramids reflects the growth status of the population. (a) Expanding

(b) Stable

(c) Declining 119

Organisms and Populations

Evolutionary changes through natural selection takes place at population level. 

POPULATION GROWTH 1. Population for any species is not a static parameter.

2. Food availability, predation pressure and adverse weather are the factors which affect population.

3. Population density, in a given habitat during a given period, fluctuates due to changes in Four base processes.

Two-natality, immigration increase density.

Two-mortality, emigration decrease it.

Tiger census in our national parks & tiger reserves is often based on pug marks and fecal pellets



• If N the population density al time t, then its density at time t + 1 Nt+1 = N1 [(B + I) – (D + E)] If births plus immigration (B + I) is more than deaths plus emigration (D + E), population density will increase Under normal conditions, births & deaths are most important factors influencing population density If a new habitat is just being colonised, immigration is more significant to population growth than birth rates.

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GROWTH-MODELS Exponential Growth When resources in the habitat are unlimited. z Then population grows in an exponential or geometric fashion.

Nt = Noert z

Nt = Population density at time ‘t’ N0 = Population density at time zero e = Intrinsic rate of natural increase e = Base of natural logarithms (2.71828)

(a) Exponential plot (b) Logistic plot K = Carrying Capacity = Habitat has enough resources to support a maximum possible number beyond which no growth is possible

LOGISTIC GROWTH • • • • • • • 121

(K − N) dN Nature resources are limited. = rN Sigmoid Curve dt K This leads to competition.

The fittest survive and reproduce So, it shows, lag, acceleration, deceleration and finally asymptote It gives Verhulst-Pearl logistic curve.

Logistic growth model is realistic.

Asymptote-When population density reaches the carrying capacity.

Organisms and Populations

LIFE HISTORY VARIATION • Populations evolve to maximise their reproductive fitness, also called Darwinian fitness (high ‘r’ value), in the habitat in which they live and evolve towards the most effective reproductive strategy.

Reproductive Strategies in Organisms 1. Breed only once in their life time. e.g., Pacific salmon fish, Bamboo

1. Breed many times during lifetime. e.g., Most birds & Mammals.

2. Some produce large number of smallsized off springs e.g., Oysters, Pelagic fishes

2. Others produce a small number of largesized off springs. e.g., Birds & Mammals

POPULATION INTERACTIONS Predation (+; –) • Predators act as conduits for energy transfer across trophic levels • Keep prey population under control due to prudent predators • Used as biological control method for pest-control.

• Maintain species diversity by reducing competition among prey eg.

• Prey species evolved defenses: (a) Camouflage - Insects & frogs (b) Monarch butterfly- Chemical defense (c) Thorns-Cactus, Acacia • Many plants produce and store chemicals that make herbivore sick when they are eaten, e g., Calotropis produces cardiac glycosides

Competition (–; –) • Darwin said interspecific competition is a potent force in organic evolution • Totally unrelated species can compete for same resources.

• The fitness (‘r’ the intrinsic rate of increase) of one species is significantly lower in presence of another species.

• Competitive release - The distributional range increase dramatically when the superior species is removed.

• eg. Balanus & Chthamalus • Gause’s competitive exclusion principle = eg. Abingdon tortoise and Goats in galapagos island.

• Co-Existence by resource partitioning eg. 5 closely related species of warblers.

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Parasitism (+; –) • Free lodging and meals • Parasites are host specific, i.e., co-evolve • Parasitic adaptations = Loss of sense organs, presence of adhesive organs or suckers, loss of digestive system & high capacity of reproduction.

• Human liver fluke depends on a snail and a fish to complete life cycle.

• Parasites reduce survival, growth and reproduction of host make them weak • Brood parasitism in birds eg. Cuckoo and crow. The eggs of parasitic bird had evolved to resemble host’s egg in colour and size.

• Ectoparasites on surface and Endoparasites inside host

Commensalism (+; 0) • • • •

An orchid growing as an epiphyte on a mango branch Barnacles growing on back of a whale.

Cattle egret and grazing cattle.

Sea anemone that has stinging tentacles and clown fish that lives among them.

In Amensalism, one species is harmed whereas the other is unaffected. 

Mutualism (+; +) • Lichens, Mycorrhiza • Plant - animal relationships for pollination.

• Plants offer rewards or fees like pollen, nectar for pollinators and fruits for seed dispersal.

• Safeguards against cheaters.

• Shows co-evolution and one to one relationship like fig and partner wasp.

Mediterranean orchid Ophrys employs sexual deceit to get pollination done by a species of bee by pseudo copulation.  qqq

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Organisms and Populations

Chapter

14 Ecosystem

INTRODUCTION Ecosystem is a functional unit of nature.

Entire biosphere is a global ecosystem (all local ecosystems).

Forest, grassland and desert are terrestrial ecosystems.

Pond, lake, wetland, river and estuary are aquatic.

Crop fields and an aquarium are man-made ecosystems.

Input (productivity): Transfer of energy (food chain-web, nutrient cycling). ♦ Output (degradation and energy loss) are the major functions of ecosystem. ♦ ♦ ♦ ♦ ♦ ♦

ECOSYSTEM - STRUCTURE AND FUNCTION • Interaction of biotic and abiotic components result in a physical structure.

• Stratification: Vertical distribution of different species occupying different levels, like trees at top vertical strata, shrubs second and herbs and grasses occupy bottom layers.

ECOSYSTEM COMPONENTS FUNCTION AS A UNIT (1) (2) (3) (4)

Productivity Decomposition Energy Flow Nutrient Cycling

Productivity • Primary production: Amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.

• Expressed in terms of weight (gm–2) or energy (K cal m–2).

• Rate of biomass production is productivity, expressed as gm–2 yr–1 or (K cal m–2) yr–1. It can be divided into: (i) Gross primary productivity (GPP): Rate of production of organic matter during photosynthesis. (ii) Net primary productivity (NPP): Available biomass for the consumption to heterotrophs (herbivores and decomposers).

NPP = GPP - R (respirator loss) • Primary productivity depends on a plant species inhabiting a particular area.

• Depends on environmental factors, availability of nutrients and photosynthetic capacity of plants.

• Varies in different ecosystems: Annual net primary productivity of whole biosphere is approximately = 170 billion tons (dry wt.) of organic matter.

Productivity of oceans (70% of surface) = 55 billion tons, rest is on land.

• Secondary productivity: Rate of formation of new organic matter by consumers.

DECOMPOSITION • Breakdown of complex organic matter into inorganic substances like CO2, water and nutrients.

• Raw material: Detritus, i.e., dead plant remains like leaves, bark, flowers and dead remains of animals, including fecal matter.

DECOMPOSITION Break down of detritus into smaller particles by detritivores (e.g., Fragmentation earthworm).

Leaching

Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.

Catabolism

Bacterial and fungal enzymes degrade detritus into simpler inorganic substances.

Humification

Accumulation of dark, amorphous Humus which is highly resistant to microbial action. Colloidal reservoir of nutrients.

Humus undergoes decomposition at an extremely slow rate in soil.

Mineralisation

Humus is further degraded by microbes to release inorganic nutrients.

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Ecosystem

• Fragmentation + Leaching + Catabolism (operate simultaneously) = Detritus.

Rate of Decomposition Composition of Detritus Climatic Factors Slower

Rich in lignin and chitin

Low temperature and anaerobiosis

Quicker

Rich in nitrogen and water Warm and moist environment. soluble substances like Oxygen requiring process sugar

• Temperature and soil moisture are most important climatic factors that regulate decomposition.

ENERGY FLOW

Unidirectional from sun to producers and then to consumers.

SUN PAR (< 50%) Plants (Incident solar radiation)

Photosynthetic bacteria (autotrophs) Sustain the ENTIRE WORLD

2-10% of PAR Food (simple sugars)

TROPHIC LEVELS IN AN ECOSYSTEM

HETEROTROPH

• Amount of energy decreases at successive trophic levels.

• Only 10% of the energy is transferred to each trophic level from the lower trophic level (10% Law).

Tertiary consumer

Fourth trophic level (T4) (secondary carnivores)

Man, lion

Large fishes

Secondary consumer

Third trophic level (T3) (primary carnivores)

Birds, wolf

Fishes

Primary consumer

Second trophic level (T2) Insects, birds, Zooplanktons, (herbivores) mammals molluscs

Primary producer Autotrophs

First trophic level (T1) (green plants)

Herbaceous, Algae, woody plants phytoplanktons and higher plants

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DETRITUS FOOD CHAIN Begins with dead organic matter. z Made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria. They meet their energy and nutrient requirements by degrading dead organic matter or detritus known as saprotrophs. z In a terrestrial ecosystem, larger fraction of energy flows through the detritus food chain than through the grazing food chain. z

z

z

z

STANDING CROP Each trophic level has a certain mass of living material at a particular time.

Measured as the mass or living organisms (Biomass) or the number in a unit area.

Measurement of biomass in terms of dry weight is more accurate.

z z

z

z

z

z

z

GRAZING FOOD CHAIN Sun is the source of energy.

Autotrophs assimilate food using simple inorganic materials and radiant solar energy.

The energy flows from autotrophs to heterotrophs as per the law of thermodynamics.

In an aquatic ecosystem, grazing food chain is the major conduit for energy flow.

STANDING STATE Organisms need a constant supply of nutrients to grow, reproduce and regulate various body functions.

The amount of nutrients such as carbon, nitrogen, phosphorus, calcium etc., present in the soil at any given time.

It varies in different kinds of ecosystems and also one seasonal basis.

ECOLOGICAL PYRAMIDS • Food or energy relationship between organisms at different trophic levels is expressed in terms of number, biomass or energy.

• Base of each pyramid.

• Producers or the first trophic level.

• Apex Tertiary or top level consumer.

• The trophic level represents a functional level, not a species as such.

A given species may occupy more than one trophic level in the same ecosystem at the same time.

• Three types of ecological pyramids are usually studied: (a) pyramid of number (b) pyramid of biomass (c) pyramid of energy.

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Ecosystem

Trophic level

Number of individuals

TC (Tertiary consumer)

3

SC (Secondary consumer)

3,54,000

PC (Primary consumer)

708,000

P (Producer)

5,842,000 (a) Dry weight (kg m–2)

Trophic level 1.5

TC

11

SC

37

PC

809

P (b) 21

PC 4

P (c)

Fig.: (a) Pyramid of numbers in a grassland ecosystem. Only three top-carnivores are supported in an ecosystem based on production of nearly 6 millions plants (b) Pyramid of biomass shows a sharp decrease in biomass at higher trophic levels (c) Inverted pyramid of biomass-small standing crop of phytoplankton supports large standing crop of zooplankton

LIMITATIONS OF ECOLOGICAL PYRAMIDS • It does not take into account the same species belonging to two or more trophic levels.

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• It assumes a simple food chain that never exists in nature. It does not accommodate a food web.

• Saprophytes are not given any place in ecological pyramids even though they play a vital role in the ecosystem.

Pyramid of Number • Upright in most ecosystems.

• A big tree ecosystem is inverted or spindle shaped.

Pyramid of Biomass • Upright in most ecosystems.

• In sea, it is generally inverted.

Pyramid of Energy • Always upright and can never be inverted.

• When energy flows from a particular trophic level to next trophic level, some energy is always lost as heat.

ECOLOGICAL SUCCESSION • Composition and structure of all communities constantly change in response to the changing environmental conditions which is orderly and sequential, parallel with changes in the physical environment, leading finally to a community that is in near equilibrium to the environment and is called climax community.

• Ecological succession: Gradual and fairly predictable change in the species composition of a given area.

• The entire sequence of communities that successively change in a given area are called SERE(s) and individual transitional communities are termed seral stages or seral communities.

• In the successive seral stages change in diversity of species of organisms, increase in the number of species and organisms as well as an increase in total biomass is seen.

• Primary succession: Starts in an area where no living organisms ever existed, like on bare rock, newly cooled larva, newly created pond or reservoir, so it is slow and can take several hundred to thousand years.

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Ecosystem

• Secondary succession: Takes place in areas that somehow lost all the living organisms that existed there, like abandoned farm lands, burned or cut forests, lands that have been flooded. Since some soil or sediment is present, succession is faster than primary succession.

Climax reached more quickly.

• The species that invade a bare area are called pioneer species.

• After several more stages, ultimately a stable climax forest community is formed.

SUCCESSION OF PLANTS HYDRARCH (In Wet Areas) Phytoplankton (pioneer) species

Submerged plant stage

Submerged free floating stage Reed-swamp stage

Forest (climax) MESIC

Scrub stage

Marsh-meadow stage

XERARCH (Xeric/dry Condtions) Lichens (pioneer) species

Bryophytes

Higher plants

MESIC (climax) Forest • Both hydrach and xerarch lead medium water condition (MESIC).

NUTRIENT CYCLING • Nutrients which are never lost from the ecosystems, they are recycled time and again indefinitely, it is called biogeochemical cycles (bio-living organism, geo-rocks, air, water).

• Two types: (a) Gaseous (e.g., Nitrogen, carbon cycle) (b) Sedimentary (e.g., Sulphur, phosphorus cycle) Hand Book (Biology)

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Carbon-Cycle z z z z z

Natural reservoir is atmosphere Carbon constitutes 49% of dry weight organisms and is next only to water.

71% of global carbon is dissolved in oceans which regulates amount of CO2 in atmosphere.

Fossil fuel represent a reservoir of carbon.

4 × 10 13 kg of carbon is fixed annually in biosphere through photosynthesis.

Phosphorus-Cycle z z z z z

Phoshphorus is a major constituent of biological membranes, nucleic acids and cellular energy transfer system.

Needed to make shells, bones and teeth.

Natural reservoir is rock.

Atmospheric inputs of phosphorus through rain fall are much smaller than carbon inputs.

Gaseous exchanges of phosphorus between organism and environment are negligible.

ECOSYSTEM SERVICES z

z

z

z

131

Healthy forest ecosystem purify air and water, mitigate droughts and foods, cycle nutrients, generate fertile soils, provide wildlife habitat, maintain biodiversity, pollinate crops, provide storage site for carbon and also provide aesthetic, cultural and spiritual values.

Robert Constanza tried to put price tags of average US $33 trillion a year for these ecosystem services, which is largely taken for granted, because they are free. This is nearly twice the value of global GNP of US $18 trillion.

Out of the total cost soil formation accounts for about 50%, recreation and nutrient cycling less than 10% each and climate regulation and habitat for wildlife 6% each.

Products of ecosystem processes are named as ecosystem services e.g., Purification of air and water by forests. qqq

Ecosystem

Chapter

15 Biodiversity and Conservation

INTRODUCTION ♦ More than 20,000 species of ants, 3,00,000 species of beetles, 28,000 species of fishes and nearly 20,000 species of orchids.

BIODIVERSITY • Immense diversity (or heterogeneity) exists not only at the species level but at all levels of biological organisation ranging from macromolecules within cells to biomes.

• The term Biodiversity was popularised by the socio-biologist Edward Wilson.

Genetic Diversity • A single species might show high diversity at genetic level over its distributional range.

• E.g., Genetic variation shown by Rauwolfia vomitoria in different Himalayan ranges in potency and concentration of reserpine.

• India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.

Species Diversity • Diversity at the species level • E.g., Western ghats have a greater amphibian species diversity than Eastern ghats.

Ecological Diversity • At the ecosystem level • E.g., India with its deserts, rain forests, mangroves and alpine meadows has a greater ecosystem diversity than a Scandinavian Country like Norway.

SPECIES ON EARTH AND INDIA • According to IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million.

• A conservative and scientifically sound estimate made by Robert May places the global species diversity at about 7 million.

Interesting Aspects of Earth's Biodiversity (a) More than 70% of all species recorded are animals while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22% of the total. (b) Among animals, insects make more than 70% of total, i.e., out of every 10 animals on this planet, 7 are insects. (c) Number of fungi species are more than fishes, amphibians, reptiles and mammals combined.

• Although, India has only 2.4% of world’s land area, its share of the global species diversity is an impressive 8.1 percent.

• India is one of the 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India.

• If we accept May's global estimates, only 22 percent of the total species have been recorded so far, then, India has more than 1,00,000 plant species and 3,00,000 animal species yet to be discovered.

Vertebrates

Invertebrates Other animal group Crustaceans Molluscs

Mammals Fishes Birds

Insects Reptiles Amphibians Plants Ferns and mosses allies

Fungi

Angiosperms

Algae

Lichens

Representing global biodiversity

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PATTERNS OF BIODIVERSITY A. LATITUDINAL GRADIENTS • Species diversity decreases as we move from equator towards the poles.

• Tropics (23.5º N to 23.5ºS) harbour polar areas.

Eg., Colombia Newyork Near Equator 41ºN temperate 1,400 bird 105 bird species species

more species than temperate or Greenland 71ºN poles 56 bird species

India Tropics 1,200 bird species

• A forest in a tropical region like Equador has upto 10 times more vascular plants, as a forest of equal in temperate midwest of USA.

LARGELY TROPICAL AMAZON RAIN FOREST IN SOUTH AMERICA has greatest biodiversity on Earth • 40,000 species of plants • 3,000 of fishes • 1,300 of birds • 427 of mammals.

• 427 of amphibians • 378 of reptiles • More than 1,25,000 invertebrates

Ecologists and Evolutionary biologists have proposed various hypotheses to explain greater biological diversity at the tropics (a) Unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes remained undisturbed, having long evolutionary time for species diversification (b) Constant, less seasonal tropical environments promote niche specialisation and lead to greater species diversity (c) More solar energy in tropics contributes to higher productivity and might contribute indirectly to greater diversity

B. SPECIES-AREA RELATIONSHIPS (by German naturalist Alexander Von Humboldt) • Species richness within a region increased with increasing explored area, but only upto a limit Hand Book (Biology)

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• The relation between species richness and area for a wide variety of taxa (angiosperms, birds, bats, freshwater fishes) is a rectangular hyperbola. On a logarithmic scale, it is a straight line, described by the equation. logS = logC + Z logA where S = species richness, A=Area; Z = Slope of the line (regression coefficient), C = Y intercept.

• The value of Z lies in the range of 0.1 to 0.2 regardless of region or taxa • Slope of the line is much steeper in very large areas like the entire continents, e.g., For frugivorous birds and mammals in tropical forests the, slope is 1.15.

S = CAZ

Species richness

log S = log C + Z log A

le

ca

s log

-

log

Area

IMPORTANCE OF SPECIES DIVERSITY TO THE ECOSYSTEM • Communities with more species, tend to be more stable than those with less species.

• A stable community must be resistant or resilient to occasional disturbances (natural or man-made) and it must also be resistant to invasions by alien species.

• David Tilman’s long-term ecosystem experiments using outdoor plots show that plots with more species showed less year-to-year variation in total biomass and increased diversity contributed to higher productivity.

• The ‘rivet popper hypothesis’ of Stanford ecologist Paul Ehrlich, puts the importance of a species in proper perspective.

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AIR PLANE

ECOSYSTEM

Rivets

Species

Rivet on the wings

Key species

(i) Popping a rivet (causing a species to become extinct) may not affect flight safety (proper functioning of ecosystem) initially, but if more rivets are removed, the plane will become dangerously weak. (ii) Loss of rivets on the wings (Key species, that drive major ecosystem functions) will be serious. So, each species is important for the ecosystem.

LOSS OF BIODIVERSITY • The colonisation of tropical pacific islands by humans led to extinction of more than 2,000 species of native birds. The IUCN red list (2004) documents extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 yrs.

• The last 20 years alone witnessed disappearance of 27 species.

• Amphibians appear more vulnerable to extinction.

• 15,500 species world-wide are facing threat of extinction.

• There were five episodes of mass extinction of species in the past, before humans appeared.

• The Sixth Extinction presently in progress is 100 to 1000 times faster than pre-human times and our activities are responsible for the faster rates.

• Loss of biodiversity in a region may lead to: (a) Decline in plant production. (b) Lowered resistance to environmental perturbations like drought. (c) Increased variability in plant productivity water use and pest and disease cycles.

Recent Extinctions 1. Dodo

- Mauritius

2. Quagga

- Africa

3. Thylacine

- Australia

4. Steller’s sea cow

- Russia

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Species Facing Threat of Extinction in World 12% Birds 23% Mammals 32% Amphibians 31% Gymnosperms

CAUSES OF BIODIVERSITY LOSSES: THE EVIL QUARTET-FOUR MAJOR CAUSES Habitat Loss and Fragmentation (Most Important Cause) • Tropical rain forests once covered more than 14% of earth’s land, now it is just 6%.

• Amazon rain forest (lungs of the planet), being cut for soyabeans cultivation and grasslands for raising beef cattle.

• Mammals and birds requiring large territories and animals with migratory habits are badly affected, leading to population declines.

Over-Exploitation • When need turns to greed, there is overexploitation • In the last 500 years steller’s sea cow, passenger pigeon became extinct due to over-exploitation.

• Marine fish populations are over harvested, endangering commercially important species.

Alien Species invasions • Nile perch introduced in Lake Victoria in East Africa led to the extinction of 200 species of Cichlid fish in the lake.

• Carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia) are invasive weeds.

• African catfish Clarias gariepinus are posing threat to indigenous cat fishes.

Co-Extinctions (Obligatory Associations) • When a host species becomes extinct, its parasites meets the same fate.

• Co- evolved plant-pollinator mutualism is another example 137

Biodiversity and Conservation

BIODIVERSITY CONSERVATION Narrowly Utilitarian Arguments • Humans derive countless direct economic benefits from nature — food, firewood, fibre, construction material, industrial products and medicinal products.

• More than 25% drugs are derived from 25,000 species of plants.

• Nations endowed with rich biodiversity can reap enormous benefits by ‘bioprospecting’ — exploring molecular, genetic and species level diversity for products of economic importance.

Broadly Utilitarian Arguments • Biodiversity plays a major role in many ecosystem services that nature provides.

• Amazon rain forest produce approx 20% of total oxygen of Earth's atmosphere by photosynthesis.

• Pollination by bees, bumble-bees, birds and bats.

Ethical Arguments • Philosophically or spiritually, we have to understand that each species has a intrinsic value.

• We have a moral duty to care for their well-being.

• We need to pass on our biological legacy in good order to future generations.

HOW DO WE CONSERVE BIODIVERSITY? In-situ Conservation When we conserve and protect whole ecosystem, i.e., saving the entire forest to save the tiger, it is called in-situ (on site) conservation.

• Organisms facing a very high risk of extinction in the wild in near future and needs urgent measures to save it from extinction, then exsitu (offsite) conservation is desirable.

• Biodiversity Hot Spots: Regions with very high levels of species richness and high degree of endemism (species confined to a particular region & not found anywhere else).

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• Total number are 25 (initially) +9 (added later) = 34; Three of these—Western ghats and Sri Lanka, IndoBurma & Himalaya— cover our country’s regions. They (all 34) cover less than 2% of Earth’s land area and their strict protection could reduce the ongoing mass extinctions by 30%.

• 14 biosphere reserves, 90 National Parks and 448 wild life sanctuaries provide legal protection in India.

• Sacred groves in Khasi and Jaintia Hills of Meghalaya, Aravali Hills (Rajasthan), Western Ghats, Sarguja, Chanda and Bastar regions (Madhya Pradesh) are the last refuges of rare and threatened plants.

Ex-situ Conservation • Zoological Parks, Botanical gardens and wild-life Safari parks.

• Many animals have become extinct in the wild but are maintained in zoological parks.

• Cryopreservation to protect and preserve gametes of threatened species in viable and fertile condition.

• Plants can be propagated using tissue culture methods.

• Seeds of different genetic strains of commercially important plants can be kept for long periods in seed banks.

• The historic Convention on Biological diversity (The Earth Summit) was held in Rio de Janeiro (1992) for biodiversity conservation and sustainable utilisation of benefits • World Summit on sustainable development (WSSD) held in 2002 in Johannesburg, South Africa, 190 countries pledged for significant reduction in current rate of biodiversity loss at global, regional and local levels by 2010. qqq

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Chapter

16 Environmental Issues

INTRODUCTION ♦ Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil. ♦ Pollutants: Agents that bring about such undesirable change ♦ The government of India passed the Environment (protection) Act, 1986 to protect and improve the quality of our environment.

AIR POLLUTION AND ITS CONTROL • Air pollutants cause injury to all living organisms as they reduce the yield of crops and also deleteriously affect the respiratory system of humans and animals.

• Harmful effects depends on concentration of pollutants, duration of exposure and the organism.

• Smoke stacks of thermal power plants, smelters and other industries release particulate and gaseous air pollutants. These pollutants must be separated/filtered out before releasing the harmless gases into the atmosphere.

• According to CPCB, particulate size 2.5 mm or less in diameter (PM2.5), can be inhaled deep into the lungs causing respiratory symptoms, irritation, lungs damage and premature death.

Control Strategies • Electrostatic precipitator can remove 99% particulate matter present in exhaust from a thermal power plant.

• Scrubber can remove gases like SO2.

• Catalytic converter with platinum, palladium and rhodium-as catalysts, in automobiles, convert unburnt hydrocarbons into CO2 and H2O and carbon monoxide and nitric oxide to CO2 and nitrogen gas. Lead inactivates the catalyst.

Noise as an Air pollutant • Air (Prevention and control of pollution) Act 1981, was amended in 1987, to include noise as an air-pollutant.

• Noise is undesired high level of sound.

• A brief exposure of extremely high sound level 150 dB or more generated by jet plane or rocket can damage ear drums and can cause permanent loss of hearing ability.

• Chronic exposure of lower noise level may permanently damage hearing abilities.

• Noise also causes sleeplessness, increased heart beat, altered breathing pattern, thus considerably stressing humans.

• To control noise pollution, use of sound-absorbent materials or by muffling noise; delimitation of harm-free zones, timings for loudspeakers etc. need to be enforced.

CONTROLLING VEHICULAR AIR-POLLUTION-A CASE STUDY OF DELHI • In the 1990s, Delhi ranked 4th among the 41 most polluted cities of the world and a PIL was filed in the Supreme Court of India and under its directives All buses of Delhi were converted to run on CNG by the end of 2002, as CNG burns efficiently, was cheaper and cannot be siphoned off by thieves and adulterated like petrol and diesel.

Old vehicles were phased out.

Use of unleaded petrol.

Use of low-sulphur petrol/diesel.

Use of catalytic converters and stringent pollution norms etc.

• More stringent norms for fuels means steadily reducing sulphur and aromatic content in petrol and diesel fuels.

• Euro III Norms stipulate sulphur at 350 ppm in diesel and 150 ppm in petrol.

• Aromatic hydrocarbon at 42% road map is to reduce sulphur to 50 ppm in petrol and diesel and aromatic hydrocarbon to 35%.

141 Environmental Issues

WATER POLLUTION AND ITS CONTROL • Government of India passed the water (prevention and control of pollution) Act, 1974 to safeguard our water resources.

DOMESTIC SEWAGE AND INDUSTRIAL EFFLUENTS • 0.1% impurities make domestic sewage unfit for human use.

• Contains biodegradable organic matter, which decomposes readily by the help of bacteria and other micro-organisms.

• Amount of bidegradable organic matter in sewage is estimated by measuring the Biochemcial Oxygen Demand (BOD).

• Micro-organisms involved in biodegradation of organic matter in the receiving water body consume a lot of oxygen, as a result there is a sharp decline in Dissolved Oxygen (DO), causing mortality of fishes and other aquatic creatures.

• Large amounts of nutrients causes algal bloom, which imparts colour to water bodies, deteriorates water quality and cause fish mortality.

Bloom forming algae are extremely toxic to human beings and animals.

• Eichhormina crassipes (water hyacinth) world's most problematic aquatic weed also called Terror of Bengal; was introduced in India for their lovely flowers, have caused havoc by excessive growth and blocking water ways.

Biomagnification

Eutrophication

• Increases in the concentration of toxicant • Natural aging of lake by nutrient at successive trophic levels, in the aquatic enrichment of its water, which may span food chain, As the toxic substance is neither thousands of years. metabolised nor excreted, so passed on to next • Cultural of Accelerated Eutrophication: trophic level.

Pollutants from man's activities like e.g: Mercury or DDT. effluents from industries and homes can Water → Zooplanktons → Small fish radically accelerate the aging process.

(0.003 ppb) (0.04 ppm) (0.5 ppm) Prime contaminants are nitrates and phosphates, which act as plant nutrients. ↓ Fish-eating birds → Large fish They overstimulate algal growth causing (25 ppm) (2ppm) unsightly scum and unpleasant odours, robbing water of dissolved oxygen vital to other aquatic life.

Other pollutants flowing into a lake may poison for the whole populations of fish.

The lake can literally choke to death.

• Heated (thermal) Waste Waters from thermal power plants, eliminates or reduces the number of organisms sensitive to high temperature and may enhance the growth of plants and fish in extremely cold areas, after causing damage to indigenous flora and fauna.

142 Hand Book (Biology)

CASE STUDY-INTEGRATED WASTE WATER TREATMENT • Town of Arcata - along Northern coast of Californa (with biologists from Humboldt state university) utilising a mix of artificial and natural processes, the towns people created an integrated waste water treatment process within a natural system. The cleaning occurs at two stages: The conventional sedimentation, filtering and chlorination.

The biologists developed six connected marshes over 60 hectares of marsh and seeding appropriate plants, algae, fungi and bacteria, which neutralise, absorb and assimilate the pollutants and water flows through the marshes and gets purified naturally. The marshes constitute a sanctuary with high biodiversity. Friends of the Arcata Marsh (FOAM) is responsible for the upkeep and safeguarding of this wonderful project.

• 'Ecosan' toilets: Ecological sanitation is a sustainable system for handling human excreata, using Dry Composting Toilets: a practical, hygienic, efficient and cost-effective solution to human waste disposal.

• By this method, human excreta can be recycled into natural fertiliser, which reduces the need of Chemical fertiliser. Ecosan toilets are working in many areas of Kerala and Sri Lanka.

Domestic sewage, most common source of pollution of water bodies, reduces DO but increases BOD of receiving water.

Domestic sewage are rich in nutrients like nitrogen and phosphorus which cause eutrophication and algal blooms. 

SOLID WASTES • Everything that goes out in trash is solid waste.

(A) Municipal solid waste: Comprise paper, food wastes, plastics glass, metals, rubber, leather, textile, etc. Burning reduces volume of wastes.

Open dumps serve as breeding grounds of rats and flies.

Sanitary land fills are a substitute for open burning dumps. Wastes are dumped in a depression or trench after compaction and covered with dirt everyday.

Landfills get filled in metros due to large amount of garbage and danger of seepage of chemicals which pollute underground water resources.

(B) Electronic wastes (e-wastes): Irreparable computers and other electronic goods. E-wastes are burried or incinerated.

143 Environmental Issues

Over half of e-wastes generated in developed world are exported to developing countries like China, India and Pakistan where metals like copper, iron, silicon, nickel and gold are recovered during recycling process. Recycling is the only solution for treatment of e-wastes.

(C) Hospitals generate hazardous wastes that contain disinfectants and other harmful chemicals and pathogenic micro-organisms, The use of incinerators is crucial to disposal of hospital waste.

CASE STUDY OF REMEDY FOR PLASTIC WASTE • Ahmed Khan, realised that plastic waste was a real problem • Polyblend, a fine powder of recycled modified plastic, was developed by his company. This mixture is mixed with bitumen that is used to lay roads.

• In collaboration with R.V. College of Engineering and Bangalore city corporation, Ahmed Khan proved that blends of polyblend and bitumen, when used to lay roads, enhanced the bitumen’s water repellant properties and helped to increase road life by a factor of three • The raw material is any plastic film waste. So, against the price of ` 0.40/kg, Khan now offers Rs 6 to ragpickers.

• Using Khan’s technique by the year 2002, more than 40 kms of road in Bangalore has already been laid.

AGRO-CHEMICALS AND THEIR EFFECTS • Pesticides, herbicides, fungicides, etc. are toxic to non-target organisms that are important components of soil ecosystem.

CASE STUDY OF ORGANIC FARMING • Integrated organic farming is a cyclical, zero-waste procedure where waste products from one process are cycled in as nutrients for other processes. This allows maximum utilisation of resource and increases the efficiency of production.

• Ramesh Chandra Dagar, a farmer in Sonipat, Haryana, includes bee-keeping, dairy management, water harvesting, composting and agriculture in a chain of processes and allow an extremely economical and sustainable venture.

• No need to use chemical fertilizers, cattle dung used as manure, crop waste to create compost or used to generate natural gas for energy needs of farm. Dagar created by the Haryana Kisan Welfare Club, with membership of 5000 farmers.

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RADIOACTIVE WASTES Nuclear energy has two very serious inherent problems Accidental Leakage Safe disposal of radioactive wastes Three mile island Radiation from nuclear waste causes mutations at a very high rate.

Chernobyl Higher doses is lethal; lower doses creates various disorders like cancer.

GREENHOUSE EFFECT AND GLOBAL WARMING • Greenhouse effect is a naturally occurring phenomenon responsible for heating Earth’s surface and atmosphere. Without this, average temperature at surface of earth would be chilly - 18°C rather than the present average of 15°C. • Greenhouse gases absorb long wave (infrared) radiation from earth and emit it again towards the earth. The cycle continues till the earth’s surface has no long wave radiation to emit.

• Relative contribution of various greenhouse gases to total global warming is CO2 (60%); CH4 (20%); CFCs (14%) and N2O (6%).

• Increase in level of greenhouse gases led to considerable heating of earth leading to Global warming and odd climatic changes (e.g., El Nino effect), melting of polar ice caps and Himalayan snowcaps, rise in sea-level and submergence of coastal areas.

OZONE DEPLETION IN THE STRATOSPHERE Type of Ozone Good Ozone Bad Ozone Found in upper atmosphere, the Found in lower atmosphere, the stratosphere acts as a shield absorbing troposphere that harms plants and UV radiation from sun animals.

DNA and proteins absorb UV rays, so it is highly injurious to living organisms.

• Chloro-Fluoro-Carbons (CFCs) used as refrigerants degrade ozone layer, by releasing Cl-atom • Permanent and continuing effects on ozone levels.

• UV radiations, shorter to UV-B are completely absorbed by ozone layer.

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Environmental Issues

• UV-B-damages DNA, causes aging of skin, inflammation of cornea called snow blindness (cataract) etc.

• Montreal protocol signed in 1987 (effective in 1989) controls emission of ODS, i.e., CFCs. • Thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of dobson units (DU) • Ozone hole over Antarctica develops each year between late August and early October.

DEGRADATION BY IMPROPER RESOURCE UTILISATION AND MAINTENANCE Soil Erosion and Desertification • Development of top soil takes centuries.

• Over-cultivation, unrestricted grazing, deforestation and poor irrigation degrades it making arid patches of land.

• Large barren patches meet to form desert • Desertification has become a major problem due to increased urbanisation.

Water Logging and Soil Salinity • Irrigation without drainage results in water logging • Water logging draws salt on surface of soil, depositing in a thin crust or collects at the roots, affecting growth.

• Water logging and salinity have come due to Green Revolution

Deforestation • 40% forests have been lost in tropics compared to only 1% in temperate region.

• National forest policy (1968) of India re-commended 33% forest for plains and 67% for hills.

• Slash and burn agriculture (Jhum cultivation) in North-East of India contribute to deforestation • Enhanced CO2 concentration, loss of biodiversity, disturbed hydrologic cycle, soil erosion and desertification are the consequences of deforestation.

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CASE STUDY-PEOPLE’S PARTICIPATION IN CONSERVATION OF FOREST • A Bishnoi woman Amrita Devi, her three daughters and hundreds other lost their lives saving trees by hugging and daring king’s men at Jodhpur.

• The Government of India instituted Amrita Devi Bishnoi wildlife protection award for individuals or communities from rural areas that have shown extraordinary courage and dedication in protecting wildlife.

• Chipko Movement of Garhwal Himalayas (1974): Local women showed bravery in protecting trees people all over world have acclaimed Chipko movement.

• Government of India in 1980s introduced Joint Forest Management (JFM). Local communities protect and manage forest, in return they get benefit of various forest products (fruit, gum, rubber etc.). qqq

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Environmental Issues