Grade 8 Biology

IL FOUNDATION SERIES

BIOLOGY

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ISBN 978-81-985385-7-4 Second Edition

Contents 1.

Crop Production and Management

01

2. Microorganisms: Friend and Foe

23

3. Cell - Structure and Functions

48

4. Conservation of Plants and Animals

73

5. Reproduction in Animals

102

6. Reproduction in Plants

127

7. Reaching the Age of Adolescence

155

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CROP PRODUCTION AND MANAGEMENT

1.1 INTRODUCTION Food is one of the most important things we need to survive, along with oxygen and water. We require food to have enough energy for our daily activities. Agriculture involves the cultivation of plants and the raising of animals to produce food and other useful items. The primary aim of agriculture is to ensure an adequate food supply. As the human population continues to grow, there is an increasing demand for food. Crop improvement programmes and animal husbandry play an important role in increasing food production. The care and management of animals on a large scale to obtain food and other useful products is known as animal husbandry. Whereas developing the existing varieties of crops to produce new varieties that are more advanced in terms of food production, disease resistance, etc., falls under crop improvement.

1.2 AGRICULTURAL PRACTICES Over time, humans shifted from hunting and gathering to agriculture for a more reliable food source, allowing them to settle in one place and cultivate crops.

1.2.1 Crops and their types The same kind of plants grown, cultivated and harvested on a large scale on a piece of land are known as crop or crop plants. Examples of crops include cereals, pulses, oil seeds, fruit crops, etc.

These crops are usually grown to produce a lot of food, which can be sold in the market for money.

Some crops, such as fodder crops, are also grown specifically to provide food for animals.

Crops can be categorised as follows based on the seasons in which they are grown.

• Kharif crops • Rabi crops • Zaid crops

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CROP PRODUCTION AND MANAGEMENT

Kharif crops

Kharif crops are known as monsoon crops, as they are cultivated during the rainy season, which typically runs from July to October.

Rice, maize, soybean, cotton and other crops that thrive in such conditions are examples of kharif crops.

Fig. 1.1 Kharif crop (rice) Rabi crops

Rabi crops are winter crops and are cultivated during the winter season, which usually spans from October to March. Wheat, mustard, linseed and other crops that are suitable for cooler temperatures fall under this category.

Fig. 1.2 Rabi crop (wheat) Zaid crops

Zaid crops are referred to as summer crops and are cultivated during the summer season, from March to June. Watermelon, pumpkin, gourd and other crops that flourish in warmer conditions are considered zaid crops.

Fig. 1.3 Zaid crop (watermelon)

1.3 BASIC PRACTICES OF CROP PRODUCTION Crops require time to grow and be ready for harvest. For successful cultivation, farmers follow a set of practices. These practices make the crop grow throughout their growth span. Various steps involved in agriculture are as follows:

Preparation of soil

Storage

Adding manures and fertilizers

Sowing

Harvesting

Weeding

Fig. 1.4 Steps in agricultural practices

2

Irrigation

IL Foundation Series Class 8

1.4 PREPARATION OF SOIL Soil plays a vital role in agriculture because it provides nutrients for the plants to grow and survive.

Due to the composition of the soil, it is diverse in different places. The soil composition influences the crop quality. It is essential to prepare the soil such that it supports crop growth. Preparation of soil involves ploughing, levelling and manuring. The process of loosening and turning the soil is called tilling or ploughing.

Agricultural implements help farmers prepare the soil before sowing the seeds. It includes plough, hoe and cultivator.

1.4.1 Plough It is a tool used to plough the field that brings the nutrient-rich soil to the top. This tool is made of iron and wood and is operated by farmers or animals like cows or oxen. It has three parts: ploughshare, ploughshaft, and beam. Ploughshare is an iron strip in a triangular shape. The plough shaft is a long wooden log. The beam is the part that is placed on the animal's neck.

Beam

ploughshaft ploughshare

Fig. 1.5 Plough

1.4.2 Hoe Hoe is used to remove weeds and loosen soil. It is made of a wood rod with an iron plate at the end. grip

beam handle

bent plate rod

Fig. 1.6 Hoe

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CROP PRODUCTION AND MANAGEMENT

1.4.3 Cultivator Ploughing is done with the help of a cultivator driven by a tractor. A cultivator has the ability to penetrate deep in soil and break it up. This saves time and labour.

Fig. 1.7 Cultivator attached to a tractor

1.4.4 Levelling and manuring Tilled soil may have big chunks of soil. This needs to be crushed, and the soil should be levelled.

This is usually done with the help of a wooden or iron leveller.

The process of adding organic minerals and adding nutrients to the soil is called manuring.

Manuring is done to increase the soil's fertility.

1.5 SOWING Before planting, it is important to make sure the seeds are of good quality. Using bad or damaged seeds can reduce how much the plants grow. It is also essential to plant or sow the seeds at the same distance from each other to avoid overcrowding. This helps the plants get enough sunlight, nutrients, and water. There are different methods that use different tools for sowing seeds.

1.5.1 Traditional tools Seeds can be sown manually by sprinkling them into the soil by hand. This process is called broadcasting.

In the traditional method, seeds are sowed manually by using funnel-shaped tools.

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IL Foundation Series Class 8

Fig. 1.8 Traditional method of sowing

1.5.2. Modern tools A seed drill machine is used to drop seeds in the soil. This tool helps to maintain proper space between the seeds. It is operated with the help of a tractor.

Fig. 1.9 Seed drill

1.6 ADDING MANURE AND FERTILISER Plants get nutrients from the soil. But, growing crops in the same place for a long time causes the soil to lose its fertility. To overcome this, nutrients are added to the soil in two ways: natural methods or by adding manures and fertilisers to the soil.

1.6.1 Manure Manure is made from decomposed waste from plants and animals. It is rich in organic matter and helps improve the quality of the soil. Green manure consists of plant waste that improves soil fertility. Animal manure is obtained from animal waste. Compost is produced by the decomposition of plant and animal waste with the help of bacteria and fungi. The conversion of organic matter into rich humus is known as composting. In general, the compost is rich in organic nutrients except for some important nutrients like nitrogen, phosphorus and potassium.

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CROP PRODUCTION AND MANAGEMENT

Fig. 1.10 Composting

1.6.2 Fertiliser Plants need important nutrients such as nitrogen, phosphorus and potassium. Fertilisers, on the other hand, are chemicals made in factories. They contain important nutrients like nitrogen, phosphorus, and potassium (also known as NPK) that plants need to grow. Urea is an example of a fertiliser. The overuse of fertiliser can harm the soil and affect its fertility. Fertiliser washed off from the soil reaches the water sources. It affects the water sources and aquatic animals.

In general, farmers use fertiliser and manure in different combinations as both have different properties.

Manures

Fertilisers

It is made from animal, human, and plant waste. It is made in factories, using chemical substances.

It is organic in origin and is environment friendly. Not harmful in nature.

It is chemical in origin and causes pollution. Harmful in nature.

It is good for long-term soil fertility.

It is bad for long-term soil fertility if used in excess.

It is cheap and easily made.

It is expensive.

Rich in organic matter. Compared to fertilisers, they are poor in nutrients.

Very rich in plant nutrients.

Ex-bio fertilisers, vermicompost, green manure, etc.

Ex-NPK, ammonium sulphate, urea, etc.

Table. 1.1 Difference between manure and fertiliser

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IL Foundation Series Class 8

1.6.3 Natural methods Field fallow

Agricultural land is ploughed but left for some time without being sowed. The land replenishes all the lost minerals and nutrients by itself. After nutrients are restored, land can be cultivated again.

Crop rotation

Growing two or more crops sequentially on the same land is called crop rotation. Different crops use different sets of nutrients. Crop rotation ensures one particular crop doesn’t grow continuously and depletes the nutrients from the soil. An example of crop rotation might involve planting rice one year, followed by legumes the next year. Rice uses up large amounts of nitrogen, which can be replenished by the leguminous plants. Rhizobium present in the root nodules of legumes fix the atmospheric nitrogen and help to replenish the soil with nitrogen. Now, the soil is ready for the next rice crop.

1.7 IRRIGATION After sowing seeds, it is important to water them for the healthy growth of the plant. The crop requires water at regular intervals. Supplying water to crops at regular intervals is called irrigation.

It is often used in places where rainfall is irregular or during droughts. Water for irrigation can come from different sources like wells, rivers, lakes, and treated wastewater. To have healthy crops, the fields need to be watered regularly. The major sources of irrigation are wells, tube wells, ponds, lakes, rivers, dams and canals.

Fig. 1.11 Sources of water for irrigation

Irrigation is broadly classified into traditional methods and modern methods.

1.7.1 Traditional methods The traditional methods are dependent on humans or cattle to irrigate the fields. The efficiency of this method is less. The different traditional methods are as follows: Moat (pulley system)

It is a manual irrigation method that uses a moat or pulley system to draw water from a water source like a well to water the plants.

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CROP PRODUCTION AND MANAGEMENT

Fig. 1.12 Moat Chain pump

The chain pump method of irrigation involves a continuous loop of buckets that lift water from a lower to a higher elevation. It is driven by a rotating chain powered by a motor or manual labour. It efficiently transports water for agricultural purposes, aiding in crop growth and land fertility.

Fig. 1.13 Chain pump Dhekli

In dhekli, a bucket is connected to a pole using a rope and water is pulled from the well to the ground surface.

Fig. 1.14 Dhekli

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IL Foundation Series Class 8

Rahat

It is a lever system that uses animals like oxen and buffalo to take water from the well. The animals are attached to the wheel that rotates when the animals move.

Fig. 1.15 Rahat

1.7.2 Modern irrigation The modern method of irrigation reduces the labour and cost of irrigation. The different methods of modern irrigation are: Sprinkler system

A sprinkler system is used when water availability is low, and the land is uneven. It consists of rotating pipes with a nozzle at the top that are connected to the main pipeline. Water escapes through the rotating nozzle and is sprinkled on the crop. It covers small to larger areas most effectively.

Fig. 1.16 Sprinkler system Drip irrigation

Water is supplied to the roots of plants in small droplets, a method known as drip irrigation. This method proves to be highly efficient, especially in areas with limited water availability. By utilising

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CROP PRODUCTION AND MANAGEMENT

drip irrigation, water wastage is reduced to a minimum. Drip irrigation improves the water-holding capacity of soil and reduces soil erosion.

Fig. 1.17 Drip irrigation

1.8 PROTECTION FROM WEEDS Weeds are unwanted plants that naturally grow with crops. It is important to remove them because they compete with the crops for nutrients, water, sunlight, and space. The process of removing weeds is called weeding. Usually, weeding is done before the weeds start flowering.

There are different ways to remove weeds: 1. Manual removal: We can uproot or cut the weeds near the ground using our hands or tools, like a khurpa (trowel), hoe or rake. The manual method is time consuming and requires a lot of labour.

2. Use of weedicides: Weeding is done by spraying chemicals on the crops called herbicides or weedicides. Weedicides help to control weeds. They do not harm the crops. An example of a weedicide is 2, 4-D (2, 4-dichlorophenoxy acetic acid).

3. Ploughing: Ploughing the field helps to uproot the weeds, causing them to die.

4. Animal grazing: Allowing animals like goats or cows to eat the weeds helps in weed control.

These methods are used to get rid of weeds and ensure that the crops can grow without any competition from unwanted plants.

1.8.1 Protection of crops from pests Like weeds, crops must be protected from pests. The organisms that can cause damage to crops are called pests. Some of the pests are bacteria and insects. It is necessary to control pests because they reduce yield. The pests can be controlled by using pesticides. Pesticides are chemicals that can kill

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IL Foundation Series Class 8

pests and protect crops from damage. Some of the pesticides that are used to control pests are DDT, BHC, and Malathion.

1.9 HARVESTING Once the crop matures, it is ready to be harvested. Harvesting is the term used for collecting mature crops and separating the valuable parts, like grains. The crops are harvested manually using a sickle or with the help of the harvester. The harvesting process is followed by two steps: Threshing: Threshing refers to the separation of grain seeds from the harvested crop. A machine called a combine can be used for both harvesting and threshing.

Winnowing: Winnowing is the process of separating grains from the chaff, which is the outer covering of the grain. In this process, the mixture is dropped from a height, where the lighter chaff gets blown away by the wind and falls at a distance. Winnowing can be done by a winnowing machine.

Fig. 1.18 Harvesting

1.10 STORAGE Storing harvested grains properly is important as it helps in ensuring food security, economic stability, and the preservation of the nutritional quality of crops. If grains are not stored correctly, they can be damaged by insects, pests, rats, or microorganisms, and this will lead to grain loss.

• Before storing, it is necessary to dry the grains in sunlight to remove moisture. If freshly harvested grains are stored without drying, they may spoil or be attacked by microorganisms.

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CROP PRODUCTION AND MANAGEMENT

• Grains can be stored in large silos or granaries. Chemical insecticides can be sprayed to prevent bugs and pests.

• For smaller amounts of grains, jute bags (gunny bags) or metallic bins are used for storage.

Instead of using chemicals, dried neem leaves or turmeric can be used to keep away insects and pests.

Fig. 1.19 Silos for storing grains

1.11 ANIMAL HUSBANDRY Animal husbandry is a branch of agriculture that focuses on raising animals for products. It involves activities like dairy farming, poultry, and pisciculture. Animals that are domesticated for commercial purposes, such as cows, sheep, and other similar animals, are known as livestock.

1.11.1 Dairy farming Dairy farming is breeding, feeding and caring for animals, like cows, sheep, buffaloes, and goats, to obtain milk and milk products. The amount of milk they produce depends on the type of breed.

Fig. 1.20 Dairy farming

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IL Foundation Series Class 8

1.11.2 Poultry farming Poultry farming refers to raising birds like chickens, ducks, turkeys, and geese for their products, such as meat and eggs.

Fig. 1.21 Poultry farming

1.11.3 Sericulture Sericulture is the process of breeding silkworms to produce silk. It is also known as silk farming. The most commonly used silkworm for sericulture is the mulberry silkworm, scientifically known as Bombyx mori.

Fig. 1.22 Sericulture

1.11.4 Apiculture Apiculture involves raising honeybees to produce honey and beeswax. Honey is a sweet and edible liquid that has medicinal properties. It contains sugars, minerals, vitamins, and more. Beeswax is important for industries, as it is used in cosmetics, ointments, furniture, polishes, and other products.

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CROP PRODUCTION AND MANAGEMENT

Fig. 1.23 Apiculture

1.11.5 Pisciculture Pisciculture, also called fish farming, is the practice of large-scale rearing of fish mainly for food.

Fish have multiple uses, including being an excellent source of protein and vitamins. Some fish, like Gambusia, can be helpful in controlling the spread of diseases, such as malaria, carried by mosquitoes.

Fig. 1.24 Pisciculture

QUICK REVIEW • Agriculture involves the cultivation of plants and the raising of animals for human use.

• The same kind of plant grown and harvested in the field on a large scale is known as crops.

• The types of crops are the Kharif crop, the Rabi crop, and the Zaid crop.

• The preparation of soil includes ploughing and removing weeds by using tools like a plough, hoe, and cultivator.

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IL Foundation Series Class 8

• Sowing is the process of planting seeds carefully and maintaining proper spacing using traditional tools or seed drills.

• Adding manure and fertiliser enhances soil fertility with organic (manure) and chemical (fertiliser) nutrients.

• Irrigation is supplying water through traditional (moat, chain pump) or modern (sprinkler, drip irrigation) methods.

• The crops must be protected from unwanted plants to prevent competition for resources.

• Harvesting is the process of collecting mature crops, separating grains, threshing, and winnowing.

• Grains are stored properly to avoid damage from insects, pests, or microorganisms.

• Animal husbandry is the branch of study that deals with the rearing of animals for their useful products.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Agricultural practices 1. Which one of the following countries is the largest producer of rice in the world? a. China

b. Japan

c. Phillippines

d. Bangladesh

2. When are Rabi crops grown? a. November to February

b. January to March

c. September to December

d. April to June

3. What are crops sown in the rainy season called? a. Wet crops

b. Rabi crops

c. Monsoon crops

d. Kharif crops

c. Kharif crop

d. Weed

c. Summer

d. Spring

4. What type of crop is mustard? a. Rabi crop

b. Zaid crop

5. In which season are Zaid crops grown? a. Winter

b. Monsoon

6. Which of the following crops is not categorised as a Rabi crop?

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CROP PRODUCTION AND MANAGEMENT

a. Maize

b. Wheat

c. Linseed

d. Mustard

c. Broadcasting

d. Sowing

II. Sowing

1. Which term is used for scattering seeds by hand? a. Cultivating

b. Transplanting

2. Why do seeds placed deep inside the soil not germinate? a. Unable to get sufficient oxygen

b. Without sufficient food to bring a seedling to the surface

c. Under the pressure of overlying soil

d. Unable to get light

layers 3. Which of the following is used for sowing seeds? a. Sickle

b. Plough

c. Seed drill

d. Khurpi

III. Manure and fertilisers

1. Dried leaves can be used to ________________. a. Repel insects

b. Control weeds

c. Increase soil fertility

d. None of these

2. What is the organic matter formed by the decomposition of plant wastes called? a. Manure 3.

b. Fertiliser

c. Mulch

d. Weedicide

NPK, an example of a nutrient combination used in farming, is used as a. Weedicide

b. Manure

c. Fertiliser

d. Insecticide

4. Which statement below is inaccurate? a. Fertilisers contribute to the addition of

b. Manure supplies all primary nutrients.

humus in the soil. c. Long-term use of fertiliser diminishes soil fertility.

d. Crop rotation prevents the depletion of a specific nutrient from the soil.

IV. Irrigation

1. Which method is considered the most efficient for irrigation?

16

a. Sprinkler irrigation

b. Drip irrigation

c. Flood irrigation

d. Furrow irrigation

IL Foundation Series Class 8

2. Which type of irrigation method involves water falling drop by drop at the position of roots? a. Surface irrigation

b. Drip irrigation

c. Sprinkler irrigation

d. Manual irrigation

3. Which of the following is not a traditional irrigation method? a. Moat

b. Chain pump

c. Lever system

d. Drip system

c. Rhizobium

d. Streptococcus

V. Preparation of soil

1. Which bacterium can perform nitrogen fixation? a. E. coli

b. Salmonella

2. What is it called when different crops are planted on the same land simultaneously? a. Crop rotation

b. Fallowing

c. Intercropping

d. Monoculture

3. What is the term for leaving the land uncultivated for one or more seasons? a. Crop rotation

b. Intercropping

c. Field fallowing

d. Both options (a) and (b)

VI. Protection from weeds

1. What are chemicals used to control weeds called? a. Fertilisers

b. Pesticides

c. Insecticides

d. Weedicides

VII. Storage

1. Which of the following options is used for storing grains produced at a large scale? a. Silos

b. Jute bags

c. Granaries

d. Both options (a) and (c)

2. Statement I: Dried neem leaves are used for storing food grains.

Statement II: Farmers store grains in jute bags or metallic bins. a. Statement (I) is correct, while

b. Statement (II) is correct, while

statement (II) is incorrect.

statement (I) is incorrect.

c. Both statements are correct.

d. Both statements are incorrect.

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CROP PRODUCTION AND MANAGEMENT

VIII. Animal husbandry

1. Which silkworm is widely used for sericulture? a. Bombyx mori

b. Antheraea mylitta

c. Attacus atlas

d. Samia ricini

2. What does pisciculture involve rearing? a. Pigs

b. Poultry

c. Fish

d. Cattle

3. What is another term for sericulture? a. Apiculture

b. Aquaculture

c. Seripopiculture

d. Silk farming

4. What are domesticated animals raised for commercial purposes called? a. Livestock

b. Pets

c. Wildlife

d. Exotics

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. What are plants of the same kind cultivated at one place on a large scale called? a. Crops

b. Plantation

c. Fields

d. Forests

2. Read the statements carefully and choose the correct alternative from the following: Statement I: Kharif crops are grown in the rainy season.

Statement II: Kharif crops require more water. a. Both the statements are true, and statement II is the correct explanation

statement II is not the correct

of statement I

explanation of statement II

c. Statement I is true, and statement II is false

18

b. Both the statements are true, but

d. Statement I is false, and statement II is true

IL Foundation Series Class 8

3. Which of the following combinations accurately represents examples of Rabi crops? a. Soybean, groundnut, and maize

b. Groundnut, pea, and mustard

c. Paddy, maize, and gram

d. Wheat, gram, and pea

4. Which of the following statements is incorrect with respect to different types of crops? i. In India, Kharif crops are generally sown from June to September. ii. Examples of Rabi crops are mustard, pea, and wheat. iii. Examples of Kharif crops are linseed, gram, and wheat. iv. The crops grown from October to March are called Kharif crops a. i and ii

b. ii and iii

c. iii and iv

d. ii and iv

5. Analyse the given statement.

Assertion (A): Maize is classified as a Kharif crop.

Reason (R): Maize cultivation predominantly takes place during the rainy season. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation for Assertion (A). b. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation for Assertion (A). c. Assertion (A) is true, but Reason (R) is false. d. Assertion (A) is false, but Reason (R) is true.

6. What is the primary purpose of turning and loosening the soil before growing crops? a. Enhance soil colour

b. Promote weed growth

c. Improve root penetration and aeration

d. Increase soil compaction

7. How does the addition of manure to the soil before tilling contribute to crop cultivation? a. It enhances soil colour.

b. It provides nutrients for immediate plant use.

c. It improves soil compaction.

d. It ensures proper mixing of manure with soil.

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CROP PRODUCTION AND MANAGEMENT

8. Which of the following statements is incorrect? i. The presence of earthworms and microbes is beneficial in cultivated soil as it enhances soil fertility and structure. ii. The term used to describe the process of turning and loosening the soil using a plough is called levelling. iii. Breaking up clumps of soil (crumbs) after ploughing is to improve the soil colour. a. i and ii

b. ii only

c. ii and iii

d. i only

9. Which tool is traditionally used for tilling the soil, adding fertilisers, removing weeds, and turning the soil? a. Cultivator

b. Hoe

c. Plough

d. Seeder

10. What is the primary objective of sowing seeds at an appropriate depth in the soil? a. To protect seeds from pests and diseases c. To minimise water absorption by seeds

b. To facilitate easy germination and establishment of seedlings d. To promote shallow root development

11. What is the primary reason for maintaining an appropriate distance between seeds during sowing? a. To maximise competition among plants for resources c. To facilitate easy growth of weeds

b. To reduce chances of rapid germination and emergence d. To ensure adequate sunlight, nutrients, and water for plants

12. What unique benefit does manure offer for long-term soil health? a. Decreasing soil organic matter content

b. Promoting soil compaction and erosion

c. Nurturing beneficial soil nematodes

d. Leaching essential nutrients from the

and soil fertility

soil

13. How does manure contribute to improved water-holding capacity in soil? a. By causing excessive water runoff

b. By compacting the soil particles

c. By reducing soil porosity

d. By enhancing soil structure and organic matter content

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14. What environmental advantage does using manure provide over synthetic fertilisers? a. Increased greenhouse gas emissions

b. Enhanced risk of water pollution

c. Reduced dependence on nonrenewable

d. Diminished soil microbial activity

resources 15. What is the key advantage of using manure over fertilisers? a. Manure releases nutrients quickly,

b. Manure is cost effective compared to

promoting rapid plant growth. c. Manure enhances soil microbial activity, unlike fertilisers.

expensive fertilisers. d. Manure provides a balanced ratio of essential nutrients for optimal plant growth.

16. In terms of nutrient composition, how do fertilisers and manure differ? a. Fertilisers contain only nitrogen, phosphorus, and potassium, while manure contains various nutrients. b. Fertilisers supply only macronutrients, while manure supplies micronutrients. c. Fertilisers have lower nutrient content than manure. d. Fertilisers provide slow-release nutrients, while manure provides fast-release nutrients.

17. Which statement accurately distinguishes fertilisers from manure? a. Fertilisers are organic, while manure is inorganic. b. Fertilisers are derived from animal waste, while manure is chemically synthesised. c. Fertilisers are nutrient-rich substances, while manure is a mixture of decaying organic matter. d. Fertilisers enhance soil structure, while manure primarily provides immediate nutrients to plants.

18. What is the key advantage of the drip system in regions with poor water availability? a. It facilitates surface irrigation on level

b. It allows efficient watering of lawns.

fields. c. It conserves water and reduces wastage.

d. It promotes rapid germination of crops.

19. What is the main advantage of the sprinkler irrigation system? a. It minimises water usage by targeting root zones.

b. It is most suitable for surface irrigation on level fields.

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CROP PRODUCTION AND MANAGEMENT

c. It requires less pressure to function properly.

d. It efficiently waters lawns and coffee plantations.

20. Which type of crops benefit the most from the drip irrigation system? a. Crops with extensive root systems

b. Crops grown in marshy areas

c. Crops with high water requirements

d. Fruit plants, gardens, and trees

21. What is the significance of cutting crops close to the ground during harvesting? a. It reduces the risk of soil erosion.

b. It improves the quality of the crop.

c. It prevents pests from infesting the

d. It ensures easier manual harvesting.

crop.

22. How long does it generally take for a cereal crop to mature? a. 1 to 2 weeks

b. 1 to 2 months

c. 3 to 4 months

d. 5 to 7 months

23. What is the significance of winnowing in post-harvest activities?

22

a. Enhancing crop flavour

b. Preventing pest infestations

c. Separating grain from chaff

d. Removing soil from harvested crops

MICROORGANISMS: FRIEND AND FOE

2

2.1 MICROORGANISMS The organisms that are not visible with the naked eye and viewed under the microscope are called microscopic organisms, microorganisms or microbes. Microbes include protozoans, yeasts, bacteria, viruses, certain algae, and certain fungi. Bacteria, cyanobacteria, and actinomycetes belong to the kingdom Monera. Rusts, smuts, and moulds belong to the kingdom of Fungi. Protozoans belong to the kingdom Protista. The viruses, viroids, and prions are mostly proteinaceous infectious agents.

Types of Microorganisms

Bacteria

Virus

Protist

Fungi

Algae

Fig. 2.1 Types of microorganisms

Microbes are causal agents of most infectious diseases. They also spoil our food and other edible items. However, some microbes can be useful to human beings and nature in many important processes. They are more friendly and useful to man than harmful. Besides macroscopic plants and animals, microbes are the major components of biological systems on this Earth.

Fig. 2.2 Rod-shaped bacteria

Fig. 2.3 Spherical-shaped bacteria

23

MICROORGANISMS: FRIEND AND FOE

Nucleic acid (DNA) Tall tube and sheath

Capsid

DNA genome

Collar

Hexon Penton base

Baseplate Long tail fibre

Fibre Spikes Fig 2.4 Structure of a bacteriophage

Fig. 2.5 Adenovirus morphology

2.3 nm

18 nm

30 nm

Fig. 2.6 Rod-shaped tobacco mosaic virus (TMV)

Fig. 2.7 Colonies of bacteria growing in a petri dish

Fig. 2.8 Fungal colony growing in a petri dish

2.2 WHERE DO MICROORGANISMS LIVE? After the invention of the microscope, it was found that microorganisms are present everywhere.

They make up nearly half the total weight of all the living organisms present on the Earth.

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IL Foundation Series Class 8

Microorganisms are found in water (ponds, lakes, rivers, and oceans), soil, marshlands, and even inside our bodies. They are as common in polar regions as they are in hot deserts.

Seafloor cracks are home to certain microorganisms. In very harsh environments like hot springs, deserts, snow, and deep oceans where very few other living forms can exist, certain bacteria may both survive and flourish. Some have even been known to survive volcanic eruptions. Under such harsh circumstances, they stay dormant and reactivate when favourable conditions arise.

2.3 MICROORGANISMS AND US 2.3.1 Microorganisms in household products Curd

We use microbes or products derived from them every day. A common example is the production of curd from milk. Microorganisms such as Lactobacillus and others commonly called LAB (lactic acid bacteria) grow in milk and convert it to curd. During growth, the LAB produces acids that coagulate and partially digest the milk proteins. A small amount of curd added to fresh milk as inoculum or starter contains millions of LAB, which multiply at suitable temperatures, thus converting milk to curd. LAB also improves curd's nutritional quality by increasing vitamin B12. In our stomach, too, the LAB plays a beneficial role in checking disease-causing microbes.

Cheese

Distinct varieties of cheese are recognised by their unique texture, flavour, and taste, influenced by the specific microbes employed. For instance, the prominent holes in 'Swiss cheese' result from the abundant production of CO2 by a bacterium called Propionibacterium sharmanii. 'Roquefort cheese' acquires its distinctive flavour through the ripening process involving the growth of a specific fungus. Yoghurt is crafted by curdling milk with the help of Streptococcus thermophilus and Lactobacillus bulgaricus at a temperature of 45°C. Making bread

The main ingredient in the baking process is yeast. Sugar is the food source for the yeast. When sugar breaks down, carbon dioxide is released, and alcohol is created. We call this process fermentation. Yeast breaks down the sugar present in the dough. The dough rises when carbon dioxide bubbles are released. Bread is made with this dough. The heat from the baking process causes more gas bubbles to emerge in the dough. The bread rises and gets soft and fluffy as the gas leaves. The alcohol evaporates in the baking process due to heat.

2.3.2 Commercial use of microorganisms Even in industry, microbes are used to synthesise several products valuable to human beings.

Beverages and antibiotics are some examples. Production on an industrial scale requires the growth of microbes in very large glass vessels, metal vessels, or plastic vessels called fermenters.

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MICROORGANISMS: FRIEND AND FOE

Fermented beverages

Microbes, particularly yeasts, have been used since ancient times to produce beverages such as wine, beer, whisky, brandy, and rum. For this purpose, the same yeast, Saccharomyces cerevisiae, commonly known as brewer's yeast as used in bread making, is utilised to ferment cereals and fruit juices, leading to the production of ethanol. The varied types of alcoholic drinks obtained depend on the raw material used for fermentation and the processing method (with or without distillation).

Wine and beer are created through fermentation alone, while whisky, brandy, and rum involve distillation of the fermented mixture.

S. no.

Alcohol

Substrate used of alcohol

1.

Beer

Barley malt

2.

Wine

Fruit juices

3.

Whisky

Fermented cereals

4.

Brandy

Fruit juices

5.

Rum

Molasses

6.

Gin

Ray malt

7.

Vodka

Potato

Table 2.1 Alcohols and the substrate used to make them Chemicals, enzymes, and bioactive molecules

Acid production Microbes play a crucial role in the commercial and industrial production of various chemicals, including organic acids, alcohols, and enzymes. Examples include Aspergillus niger, a fungus responsible for producing citric acid; Acetobacter aceti, a bacterium producing acetic acid; Clostridium butylicum, a bacterium involved in butyric acid production; and Lactobacillus, a bacterium producing lactic acid. Yeast, such as Saccharomyces cerevisiae, is employed for the commercial production of ethanol.

Microbes

Product

Usage

Aspergillus niger

Citric Acid

Employed in dyeing inks, medicines, flavouring, and preservation of food

2. Acetobacter aceti

Acetic Acid

Used in the preparation of vinegar

3. Clostridium butylicum

Butyric acid

Used for making rancid butter

4. Lactobacillus

Lactic Acid

Curd

Gluconic acid

Gluconate is a source of calcium for infants, cows and lactating mothers

1.

5.

Aspergillus niger, Penicillium

Table 2.2 Microbes involved in acid production and their applications

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IL Foundation Series Class 8

In addition to acid production, microbes contribute to the production of enzymes. For instance, lactic acid, the first organic acid produced industrially through fermentation, is an essential product. Lipases produced by microbes are used in detergent formulations to efficiently remove oily stains from laundry.

Commercially available bottled fruit juices are clearer than homemade ones, thanks to enzymes like pectinases and proteases for clarification. Streptokinase, produced by the bacterium Streptococcus and modified through genetic engineering, serves as a 'clot buster', aiding in the removal of clots from the blood vessels of patients who have experienced a myocardial infarction (heart attack).

Bioactive molecules

Microbes are also involved in producing bioactive molecules. Cyclosporin A, an immunosuppressive agent used in organ transplant patients, is produced by the fungus Trichoderma polysporum. Statins, which act as blood cholesterol-lowering agents, are produced by the yeast Monascus purpureus through the competitive inhibition of the enzyme responsible for cholesterol synthesis. Overall, microbes contribute significantly to the industrial synthesis of various chemicals and bioactive compounds.

Enzymes produced by microbes

Proteases: Degrade proteins and polypeptides obtained from Moiterella renisports, Aspergillus, and Bacillus sp. used in the baiting of hides in the leather, silk, and dry-cleaning industry.

Streptokinase: It has a fibrinolytic effect, so it helps in clearing blood clots inside the flow.

2.3.3 Medicinal use of microorganisms Antibiotics

The term 'antibiotic' was introduced by Waksman. Antibiotics have made significant contributions to human society. It is a combination of the Greek words 'anti', meaning 'against,' and 'bios', meaning 'life', signifying substances that act against life, particularly targeting disease-causing organisms. Despite the label 'against life', antibiotics prove to be essential for human well-being.

These chemical substances, produced by specific microbes, possess the capability to either kill or inhibit the growth of other microbes responsible for causing diseases.

The pivotal discovery of the first antibiotic, penicillin, is attributed to Alexander Fleming. While working with Staphylococci bacteria, Fleming observed mould growing in one of his unwashed culture plates, creating an area where Staphylococci could not thrive. Further investigation revealed that this inhibition was due to a chemical produced by the mould, and he named it penicillin after the mould Penicillium notatum. The full potential of penicillin as an effective antibiotic was later established by Ernest Chain and Howard Florey.

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MICROORGANISMS: FRIEND AND FOE

Fig. 2.9 Penicillium notatum

During World War II, penicillin played a crucial role in treating wounded American soldiers, leading to Fleming, Chain, and Florey being awarded the Nobel Prize in 1945 for their groundbreaking discovery. After penicillin, various antibiotics have revolutionised our ability to combat deadly diseases such as plague, whooping cough, diphtheria, and leprosy, which used to claim millions of lives worldwide.

Most antibiotics are obtained from three groups of microorganisms: bacteria, actinomycetes, and fungi.

Antibiotic 1.

2.

From Bacteria Bacitracin From Actinomycetes Chlorotetracycline or aureomycin (or tetracycline) Chloramphenicol or chloromycetin Erythromycin Streptomycin Oxytetracycline/Terramycin Neomycin

Source Bacillus licheniformis Streptomyces aureofaciens S. venezuelae S. erythreus S. griseus S. rimosus Streptomyces fradiae

Table 2.3 Antibiotics and their source Vaccines

Microorganisms are used to make vaccines. These vaccines help to protect humans and other animals from several diseases. Diseases such as cholera, typhoid, tuberculosis, hepatitis, measles, polio, and smallpox can be prevented by vaccination. Vaccines contain dead or weakened microbes.

When these are swallowed or injected into a patient's body, the body produces antibodies to fight them. The antibodies remain in the body and protect it from any future attack of the disease germs.

The body is then said to have developed immunity against that disease. Vaccination helps in

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IL Foundation Series Class 8

immunisation. Immunisation is the process of safeguarding the body against diseases by introducing vaccines to stimulate the immune system's response.

2.3.4 Environmental use of microorganisms Soil fertility

Plants need food and nutrients just like human beings. They derive their nutrients from the soil.

Fertile soil contains all the major nutrients required for plant nutrition, like nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron, etc. If the soil loses its fertility, the plants will not grow and reproduce in such soil. To cope with this, the soil needs to replenish its nutrients.

Microorganisms that are present in the soil are responsible for replenishing the nutrients of the soil to be used by the plants.

Some bacteria live in the root nodules of plants like peas, gram, bean, etc. These bacteria can fix the nitrogen in the atmosphere and convert it into nitrates, which act as a natural fertiliser for plants.

Cyanobacteria (blue-green algae) like Nostoc, Anabaena, etc., can fix the atmospheric nitrogen to be utilised by the plants.

Fig. 2.10 Nitrogen-fixing blue-green algae Decomposition

Microorganisms decompose plant and animal waste and convert them into manure. This manure is a rich source of nutrients and is used to make the land fertile. Also, many times, we have seen dead plants and animals on the ground disappearing after a couple of weeks. Microbes like bacteria and fungi can convert the dead and decaying organic waste of plants and animals into simpler substances and mix them with the environment. This process is called decomposition. These simpler substances produced by decomposition can be used again by plants and animals. Polythene bags, plastic bottles, glasses, and broken plastic toys are examples of things that microbes cannot degrade. Therefore, it is advised to lessen the use of plastic materials.

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MICROORGANISMS: FRIEND AND FOE

2.4 HARMFUL MICROORGANISMS Microbes are harmful to us because they destroy food and cause diseases. Diseases in humans, plants, and animals are caused by microbes. Microorganisms harm us economically by damaging our valuable agricultural plants and causing diseases in animals like cows, buffaloes, chickens, etc. As a result, their negative consequences fall into the following categories: • Diseases • Food spoilage 2.4.1 Diseases The microorganisms that cause illnesses are called pathogens or germs.

The pathogen must first enter our bodies to make us sick.

Pathogens can enter our bodies in different ways - through the air we breathe, the water we drink, or the food we eat. They can also spread when we directly touch an infected person or encounter animals carrying germs. Diseases caused by microbes that can pass from an infected person to a healthy one through air, water, food, or physical contact are called communicable diseases.

The modes of entry of microorganisms in our body are as follows: • Microbes are discharged into the atmosphere when a person with a common cold or flu sneezes. Inhaling this air can cause infection in a healthy individual. A few illnesses that can spread via the air are the flu, polio, measles, mumps, chickenpox, and tuberculosis.

• Via food and drink, such as cholera, typhoid, and hepatitis.

• Via close contact with an infected individual, such as ringworm, the common cold, the flu, chickenpox, or polio.

• Via insects like fleas, flies, and mosquitoes. These are carriers of germs called vectors. Vectors are those animals, usually insects, that serve as carriers of disease-causing microorganisms but do not cause disease directly. Vectors themselves remain unaffected by the pathogens.

• For instance, the malaria virus is carried by the female Anopheles mosquito. The dengue virus is spread by female Aedes mosquitoes.

• Numerous pathogens are frequently carried by houseflies. Germs adhere to the bodies of houseflies as they sit in the dirt. They spread the germs to food when they sit on it. It's possible for the person eating the meal to get sick.

• Through cuts and wounds, such as infections that cause tetanus.

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IL Foundation Series Class 8

Fig. 2.11 Female Anopheles mosquito

Microorganisms also cause diseases in animals and plants. For example, Anthrax is a disease that affects both humans and cattle. It is caused by a bacterium, Bacillus anthracis. A virus causes dangerous foot and mouth disease in cattle. The rust of wheat is a fungal disease that spreads by air.

Citrus canker is a bacterial disease that affects plants of the citrus fruits and is spread by air. Yellow vein mosaic, which affects vegetables like bhindi, is a viral disease spread by insects.

Some human diseases caused by microorganisms

Some of the common diseases affecting humans, their mode of transmission, and a few general methods of prevention are given in the table below.

S.No.

Human disease

Causative microorganism

Modes of transmission

1.

Tuberculosis

Bacteria

Air

Measles

Virus

Air

Chickenpox

Virus

Air/Contact

Polio

Virus

Air/Water

Preventive measures • The sick person should be in complete isolation • The personal belongings of the sick patient should be kept away • Vaccinations should be given at a suitable age.

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MICROORGANISMS: FRIEND AND FOE

2.

3.

Cholera

Bacteria

Food/Water

Typhoid

Bacteria

Water

Hepatitis B

4.

Virus

Malaria

Water

Protozoa

Vector (mosquito)

•

Maintain personal hygiene and good sanitary habits.

•

Consume properly cooked food and boiled drinking water.

•

Vaccination

•

Drink boiled water

•

Vaccination

•

Use mosquito repellent and net.

•

Spray insecticides and control the breeding of mosquitoes by not allowing water to collect in the surroundings.

Table 2.4 Common human diseases caused by microorganisms S. No.

Animal disease

Causative agent

1.

Foot and mouth disease (in cattle)

Virus

2.

Anthrax disease (in cattle)

Bacteria

3.

Sleeping sickness (in cattle, pigs, horses)

Protozoa

Table 2.5 Common animal diseases caused by microorganisms S. No.

Plant disease

Causative microorganism

Mode of transmission

1.

Rust of wheat

Fungi

Air, Seeds

2.

Citrus canker

Bacteria

Air

3.

Yellow mosaic disease of lady's finger (okra)

Virus

Insects

Table 2.6 Common plant diseases caused by microorganisms

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IL Foundation Series Class 8

2.4.2 Food poisoning Some microorganisms are harmful to plants and animals, including humans. Food contaminated with harmful microorganisms, when consumed, may lead to the manifestation of symptoms of a disease. The diseased condition is referred to as food poisoning. It is so-called because the contaminated food contains toxins released by harmful microorganisms like viruses and bacteria.

These toxins harm our bodies.

In most cases of food poisoning, the stomach and intestines are affected. Symptoms of food poisoning vary depending on the cause and can include vomiting, fever, stomach ache, and diarrhoea.

2.5 FOOD PRESERVATION Food preservation refers to the conservation of food in a safe manner for future consumption.

Preserving food involves two main steps: 1. Killing the microbes in the food 2. Preventing their growth By taking these measures, we can make sure that the food remains fresh or preserved for a longer period without spoiling. Additionally, preservation includes slowing down the oxidation of fats, which is responsible for causing rancidity.

Some common methods of food preservation are: 2.5.1 Drying Drying or dehydrating is one of the most effective ways of preserving food. It removes water from food, making it difficult for bacteria and fungi to grow. This method is particularly good for meat, fish, fruits, and vegetables.

2.5.2 Smoking Smoking uses treatment with smoke to preserve the food. Usually, this method is used to prevent meat and fish from getting spoiled due to microbial growth.

2.5.3 Canning Canning, as a food preservation method, is carried out by sealing the edible food items in sterile cans and jars and then boiling these cans, bottles, and jars to kill any of the remaining harmful microorganisms. Even a little negligence in carrying out this process can lead to easy and rapid contamination of canned food products.

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MICROORGANISMS: FRIEND AND FOE

2.5.4 Heating Heating food at high temperatures kills microbes. For example, milk and water are boiled to kill microbes. Ultraheat treatment (UHT) is a method that partially sterilises milk by quickly heating it for 1-2 seconds at a temperature higher than 135 degrees Celsius. Milk treated through UHT and packaged in tetra packs can last for six months or longer if the package remains unopened.

2.5.5 Pasteurisation Boiling kills many microorganisms. One method of making milk free from microbes was devised

by Louis Pasteur. This technique of food preservation came to be known as pasteurisation. In pasteurisation, milk is heated to about 70 degrees Celsius for 15-30 seconds and then suddenly cooled and stored. By doing so, most of the pathogens in the milk are killed.

2.5.6 Refrigeration Keeping food in the refrigerator halts the growth and reproduction of microbes, effectively preserving the food. Refrigerators maintain a temperature of around 5 degrees Celsius, preventing spoilage for a few days. On the other hand, a deep freezer keeps food preserved at temperatures below minus 18 degrees Celsius, extending its shelf life for several months. However, once the food is taken out of the freezer and warmed, microbes can start growing again.

2.5.7 Blanching Blanching is a technique where food, typically vegetables, is briefly plunged into boiling water and then immediately transferred to ice water. Blanching helps preserve the colour, flavour, and nutritional value of vegetables before freezing.

2.5.8 Preservatives A. Salt

Common salt prevents the growth of microbes in meat and fish. It usually checks the growth of bacteria by making them lose water through the process of osmosis. In this method, meat and fish are covered with salt to prevent the growth of bacteria. Salting is also used to preserve food items like amla, raw mangoes, and tamarind.

B. Sugar

Sugar is used as a preservative in jams, jellies, and squashes, as it inhibits the growth of bacteria by water loss through osmosis.

C. Oil and vinegar

By using oil and vinegar, the pH of food becomes 4.6 or lower, which is sufficient to kill most bacteria. Vegetables, fruits, fish, and meat are often preserved by this method.

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IL Foundation Series Class 8

D. Chemical preservatives

Many chemicals kill microorganisms or stop their growth, but most of these are not permitted in foods. Chemicals that are permitted to be added to food items to kill the microorganisms are called food preservatives. Chemical food preservatives are those substances that are added in very low quantities (up to 0.2%) and which do not alter the properties of the foods. Sodium benzoate, sodium meta-sulphide, and benzoic acid are some examples of preservatives used in food.

2.6 NITROGEN CYCLE The process of absorption, utilisation, and assimilation of nitrogen into its organic form is called nitrogen metabolism. Soil contains 0.1 to 1.0% of nitrogen, mostly in inorganic form. The ultimate source of nitrogen is the free nitrogen present in the atmosphere. The atmosphere comprises 78% nitrogen by volume.

The cyclic movement of nitrogen from the atmosphere to soil and soil to the atmosphere through plants and animals is called the nitrogen cycle.

This biogeochemical cycle is completed in five steps. They are: 1. Nitrogen fixation 2. Nitrogen assimilation 3. Ammonification 4. Nitrification 5. Denitrification tion

ixa

F gen

itro

N

N2 in the atmosphere Burning of Fossil fuels

Lightning

Nitr ogen

Assimilation in animals

Nitrogen-fixing bacteria in root nodules

Bacteria and fungi Ammonification tion

NH4+ Nitrogen-fixing soil bacteria

Nitrifica

NO2-

NO3-

a

fic

tri

Ni

n tio

tion Fixa

Assim ila in pla tion nts

Fossil Decomposition fuels

Nitrifying bacteria Nitrifying bacteria

Natural activities Human activities

Fig. 2.12 Nitrogen cycle

2.6.1 Nitrogen fixation The conversion of molecular nitrogen in the environment into nitrogenous salts is called nitrogen fixation. It is of two types, namely physical (abiological) nitrogen fixation and biological nitrogen 35

MICROORGANISMS: FRIEND AND FOE

fixation. Biological nitrogen fixation is carried out by both free-living (Azotobacter, Clostridium) and symbiotic bacteria (Rhizobium).

2.6.2 Nitrogen assimilation The nitrates and ammonia absorbed by plants are utilised in the production of organic nitrogen (chlorophyll, enzymes, proteins) in plants. In the living cells of green plants, nitrates reduced to ammonia enter as an amino group in the formation of the amino acid.

2.6.3 Ammonification The nitrogenous organic compounds in the dead bodies of plants and animals are decomposed into ammonia or ammonium ions in the soil (mineralisation). This is called ammonification and is carried out by ammonifying bacteria like Bacillus. Volcanic eruptions and animals excrement are also sources of ammonia in the soil.

2.6.4 Nitrification Most of the ammonia in the soil is converted to nitrites and nitrates by Nitrosomonas and Nitrobacter bacteria, respectively. These bacteria are called nitrifying bacteria. The former converts ammonia to nitrite, and the latter converts nitrite to nitrate; the entire process is called nitrification.

2.6.5 Denitrification Represents the last and final step of the nitrogen cycle, wherein the nitrates (NO3- )present in the soil are converted into molecular dinitrogen to maintain the equilibrium of nitrogen in the atmosphere. The bacteria responsible for this reaction are called denitrifying bacteria.

QUICK REVIEW • Microorganisms are too small and are not visible to the naked eye.

• They can live in all kinds of environments, ranging from ice-cold climates to hot springs and deserts to marshy lands.

• Microorganisms are found in air, water, and the bodies of plants and animals.

• They may be unicellular or multicellular.

• Microorganisms include bacteria, fungi, protozoa, and some algae.

• Some microorganisms are useful for the commercial production of medicines and alcohol.

• Some microorganisms decompose the organic waste and dead plants and animals into simple substances and clean up the environment.

• Some of the microorganisms that grow on our food cause food poisoning.

• Some microorganisms reside in the root nodules of leguminous plants. They can fix nitrogen from air into the soil and increase soil fertility.

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IL Foundation Series Class 8

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Microorganisms and us 1. Germinating barley seeds are used in the preparation of: a. Lactic acid

b. Wine

c. Cheese

d. Beer

2. LAB stands for: a. Lactic acid bacteria

b. Lactobacillus acidophilus bacteria

c. Lactose acetaldehyde bacteria

d. Laboratory

3. Cheese and yoghurt are products of: a. Pasteurisation

b. Fermentation

c. Dehydration

d. Distillation

4. Baker's yeast is: a.

Saccharomyces cerevisiae

b. S. ludwigii

c.

S. octosporus

d. Schizosaccharomyces

5. The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is: a. Vitamin C

b. Vitamin D

c. Vitamin B12

d. Vitamin E

6. Which of the following is responsible for yoghurt formation? a.

Streptococcus pneumoniae

b. Lactobacillus acidophilus

c.

Lactobacillus bulgaricus

d. Streptococus cremoris

7. Lactobacillus mediated conversion of milk to curd results because of: a. Coagulation and partial digestion of milk fats b. Coagulation and partial digestion of milk proteins c. Coagulation of milk proteins and complete digestion of milk fats d. Coagulation of milk fats and complete digestion of milk proteins 8. Big holes in Swiss cheese are made by: a. A machine b. A bacterium that produces methane gas c. A bacterium producing a large amount of carbon dioxide d. A fungus that releases a lot of gases during its metabolic activities

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MICROORGANISMS: FRIEND AND FOE

9. Choose the correct option about statements (I) and (II): I. Lactic acid bacteria (LAB) are responsible for converting milk into curd II. LAB creates an acidic medium necessary to coagulate and fully digest the milk proteins a. Both statements (I) and (II) are true b. Both statements (I) and (II) are false c. Statement (I) is true, but (II) is false d. Statement (II) is true, but (I) is false 10. Penicillin was discovered by: a. Fleming

b. Waksman

c. Burkholder

d. Dubois

11. The first antibiotic to be isolated was: a. Terramycin

b. Streptomycin

c. Neomycin

d. Penicillin

12. Which one of the following alcoholic drinks is produced without distillation? a. Wine

b. Whisky

c. Rum

d. Brandy

13. Wine yeast is: a. Candida milleri

b. Brettanomyces bruxellensis

c. Hanseniaspora uvarum

d. S. cerevisiae

14. Fermented beverage with maximum alcohol content is: a. Beer

b. Wine

c. Whisky

d. Detrivores

15. A compound produced by an organism that inhibits the growth of another microorganism is: called a. Antiseptic

b. Antibiotic

c. Anticoagulant

d. Antibody

16. Which one is used in alcohol production? a.

Saccharomyces cerevisiae

b. Torulopsis utilis

c.

Clostridium botulinum

d. Leuconostoc citrovorum

17. Penicillin inhibits bacterial multiplication because of it:

38

a. Checks RNA synthesis

b. Checks DNA synthesis

c. Destroys chromatin

d. Inhibits cell wall formation

IL Foundation Series Class 8

18. Which of the following statements is correct?

A. Wine and beer are produced without distillation of fermented broth.

B. Wine and beer are produced with distillation of fermented broth.

C. Whisky brand and rum are produced by distillation of fermented broth.

D. Whisky brand and rum are produced without distillation of fermented broth. a. (A) and (B)

b. (A) and (C)

c. (B) and (A)

d. (B) and (C)

19. The chemicals that are pro-life concerning human beings: a. Are regarded as one of the most significant discoveries of the twenty-first century. b. Can kill or retard the growth of disease-causing microbes. c. Have rarely contributed to human welfare. d. Are produced by some plants and all animals.

20. Identify the correct statements for antibiotics: A. Fleming, Chain, and Florey were awarded the Nobel Prize in 1945.

B. Antibiotics have greatly improved our capacity to treat deadly diseases.

C. Penicillin was used to treat American soldiers wounded in World War I. a. (A) and (B)

b. (A) and (C)

c. (B) and (C)

d. All of these

21. Which one of the following is not true about antibiotics? a. The first antibiotic was discovered by Alexander Fleming. b. The term 'antibiotic' was coined by S. Waksman in 1942. c. Some people can be allergic to a particular antibiotic. d. Each antibiotic is effective only against one kind of germ.

22. Citric acid is produced by: a.

Acetobacter aceti

b. Clostridium butylicum

c.

Lactobacillus

d. Aspergillus niger

23. Match the following list of bacteria and their commercially important products: Bacterium

Product

i. Aspergillus niger

a. Lactic acid

ii. Acetobacter aceti

b. Butyric acid

iii. Clostridium butylicum

c. Acetic acid 39

MICROORGANISMS: FRIEND AND FOE

iv. Lactobacillus

d. Citric acid

a. i - b, ii - c, iii - d, iv - a b. i - d, ii - c, iii - b, iv - a c. i - b, ii - d, iii - c, iv - a d. i - d, ii - a, iii - c, iv - b 24. Which one of the following is not a nitrogen-fixing organism? a.

Anabaena

b. Nostoc

c.

Azotobacter

d. Pseudomonas

II. Harmful microorganisms

1. The carrier of malaria-causing protozoan is a. Female Anopheles mosquito

b. Cockroach

c. Housefly

d. Female Aedes mosquito

2. Which among the following is a common carrier of communicable diseases? a. Ant

b. Housefly

c. Dragonfly

d. Spider

3. Which of the following acts as a host for the virus that causes dengue fever? a. Mosquitoes

b. Houseflies

c. Rats

d. Humans

4. Ringworm can be prevented by a. Vaccination

b. Vector control

c. Improving personal hygiene

d. Using antibiotics

5. Tuberculosis spreads by a. Mosquitoes

b. Houseflies

c. Contaminated water

d. Droplets of sneezing and cough

6. The bacterial virus is also called: a. Cyanophage

b. Bacteriophage

c. Mycophage

d. Prophage

7. The common cold is a a. Viral disease

b. Bacterial disease

c. Algal disease

d. Protozoan disease

8. What is a common symptom of plant diseases caused by fungi?

40

a. Ring spots on leaves

b. Powdery mildew

c. Yellowing of leaves

d. Wilting of stems

IL Foundation Series Class 8

9. Which microorganism causes the disease 'rust' in plants? a. Bacteria

b. Fungi

c. Viruses

d. Protozoa

III. Food spoilage and preservation

1. The fruits get covered with whitish or orange powder because: a. It is preserved

b. It is fit for eating

c. It is spoiled

d. It is boiled

2. Pasteurisation was invented by a. Edward Jenner

b. Alexander Fleming

c. Louis Pasteur

d. Robert Koch

3. The working principle for a chemical preservative is to ______________. a. Influence the osmotic potential of the solution b. Change the bacterial temperature c. Influence the metabolic growth of bacteria d. Induce changes in the food so that bacteria cannot grow over them 4. What role does salt play in the preservation of foods, particularly meats and fish? a. It acts as an antioxidant to prevent lipid oxidation. b. It lowers the pH of the food, inhibiting bacterial growth. c. It disrupts the cell membranes of microorganisms, causing cell lysis. d. It reduces water activity, inhibiting microbial growth and enzyme activity.

5. What is the significance of airtight packaging in food preservation? a. Reduces moisture

b. Increases microbial growth

c. Enhances flavour

d. Causes oxidation

6. What is the function of nitrites in preserving processed meats like bacon? a. Enhances colour

b. Delays spoilage

c. Promotes rancidity

d. Increases sweetness

IV. Nitrogen cycle

1. Nitrification is the process of conversion of: a. Ammonia

b. Nitrite

c. Nitrate

d. All of these

2. The conversion of nitrate to nitrogen is called: a. Nitrification

b. Denitrification

c. Ammonification

d. Nitrogen fixation

41

MICROORGANISMS: FRIEND AND FOE

3. The conversion of N2 to ammonia is known as: a. Nitrogen fixation

b. Nitrification

c. Denitrification

d. Ammonification

4. The decomposition of organic nitrogen of dead plants and animals into ammonia is called: a. Nitrogen fixation

b. Nitrification

c. Denitrification

d. Ammonification

5. Nitrifying bacteria convert: a. Nitrate to nitrogen

b. Ammonia to nitrogen

c. Ammonia to nitrate

d. Nitrogen into insoluble form

6. Nitrogen fixation by Rhizobium occurs inside a. Soil

b. Rhizosphere association

c. Fuller association

d. Nodulated roots

7. Denitrification is carried out by a.

Pseudomonas and Nitrococcus

b. Nitrosomonas and Nitrobacter

c.

Nitrosomonas and Nitrococcus

d. Pseudomonas and Thiobacillus

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. Conversion of milk to curd improves its nutritional value by increasing the amount of: (NEET 2018)

a. Vitamin D

b. Vitamin A

c. Vitamin B12

d. Vitamin E (NEET 2020)

2. Match the following columns and select the correct option.

Column-I

Column-II

A. Clostridium butylicum

i.

Cyclosporin A

B. Trichoderma polysporum

ii.

Butyric acid

C. Monascus purpureus

iii.

Citric acid

D. Aspergillus niger

iv.

Blood cholesterol-lowering agent

a. A-(iii), B-(iv), C-(ii), D-(i)

b. A-(i), B-(ii), C-(iv), D-(iii)

c. A-(ii), B-(i), C-(iv), D-(iii)

d. A-(iv), B-(iii), C-(ii), D-(i)

3. Which of the following is a commercial blood cholesterol-lowering agent?

42

a. Lipase

b. Cyclosporin A

c. Statin

d. Streptokinase

(NEET 2019)

IL Foundation Series Class 8

(NEET 2019)

4. Match the following organisms with the products they produce.

Column I

Column II

A. Lactobacillus

i. Cheese

B. Saccharomyces cerevisiae

ii. Curd

C. Aspergillus niger

iii. Citric acid

D. Acetobacter aceti

iv. Bread v. Acetic acid

a. A-(ii), B-(i), C-(iii), D-(v)

b. A-(ii), B-(iv), C-(v), D-(iii)

c. A-(ii), B-(iv), C-(iii), D-(v)

d. A-(iii), B-(iv), C-(v), D-(i)

5. Which of the following is correctly matched to the product produced by them? (NEET 2017) a.

Methanobacterium: Lactic acid

b. Penicillium notatum: Acetic acid

c.

Saccharomyces cerevisiae: Ethanol

d. Acetobacter aceti: Antibiotics

6. Match column I with column II and select the correct option using the codes given below.

Column I

(NEET-II 2016)

Column II

A. Citric acid

i. Trichoderma

B. Cyclosporin

ii. Clostridium

C. Statins

iii. Aspergillus

D. Butyric acid

iv. Monascus

a. A-(iii), B-(i), C-(ii), D-(iv)

b. A-(iii), B-(i), C-(iv), D-(ii)

c. A-(i), B-(iv), C-(ii), D-(iii)

d. A-(iii), B-(iv), C-(i), D-(ii)

7. Match the following list of microbes and their importance.

Column I

Column II

A. Saccharomyces cerevisiae

i. Production of immuno-suppressive agent

B. Monascus purpureus

ii. Ripening of Swiss cheese

C. Trichoderma polysporum

iii. Commercial production of ethanol

D. Propionibacterium shermanii

iv. Production of blood-cholesterol-lowering agents

a. A-(iv), B-(ii), C-(i), D-(iii)

b. A-(iii), B-(i), C-(iv), D-(ii)

c. A-(iii), B-(iv), C-(i), D-(ii)

d. A-(iv), B-(iii), C-(ii),D-(i)

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MICROORGANISMS: FRIEND AND FOE

8. Which of the following can be used as a biocontrol agent in the treatment of plant disease?

(NEET 2019)

a. Lactobacillus

b. Trichoderma

c. Chlorella

d. Anabaena

9. A nitrogen-fixing microbe associated with Azolla in rice fields is a.

Spirulina

b. Anabaena

c.

Frankia

d. Tolypothrix

10. Which one of the following microbes forms a symbiotic association with plants and helps them in their nutrition? a.

Azotobacter

b. Aspergillus

c.

Glomus

d. Trichoderma (JIPMER 2000)

11. The term 'antibiotic' was coined by a. Louis Pasteur

b. Alexander Flemming

c. Edward Jenner

d. Selman Waskman (AIPMT 2011)

12. Nitrifying bacteria a. Convert free nitrogen to nitrogen compounds b. Convert proteins into ammonia c. Reduce nitrates to free nitrogen d. Oxidize ammonia to nitrates

(Kerala CEE)

13. Which of the following is a bacterium involved in denitrification? a.

Nitrococcus

b. Nitrosomonas

c.

Pseudomonas

d. Nitrobacter

14. Pathogenic microorganisms present in host cells are killed by medicines called: a. Pain killers

b. Antibodies

c. Antibiotics

15. The process of decay of dead organic matter is known as: a. Denitrification

b. Nitrification

c. Nitrogen fixation

d. Ammonification

d. Vaccines (BHU 2007)

16. Which microbial process is responsible for the tangy flavour in various dairy products like: cheese and buttermilk? a. Nitrogen fixation

b. Photosynthesis

c. Lactic acid fermentation

d. Ethanol production

17. Which microorganism is commonly used in bread and beer production and plays a crucial role in the fermentation process of these products?

44

IL Foundation Series Class 8

a.

Escherichia coli

b. Saccharomyces cerevisiae

c.

Staphylococcus aureus

d. Streptococcus pyogenes

18. What role do enzymes play in the fermentation process of beverages? a. Enzymes convert complex carbohydrates into sugars b. Enzymes convert simple sugars into acids c. Enzymes enhance the colour of the beverage d. Enzymes act as preservatives to extend shelf life 19. The fermentation of beer involves the conversion of malt sugars by yeast into alcohol and: a. Carbon dioxide

b. Caffeine

c. Fructose

d. Calcium

20. Which microorganism is crucial for the fermentation of grapes into wine and the conversion of sugars into alcohol and carbon dioxide? a.

Lactobacillus plantarum

b. Saccharomyces cerevisiae

c.

Escherichia coli

d. Pediococcus pentosaceus

21. What is the basic principle of immunisation and vaccination? a. It is based on the number of B and T lymphocytes. b. It is based on the property of memory of the immune system. c. It is based on antigen-antibody interactions. d. It is based on the number of white blood cells.

22. Which of the following statements is incorrect?

A. HPV vaccine is administered to young girls to prevent oral cancer.

B. Smallpox disease was first eradicated through vaccination.

C. A booster dose is an additional dose of a vaccine given to enhance immunity against a particular infection. a. Only (A)

b. Only (B)

c. Only (C)

d. Only (A) and (C)

23. When comparing pasteurisation and sterilisation, what is the primary difference between the two methods in terms of temperature and microbial reduction? a. Pasteurisation uses higher temperatures and achieves complete sterilisation. b. Sterilisation uses lower temperatures and retains higher nutritional content. c. Pasteurisation uses lower temperatures and reduces microbial load significantly. d. Sterilisation uses ultra-high temperatures and is mainly applied to beverages.

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MICROORGANISMS: FRIEND AND FOE

24. Why is blanching an essential pre-treatment before freezing vegetables for long-term preservation? a. It helps in expediting the browning of vegetables during freezing. b. It prevents the loss of water-soluble vitamins that might be lost during freezing. c. It activates enzymes that enhance the texture of frozen vegetables. d. It eliminates the need for a cold storage environment.

25. Which type of heat treatment is commonly used in the dairy industry to eliminate harmful pathogens while minimising changes to the sensory and nutritional qualities of the product? a. Pasteurisation

b. Sterilisation

c. Blanching

d. High temperature short-time (HTST) treatment

26. How does salting prevent the growth of microorganisms in food? a. By providing nutrients that favour beneficial microorganisms b. By lowering the pH of the food c. By creating a hypertonic environment that draws water out of microorganisms d. By promoting anaerobic conditions 27. What does a refrigerator do to prevent food spoilage? a. Warms the food

b. Delays microbial growth

c. Speeds up decay

d. Causes dehydration

28. What role does oil play in the preservation of certain foods, such as herbs or vegetables, in oil infusion? a. It activates the growth of yeast. b. It acts as an effective solvent for extracting and retaining the flavours. c. It increases the water activity of the food for a better taste. d. It accelerates enzymatic browning.

29. Which factor is crucial for preventing microbial growth when using oil as a preservation method? a. High moisture content

b. High pressure

c. Low temperature

d. Absence of oxygen

30. What is the primary mechanism by which sugar acts as a preservative in food preservation?

46

a. Osmotic pressure

b. Acidification

c. Enzyme inhibition

d. Oxidation-reduction

IL Foundation Series Class 8

31. In jam and jelly making, what role does sugar play besides its preservative function? a. Enhancing colour retention

b. Providing essential nutrients

c. Reducing acidity

d. Promoting microbial fermentation

32. What is true about viral pathogens?

A. They can be crystallised and stored for years.

B. Viruses do not occur as parasites in living cells.

C. They cannot be cultured on artificial media.

D. They are devoid of genetic material of their own. a. (A) and (B) are correct.

b. (B) and (D) are correct.

c. (A) and (C) are correct.

d. Only (A) is correct.

33. Which bacterial disease is caused by a bacterium that can evade the immune system by hiding within host cells and can lead to complications such as pelvic inflammatory disease (PID) if left untreated? a. Tuberculosis

b. Salmonellosis

c. Chlamydia

d. Botulism

34. What is the role of antibiotics in treating bacterial diseases in animals? a. Controlling fungal growth

b. Inhibit bacterial growth

c. Treating viral infections

d. Enhance animal immunity

35. Which microorganism causes the disease known as 'ringworm' in animals? a. Bacteria

b. Fungi

c. Viruses

d. Protozoa

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3

CELL – STRUCTURE AND FUNCTIONS

3.1 INTRODUCTION Cells are the basic structural and functional units of life. A cell is the smallest individual unit of matter capable of performing all essential life processes by itself. Cells vary in size and shape yet share common features such as a cell membrane, cytoplasm, and genetic material. Cells carry out essential functions like metabolism, growth, and reproduction.

3.2 DISCOVERY OF CELL Cells were discovered by Robert Hooke in 1665 when he examined a thin cork slice under his microscope, revealing numerous small box-like structures resembling a honeycomb. The boxes were separated from each other by a partition. He called these boxes cells. However, the cells discovered

by Hooke were dead, and only cellulose walls were visible.

In 1674, Antonie van Leeuwenhoek, a Dutch scientist, observed the first living cell under a microscope. He could also see some minute components within the cells with the help of his improvised microscope.

Discovery of observation Cell Fig. 3.1 Robert Hooke’s 3.3 THE CELL Cells are like tiny building blocks that make up living things. They work together to form the body of every living organism, just like bricks build a house. Every living entity comprises cells, making them essential for the existence and functioning of life forms.

48

IL Foundation Series Class 8

3.4 THE CELL THEORY Mathias Schleiden, a German botanist, stated that all plants are composed of cells, which form tissues. Theodore Schwann, a British zoologist, by observing animal cells, concluded that cells are bound by a plasma membrane. He also concluded that the presence of a cell wall is a unique characteristic of the plant cells. Schwann proposed the hypothesis that plant and animal bodies are composed of cells and products of cells.

The 'Cell theory,' formulated by Schleiden and Schwann, did not explain the origin of new cells.

Rudolf Virchow explained that new cells are formed from pre-existing cells through division (Omnis cellula-e-cellula).

The 'Cell theory' modified by Virchow states that: •

All living organisms are composed of cells and products of cells.

•

Cells are the basic unit of structure and function in living organisms.

•

All cells arise from pre-existing cells.

3.5 AN OVERVIEW OF CELL While preparing temporary mounts of peels of onions of different sizes, we observe similar structures. Together, they form a big structure like an onion bulb! This shows that onion bulbs of different sizes have similar small structures visible under a microscope. The onion peel cells will all look the same, regardless of the size of the onion they came from. These small structures are the basic building units of the onion bulb. Living cells show variations in size, shape number, and activities.

3.5.1 Number of cells Different organisms have different numbers of cells. Based on the number of cells present in organisms, they are classified into unicellular organisms and multicellular organisms.

Unicellular organisms: Organisms that are made up of single cells are called unicellular organisms. Although made up of single cells, they perform all activities necessary for life. Examples include Amoeba, Chlamydomonas, Paramecium, bacteria, etc.

Multicellular organisms: Organisms with multiple cells are called multicellular organisms.

Examples include plants and animals. All multicellular organisms begin their life as a single cell, which is the fertilised egg.

49

CELL - STRUCTURE AND FUNCTIONS

Unicellular Organisms

Multicellular Organisms

Bacteria

Paramecium

Octopus

Amoeba

Chlamydomonas

Petromyzon

Fig. 3.2 Some common unicellular and multicellular organisms

Unicellular organisms

Multicellular organisms

Organisms are made up of one cell.

Organisms are made up of many cells.

One cell carries out all the functions.

Different cells carry out different functions.

The death of one cell leads to the death of The death of one cell does not lead to the the organism. death of the organisms.

Unicellular organisms do not show levels of organisation.

Multicellular organisms show various levels of organisation.

Examples: Amoeba, Paramecium, bacteria, etc.

Examples: Man, crow, dog, tree, etc.

Table 3.1 Difference between unicellular organisms and multicellular organisms

3.5.2 Shape of the cells The shape of the cell varies from organism to organism. In most cases, the shape of the cell is round.

However, in some, it is irregular, as in Amoeba and leucocytes, whereas in bacteria, the shape is rodlike, spiral and comma-shaped.

Some cells, such as muscle cells and nerve cells, are long and thin multicellular organisms. The shape of the cells varies considerably in multicellular organisms; they are flat, columnar, elliptical, spindle-shaped, cuboidal, polygonal, and so on.

50

IL Foundation Series Class 8

Red blood cells (round and biconcave)

White blood cells (amoeboid)

Columnar epithelial cells (long and narrow)

Nerve cells (branched and long)

Fig. 3.3 Different types of cells showing different shapes

3.5.3 Size of cells Cells display significant variation in size. Mycoplasma, the smallest known cell, measures only 0.3 µm in length, whereas bacteria can range from 3 to 5 µm. The largest individual cell is found in the ostrich egg. In multicellular organisms, human red blood cells have a diameter of approximately 7.0 µm. Nerve cells are the longest cells in the human body. Size differences in cells reflect their specialised functions and the diverse requirements of organisms.

3.5.4 Types of cells The cells can be divided into two types according to the differences in their cellular organisation.

Prokaryotic cells: The cells which do not have a well-defined nucleus and membrane-bound organelles are called prokaryotic cells, for example, bacterial cells.

Eukaryotic cells: The cells with a true nucleus and membrane-bound organelles are called eukaryotic cells, for example, plant and animal cells.

3.6 PARTS OF THE CELL 3.6.1 Cell membrane The cell membrane is the outermost living covering of the cell, present in both plants and animals. It is also called plasma membrane or cytoplasmic membrane. Its detailed structure was studied with 51

CELL - STRUCTURE AND FUNCTIONS

an electron microscope. The plasma membrane is selectively permeable as it allows the entry and exit of some materials in and out of the cell. It consists of a double layer of lipid layer and protein molecules. In the bilipid layer, polar heads (hydrophilic) are arranged towards the outer sides and non-polar tails (hydrophobic) towards the inner part. The lipid component of the membrane mainly consists of phosphoglycerides. The cell membrane also possesses protein and carbohydrates.

Sugar

Lipid bilayer

Peripheral protein

Integral protein

Cholesterol Fig. 3.4 Structure of cell membrane

The proteins are of two types: 1. Peripheral proteins: They lie on the surface of the membrane 2. Integral proteins: They are partially or totally buried in the membrane.

According to the widely accepted "Fluid mosaic model" proposed by Singer and Nicolson, the quasifluid nature of lipids enables lateral movement of proteins within the overall bilayer. The fluid nature of the membrane is also important for cellular functions like cell growth, formation of intercellular junctions, secretion, endocytosis, cell division, etc. The main function of the plasma membrane is to regulate the movement of materials in and out of the cell. It helps to maintain the proper composition of the cell and also protects the cell from external injury.

3.6.2 Cell wall The presence of cell walls is a distinguishing feature of plant cells. The cell wall was first observed

by Robert Hooke in the cork tissue of an oak tree (Quercus suber). It is a non-living rigid structure that forms an outer covering for the plasma membrane of most fungi and plants. Algae have cell walls made up of cellulose, galactans, mannans and minerals like calcium carbonate. In plants, it is made up of cellulose, hemicellulose, pectins, and proteins. The fungal cell wall is primarily composed of chitin.

52

IL Foundation Series Class 8

Nucleus

Vacuole

Cell wall Chloroplast Cytoplasm

Mitochondria

Fig. 3.5 Cell wall

The cell walls of adjacent cells are joined together by the middle lamella, which is a jelly-like substance. The cell wall provides strength and rigidity to the plant cell and is freely permeable. It helps to determine the size and shape of the cell.

3.6.3 Cytoplasm Cytoplasm is a jelly-like substance (cytosol or cytoplasmic matrix) present between the cell membrane and the nucleus. Autonomic movement of the matrix in the cytoplasm in a cell is called cytoplasmic streaming or cyclosis. Various other components or organelles of cells are present in the cytoplasm. These are endoplasmic reticulum, mitochondria, Golgi bodies, ribosomes, lysosomes, vacuoles, chloroplasts, nuclei, etc. The entire content of the living cell is known as protoplasm. The protoplasm includes the cytoplasm, nucleus, and other cell organelles. It is regarded as the living substance of the cell.

All life functions take place in the cytoplasm. It produces all the carbohydrates and proteins that are required by the cell, by breaking down food materials taken in by the cell. It also recycles unwanted proteins and other chemicals into useful materials for the cell. It holds the cell's organelles in place.

3.6.4 Cell organelles Nucleus

The nucleus was discovered by Robert Brown in 1831. The nucleus is a spherical structure located in the centre of the cell. It is separated from the cytoplasm by the nuclear membrane. The outer membrane is usually continuous with ER and bears ribosomes. The membrane is porous and allows the movement of material between the nucleus and cytoplasm. A nuclear pore is formed by the fusion of two membranes that help in this movement.

Nuclear pore Chromatin Nucleolus Nucleoplasm Nuclear envelope Fig. 3.6 Nucleus

53

CELL - STRUCTURE AND FUNCTIONS

Nucleoplasm is the matrix of the nucleus consisting of nucleolus and chromatin. The nucleolus (plasmosome) is not a membrane-bound structure. It is a site for active rRNA synthesis. A loose, indistinct network of nucleoprotein fibrils called chromatin is present in nucleoplasm. It is made up of DNA, histone proteins, some non-histone proteins and RNA. During cell division, the chromatin condenses to form chromosomes. A single human cell (2n) has an approximately two-meter-long thread of DNA distributed among 46 chromosomes.

Chromosome

Condensed chromatin transforms into a specific number of chromosomes. Each chromosome consists of a primary constriction or centromere.

Two disc-like structures present on the sides of the centromere are called kinetochores.

Chromosomes are of the following types based on the position of the centromere. Non-stained secondary constrictions are also present in a few chromosomes. The small fragment, usually spherical, beyond secondary constriction is called a satellite. A set of chromosomes is called the karyotype of a species. A diagrammatic representation of the karyotype of a species is called an idiogram.

Telomere Short arm Centromere Longer arm Sister chromatid

Fig. 3.7 Chromosome

Endoplasmic reticulum

A network or reticulum of tiny tubular structures scattered in the cytoplasm and observed in the electron microscope is called the endoplasmic reticulum. The term endoplasmic reticulum was coined by K.R. Porter. If ribosomes (80S) are attached to its outer surface, it's called Rough ER (RER), and without ribosomes, it is called Smooth ER (SER). RER is frequently observed in the cells actively involved in protein synthesis and secretion. SER is the major site for lipid synthesis.

In animal cells, it is involved in the synthesis of lipid-like steroidal hormones and the detoxification of chemicals in liver cells.

Nucleus Cisternal space Ribosomes Smooth Endoplasmic Reticulum (SER)

Rough Endoplasmic Reticulum (RER) Cisternae

Fig. 3.8 Rough endoplasmic reticulum and smooth endoplasmic reticulum

54

IL Foundation Series Class 8

Golgi apparatus

Densely stained reticular structures near the nucleus were first observed and named by Camilo Golgi. The Golgi complex consists of many flat, disc-shaped stacked sacs of cisternae (0.5 µm to 1.0 µm). Cisternae are concentrically arranged near the nucleus. The Golgi body shows polarity.

The convex cis or formation face and concave trans or the maturation face are interconnected and are entirely different. Golgi apparatus is principally involved in packaging material to be delivered either to the intra-cellular targets or secreted outside the cell. Material to be packaged in the form of vesicles from the ER fuse with the cis face and move towards the maturing face. (coordinated function) Incoming transport vesicle Cisternae Cis face

Trans face

Secretory vesicle

Newly forming vesicle Fig. 3.9 Golgi apparatus

The Golgi complex is an important site for the formation of glycoproteins and glycolipids. In plants, the Golgi complex is called dictyosomes. It is involved in the synthesis of cell wall materials and in the formation of cell plates during cell division. Root cap cells are rich in Golgi bodies, which secrete mucilage for the lubrication of the root tip. The eukaryotic cells process the Golgi apparatus, but many fungi and ciliated protozoans lack well-formed Golgi bodies.

Lysosomes

Lysosomes are small,sac-like single membrane structures found regularly distributed in the cytoplasm. These membrane-bound vesicular structures are formed from the Golgi complex. They are rich in hydrolytic enzymes, which are involved in the digestion of carbohydrates, proteins, lipids, and nucleic acids. Enzymes of lysosomes are optimally active at acidic pH. Lysosomes are involved in autolysis by digesting cellular contents under starvation and are hence called suicidal bags of the cell.

55

CELL - STRUCTURE AND FUNCTIONS

Membrane

Hydrolytic enzymes Animal cell

Transport proteins

Fig. 3.10 Lysosomes

Endomembrane system: The endomembrane system is a network of membranes found throughout the cytoplasm of eukaryotic cells. It includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and plasma membrane. These organelles work together to modify, package, and transport proteins and lipids within the cell and to the cell membrane.

Mitochondria

Mitochondria are double membrane-bound cell organelles associated with the oxidation of food and the production of cellular energy in the form of ATP. They are not visible under the microscope unless stained (Janus green-B stains mitochondria).

Number of mitochondria per cell is variable depending on physiological activity. For example, meristematic cells, which are physiologically more active, have a larger number of mitochondria.

Mitochondria divide by fission. The typical shape is sausage-shaped or cylindrical.

Outer Intermembrane Inner membrane space membrane Ribosomes Matrix

DNA

Granules

Cristae

Fig. 3.11 Mitochondria

Infoldings of the inner membrane which increase the surface area are called cristae. The two membranes have their own specific enzymes associated with mitochondrial function. The inner 56

IL Foundation Series Class 8

compartment of mitochondria is called the matrix. The matrix consists of a single circular DNA, a few RNA molecules, 70S ribosomes and components required for the synthesis of proteins. The outer membrane is chemically 40% lipid and 60% protein, and the inner selectively permeable membrane has 80% protein and 20% lipids and is rich in cardiolipins. The inner membrane consists of elementary particles or particles of Fernandez & Moran or F1 particles or oxysomes, which play a crucial role in generating ATP. The mitochondria are called the powerhouse of the cell.

Plastids

Double membrane-bound cell organelles, which are involved in the synthesis and storage of food and bear pigments, are called plastids. They are present only in all plants and in euglenoids.

Based on the type of pigments, they can be classified into: 1. Chloroplasts 2. Chromoplasts 3. Leucoplasts Types of plastids: 1. Leucoplasts are colourless plastids involved in the storage of food.

There are three types of leucoplasts: i.

Starch-storing amyloplasts, e.g. potato.

ii. Oils/fats-storing elaioplasts iii. Protein-storing aleuroplasts 2. Chromoplasts are coloured plastids other than green.

They contain fat-soluble pigments like carotenoids (carotenes and xanthophylls) and impart yellow, orange, or red colour to plant parts.

3. Chloroplasts are double-membrane, green-coloured plastids that contain chlorophyll and carotenoid pigments, which trap light energy required for photosynthesis.

The majority of the chloroplasts are found in the mesophyll cells of the leaves. Their shape varies from lens, oval, spherical, discoid to ribbon-like. They measure about 5 – 10 µm in length and 2 - 4 µm in width. Their number varies from one per cell in Chlamydomonas (green alga) and 20 - 40 per cell in mesophyll. The inner chloroplast membrane is relatively less permeable. The space inside of the inner membrane is called stroma.

57

CELL - STRUCTURE AND FUNCTIONS

Intermembrane space Internal membrane External membrane Plastoglobule Granum Ribosome Chloroplast DNA Stroma

Thylakoid Thylakoid membrane Lamella Lumen Fig. 3.12 Structure of chloroplasts

Organised flattened membranous sacs present in the stroma are called thylakoids. Thylakoids arranged like piles of coins (stacks) are called grana. The matrix found inside the chloroplast is called stroma. Photosynthetic pigments are present in the thylakoid membranes. The space inside of the thylakoids is called the lumen. Light reaction of photosynthesis occurs in the grana region.

Stroma contains enzymes required for carbohydrate and protein synthesis. Stroma consists of double-stranded circular DNA and 70S ribosomes. Due to the presence of DNA, chloroplast, along with mitochondria, are called semiautonomous cell organelles. Chloroplasts also divide by fission, like mitochondria.

Vacuoles

These are membrane-bound spaces present in the cytoplasm of mainly plant and fungal cells. The membrane that covers the vacuole is called tonoplast. Vacuolar sap (tonoplasm) mainly consists of water, metabolic by-products, excretions, other waste materials, and pigments like anthocyanin.

In mature plant cells, the vacuoles occupy up to 90% of the volume of the cell. Vacuole plays a significant role in osmoregulation. In Amoeba, excretion is by the contractile vacuole. In protists, food vacuoles are formed by engulfing the food particles.

Endoplasmic Reticulum Cytoplasm Nucleus Chloroplast

Fig. 3.13 Vacuole

58

Cell Wall

Tonoplast

Cell Membrane

Central vacuole

Vacuole Mitochondria

Cell sap

Golgi Apparatus Fig. 3.14 Tonoplast

IL Foundation Series Class 8

3.7 COMPARISON OF PLANT AND ANIMAL CELLS Plant and animal cells are two primary types of eukaryotic cells that constitute the basic units of life. While both share fundamental characteristics such as a cell membrane, cytoplasm, and genetic material, they also exhibit distinct features tailored to their specific functions and environments.

Feature

Plant cell

Animal cell

Cell wall

Present

Shape

Usually rectangular or polygon Round or irregular shape in shape

Chloroplast

Present

Absent

Vacuoles

Large central vacuole present

Small and numerous vacuoles maybe present

Lysosomes

Rarely found

Commonly found

Centrioles

Absent

Present, typically in pairs near the nucleus

Storage of food

Stored in the form of starch

Stored in the form of glycogen or fat

Organelles

Absent

Have plastids (chloroplasts, Lack plastids but may have chromoplasts) specialised structures Table 3.2 Difference between plant cell and animal cell

QUICK REVIEW • A cell is the fundamental structural and functional unit of all living organisms.

• Cell theory formulated by Schleiden and Schwann did not explain the origin of new cells.

• Rudolf Virchow explained that new cells are formed from pre-existing cells by division (omnis cellulae-cellulla).

• Cells that have membrane-bound nuclei are called eukaryotic cells.

• Cells that lack a well-defined nucleus and membrane-bound cell organelles are prokaryotic cells.

• Eukaryotic cells have a well-defined nucleus and membrane-bound cell organelles.

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CELL - STRUCTURE AND FUNCTIONS

• Plant cells are characterised by the presence of cell walls, plastids, and a large central vacuole.

• Animal cells have centrioles, which are absent in almost all plant cells.

• The cell membrane is the living boundary for protoplasm present in all living cells.

• The fluid mosaic model was proposed by Singer and Nicolson.

• ER, Golgi complex, lysosomes, and vacuoles whose functions are coordinated are described as the endomembrane system.

• RER is frequently involved in protein synthesis and secretion.

• SER is the major site for lipid synthesis.

• Golgi apparatus is principally involved in packaging material.

• Enzymes of lysosomes are optimally active at acidic pH. • Double membrane-bound cell organelles associated with food oxidation and the production of cellular energy in ATP are called mitochondria.

• Double membrane-bound cell organelles involved in the synthesis and storage of food and bear pigments are called plastids.

• The membrane that covers the vacuole is called the tonoplast.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I.

Discovery of cell and cell theory

1. The living cell was first discovered by: a. R. Hooke

b. A.V. Leeuwenhoek

c. N. Grew

d. R. Brown

2. Cell was first discovered by: a. Robert Hooke

b. Leeuwenhoek

c. Dujardin

d. Janssen

3. Select the correct statement. a. Anything less than a complete structure of a cell does not ensure independent living

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IL Foundation Series Class 8

b. Anton Von Leeuwenhoek first saw and described a living cell c. Robert Brown discovered the nucleus d. All of the above 4. Who first applied cell theory to plants? a. T. Schwann

b. R. Virchow

c. M. Schultz

d. M. J. Schleiden

5. The scope of cell theory was extended by a. Schleiden & Schwann

b. R.Virchow

c. Robert Hooke

d. Corti

6. Match the following.

Column I

Column II

A. Cell theory

1. Sutton and Boveri

B. Protoplasm theory

2. R. Virchow

C. Cell lineage theory

3. Schleiden

D. Chromosomal theory

4. Hertwig

a. A-3, B-2, C-4, D-1

b. A-3, B-4, C-2, D-1

c. A-1, B-3, C-2, D-4

d. A-1, B-3, C-4, D-2

7. Which of the following statements is not a part of the final cell theory? a. Cells have a thin outer layer called plasma membrane b. All living organisms are made up of cells and products of cells c. All cells arise from pre-existing cells d. All of the above II.

Overview of cell

1. The smallest cells are a. Bacteria

b. Cyanobacteria

c. Mycoplasma

d. RBC

2. The largest individual cell is: a. Egg of ostrich

b. RBC

c. WBC

d. Mesophyll cell

3. Match the following.

Type of cell

Shape of the cell

A. Red blood cells

1. Branched and long

B. Epithelial cells

2. Biconcave 61

CELL - STRUCTURE AND FUNCTIONS

C. Nerve cell

3. Long and narrow

D. WBC

4. Elongated 5. Amoeboid

a. A-4, B-2, C-1, D-3

b. A-2, B-3, C-1, D-5

c. A-5, B-1, C-3, D-2

d. A-2, B-1, C-3, D-5

4. Unicellular organisms are a. Not capable of independent existence because they cannot perform all the essential functions of life b. Not capable of independent existence but they can perform all the essential vital functions c. Are capable of independent existence and perform all the essential vital functions d. Are capable of leading independent existence, but they perform some vital functions III. Parts of the cell

1. Common cell wall materials found in plant cells are a. Cellulose

b. Hemicellulose

c. Pectin

d. All of the above

2. Neighbouring cell walls are joined by a. Middle lamella

b. Primary cell wall

c. Secondary cell wall

d. Plasma membrane

3. Which of the following are not membrane-bound? a. Ribosomes

b. Lysosomes

c. Mesosomes

d. Vacuoles

4. All living cells have a. Cell wall

b. Cell membrane

c. Chloroplasts

d. Mitochondria

5. Which of the following is a function of the cell wall? a. Absorption

b. Secretion

c. Protection

d. All

6. Major cell wall material present in the cell wall of fungal cells is a. Cellulose

b. Suberin

c. Chitin

d. Cutin

7. Middle lamella is chemically rich in

62

a. Suberin

b. Pectin

c. Chitin

d. Lignin

IL Foundation Series Class 8

8. Eukaryotic cells may differ from prokaryotic cells in having a. Locomotory structures

b. Cytoskeleton

c. Nucleus with nuclear membrane

d. Both (b) and (c)

9. The plasma membrane consists mainly of a. Phospholipids embedded in a protein bilayer b. Protein embedded in a phospholipid bilayer c. Proteins embedded in a polymer of glucose molecules d. Proteins embedded in a carbohydrate bilayer 10. Amembranous cell organelles in animal cells are a. Ribosomes and vacuole

b. Ribosomes and lysosomes

c. Ribosomes and centromere

d. Centrosome and ribosomes

11. A similar characteristic between prokaryotic cells and eukaryotic cells is a. Cell wall composition b. Presence of slime layer c. Composition of plasma membrane d. Nature of nucleus 12. Which of the following is a major component of the plant cell wall? a. Cellulose

b. Cholesterol

c. Collagen

d. Keratin

13. Which of the following statements about the plasma membrane is incorrect? a. The ratio of proteins and lipids varies considerably in different cell types. b. 50% protein and 40% lipids are generally present in the plasma membranes. c. The arrangement of proteins (P) and lipids (L) is L-P-P-L. d. Head of lipid (fatty acid) is hydrophilic.

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CELL - STRUCTURE AND FUNCTIONS

14. Consider the following statements: A. The middle lamella is a layer mainly of calcium pectate, which holds or glues the different neighbouring cells together.

B. A non-living rigid structure called the cell wall forms an outer covering for the plasma membrane of fungi and plants.

C. Peripheral proteins lie on the surface of the cell membrane, while the integral proteins are partially or totally buried in the membrane.

D. Biochemical investigation clearly revealed that the cell membranes also possess protein and carbohydrate.

How many of the above statements are incorrect?

a. All of these

b. Two

c. Three

d. None of these

15. Luminal and extra luminal compartments in the intracellular space of a cell are distinguished by the presence of a. Mitochondria

b. Endoplasmic reticulum

c. Ribosomes

d. Cytoskeleton

16. Lipoprotein network of tubular structures scattered in the cytoplasm of the eukaryotic cell is a. Cytoskeleton

b. Microtubules

c. Endoplasmic reticulum

d. Plastids

17. Rough ER is associated with a. Ribosomes

b. Nucleus

c. Mesosomes

d. Peroxisomes

18. From which cellular processes does the endoplasmic reticulum arise? a. Intracellular transport

b. Protein synthesis

c. Secretion

d. All of the above

19. SER differ from RER with regard to a lack of a. Polysomes

b. Ribosomes

c. Nucleus

d. Centrioles

20. The important site for the formation of glycoproteins and glycolipids in a cell is

64

a. Golgi complex

b. SER

c. Lysosomes

d. Mitochondria

IL Foundation Series Class 8

21. Major structural components of the Golgi apparatus are a. Tubules

b. Vesicles

c. Cisternae

d. All of the above

22. The diameter of the cisternae ranges from a. 0.5 - 1.0 µm c. 1.5 - 2.0 µm

b. 1.0 - 1.5 µm d. 0.5 - 1.5 µm

23. The cell organelle, rich in almost all types of hydrolytic enzymes in a cell, is a. Mitochondria

b. Chloroplast

c. Lysosomes

d. Cytoplasm

24. Hydrolytic enzymes present in the lysosome are optimally active at a. Acidic pH

b. Basis pH

c. Neutral pH

d. No influence of pH

25. Cisternae, vesicles and tubules are the common components of a. Chloroplast

b. Lysosomes

c. Golgi complex

d. Plasma membrane

26. Suicidal bags of a cell were discovered by: a. De Duve

b. Fontana

c. Palade

d. Golgi

27. Hydrolysing enzymes are present in a. Nucleoplasm, peroxisomes

b. Lysosomes, peroxisomes

c. Glyoxysomes, nucleoplasm

d. Lysosomes, nucleoplasm

28. What is untrue about lysosomes? a. Polymorphic organelle

b. Bring about autolysis

c. Carry out intracellular digestion

d. Formation of cell plate

29. Which cell organelle plays a role in reducing the number of other cell organelles? a. Mitochondrion

b. Elaioplast

c. Lysosome

d. Golgi complex

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CELL - STRUCTURE AND FUNCTIONS

30. Cell organelles which are not included in the endomembrane system of a cell are a. Mitochondria

b. Peroxisome

c. Chloroplast

d. All of the above

31. Which of the following is not a function of the Golgi complex? a. It produces cell plate. b. Primary lysosomes arise from this cell organelle. c. It is involved in the formation of desmotubules. d. Secretion is the major function of this cell organelle.

32. Select the incorrect statement about the vacuole. a. Tonoplast facilitates the transport of many ions and other materials along concentration gradients b. It contains materials not useful for the cell c. It can occupy up to 90% of the volume d. It is bound by a single membrane 33. Select the correct statement with respect to endoplasmic reticulum a. ER divides the intracellular space into two distinct compartments, that is, luminal (cytoplasm) and luminal (inside ER) compartments b. The ER often show ribosomes attached to their inner surface c. RER is frequently observed in the cells actively involved in protein synthesis d. RER is extensive and continuous with the inner membrane of the nucleus 34. Common semiautonomous cell organelles found in all eukaryotic cells are a. Plastids

b. Mitochondria

c. Nucleus

d. Plastids and mitochondria

35. The number of unit membranes which bound the mitochondria are a. 1

b. 2

c. 3

d. 4

36. The continuous, unfolded, and limited boundary of mitochondria is the a. Outer membrane

b. Inner membrane

c. Both (a) and (b)

d. None of the above

37. The cell organelle that produces the cellular energy in the form of ATP is the

66

a. Mitochondria

b. Golgi apparatus

c. Mitochondria and golgi apparatus

d. None of the above

IL Foundation Series Class 8

38. Plastids which are responsible for trapping light energy essential for photosynthesis a. Leuocoplasts

b. Chromoplasts

c. Chloroplasts

d. All of the above

39. The colourless (non-pigmented) plastids are a. Leucoplasts

b. Chloroplasts

c. Chromoplasts

d. Leucoplasts and chromoplasts

40. Leucoplasts which help in the storage of carbohydrates are a. Elaioplasts

b. Aleuroplasts

c. Amyloplasts

d. Amorphoplasts

41. Match the following.

List I

List II

A. Stroma

1. Site for respiratory enzymes

B. Matrix

2. Extension of plasma membrane

C. Mesosome

3. Site for dark reaction

D. Cristae

4. Extension of cell wall 5. Site for F0 - F1 particles

A B C D

A B C D

a. 3 1 5 2

b. 3 1 2 5

c. 3 1 2 4

d. 1 3 5 2

42. Match the following.

List I

List II

A. Golgi complex

1. Lysosome production

B. Ribosomes

2. Peptide bond formation

C. Endoplasmic reticulum

3. Secretion of lipids

D. Peroxisomes

4. Synthesis of phospholipids 5. Hydrolysis of fats

A B C D

A B C D

a. 1 2 3 4

b. 3 2 1 5

c. 4 2 1 3

d. 3 2 1 4

43. Select the incorrect statement with regard to the mitochondria. a. The two membranes have the same enzymes. b. The outer membrane and the inner membrane divide its lumen distinctly into two aqueous compartments.

67

CELL - STRUCTURE AND FUNCTIONS

c. The inner compartment is called the matrix. d. Mitochondria divide by fission.

44. Select the wrong statement from the following: a. Both chloroplasts and mitochondria contain an inner and an outer membrane. b. Both chloroplast and mitochondria have an internal compartment, the thylakoid space. bounded by the thylakoid membrane c. Both chloroplasts and mitochondria contain DNA. d. The chloroplasts are generally much larger than mitochondria.

45. Which of the following is true about the nucleus?

A) Chlorophylls

B) Carotene

C) Xanthophylls

D)Anthocyanin

a. It is the site of protein synthesis.

b. It synthesises lipids and steroid hormones.

c. It is responsible for ATP production.

d. It contains the majority of the cell's genetic material.

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. The scientist who first proposed that the presence of cell wall is a unique character of the plant cells is a. T. Schwann

b. M.J. Schleiden

c. R. Virchow

d. R. Brown

2. Cell theory, as proposed by Schleiden & Schwann, does not explain a. Cell is the structural unit of all organisms b. All cells arise from pre-existing cells c. Cell is the functional unit of all living organisms d. All living organisms are composed of cells and products of cells 3. Which of the following statements is incorrect? a. Unicellular organisms are capable of independent existence b. Any structure less than complete of a cell does not ensure independent living

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IL Foundation Series Class 8

c. Schleiden, a zoologist, discovered the nucleus d. Robert Brown discovered the nucleus 4. The cytoplasm of adjacent cells is interconnected by a. Plasma membrane

b. Primary cell wall

c. Plasmodesmata

d. Pits

5. All living cells have a. Cell wall

b. Cell membrane

c. Chloroplast

d. Mitochondria

6. The structure that acts as an intercellular cementing substance and binds adjacent cells together is: a. Desmosomes

b. Primary cell wall

c. Middle lamella

d. Secondary cell wall

7. Which model explains the selective permeability of plasma membrane? a. Sandwich model

b. Fluid mosaic model

c. Trilamellar model

d. Unit membrane model

8. The outermost living limit of a plant cell is a. Cell wall

b. Plasma membrane

c. Cytoplasm

d. Tonoplast

9. Cell wall components found in algae are a. Lignin, suberin, pectin

b. Cellulose, galactans, mannans

c. Cellulose, silica, suberin

d. Galactan, lignin, cellulose

10. Which of the following statements regarding the cell wall is incorrect? a. The primary component of bacterial cell walls is peptidoglycan b. Fungi possess a cell wall primarily composed of peptin c. The cell walls of plant cells contain cellulose as a major structural component d. Animal cells lack a cell wall but may have an extracellular matrix for structural support 11. Find out the correct statement with respect to the fluid mosaic model of the plasma membrane a. It was proposed by Robertson b. Lipids of bilayer do show flip-flop movement 69

CELL - STRUCTURE AND FUNCTIONS

c. Glycocalyx is a short chain of oligosaccharides attached to the cytoplasmic face of proteins d. Extrinsic proteins are present on the outer side only 12. What is the function of the nuclear matrix? a) Providing shape to the cell b) Protecting the cell from mechanical damage and infection c) Helping in cell-to-cell interaction d) Providing barrier to undesirable macromolecules e) Imbibition of water a. It regulates the passage of molecules

b. It provides structural support to the

through nuclear pores. c. It catalyses protein synthesis.

nucleus. d. It synthesises lipids.

13. Endoplasmic reticulum arises from a. Inner karyotheca

b. Outer karyotheca

c. Plasma membrane

d. Endomembrane system

14. Major site for lipid synthesis in a cell is a. RER

b. SER

c. Mitochondria

d. Nucleus

15. The cell organelle which principally performs the function of packaging materials in a cell is a. RER

b. SER

c. Golgi complex

d. Cell wall

16. Hydrolytic enzymes present in the lysosome are optimally active at a. Acidic pH

b. Basis pH

c. Neutral pH

d. No influence of pH

17. Polymorphic cell organelles are a. All semiautonomous cell organelles and lysosomes b. Suicidal bags of cells and exclusive semiautonomous plant cell organelles c. Lysosomes and peroxisomes d. Endoplasm reticulum and chloroplast

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IL Foundation Series Class 8

18. ER extends from a. Middle lamella to plasma membrane b. Tonoplast to plasma membrane c. Nuclear envelope to plasma membrane d. Primary wall to secondary wall 19. Statement - I: Endoplasmic reticulum plays an important role in the origin of plasmodesmata.

Statement - II: Plasmodesmata are cytoplasmic strands through which one cell communicates with another. a. Both statements are true b. Both statements are false c. Statement - I is true, Statement - II is false d. Statement - I is false, Statement - II is true 20. Which of the following is not true for vacuoles? a. These are non-cytoplasmic areas. b. They are supposed to be greatly expanded mitochondria. c. Vacuoles of animal cells are bounded by a lipoproteinaceous membrane. d. In plant cells, the vacuoles can store pigments, inorganic nutrients, etc.

21. The surface area of the mitochondria can be increased by the a. Outer membrane

b. Cristae

c. Matrix

d. All of the above

22. The site of the aerobic part of respiration in a eukaryotic cell is a. Plasma membrane

b. Cytoplasm

c. Mitochondria

d. Peroxisome

23. The matrix of both chloroplast and mitochondria are similar in having, except: a. Flagella

b. 70S Ribosomes

c. RNA

d. Circular DNA

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CELL - STRUCTURE AND FUNCTIONS

24. Match the items listed in Column I with appropriate items from Column II. Column I

Column II

A. Cristae

i. Flat membrane sacs in stroma

B. Cisternae

ii. Infoldings in mitochondria

C. Thylakoids

iii. Disc-shaped sacs in Golgi apparatus

a. A-ii, B-iii, C-i

b. A-iii, B-ii, C-i

c. A-i, B-ii, C-iii

d. A-ii, B-i, C-iii

25. Plastids with carotenoid pigments are a. Chloroplasts

b. Leucoplasts

c. Chromoplasts

d. Chloroplasts and chromoplast

26. The matrix of mitochondria consists of a. Single, circular DNA molecule, a few RNA molecules, and ribosomes b. Enzymes for Krebs cycle and glycolysis, and ribosomes 70S c. DNA, RNA, and enzymes for light and dark reactions of photosynthesis d. Oxysomes, enzymes of ETC, and DNA molecules 27. Which of the following statements regarding the mitochondrial membrane is not correct? a. The outer membrane resembles a sieve. b. The outer membrane is permeable to all kinds of molecules. c. The enzymes of the electron transfer chain are embedded in the outer membrane. d. The inner membrane is highly convoluted, forming a series of infoldings.

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CONSERVATION OF PLANTS AND ANIMALS

4

4.1 INTRODUCTION The Earth serves as a habitat for millions of plants, animals, and various organisms, collectively forming a diverse and interconnected web of life. The plant life is known as flora, while animals are referred to as fauna. Together, they constitute the biodiversity of a specific area. Flora and fauna are vital renewable natural resources. Thus, the management of forest and wildlife resources becomes crucial in maintaining ecological balance.

The accelerated rates of species extinctions that the world is facing now are largely due to human activities. The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years. Some examples of recent extinctions include the dodo (Mauritius), quagga (Africa), thylacine (Australia), steller's sea cow (Russia) and three subspecies (Bali, Javan, Caspian) of tiger. Presently, 12 per cent of all bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31 per cent of all gymnosperm species in the world face the threat of extinction.

Thylacine

Javan tiger

Dodo

Passenger pegion

Caspian tiger

Steller’s sea cow

Bali tiger

Fig. 4.1 Extinct animals

However, the increasing human population has led to the exploitation of natural resources, posing a significant threat to biodiversity. Unregulated felling of trees results in deforestation, leading to the loss of habitats for a wide range of organisms. Human activities also contribute to changes in climatic conditions, affecting temperature and rainfall patterns.

To counteract these challenges, both governmental and non-governmental organizations have actively engaged in biodiversity conservation efforts. Many countries have implemented legislation to prohibit the killing of wild animals and have established conservation areas such as zoos, national 73

CONSERVATION OF PLANTS AND ANIMALS

parks, botanical gardens, and biosphere reserves. These initiatives aim to safeguard and preserve the rich diversity of life on Earth.

4.2 DEFORESTATION One of the major threats to the loss of biodiversity is habitat loss and fragmentation. Deforestation, which includes activities like logging, filling a wetland, burring forest or ploughing a grassland, is a major cause of species extinction.

Natural wetland systems have been drained to establish croplands, resulting in the loss of aquatic species. The tropical rainforests that once covered 14% of the land are now reduced to at most 6%.

The Amazon rain forests, called the "lungs of the planet," are cleared for soya cultivation or grasslands to raise beef cattle. Multistorey natural forests are converted into forests of teak, sal, etc.

The division of natural areas into smaller, isolated patches due to human activities impacting wildlife survival and biodiversity are called fragmented habitats. A forest patch surrounded by croplands, orchards, plantations, or urban areas is an example of fragmented habitats. Whenever habitats are fragmented, mammals and birds requiring large habitats decline in population, leading to extinction.

Fig. 4.2 Deforestation

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IL Foundation Series Class 8

4.2.1 Causes of deforestation The most common reasons for deforestation are : 1. Forest fire: Forest fires are a big problem in forests. They happen when dry leaves and twigs in the forest catch fire easily, especially during hot and dry times like summer. This harms the trees and disrupts the balance of plants and animals living there, affecting the variety of life in that area.

In some places, like the Garhwal Himalayas, forest fires are becoming more common, causing a lot of damage.

Sometimes, forest fires start because of lightning, but rain can help stop them. Human activities like leaving a burning cigarette or beedi can also accidentally start fires. Some people even purposely start fires to clear land for farming.

2. Volcanoes: Volcanoes can be dangerous for forests. When a volcano erupts, the lava can burn down large areas of trees. The gases released, like CO2, can be harmful to wildlife. CO2 is heavy, so it stays close to the ground and can be deadly for animals. Sometimes, animals are attracted to areas where the grass grows a lot due to the extra CO2, but they can end up getting hurt or killed by the poisonous gas. However, these situations are not very common and don't usually pose a big threat to most animals.

3. Drought: Drought happens when there has not been enough rain for a long time. This is not good for forests because it weakens the whole system. The lack of water can make the forest drier and more prone to events like fires. It also makes it easier for diseases to spread among plants. In a drought, the air becomes less humid, and there is less rainfall. This makes the ground and leaves dry up, affecting the insects and microorganisms that help the forest stay healthy.

4. Earthquakes and landslides: Earthquakes happen when the Earth's tectonic plates move suddenly, shaking the ground and causing massive destruction. This movement can also trigger landslides, where soil and rocks slide down a slope. Both earthquakes and landslides can uproot many trees, leading to deforestation and disrupting the balance of the forest.

5. Pests, Viral, and Fungal diseases of plants: Plant diseases caused by pests, viruses, or fungi might not be as visible as fires or earthquakes, but they can still cause significant damage. These diseases can affect how well trees grow, survive, and produce wood and other forest products. They can also impact the health of the soil and water in the forest.

6. Flood: Floods occur when there is too much water in an area. This can happen because of heavy rain, fast melting snow, or even when dams burst. Floods can lead to deforestation because the excess water can harm plant roots and cause the death of many trees.

Human activities, like cutting down trees for farming or building, also contribute to deforestation.

4.2.2 Consequences of deforestation Deforestation has become more pronounced due to increased industrialization and population growth, leading to higher demand for building materials, paper, furniture, and clothing (such as rayon). The extensive clearing of large forest areas to accommodate housing, agriculture, and industries poses a significant threat to the environment, resulting in various adverse effects: 75

CONSERVATION OF PLANTS AND ANIMALS

1. Change in soil properties: Trees play a crucial role in binding soil. When trees are removed, soil erosion increases and topsoil is easily washed away by wind or water, leading to decreased soil fertility. Over time, this process can turn fertile land into barren areas, contributing to desertification.

2. Reduced rainfall: Deforestation disrupts the water cycle, leading to reduced rainfall in the affected areas. The decrease in plant life negatively impacts the natural balance of the environment, affecting the availability of water.

3. Imbalance of atmospheric gases: Plants absorb carbon dioxide during photosynthesis and release oxygen. Deforestation disrupts this balance, leading to an increased concentration of carbon dioxide in the atmosphere.

4. Changes in climate: Elevated carbon dioxide levels contribute to the greenhouse effect, resulting in global warming and significant climatic changes. Scientists have reported widespread climatic shifts, causing concerns about the long-term impact on the planet.

5. Natural calamities: Deforestation contributes to soil erosion, making land more susceptible to landslides. Decreased absorption of rainwater can lead to increased risks of floods.

6. Scarcity of products: Increased demand for wood, paper, furniture, and other products derived from plants contributes to deforestation. This reliance on plant-based products may lead to shortages if sustainable alternatives are not explored.

7. Degradation of habitat: Forests serve as habitats for numerous organisms, birds, and animals.

Deforestation directly impacts the fauna of an area, disrupting the delicate balance of the ecosystem.

4.3 REFORESTATION Conserving forests is crucial to ensure a steady supply of forest products and to maintain the balance of nature. Here are some ways to achieve this: • Forest resources should be used wisely and efficiently. Avoiding wasteful practices and using resources economically helps in sustaining the health of forests.

• Cutting down trees should be strictly regulated, and it should be made a punishable offence.

Governments can enforce complete restrictions on tree cutting to prevent deforestation.

• Large-scale planting of trees, known as afforestation, is vital to restore forest cover and wealth. Both central and state governments can undertake afforestation programs to replenish and enhance the forested areas.

• Reforestation is the process of replanting new trees in areas where forests have been destroyed. It is essential to plant trees of the same species that were originally found in the forest. It is recommended to plant at least as many trees as we cut down to maintain a balance.

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IL Foundation Series Class 8

• Creating awareness among people is crucial for forest conservation. This can be achieved through various media channels and mass movements.

Fig. 4.3 Reforestation

4.4 RECYCLING OF PAPER The paper industry heavily relies on trees, with about 17 fully grown trees needed to produce one tonne of paper. This contributes to deforestation. To address this issue, we can take steps to save paper by: • Using paper sheets carefully and avoiding unnecessary waste.

• Avoiding tearing paper when not needed.

• Saving at least one sheet of paper daily.

• Reusing paper that has already been used.

• Recycling paper as it can be recycled five to seven times.

By implementing these practices, we not only reduce our paper consumption but also contribute to saving trees and minimizing the energy and water used in the paper manufacturing process.

4.5 FLORA AND FAUNA Estimates of global species diversity range widely from 2 million to 100 million species, with only 1.6 million eukaryotic species formally named to date. Among these named species, roughly 250,000 are plants, and 750,000 are insects, comprising the majority of known eukaryotes. Animals represent over 70% of recorded species, while plants comprise about 22%. In the animal kingdom, insects 77

CONSERVATION OF PLANTS AND ANIMALS

account for over 70% of total species. Fungi and angiosperms dominate the plant kingdom, with orchids alone comprising 20,000 species. Additionally, around 20,000 species of ants, 300,000 species of beetles, and 28,000 species of fishes are known to science. New species continue to be discovered annually, with plants, insects, and vertebrates being the most extensively studied groups.

According to the scientific estimate made by Robert May, the global species diversity is approximately 7 million. Only 1.75 million species have been described to date, and the distribution is highly uneven. According to IUCN, the animal species described so far is approximately 1.5 million. Most species of temperate regions were described. However, a large proportion of tropical species have yet to be discovered. More than 70% of all the species recorded are animals, and plants (including algae, fungi, bryophytes, gymnosperms, and angiosperms) comprise no more than 22 % of the total. Among animals, insects are the most species-rich taxonomic group. The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles and mammals.

Although India has only 2.4% of the world's land area, it accounts for 8.1% of global species diversity. It is one of the 12 most mega-diverse countries in the world. About 45,000 floral species and almost double the number of animal species have been recorded from India. According to Robert May's estimate, only 22 % of the total species have been recorded till now. There could be probably more than 1,00,000 plant species, and more than three lakh animal species are yet to be discovered. The taxonomists are trying to discover new species. Unfortunately, it appears that many of them may face the threat of becoming extinct even before they are discovered.

4.6 CONSERVATION OF FOREST AND WILDLIFE The conservation of biological diversity has become a global concern. There are basically two main types of conservation options: in-situ conservation and ex-situ conservation. In-situ is usually seen as the ideal conservation strategy. Ex-situ conservation can provide a backup solution to insitu conservation projects. Some believe both types of conservation are required to ensure proper preservation.

In-situ conservation (on-site conservation): It is the process of protecting an endangered species or threatened in its natural habitat. The in-situ approach includes the protection of a group of ecosystems through a network of protected areas like national parks and sanctuaries, biosphere reserves and sacred forests. The benefit of in-situ conservation is that it maintains recovering populations in the surroundings where they have developed their distinctive properties. Ecologically unique and biodiversity-rich regions are legally protected in India as biosphere reserves, national parks, and sanctuaries. In India, there are 18 biosphere reserves, 104 national parks, and 544 wildlife sanctuaries.

Ex-situ conservation (off-site conservation): It means protecting endangered plants or animals outside their natural homes. It involves moving them to new places, like zoos or wildlife sanctuaries,

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IL Foundation Series Class 8

where they are looked after by humans. Botanical gardens, zoos, and aquariums are examples of exsitu conservation.

4.6.1 Endemic species Some plants and animals are unique to specific areas and are not naturally found anywhere else.

These special species are known as endemic species. They are exclusive to a particular state, country, or geographical region. For instance, the Asiatic lion, also called "babbar sher," is endemic to the Gir forests in Gujarat. The Himalayan weasel is found only in the Himalayan region, while the snow leopard is endemic to the Himalayan range, spanning from Kashmir to Sikkim. In the Pachmarhi Biosphere Reserve, wild mangoes and sal trees are part of the endemic flora, while the bison, the Indian giant squirrel, and the flying squirrel are examples of endemic fauna in the same reserve.

Unfortunately, the existence of these unique species is often threatened by the introduction of exotic species from other geographical areas. This intrusion can disrupt the delicate balance of ecosystems and pose a risk to the survival of endemic species.

Snow Snow leopard leopard

Indian rhinoceros Indian rhinoceros

Barasingha Barasingha

Golden langur langur Golden

Asiaticelephant elephant Asiatic

Asiatic lion lion Asiatic

Fig. 4.4 Endemic species

4.6.2 Biosphere reserves The concept of the biosphere was launched in 1975 as a part of UNESCO's Man and Biosphere (MAB) programme, dealing with the conservation of ecosystems and genetic resources contained

79

CONSERVATION OF PLANTS AND ANIMALS

therein. Biosphere Reserve is an area that is set aside for the conservation of biosphere resources and for the improvement of the relationship between man and the environment. There are 18 biosphere reserves in India.

Biosphere Reserve

Location

Nilgiri

Karnataka, Kerala, Tamil Nadu

Nanda Devi

Uttar Pradesh

Nokrek

Meghalaya

Kaziranga

Assam

Sunderbans

West Bengal

Thar Desert

Rajasthan

Kanha

Madhya Pradesh

Namdapha

Arunachal Pradesh

Gulf of Mannar

Tamil Nadu

Rann of Kutch

Gujarat

Manas

Assam

Simlipal

Odisha

Pachmarhi

Madhya Pradesh

Achanakmar-Amarkantak

Madhya Pradesh, Chhattisgarh

Agasthyamalai

Kerala, Tamil Nadu

Great Nicobar

Andaman and Nicobar Islands

Dibru-Saikhowa

Assam

Cold Desert

Himachal Pradesh

Table 4.1 Biosphere reserves in India

4.6.3 Wildlife sanctuaries Wildlife sanctuaries are special areas set aside for the protection and conservation of wild animals and birds. These areas are like safe places where hunting is strictly prohibited, aiming to safeguard the well-being of the diverse animal and bird species living there. Although hunting is prohibited, people may have certain rights for activities like collecting minor forest products, cutting down some trees for timber, and cultivating land, as long as it does not harm the wildlife. In India, there are 550 wildlife sanctuaries. These sanctuaries are crucial for the protection of endangered animals like black buck, white-eyed buck, elephants, golden cat, pink-headed duck, gharial, marsh crocodile, python, rhinoceros, and many more. The goal is to create a safe space where these animals can thrive without the threat of hunting or habitat destruction.

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Fig. 4.5 Great Egret in Bharatpur bird sanctuary

Name of the sanctuary

Organisms popular in the sanctuary

Dachigam sanctuary (Jammu and Kashmir)

Kashmir stag (hangul)

Bharatpur bird sanctuary (Rajasthan)

Siberian crane

Rann of Kutch sanctuary (Gujarat)

Wild ass, flamingo, Star tortoise

Gir sanctuary (Gujarat)

Asiatic lion, chital

Bandipur sanctuary (Karnataka)

Indian elephant

Mudumalai sanctuary (Tamil Nadu)

Indian elephant

Table 4.2 Wildlife sanctuaries in India

4.6.4 National parks A national park is a reserve of natural, semi-natural, or developed land that a sovereign state declares or owns. The International Union for Conservation of Nature (IUCN) and its World Commission on protected areas have defined national parks as category II of protected areas. The first national park established in the world was Yellowstone national park, USA, in 1872. The largest national park in the world is the Northeast Greenland national park. Natural habitats (forests) of certain endangered species are earmarked as national parks where such threatened animals are protected. Some important national parks include: Jim Corbett national park - Uttaranchal Kaziranga national park - Assam Bandipur national park - Karnataka Ranthambore national park- Rajasthan Bandhavgarh national park- Madhya Pradesh Gir national park- Gujarat Periyar national park- Kerala Kanha national park- Madhya Pradesh Tadoba Andhari tiger reserve- Maharashtra Sundarbans national park- West Bengal 81

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Fig. 4.6 Kaziranga national park in Assam protects one-horned rhino

Fig. 4.7 Lion-tailed macaque is protected in Silent Valley national park, Kerala

4.7 RED DATA BOOK The Red Data Book is a vital record containing information about plant and animal species that are at risk of becoming extinct. This book is managed by the International Union for Conservation of Nature (IUCN), now known as the World Conservation Union (WCU). It serves as a valuable resource by providing details on the distribution and status of species facing threats.

Periodically, the Red Data Book is updated to reflect the current situation. According to the 2004 IUCN records, a total of 15,589 species were identified as facing the risk of extinction. This alarming number includes one in four mammals, one in eight birds, one in three amphibians, and nearly half of all freshwater turtles.

The information compiled in the Red Data Book is crucial for developing and implementing conservation programs to protect these vulnerable species and their habitats. It highlights the urgency of taking action to prevent further loss of biodiversity and preserve the delicate balance of ecosystems.

Snow Leopard Snow leopard

Indian Tiger Indian tiger

Fig. 4.8 Endangered species

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Asiaticlion Lion Asiatic

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4.8 MIGRATION Some birds travel from their homes to different geographical areas, typically following a seasonal pattern. This behaviour is called migration. It serves various purposes, including escaping harsh winter conditions, finding abundant food sources, and finding warm places to lay eggs and incubate them early.

One remarkable migratory species is the Arctic tern, often called the migration champion. This seabird breeds in the northern hemisphere, reaching as far north as the Arctic. However, during the winter, it migrates to the southern hemisphere, venturing as far south as the Antarctic. This incredible round trip covers a distance of up to 35,000 kilometres each year.

The Arctic tern's migratory pattern allows it to experience more daylight than any other creature on Earth. By shuttling between the Arctic and Antarctic summers, this bird showcases an extraordinary feat of adaptation to different environments and serves as a fascinating example of the wonders of the animal kingdom. The migration of birds also causes a loss of biodiversity.

QUICK REVIEW • Biodiversity was coined for the first time by W.G. Rosen.

• May 22 is declared as the International Day of Biological Diversity.

• One of the major threats to the loss of biodiversity is habitat loss and fragmentation.

• Deforestation is the primary reason for the species extinction.

• Forest fires, volcanoes, and earthquakes are some of the causes of deforestation.

• Floods, changes in climate, and reduced rainfall are some of the consequences of deforestation.

• Reforestation should be carried out to compensate for the trees lost by deforestation.

• People can recycle paper to avoid falling trees.

• According to IUCN, the animal species described so far is approximately 1.5 million.

• The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles, and mammals.

• The IUCN Red List documents the extinction of 784 species in the last 500 years.

• Amazon produces 20% of the total oxygen in the Earth's atmosphere.

• In-situ Conservation is the process of protecting an endangered species or threatened in its natural habitat.

• The first national park established in the world was Yellowstone national park, USA, in 1872.

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• Specific endangered faunal species are well protected in the wildlife sanctuaries.

• Biosphere reserve is an area for the conservation of the biosphere's resources and for the improvement of the relationship between man and the environment.

• Ex-situ Conservation is the conservation of genetic resources of species away from their area of origin or development.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Conservation of plants and animals 1. The most important human activity leading to the extinction of wildlife is a. Pollution of water and soil b. Introduction of alien species c. Exploiting the forests for trade use d. Alteration and destruction of natural habitats 2. Habitat destruction includes a. Conversion of natural wetlands into croplands b. Erosion of barriers c. Widespread introduction of exotic species d. All the three 3. Identify the correct set of organisms in which one organism causes the extinction of the other respectively. a. Steller's sea cow and passenger pigeon b. Nile perch and Clarias gariepinus c. Nile perch and cichlid fishes d. Indigenous catfishes and Clarias gariepinus

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4. Which of the following are the integral parts of the ecosystem? i. Flora

ii. Fauna

iii. Soil

iv. Water

a. i, ii, iii, iv

b. iii, iv

c. Only ii

d. Only i

5. Which of these actions will not have an impact on the biodiversity of a forest? a. Pollution

b. Deforestation

c. Rainfall

d. Removal of animals

6. What birds leave a region when the seasons or climate change? a. Migratory birds

b. Flying birds

c. Flightless birds

d. Frugivore birds

II. Deforestation – causes and consequences 1. Which of the following are examples of natural causes of deforestation? a. Forest fires

b. Drought

c. Forest fires and drought

d. Neither forest fires nor drought

2. Identify the option which is prevented by forests. a. Natural calamities

b. Rain

c. Soil deposition

d. Rock formation

3. Which of the following can be prevented by preserving the forests? a. Soil erosion

b. Overgrazing of cattle

c. Fire

d. Habitat loss and soil erosion

4. What are the causes of natural deforestation among the following options? i. Forest fires

ii. Droughts

iii. Laying roads

iv. Cutting trees.

a. i and ii only

b. i, ii, iii, and iv

c. i and ii only

d. iii and iv only

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5. Assertion (A): Many areas of forests have been protected against human interference.

Reason (R): All organisms in nature influence each other in some way or another, so we need to protect all of them. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, and Reason(R) is not the correct explanation of Assertion (A). c.

Assertion (A) is true, but Reasoning (R) is false.

d. Both Assertion (A) and Reasoning (R) are false.

6. How does deforestation impact the conservation of plants and animals? a. Promotes biodiversity by creating new habitats b. Enhances the natural balance of ecosystems c. Reduces habitat availability and threatens species survival d. Accelerates the growth of endangered species 7. The main driver of deforestation in tropical regions is often associated with: a. Selective logging for sustainable timber extraction b. Expansion of protected areas and national parks c. Afforestation to restore degraded lands d. Clearing of land for agriculture and pasture 8. How does deforestation impact the environment and ecological systems? a. It enhances biodiversity and ecosystem stability b. It increases soil fertility and reduces nutrient loss c. It decreases carbon sequestration d. It increases vulnerability to climate change and loss of wildlife habitats

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9. The impact of deforestation on climate change stems from its contribution to the release of a specific greenhouse gas into the atmosphere. Which gas is being referred to here? a. Oxygen

b. Methane

c. Nitrogen

d. Carbon dioxide

III. Reforestation

1. Which of the following is the benefit(s) of reforestation? i. Reduction in global warming ii. Prevention of soil erosion and floods iii. Increase in biodiversity a. i and iii only

b. i only

c. i and ii only

d. i, ii, and iii

2. Choose the correct statement with respect to reforestation. a. Replanting trees in a deforested land

b. Planting of trees in a new area

c. Cutting off trees on a large scale

d. Cutting off trees in a small region

3. What role does reforestation play in promoting biodiversity? a. Reforestation leads to the loss of specific species diversity. b. Reforestation has no role in biodiversity conservation. c. Reforestation provides habitats and promotes species recovery. d. Reforestation contributes to the extinction of wildlife exclusively.

IV. Conservation of forest and wildlife

1. Which of the following best defines a biosphere reserve? a. A protected area for conserving historical landmarks b. A region dedicated solely to agricultural practices c. An area for industrial development and resource extraction d. A designated area for the conservation of biodiversity and sustainable development

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2. In which habitat are species protected in zoological parks? a. Laboratory conditions b. Natural habitat c. Habitat which mimics natural conditions d. A small cage 3. Which of the following factors drives migratory birds from Siberia to India each year? a. To overcome harsh conditions b. In search of different habitats c. For water availability only d. For space 4. Which of the following statements is the most relevant to migration? a. It is the movement of humans from plains to hills. b. It is the movement of one's natural habitat. c. It is the movement of organisms from one place to another to avoid stressful conditions. d. It is the movement of animals in unstressful conditions 5. Which of the following activities are strictly prohibited in wildlife sanctuaries? i. Killing

ii. Trapping

iii. Poaching

a. ii only

b. i, ii, and iii

c. i and iii

d. i only

6. Which of the following names best describes a species that is found only in a particular area? a. Extant species

b. Endemic species

c. Epidemic species

d. Extinct species

7. Pick the incorrect pair from the options given below. a. Species that can be found anywhere - Endemic species b. Conservation of wildlife in their natural habitat - National parks

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c. A protected area where human activities are allowed to some extent in the peripheral zone – Sanctuaries

d. Movement of birds for nestling from one region to another – Migration 8. Killing of endangered animals is strictly prohibited under the provision of a. Wildlife Act of 1972

b. Forest Conservation Act 1980

c. Environmental Protection Act – 1986

d. Indian Forest Act – 1927

9. Identify the option with the greatest biodiversity on the Earth. a. Taigas of temperate region b. Scandinavian countries c. The Amazon rain forest of tropical region d. The Amazon rain forest of the temperate region 10. A backup solution to biodiversity conservation is a. In-situ conservation b. Ex-situ conservation c. Conservation in biospheres d. Conservation in national parks 11. Natural habitats of threatened species are protected in a a. Sanctuary

b. National park

c. Botanical and zoological park

d. Labs by in-vitro preservation

12. A diverse ecosystem is more productive because a. It is less resilient b. It keeps the environment unchanged c. It changes with the environment d. It is able to withstand environmental stress 13. Which of the following is not a reason for greater biodiversity in the tropics? a. Undisturbed latitudes

b. Frequent glaciations

c. More constant and predictable

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CONSERVATION OF PLANTS AND ANIMALS

14. What is the primary purpose of the conservation of plants and animals? a. To eliminate certain species for ecological balance b. To create new hybrid species c. To maintain biodiversity and prevent extinction d. To encourage deforestation for agricultural development 15. Which of the following is an example of an endangered species that requires conservation efforts? a. Common housefly

b. Domestic cat

c. Bengal tiger

d. Dandelion plant

16. Statement - I: In-situ conservation is beneficial.

Statement - II: In in-situ conservation, the recovering population is maintained in the surroundings where it developed its distinctive characteristics. a. Both the statements are true b. Both the statements are false c. Statement I is true, Statement II is false d. Statement I is false, Statement II is true 17. Statement - I: In-situ conservation is the most potent way of conservation of threatened animals.

Statement - II: In in-situ conservation, animals are conserved in their natural habitats. a. Both the statements are true

b. Both the statements are false

c. Statement I is true, Statement II is false

d. Statement I is false, Statement II is true

18. Consider the statement below and select the appropriate option.

Statement: Conservation of plants and animals is essential for maintaining ecological balance and sustaining life on Earth. a. True, as it helps eliminate certain species for a better balance. b. False, as ecological balance is not influenced by plant and animal conservation

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c. True, as it contributes to biodiversity and prevents extinction d. False, as sustaining life does not depend on the conservation of species 19. How are wildlife sanctuaries different from biosphere reserves? a. Wildlife sanctuaries are larger in size compared to biosphere reserves. b. Both wildlife sanctuaries and biological reserves allow human interference. c. Biosphere reserves focus on conserving both biodiversity and cultural diversity, while wildlife sanctuaries primarily focus on biodiversity conservation. d. There is no significant difference between wildlife sanctuaries and biosphere reserves.

20. How do wildlife sanctuaries contribute to biodiversity conservation? a. By providing safe habitats for endangered species and preserving their natural ecosystems. b. By promoting captive breeding programs to increase the population of endangered species. c. By allowing regulated hunting to control wildlife population and maintain ecological balance. d. By establishing research centres for the genetic modification of wildlife species.

21. Which of the following is NOT a primary objective of a wildlife sanctuary? a. Conservation and protection of wildlife species and their habitats. b. Promoting scientific research and studies on wildlife. c. Encouraging sustainable tourism and recreational activities. d. Facilitating the ecological balance and biodiversity conservation.

22. Which of the following national parks is home to the famous musk deer or hangul? a. Keibul Lamjao national park, Manipur b. Bandhavgarh national park, Madhya Pradesh c. Eaglenest wildlife sanctuary, Arunachal Pradesh d. Dachigam national park, Jammu and Kashmir

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23. A particular area exhibits the following key features: A. Reserved for the betterment of wildlife, both flora and fauna B. Private ownership is not allowed C. Grazing, cultivation and forestry are not permitted What is this area? a. Botanical garden

b. National park

c. Wildlife sanctuary

d. Biosphere reserve

24. In what way do biosphere reserves differ from national parks? a. Plants and animals are protected in biosphere reserves. b. Humans are an integral part of biological reserves. c. Humans are not involved in biosphere reserves. d. Hunting for commercially valuable wild-life products is allowed in national parks 25. What activities are typically allowed in a biological reserve? a. Industrial activities and resource extraction b. Construction of residential areas and commercial buildings c. Conservation-oriented research and education d. Deforestation and land conversion for agricultural purposes 26. How are biosphere reserves beneficial for biodiversity conservation? a. They prioritize the establishment of industrial zones for economic growth. b. They provide protection to endemic species and endangered ecosystems. c. They allow unrestricted hunting and fishing activities for local communities. d. They encourage deforestation and land conversion for commercial purposes.

27. Why is the conservation of biodiversity considered an important issue? a. To increase pollution and human impact on nature. b. To preserve natural resources for future generations. c. To eliminate all species except the most dominant ones. d. To accelerate climate change and its effects.

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28. The Earth Summit at Rio de Janeiro was related to. a. Prevention of afforestation

b. Conservation of biodiversity

c. Survey of natural resources

d. Soil fertility

29. Which of the following is a backup solution to the ideal conservation strategy? a. National Park, an In-situ conservation b. Biosphere Reserve, an Ex-situ conservation c. Sacred Groves, an In-situ conservation d. Gene Banks, an Ex-situ conservation V. Red Data Book 1. The Red Data Book categorises species into different threat categories. Which of the following is not one of the categories used? a. Extinct

b. Critically endangered

c. Vulnerable

d. Protected

2. IUCN stands for which of the following? a. Indian Union for Conservation of Nature in Wild b. International Union for Conservation of Nature c. International Union for Conservation of Non-natural Resources d. International Union for Conservation of Nexus 3. Which of the following books contains information on the population status of threatened species? a. Pink Data Book

b. Red Data Book

c. Green Data Book

d. White Data Book

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WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER

1. Endemic means a. Confined

b. Exotic

c. Neutralized

d. Extinct

2. A threatened species is a. Endangered

b. Rare

c. Vulnerable

d. Any of the three

3. Extinction of a species is compensated in a. Food chain

b. A population

c. Food web

d. Ecological niche

4. Deforestation has an alarming effect on a. Weed control

b. Sunlight

c. Soil erosion

d. Increased grazing

5. Where do tropical forests occur in India? a. Gangetic plain

b. Alpine region of the Himalayas

c. Jammu and Kashmir

d. Andaman and Nicobar Islands

6. Logging, hunting, poaching, fishing, etc. activities mean a. Underutilisation of biotic resources

b. Upkeeping eco-balance

c. Establishment of biotic species

d. Overexploitation of resources

7. The category, which refers to the conservation of non-dependent species, is

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a. Extinct

b. Vulnerable

c. Critically endangered

d. Endangered

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8. Deforestation will result in the extinction of many species due to a. Overexploitation

b. Co-extinction

c. Habitat loss

d. Introduction of exotic species

9. Lion-tailed macaques are protected in a. Silent Valley national park

b. Kaziranga national park

c. Bharatpur bird sanctuary

d. Satpura national park

10. Which one of the following is a correct statement? a. Overexploitation of species helps increase the population of many species. b. Silent Valley national park is an example of an in-situ conservation method that conserves wildlife outside its natural habitat. c. Endemic species are organisms that are found only in a particular area. d. Biodiversity refers to genetic and species diversity only.

11. The record that includes all flora and fauna that are on the verge of extinction is a. Blue Data Book

b. Red Data Book

c. Green Data Book

d. None of the above

12. Which animal has become extinct in India? a. Snow leopard

b. Hippopotamus

c. Wolf

d. Cheetah

13. If forest cover is reduced to half, which among the following is most likely to happen on a longterm basis? a. Tribal populations living in these areas will starve to death. b. Domestic animals in these areas will die due to a lack of fodder. c. Large biomes will become deserts. d. Crop breeding programmes will suffer due to a reduced ability of a variety of germplasm.

14. What kind of a resource is flora? a. Natural

b. Human-made

c. Artificial

d. Synthetic

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15. Which of the following summarises the biodiversity of the Panchmarhi biosphere reserve? a. The reserve boasts diverse ecosystems, housing rare species like the Indian giant squirrel and endemic plant species. b. The reserve primarily features desert ecosystems with a focus on conserving cacti species and small reptiles. c. The reserve is dominated by marine life, harbouring diverse fish species and coral reefs. d. The reserve focuses on avian conservation, providing a haven for migratory birds and birds of prey.

16. The endemic fauna and flora of Panchmarhi biosphere reserve are: a. Bison and Sal tree

b. Indian Gecko and Banyan tree

c. Indian Bustard and Sal tree

d. Indian Peacock and Peepal tree

17. Which state is home to Periyar national park? a. Tamil Nadu

b. Kerala

c. Karnataka

d. Andhra Pradesh

18. Determine which of the following are affected by deforestation. i. Animals

ii. Plants

iii. Human beings

a. i only

b. ii only

c. i, ii, and iii

d. iii only

19. Which of the following has a sizable area that safeguards tribal members' traditional ways of life? a. Sacred forests

b. National park

c. Sanctuary

d. Biosphere reserve

20. Cutting trees causes variation in percentage composition in which of the following gases?

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a. Carbon dioxide - oxygen

b. Carbon dioxide-nitrogen

c. Oxygen-sulphur

d. Sulphur-nitrogen

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21. Migratory animals include which of the following? i. Fish

ii. Birds

iii. Insects

iv. Reptiles

a. i, and iv

b. i, ii, iii, and iv

c. i, ii, and iii

d. ii and iv

22. Migration is categorised into which of the following ways? i. Temporary ii. Seasonal iii. Annual a. i only

b. ii and iii

c. i and iii

d. i, ii, and iii

23. What are some common uses of wood obtained from cut trees? a. Wires

b. Fuel

c. Clothes

d. Soap

24. Which of the following animals is Kaziranga national park in Assam famous for? a. Single-horned rhinoceros

b. Double-horned rhinoceros

c. Tiger

d. Lion

25. Which type of animal species are wildlife sanctuaries established to protect? a. Extant animals

b. Extinct animals

c. Entrailed flora and fauna

d. Endangered flora and fauna

26. Which of the following is an endemic species of Kashmir and is named Kashmir stag? a. Asiatic lion

b. Lion-tailed macaque

c. Hangul

d. White leopard

27. Some causes of deforestation are: A. Logging practices to get forest products B. Expansion of agricultural lands C. Urbanisation and infrastructure development D. Promotion of sustainable forestry Choose the correct option based on the above question.

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a. C and D

b. A, C, and D

c. A, B, and C

d. A and D

28. Statement - I: For making compressed cardboard, bits of wood and sawdust are required.

Statement - II: This process helps in reducing deforestation. a. Statement I is true, statement II is true b. Statement I is false, statement II is false c. Statement I is true, statement II is false d. Statement I is false, statement II is true 29. Pick the correct pair: a. Flora - Plants

b. Fauna - Rauwolfia

c. Flora - Gecko

d. Fauna - Biological diversity

30. Which of these actions is not responsible for the decrease in biodiversity? a. Reforestation

b. Deforestation

c. Pollution

d. Overgrazing

31. The water holding capacity of the soil can be reduced due to which of the following? a. Deforestation

b. Afforestation

c. Reforestation

d. Silviculture

32. Which of these is not a major consequence of deforestation? a. Destruction of the natural habitat of wild animals b. Soil erosion c. Biodiversity loss d. Earthquake 33. The causes of deforestation are a. Overpopulation b. Urbanisation

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c. Industrialisation d. Overpopulation, urbanisation, and industrialisation 34. Floods can be prevented by __________. a. Making the soil less sloppy

b. Removing forest

c. Removing soil cover

d. Planting more trees

35. Deforestation results in a. Climate improvement

b. Loss of habitat

c. Addition of groundwater

d. Preventing soil erosion

36. Deforestation leads to a. Soil erosion

b. Weed control

c. Decreases drought

d. Increased habitat

37. Deforestation generally decreases a. Global warming

b. Drought

c. Soil erosion

d. Rainfall

38. Extensive planting of trees to increase forest cover is called _________________. a. Agroforestry

b. Afforestation

c. Deforestation

d. Social forestry

39. The diverse flora and fauna of the planet are under great threat mainly due to which of the following reason? a.

Energy resources

b. Global warming

c. Conservation of wildlife

d. Biosphere reserve

40. Which of the following organisations publishes the Red Data Book? a. W.W.F

b. I.C.U.W

c. I.U.W.C

d. I.U.C.N

41. Group of plants native to a particular region _____________ a. Extinct fauna

b. Extinct flora

c. Endemic flora

d. Endemic fauna

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42. Dachingam sanctuary is located in ___________. a. West Bengal

b. Madhya Pradesh

c. Jammu Kashmir

d. Rajasthan

43. Indian rhinoceros is the most important protected species in _______. a. Gir national park

b. Bandipur national park

c. Corbett national park

d. Kaziranga national park

44. Limited human activity is allowed in a ____________. a. National park

b. Sanctuary

c. Zoo

d. Botanical garden

45. Which among the following are endemic species of India? a. White tiger

b. Sparrow

c. Pigeon

d. Cobra

46. What is the long-term consequence of deforestation? a. Restoration of forest ecosystems and biodiversity b. Preservation of natural resources for future generations c. Reduction in the concentration of carbon dioxide in the atmosphere d. Degradation of soil quality and loss of ecosystem services 47. How does deforestation contribute to soil erosion? a. It enhances the stability of the soil structure. b. It increases organic matter content and nutrient retention. c. It reduces water runoff and sedimentation. d. It removes protective vegetation cover, leading to soil erosion.

48. What are the environmental impacts of deforestation? a. Increased biodiversity and habitat preservation b. Soil erosion and loss of fertility

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c. Enhanced water filtration and quality d. Promotion of ecosystem stability 49. Locals are not permitted to gather and use biomass in which of the following categories of protected areas in India? a. Biosphere reserves b. Wildlife sanctuaries c. National parks d. Wetlands declared under Ramsar convention 50. Deforestation occurs mainly due to: a. Conversion of forest land to agricultural land b. Conversion of agricultural land to forest land c. Conversion of agricultural land to construction d. Conversion of the urban area to a rural area

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5.1

REPRODUCTION IN ANIMALS

INTRODUCTION

In living beings, various processes like blood circulation, digestion, and breathing are important for survival. Additionally, reproduction plays a vital role in maintaining the continuity of species.

Without reproduction, similar kinds of organisms wouldn't exist from one generation to the next, ensuring the survival and diversity of life on Earth.

The period from birth to the natural death of an organism represents its lifespan. Lifespan differs from organism to organism.

Plant

Lifespan

Banyan Tree

More than 300 years

Wolffia

2 Weeks

Pinus

300 Years

Banana

Above 2 Years

Rice

3 to 7 Months

Rose Plant

More than 5 years

Carrot

2 Years Table 5.1 Lifespan of different plants

Reproduction can be defined as the ability of an organism to produce new individuals of the same species.

It may occur through different methods and involve a single organism or two organisms (parents) producing offspring. The process of reproduction is of two types: 1. Asexual reproduction: It is found in unicellular and lower groups of animals.

2. Sexual reproduction: It is found in most multicellular animals, like humans.

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5.2 ASEXUAL REPRODUCTION 5.2.1 Introduction The offspring produced by a single parent without the involvement of the fusion of gametes is called asexual reproduction. The offspring produced by asexual reproduction are identical to the parent and are called clones. It is common among single-celled organisms and in plants with a relatively simple organisation. It is a common method of reproduction in algae and fungi.

Some of the common methods of asexual reproduction seen in animals are: i. Binary fission ii. Budding iii. Fragmentation 5.2.2 Binary fission Binary fission is a method of asexual reproduction that involves the splitting of a parent organism into two offspring. Some examples include Amoeba and Paramecium.

In Amoeba, reproduction involves the division of the nucleus into two nuclei, followed by the cytoplasm dividing into two parts. This ensures that each part receives a nucleus, resulting in the creation of two genetically identical offspring.

Likewise, Paramecium is another organism capable of reproducing through binary fission. This process involves the division of the parent organism into two distinct entities, each possessing its own set of genetic material.

Binary fission is a prevalent reproductive mechanism among certain single-celled organisms, facilitating rapid and efficient multiplication.

Parent cell

Nucleus divides

Cytoplasm divides Two daughter cells

Fig. 5.1 Binary fission in Amoeba

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5.2.3 Budding In budding, the parent organism reproduces by developing a bud on its body. The offspring develop from the growing bud. Examples include Hydra and yeast.

In Hydra, the process unfolds as a bud initiates as an outgrowth, maturing into a distinct Hydra organism. Throughout this development, the offspring remains fixed to the parent's body, undergoing separation only upon reaching full maturity.

Bud

Developing bud

Fully mature bud

Young Hydra separates

Fig. 5.2 Budding in Hydra

5.2.4 Fragmentation Here, the parent body breaks into different fragments, and each fragment develops into an organism, for example, a starfish, Planaria, etc.

Fragmentation and regeneration are the complementary processes to produce offspring asexually in organisms such as Planaria and starfish.

Regeneration, on the other hand, is also a healing process. In some animals, a part of the body can break off, and this part can be regenerated, but the whole organism cannot be formed from the broken part, as seen in lizards.

Fig. 5.3 Fragmentation in starfish

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5.3 STORY OF DOLLY, THE CLONE Cloning is the process of creating a replica of a cell, any living component, or an entire organism.

The first successful cloning of an animal was accomplished by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland. Their breakthrough involved the cloning of a sheep named Dolly, who was born on 5th July 1996. Dolly was the first mammal born as a clone.

During the cloning of Dolly, a cell was extracted from the mammary gland of a female Finn Dorsett sheep. Simultaneously, an egg was acquired from a Scottish blackface ewe. The nucleus was removed from the egg, after which the nucleus of the mammary gland cell from the Finn Dorsett sheep was inserted into the egg of the Scottish blackface ewe, whose nucleus had been removed. The resulting egg was implanted into the Scottish blackface ewe, and Dolly developed normally and was eventually born.

Although Dolly was physically birthed by the Scottish blackface ewe, she was genetically identical to the Finn Dorsett sheep from which the nucleus was obtained. As the nucleus from the egg of the Scottish blackface ewe was replaced, Dolly did not exhibit any traits of the Scottish blackface ewe. Dolly, a healthy clone of the Finn Dorsett sheep, later gave birth to several offspring through traditional sexual reproduction. Unfortunately, Dolly passed away on 14th February 2003 due to a lung disease.

(a) Finn Dorsett sheep

(b) Scottish blackface ewe

(c) Dolly

Fig. 5.4 Cloning of sheep

5.4 SEXUAL REPRODUCTION IN HUMANS Sexual reproduction is an elaborate, complex, and slow process as compared to asexual reproduction. Sexual reproduction in animals requires the involvement of two individuals, typically one male and one female. Human reproduction is a common example of sexual reproduction.

Both males and females have special organs for this purpose, known as male reproductive organs and female reproductive organs, respectively. Special cells, called gametes, are produced by reproductive organs.

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The majority of the animals have separate male and female individuals, which produce gametes.

Such organisms are called unisexual organisms.

However, some organisms, such as earthworms and leeches, have both male and female sex organs in the same organism. Such organisms are called hermaphrodites or bisexual organisms.

5.4.1 Male reproductive organs The male reproductive system consists of the testes, scrotum, sperm ducts, accessory sex glands, and the penis.

Testes: The testes are a pair of male gonads responsible for producing male gametes, known as sperm. These organs generate millions of sperm cells. Additionally, the testes produce testosterone, which is the primary male sex hormone.

Scrotum: The scrotum is a sac-like organ that contains a pair of testes. The scrotum plays a vital role in maintaining a lower temperature than the internal body temperature as it is present outside the body. This lower temperature is essential for optimal sperm production.

Sperm ducts: Sperm ducts, also known as vas deferens, are responsible for transporting sperm from the testes to the penis.

Accessory sex glands: Accessory sex glands, which include the prostate gland, seminal vesicles, and bulbourethral gland, produce substances that nourish sperm. These substances contribute to semen, the fluid that carries sperm.

Penis: The penis, a part of the male external genitalia, serves multiple functions. It facilitates the release of urine and, during sexual intercourse, transfers semen from the male reproductive tract to the female reproductive tract.

Bladder Prostate

Penis

Rectum Urethra Testes

Fig. 5.5 Male reproductive system

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Semen: Semen is the fluid that carries sperm. In addition to sperm cells, semen contains various substances such as citric acid, free amino acids, fructose, enzymes, and prostaglandins. These components nourish sperm and aid their movement, facilitating fertilisation.

Sperm: Sperm is the male gamete, consisting of three main parts: 1. Head: Contains the nucleus and an acrosome, which houses hydrolytic enzymes like acrosin and hyaluronidase, crucial for penetrating the female gamete.

2. Middle piece: Abundant in mitochondria, it produces energy to power the movement of the sperm tail. This energy is essential for sperm mobility inside the female reproductive tract, a key factor in fertilisation.

3. Tail: Facilitates the movement of sperm within the female reproductive tract, contributing to the overall process of fertilisation.

Head Nucleus

Mitochondria

Head

Midpiece

Tail

Fig. 5.6 Structure of a sperm

5.4.2 Female reproductive organs The female reproductive system in human beings consists of ovaries, oviducts, vagina, external genitalia, and vestibular or Bartholin's glands. Associated with these organs, there are a pair of functional mammary glands for childcare.

Uterine tube

Fallopian Tube

Fimbriae

Ovary

Endometrium Myometrium

Vagina

Cervix

Fig. 5.7 Female reproductive system

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Ovaries: Ovaries are situated in pairs (right and left) and are responsible for producing the female gamete known as the egg or ovum. A single matured egg is released, and this process alternates between the two ovaries every month.

Oviduct or fallopian tube: The fallopian tube, situated between the ovaries and the uterus, serves as a pathway for the ovum released from the ovary, guiding it towards the uterus.

Uterus: The uterus looks like an inverted pear and is supported by ligaments attached to the pelvis.

It serves as the site for zygote implantation and facilitates complete foetal development.

Cervix: The cervix, the lower portion of the uterus, connects the uterus to the vagina. The cavity within the cervix is termed the cervical canal.

Vagina: The vagina is a tube-like structure extending from the cervix to the outside of the body. It plays multiple roles, serving as the site for sperm deposition during coitus, a pathway for menstrual flow, and a passage for childbirth during vaginal delivery.

Ovum or egg: The female gamete, known as an ovum or egg, is spherical. It is a single cell, and its size varies across species. For instance, the human egg is relatively small, while the ostrich egg is notably the largest cell. The process of releasing eggs from the ovaries is termed ovulation, marking a crucial phase in the female reproductive cycle.

Zona pellucida (Jelly coat) Corona radiata (follicular cells)

First polar body

Cytoplasm

Nucleolus

Nucleus

Fig. 5.8 Human ovum

5.4.3 Fertilisation Fertilisation is the process in which the male gamete (sperm) fuses with the female gamete (ovum).

This union results in the formation of a zygote, marking the initiation of an individual. During fertilisation, the nuclei of the sperm and ovum merge, and the newly formed individual inherits characteristics from both parents, the mother and the father. In humans, fertilisation typically occurs in the fallopian tube.

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In humans, sperm deposited in the vagina during sexual intercourse move towards the fallopian tube. Simultaneously, an egg is released from the ovary during ovulation. The meeting of the sperm and egg in the fallopian tube initiates the process of fertilisation.

The act of depositing semen into the female vagina during copulation is termed insemination.

During sexual intercourse, the penis delivers semen containing approximately 300 million sperm.

However, only one sperm out of this large number succeeds in fertilising the egg. This singular event leads to the formation of the zygote and the subsequent development of a new individual.

Perivitelline space Female pronucleus (haploid) Cells of corona radiata

Male pronucleus (haploid) Nucleus (diploid)

Sperm

Egg (ovum) Zone pellucida Cell membrane Fig. 5.9 Fertilisation

Types of fertilisation

There are two modes of fertilisation: 1. Internal fertilisation It takes place within the female body, where the male gametes are transferred to the female body to fuse with the female gamete. Examples include humans, cows, dogs, etc.

2. External fertilisation It takes place outside of the female body, where the gametes are released into the water bodies (aquatic environments). Examples include fish and frogs.

5.4.4 Development of embryo After fertilisation, the zygote, a single cell, undergoes successive divisions to form an embryo. Initial cell divisions occur within the fallopian tube. Subsequently, the embryo moves to the uterus and undergoes implantation, a process in which it implants into the uterine wall.

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Implantation involves changes in the uterus, notably an increase in the thickness of the inner lining or endometrium. The embryo gradually develops inside the uterus, initiating the formation of vital structures such as hands, legs, head, and eyes.

Nourishment essential for fetal development is provided by the mother through an organ called the placenta. The placenta connects the developing baby to the mother and facilitates the exchange of oxygen and nutrients, as well as the removal of waste products from the baby's body.

As the embryo progresses, it transforms into a foetus - a stage where all identifiable body parts begin to take form. This intricate process usually spans around 38 weeks for complete development within the human uterus.

Upon reaching full development, the mother gives birth to the baby. The entire sequence, from fertilisation to childbirth, marks the remarkable journey of human reproduction.

Placenta Uterus

Umbilical cord

Muscle wall

Rectum Bladder

Pubic symphysis

Vagina

Fig. 5.10 Human foetus in uterus

5.5 METAMORPHOSIS There are different ways in which organisms develop. In humans and all other viviparous animals, the newborn baby resembles its parents at the time of birth. However, in some oviparous animals, such as silkworms, butterflies, and frogs, the young ones that hatch from the eggs look very different from the adults. They are called larvae.

The process of transformation of a larva into an adult through drastic changes is called metamorphosis.

In frogs, the development of the embryo takes place outside the female body. The embryo continues to grow within the egg. After the embryo develops, the egg hatches into a larva called a tadpole.

The tadpoles are seen swimming in ponds. They are much different from adults. A tadpole grows and undergoes several changes in its form and structure, developing into an adult frog.

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Eggs

froglet

Frog Lifecycle

tadpoles

tadpoles 4 legs tadpoles 2 legs

Fig. 5.11 Metamorphosis in frog

Similarly, butterflies lay their eggs on the leaves, where the young ones may get enough supply of food when they hatch. The eggs hatch into worm-like larvae called caterpillars. The caterpillars eat leaves vigorously and grow. The larvae look very different from the adult.

The fully grown caterpillar hangs with its head down. It secretes a protective case, the cocoon around itself and changes into a pupa. The pupa does not feed or move. It represents the resting stage.

Inside the cocoon, the pupa undergoes changes and grows into the adult butterfly. It comes out by destroying the cocoon. The adult butterfly grows.

Adult Eggs

Monarch Butterfly life cycle

Larva Chrysalis Fig. 5.12 Metamorphosis in butterfly

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QUICK REVIEW • Reproduction is a process in which an organism gives rise to new individuals.

• Reproduction methods such as binary fission and budding facilitate rapid multiplication in single-celled organisms, while cloning, exemplified by Dolly the sheep, generates genetically identical replicas.

• Hermaphrodites, like earthworms, possess both male and female reproductive organs, whereas humans are unisexual, having specific male or female reproductive structures.

• Male reproductive system components (testes, scrotum, sperm ducts, accessory glands, penis) produce sperm and semen with various components to aid fertilisation.

• Female reproductive system structures (ovaries, oviducts, uterus, cervix, vagina) produce eggs, support fetal development, and facilitate childbirth.

• Fertilisation involves the fusion of sperm and egg, occurring internally in humans, cows, and dogs and externally in fish and frogs.

• After fertilisation, the zygote undergoes divisions, implants in the uterus, and develops into a fetus, with the placenta facilitating nutrient exchange.

• Human development takes around 38 weeks, leading to childbirth.

• After birth or hatching, some offspring resemble adults and develop gradually, while others, like young frogs, have distinct features and may go through larval stages.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Introduction to reproduction in animals

1. A biological process that happens with the fusion of eggs and sperm from two different organisms. Which of the following signifies the given process? a. Binary fission

b. Budding

c. Regeneration

d. Sexual reproduction

2. The number of parents involved in asexual and sexual reproduction, respectively, is _______. a. 2, 1

b. 1, 2

c. 2, 2

d. 1, 1

3. What is asexual reproduction? a. Reproduction involving two parents c. Reproduction through fertilization 112

b. Reproduction without the involvement of gametes d. Reproduction involving the fusion of gametes

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4. Dog reproduces sexually. The young one of a dog is known as a _____________. a. Puppy

b. Cub

c. Kitten

d. Fry

5. Cats reproduce sexually. The young one of a cat is called _______. a. Kitten

b. Puppy

c. Calf

d. Chick

6. Which process is essential for the continuation of any species? a. Reproduction

b. Circulation

c. Digestion

d. Respiration

7. Statement - I: Sexual reproduction is a simple and fast process.

Statement - II: Asexual reproduction is a complex and slow process. a. Both statements are true

b. Both statements are false

c. Statement - I is true, and statement - II is false

d.

Statement - I is false, and statement - II is true

8. Statement - I: In sexual reproduction, offspring are not identical to parents or amongst themselves.

Statement - II: Sexual reproduction involves the fusion of a male and female gamete. a. Both statements are true

b. Both statements are false

c. Statement - I is true, and statement - II is false

d. Statement - I is false, and statement - II is true

II. Asexual reproduction

1. In Hydra, the mode of reproduction is a. Binary fission

b. Vegetative propagation

c. Budding

d. Sporulation

2. A Paramecium reproduces by dividing itself into two daughter cells. This process is called a. Budding

b. Regeneration

c. Binary fission

d. Sporulation

3. Which of the following is NOT an example of asexual reproduction? a. Reproduction in Hydra

b. Reproduction in Amoeba

c. Reproduction in bacteria

d. Reproduction in butterfly

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4. Identify the microorganism shown in the image.

a. Bacteria

b. Virus

c. Amoeba

d. Fungus

5. The number of individuals produced by binary fission is ______________________. a. Two

b. Three

c. Four

d. Five

6. There is no natural death in single-celled organisms like Amoeba and bacteria because a. They cannot reproduce sexually

b. They reproduce by binary fission

c. The parental body is distributed among the offspring

d. They are microscopic

7. Asexual reproduction is common in ________________________. a. Single-celled organisms

b. Humans

c. Animals with multicellular organisation

d. Higher plants

8. Asexual reproduction involves a. Both maternal and paternal parents

b. Only maternal parent

c. Only paternal parent

d. One parent

9. The most common method of reproduction in bacteria is __________________________. a. Binary fission

b. Multiple fission

c. Budding

d. Spore formation

10. An equal number of daughter cells is produced from a cell through _____________________. a. Fragmentation

b. Sporulation

c. Binary fission

d. Budding

11. Amoeba and yeast reproduce asexually by fission and budding, respectively, because they are ________________________.

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a. Microscopic organisms

b. Heterotrophic organisms

c. Unicellular organisms

d. Uninucleate organisms

12. Which of the given methods of reproduction is common in Amoeba and Hydra? a. They reproduce asexually

b. They reproduce sexually

c. They reproduce asexually and sexually

d. Being multicellular, they reproduce asexually

13. Which of these is a type of asexual reproduction in which new individuals develop from the buds? a. Binary fission

b. Budding

c. Fragmentation

d. Spore formation

III. Story of Dolly, the clone

1. Dolly was born on _________. a. 5th July 1996

b. 7th July 1997

c. 8th July 1996

d. 5th July 1997

2. During a cell division, _______________. a. The nucleus divides first, and then the cytoplasm

b. Cytoplasm divides first, and then the nucleus

c. Nucleus and cytoplasm divide together

d. No such relationship

3. Dolly, the famous animal, was a ____________. a. Donkey

b. Girl

c. Cloned sheep

d. Normal sheep

4. Who among the following successfully performed the process of cloning an animal for the first time? a. Anton van Leeuwenhoek

b. Ian Wilmut

c. Joseph Priestly

d. Lavoisier

5. Which breed of sheep is the cloned animal Dolly genetically identical to? a. Finn Dorsett sheep

b. Scottish blackface ewe

c. Black Welsh Mountain

d. Shropshire sheep

6. Where is the Roslin Institute, the animal sciences research institute known for the successful cloning of an animal, located? a. Glasgow

b. Edinburgh

c. Sunderland

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IV. Male reproductive system

1. Testes of man are located _________. a. Inside the abdomen

b. In scrotal sacs

c. Above the dorsal aorta

d. On the sides of the kidney

2. 'Seminiferous tubules' are located in the _______. a. Testis

b. Ovary

c. Liver

d. Kidney

3. What is the primary male sex organ responsible for producing sperm? a. Testis

b. Penis

c. Prostate gland

d. Epididymis

4. Which among the following is not associated with the male reproductive system? a. Seminal vesicle

b. Prostate gland

c. Bulbourethral glands

d. Bartholin's glands

5. The secretion of which among the following also helps in the lubrication of the penis? a. Bulbourethral glands

b. Phallic glands

c. Brunners glands

d) Interstitial glands

6. Increasing BMR, low-pitch voice, narrowing of the pelvis, etc., happen because of ______. a. Estrogen

b. Progesterone

c. Testosterone

d. Inhibin

7. Identify the correct labelling.

A

B C

a. A – Fallopian tube, B - Ureter, C –

b. A – Sperm duct , B - Penis, C – Testis

Epididymis c. A – Vas deference, B - Urethra, C – Testis

d. A – Oviduct, B - Ureter, C – Seminiferous tubules

8. Spermatozoa from seminiferous tubules move into the _____________. a. Epididymis

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b. Vas deferens

c. Vas efferentia

d. Urethra

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9. The correct sequence of organs in the male reproductive system for the transport of sperm is a. Testis → Vas deference → Urethra c. Testis → Urethra → Ureter

b. Testis → Ureter → Urethra

d. Testis → Vas deference → Ureter

V. Female reproductive system

1. Which is correct regarding the female reproductive system in human beings? a. A pair of cervix

b. A pair of ovaries

c. An oviduct

d. A pair of uterus

2. In which of the following areas does fertilisation take place? a. Uterus

b. Fallopian tube

c. Ovary

d. Body cavity

3. In which part of the female reproductive system does the developing zygote, called the embryo, get implanted? a. Oviduct

b. Wall of uterus

c. Cervix

d. Ovary

4. After being released from the follicle, the ovum enters the _______. a. Epididymis

b. Vas deferens

c. Fallopian tube

d. Uterus

5. The number of ova released at a time in female human beings is (are) ______. a. 1

b. 3

c. 2

d. 4

6. Which of the following is/are paired structure(s) in the human reproductive system? a. Ovary

b. Testes

c. Fallopian tube

d. All of these

7. Which among the following is not a part of the human female reproductive system? a. A pair of ureters

b. A pair of oviducts

c. A pair of ovaries

d. Womb

8. Some sets of reproductive terms are given below. Choose the set that has an incorrect combination. a. Sperm, testis, sperm duct, penis

b. Menstruation, egg, oviduct, uterus

c. Sperm, oviduct, egg, uterus

d. Ovulation, egg, oviduct, uterus

9. What is the main function of the fallopian tubes? a.

Egg production

c. Menstruation

b. Fertilization of eggs d. Hormone secretion

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VI. Development of embryo

1. The correct sequence of events during reproduction in human beings is: a. Gamete formation, fertilisation, zygote, embryo

b. Embryo, zygote, fertilisation, gamete formation

c. Fertilisation, gamete formation, embryo, zygote

d. Gamete formation, fertilisation, embryo, zygote

2. The foetus is connected to the wall of the uterus of the mother by the __________. a. Placenta

b. Umbilical cord

c. Fallopian tube

d. Epididymis

3. The embryo gets its nourishment from the mother through the ________. a. Yolk

b. Placenta

c. Oviduct

d. Uterus

4. Which of the following sequences is in the correct order? a. Zygote → Embryo → Foetus → Baby c. Embryo → Zygote → Baby → Foetus

b. Zygote → Embryo → Baby → Foetus d. Foetus → Zygote → Embryo → Baby

5. The animals that live in water mostly exhibit __________. a. External fertilisation

b. Internal fertilisation

c. In vitro fertilisation

d. None of the above

6. The number of eggs produced in internal fertilisation is _________. a. More than external fertilisation

b. Less than external fertilisation

c. More or less than external fertilisation depending on the environmental conditions

d. Equal to external fertilisation

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. Which of the following statements is true about asexual reproduction? a. Offspring are produced without fusing the gametes, as only one individual is involved. b. New individuals involve the fusion of male and female gametes. c. It is a mode of reproduction that occurs only in plants. d. New individuals are produced by the fusion of dissimilar gametes.

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2. How will the offspring be in all the methods of asexual reproduction? a. Offspring produced are genetically identical to the parents. b. Offspring produced are genetically different from the parents. c. Offspring produced may or may not be identical to the parents. d. Offspring produced will have identical genes with parents after 21 days.

3. Why do offspring formed by the asexual method of reproduction have greater similarity among themselves? a. Asexual reproduction involves two individuals

b. Asexual reproduction does not involve gametes

c. Asexual reproduction occurs before sexual reproduction

d. Asexual reproduction occurs after sexual reproduction

4. Identify the method of reproduction in Hydra. a. Budding

b. Binary fission

c. Regeneration

d. Spore formation

5. Identify the type of reproduction shown in the picture.

a. Binary fusion

b. Budding

c. Binary fission

d. None of the above

6. Asexual reproduction is common in _________. a. Microorganisms

b. Dogs

c. Earthworm

d. Butterfly

7. The first successfully cloned mammals (animals) that gained worldwide publicity were _____. a. Molly (a sheep)

b. Polly (a sheep)

c. Chance (a bull)

d. Dolly (a sheep)

8. Dolly is a _______. a. Dog

b. Cat

c. Sheep

d. Bull

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9. The production of an exact copy of a cell, any other living part, or a complete organism is called as__________. a. In vitro fertilisation

b. External fertilisation

c. Tissue culture

d. Cloning

10. The cloning of an animal was first performed by _______________. a. Ian Wilmut and his colleague

b. Thomson

c. Jenner

d. Lan Wilson

11. Which among the following includes the primary sexual organs? a. Testes, ovaries & sex hormones

b. Testes, ovaries & genital ducts

c. Genital glands & and genital ducts

d. Only Testes & and ovaries

12. The genital ducts and associated genital glands together form a. Primary sexual organs

b. Secondary sexual organs

c. Accessory secondary sexual organs

d. External organs

13. Identify the accessory gland in males from the following options a. Prostate gland

b. Uterus

c. Testis

d. Penis

14. The period in which secondary sexual character appears is called _______. a. Eunich

b. Menarche

c. Menopause

d. Puberty

15. What is the purpose of the prostate gland in the male reproductive system? a. Production of testosterone

b. Storage of sperm

c. Secretion of a fluid that nourishes and protects sperm

d. Transport of urine from the bladder

16. Identify the parts 1, 2, and 3 in the following picture.

1 2 3

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a. 1-Middle piece, 2-Head piece, 3-Tail piece

b. 1-Tail piece, 2-Head piece, 3- Middle piece

c. 1-Head piece, 2- Middle piece, 3-Tail piece

d. 1-Nucleus, 2-Head piece, 3-Tail piece

IL Foundation Series Class 8

17. The male human germ cell is called the _______. a. Zygote

b. Ovum

c. Testis

d. Sperm

c. Vas deferens

d. Uterus

18. The _____ are the male reproductive organs. a. Ovaries

b. Testes

19. The acrosome of spermatozoan helps in __________. a. Digestion

b. Locomotion

c. Excretion

d. Fertilisation

20. Spermatozoa from seminiferous tubules move into the _______. a. Epididymis

b. Vas deferens

c. Vas efferentia

d. Urethra

21. The seminiferous tubules are located in the __________. a. Urethra

b. Fallopian tubes

c. Vas efferentia

d. Testis

22. The male reproductive system consists of the _________. a. Umbilical cord

b. Testes

c. Fallopian tubes

d. Placenta

23. Which of the following is called the Cowper’s Gland? a. Bulbourethral gland

b. Prostate gland

c. Seminiferous vesicle

d. Vas deferens

24. How many mature egg(s) will be released from the human ovary every month? a. 1

b. 2

c. 3

d. 4

c. Vagina

d. Ovary

25. Graafian follicles are present in the _____. a. Fallopian tube

b. Uterus

26. The stage where the organs of the baby’s body start developing such that they can be identified is called _____________. a. Foetal stage

b. Zygote

c. Blastula

d. Embryonic stage

27. Which of the following is a characteristic of an egg cell or ovum? a. Non-motile

b. Motile

c. Can be motile as well as non-motile

d. Neither non-motile nor motile

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28. Which of the following animals produces the world's largest egg? a. Ostrich

b. Dinosaur

c. Elephant

d. Whale

29. Which of the following is not a part of the female reproductive system? a. Uterus

b. Ovary

c. Oviduct

d. Penis

30. Which of the following structures has an internal wall lined with hair-like projections? a. Ovary

b. Vagina

c. Fallopian tube

d. Uterus

31. Choose the set that belongs to the female reproductive system. a. Testes, spermatic duct, penis

b. Testes, oviduct, uterus

c. Penis, uterus, ovary

d. Ovary, oviduct, uterus

32. Refer to the given figure and select the incorrect statement regarding this.

a. P represents the human male gamete, which consists of a head, middle piece, and tail.

b. The shown process is fertilisation.

c. The resulting structure formed after this process is a foetus.

d. Q represents the human female gamete which is a single cell.

33. Read the following statements and choose the correct option.

I. Only one sperm can fertilise an ovum.

II. During fertilisation, a sperm comes in contact with the zona pellucida and induces changes in the membrane that block the entry of additional sperms. a. Both statements I and II are incorrect. b. Only statement I is correct. c. Both statements are correct, and statement II is the correct explanation of statement I. d. Both statements are correct, and statement II is not the correct explanation of statement I.

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34. Which of the following adaptations is commonly observed in marine organisms that undergo external fertilisation? a. Production of a large number of gametes

b. Large body size

c. Viviparity

d. Complex courtship behaviour

35. Analyse the following statements and choose the correct answer.

Assertion: The zygote develops into a new individual in sexual reproduction in animals.

Reason: The zygote is not developed in asexual animals. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reasoning (R) is false. d. Both Assertion (A) and Reasoning (R) are false.

36. Which of the following is the correct order regarding the post-fertilisation process in hens?

1. Many protective layers are formed around the zygote.

2. The zygote divides repeatedly and travels down the oviduct.

3. The hen finally lays the egg.

4. A hard shell is formed around the developing embryo. a. 3-2-1-4

b. 2-4-1-3

c. 2-1-4-3

d. 4-1-2-3

37. Identify A, B, and C in the following equation concerning the process of fertilisation: A + B → fertilisation C

a. A - sperm, B - zygote, C - egg

b. A - egg, B - zygote, C - sperm

c. A - sperm, B - egg, C - zygote

d. A - zygote, B - sperm, C - egg

38. What is the purpose of the uterus in the female reproductive system? a. Egg production

b. Menstruation

c. Implantation and fetal development

d. Hormone secretion

39. Why do the offspring formed by sexual reproduction exhibit more variation than those formed by asexual reproduction?

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a. Sexual reproduction is a lengthy process.

b. Gametes of parents have qualitatively different genetic composition.

c. Genetic material comes from parents of two different species.

d. A greater amount of DNA is involved in sexual reproduction.

40. A few statements describing certain features of reproduction are given below: i. Gametic fusion takes place. ii. Transfer of genetic material takes place. iii. Reduction division takes place. iv. Progeny resembles their parents.

Analyze the given statements and select options that are true for both asexual and sexual reproduction from the options given below. a. ii and iv

b. ii and iii

c. i and ii

d. i and iii

41. A few statements about sexual reproduction are given below: i. Sexual reproduction does not always require two individuals. ii. Sexual reproduction generally involves gametic fusion. iii. Meiosis never occurs during sexual reproduction. iv. External fertilisation is a rule during sexual reproduction.

Choose the correct statements from the options below: a. i and iv

b. i and ii

c. ii and iii

d. i and iv

42. Which of the following statements is true/false? i. Oviparous animals give birth to young ones. ii. External fertilisation takes place in frogs. iii. An embryo is made up of a single cell. iv. A new daughter cell develops after fission in algae. v. Amoeba reproduces by binary fission. vi. A zygote is formed as a result of fertilisation.

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a. (i), (iii), (iv) are false; (ii), (v), (vi) are true

b. (i), (iii) are false; (ii), (iv), (v), (vi) are true

c. (iii), (iv) are false; (i), (ii), (v), (vi) are true

d. (iii), (v) are false; (i), (ii), (iv), (vi) are true

IL Foundation Series Class 8

43. Which of the following is NOT a characteristic feature of sexual reproduction? a. It involves the fusion of two reproductive cells. b. It is common in most organisms. c. Fertilisation may take place inside or outside the body of the female. d. The offspring receives its characteristics from one parent only.

44. Which of the following sequence of events that occurs during the entire lifespan of a living organism is correct? a. Juvenile phase → mature phase → old age → death b. Mature phase → juvenile phase → old age → death

c. Old age → mature phase → juvenile phase → death d. Juvenile phase → old age → mature phase → death

45. A tadpole develops into an adult frog by the process of _________. a. Fertilisation

b. Metamorphosis

c. Embedding

d. Budding

46. A tadpole is the young one of (A) found in (B). a. (A) Hen, (B) Land

b. (A) Butterfly, (B) Tree

c. (A) Frog, (B) Water

d. (A) Grasshopper, (B) Grass

47. Statement I: Unlike a hen’s egg, a frog’s egg is not covered by a shell, and it is comparatively very delicate.

Statement II: During the rainy season, frogs and toads move to ponds and slow-flowing streams. a. Statement I is true into Statement I is false c. Statement I is true, statement II is false.

b. Statement I is false, statement II is false. d. Statement I is false into Statement I is true

48. In a human female, the fertilised eggs get implanted in the uterus. How much time does it take for this implantation? a. After two months of fertilisation.

b. After one month of fertilisation.

c. After about 7 days of fertilisation.

d. After 3 weeks of fertilisation.

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49. Assertion: The transformation of the larva into an adult through drastic changes is called metamorphosis.

Reason: The caterpillar or the pupa of a silkworm looks very similar to the adult moth. a. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). b. Both Assertion (A) and Reason (R) are true, and Reason(R) is not the correct explanation of Assertion (A). c. Assertion (A) is true, but Reasoning (R) is false. d. Both Assertion (A) and Reasoning (R) are false.

50. What is the major difference between the human skin cell and the human egg cell?

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a. The egg cell has twice as many chromosomes as the skin cell

b. The egg cell has half as many chromosomes as the skin cell.

c. The skin cell has no genetic information in its chromosome

d. Only the egg cell has a nucleus

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REPRODUCTION IN PLANTS

6.1 INTRODUCTION Reproduction is a vital process without which species cannot survive for long. It is a biological process in which an organism gives rise to young ones similar to itself. It enables the continuity of the species generation after generation.

Types of reproduction Reproduction is of two types, namely 1. Asexual reproduction 2. Sexual reproduction

6.2 ASEXUAL REPRODUCTION In asexual reproduction, offspring are produced by a single parent without the fusion of gametes. It is common among single-celled organisms and in plants with a simple organisation. It is a common method of reproduction in algae and fungi.

6.2.1 Methods of asexual reproduction • Spores formation: Usually microscopic, adapted for dispersal, and can survive extended periods of unfavourable conditions. In bryophytes, pteridophytes and spermatophytes spores are haploid and on germination produce gametophytes. Spores without flagella are nonmotile (aplanospores). Endogenous spores are produced inside the sporangia, for example, Rhizopus. Spores with flagella are motile (zoospores swarm spores or plant spores). E.g., Chlamydomonas. Exogenous spores are produced on conidiophores, for example, Penicillium and Aspergillus.

Sporangium Spores

Rhizoids Hypha (a) Endospore in Rhizopus

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REPRODUCTION IN PLANTS Conidia Conidia

Zoospores Zoospores

Parent Parent cell cell (Zoosporangium)

Conidiophore Conidiophore

(Zoosporangium)

(b) Zoospores in Chlamydomonas

(c) Conidia in Penicillium

Fig. 6.1(a - c) Different methods of asexual reproduction in plants

• Fragmentation: In multicellular or colonial forms of algae, moulds, and mushrooms, the body breaks into several fragments, and each fragment develops into a mature individual.

An example is Spirogyra.

Nucleus Nucleus Septa Septa Spiral Spiral chloroplast chloroplast

Daughter cells Daughter cells Fig. 6.2 Fragmentation in Spirogyra

• Gemmae: Gemmae are specialised structures for reproduction via fragmentation. E.g., Liverworts (Marchantia).

Fig. 6.3 Gemma cups in Marchantia

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Vegetative propagation

It is a simple method of asexual reproduction seen in plants. In this process, a vegetative part of the plant body, such as the root, stem, or leaf, becomes detached and then regenerates in a new independent plant. Plants produced vegetative or asexually are called clones. Clones are similar both genetically and morphologically.

Vegetative propagules: In plants, the structures of vegetative propagation are capable of giving rise to new offspring. These structures are called vegetative propagules. In flowering plants, the structures that are involven in vegetative reproduction are as follows: • Rhizome -- Modified horizontally growing underground stem. E.g., ginger • Corm -- Modified vertically growing underground stem. E.g., Colacasia • Tuber -- Underground stem with eyes. E.g., potato • Bulb -- Underground stem without storage of food. E.g., Allium cepa • Runner -- Sub-aerial stem spreads to new niches and forms new plants when older parts die.

E.g., Oxalis, grass.

• Stolon -- A Slender lateral branch arises from the base of the main axis and arches down to touch the ground, producing adventitious roots. E.g., Rosa, Nerium • Sucker -- Lateral branches originate from the basal and underground portion of the main axis.

E.g., banana, pineapple • Bulbils -- Modified vegetative or floral buds. E.g., Dioscorea, Agave • Reproductive leaves -- Modified leaves with small buds arising on leaf margins. E.g., Bryophyllum In vegetatively propagated plants like banana, potato, sugarcane, and ginger, nodes present on the modified stems come in contact with damp soil or water and produce new plants. Dahlia is propagated through root tubers and nodes (having meristematic cells) present on a modified stem.

Algae and fungi reproduce asexually. It shifts to the sexual method of reproduction just before the onset of adverse conditions(unfavourable).

Internode Internode

Scale leaf Scale leaf

Adventitious Adventitious root root

a) Rhizome in ginger

Lenticels Lenticels Scale Scaleleaf leaf Lateral Lateralbud bud (eye) (eye) Bud Bud

Shoot Shoot

Stem end Stem end

Node Node

b) Stem tuber of the potato

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Node

Node

Internode

Bulb apex (Nose)

Internode

Scale leaf

Scale leaf

apex BulbBulb apex (Nose) (nose) Membranous

Membranous Membranous or Tunic Leaf leaf or tunic Fleshy Scale Fleshy (Leaf Bases) scale (leaf bases)

or Tunic Leaf Fleshy Scale (Leaf Bases)

Corm

Corm

Daughter corm

Daughter corm

Flower (bud) Lateral Bud Lateral bud

Flower (Bud)

Flower (Bud)

Lateral Bud Stem Stem Adventitious Adventitious Root root

Stem Adventitious Root

Adventitious Adventitious root root

d) Bulb of onion

c) Corm of Colocasia

Runners

e) Runners in Oxalis

f) Bulbis of Agave

Sucker Sucker

Stolon Stolon

g) Stolon of jasmine

Offset

i) Offset of Eichhornia

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h) Sucker of Chrysanthemum

Node Node Inter node Internode Bud Bud

j) Stem cutting of sugarcane

New plant New plant

Adventitious roots roots Adventitious

IL Foundation Series Class 8

Adventitious buds

New New plant plant

Old root tubers

Old Root Tubers

NewNew Root Tubers root tubers

k) Root tuber of Dahlia

l) Reproductive leaf of Bryophyllum

Fig. 6.4 Vegetative propagation

6.3 SEXUAL REPRODUCTION Most of the higher plants reproduce through the sexual mode of reproduction. In flowering plants, sexual reproduction is the fusion of the male and the female gamete. This fusion takes place in the reproductive part of the plant called flowers.

6.3.1 Flower -- general structure Flowers are the reproductive part of the plant and are biologically meant for sexual reproduction.

It is attractive and is found in various shapes, flowers, and fragrances.

The main parts of a flower are: 1. Calyx 2. Corolla 3. Stamen (androecium) 4. Carpel (gynoecium) The calyx and corolla are the non-essential parts as they do not participate in reproduction, while the stamen and carpel are the reproductive parts or essential floral organs.

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Stigma Anther Stamen Style

Filament

Pistil

Ovary Petal

Sepal

Fig. 6.5 Parts of flower

When a flower has both androecium and gynoecium, it is bisexual. A flower having either only stamens or only carpels is unisexual. A flower with all four whorls, such as calyx, corolla, stamens and carpels, is called a complete flower, and with one or more missing whorls is called an incomplete flower.

Parts of flower

1. Calyx: It is the outermost whorl of a complete flower comprising sepals called the calyx. It is green-coloured and protects the flower in bud condition. Sepals may be polysepalous (free sepals -Annona), or gamosepalous (united sepals -- Datura).

2. Corolla: It is the second whorl of a complete flower. The individual units of corolla are called petals. Petals are usually coloured and attract insects for pollination. Petals may be polypetalous (free petals -- Hibiscus) or gamopetalous (united petals -- Datura). The shape and colour of the corolla vary greatly in plants. Corolla may be tubular, bell-shaped, funnel-shaped, or wheel-shaped.

Tubular E.g.: Disc floret

Bell/Campanulate E.g.: Bell flower

Funnel E.g.: Datura

Wheel E.g.: Catharanthus

Fig. 6.6 Different shapes of corolla

3. Androecium: Androecium or stamen is the male reproductive organ of a flower, and male gametes areproduced inside it. Each stamen is composed of a long, slender stalk called a filament, which attaches it to the other parts of the flower, like a petal. It also consists of an anther that bears pollen grains, which is the male gamete located at the top of the filament. The stamen in a flower

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may either remain free (polyandrous) or may be united.

Pollen grains Anther

Pollen sacs Anther Filament

a

b

(a) Stamen

(b) Anther (T.S.)

Fig. 6.7 Flower -- general structure

4. Gynoecium: The gynoecium is the female reproductive whorl of the flower. It is composed of one or more carpels. Each carpel consists of three parts, i.e. stigma, style, and ovary. The stigma is the terminal end of the style, recipient of the pollen grains, and is generally knob-like and sticky. The style is the slender projection of the ovary and bears a stigma at its terminal end. The swollen basal part of the pistil, which is single or many-chambered, is termed an ovary.

The ovary contains one or more ovules which are attached to the placenta. Each ovule contains a large embryo sac at maturity. The ovary gives rise to the fruit, and the ovules give rise to the seeds after fertilisation.

Stigma Style

Ovary Thalamus Fig. 6.8 Pistil of Hibiscus

In flowering plants, sexual reproduction involves the formation of gametes and pollination, where pollen grains move from the anthers to the stigma. This is followed by fertilisation, where the pollen 133

REPRODUCTION IN PLANTS

tube delivers sperm cells to fuse with an egg cell and a central cell. After fertilisation, the ovule becomes a seed within a fruit, which helps in seed dispersal. The seed germinates into a new plant, completing the reproductive cycle. The process of sexual reproduction involves three phases such as 1. Pre-fertilisation phase 2. Fertilisation phase 3. Post-fertilisation phase

6.4 PRE-FERTILISATION PHASE In the flower, the male and female reproductive structures, the androecium and the gynoecium, differentiate and develop. The androecium consists of a whorl of stamens representing the male reproductive organs, and the gynoecium represents the female reproductive organ.

The pre-fertilisation phase includes the events before the fusion of gametes. The major events are gamete formation and gamete transfer. Gamete formation includes the formation of pollen grains and ovules. Gamete transfer happens via the process of pollination.

6.4.1 Pollen grains The pollen grain represents the male gamete. Each pollen grain or microspore is a unicellular, haploid, oval, or rounded structure. Pollen grains are generally spherical, measuring about 25 -- 50 micrometres in diameter. It has two layered walls, an exine and an intine. The outer layer, called exine, is thick and tough. The outer layer has prominent apertures called germ pores. The inner layer, called intine, is thin and smooth.

Vacuole Generative cell

Generative nucleus Germ pore

Tube nucleus Intine

Vegetative nucleus Exine

Fig 6.9 Structure of pollen grain

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6.4.2 Ovule The ovule is the structure that gives rise to and contains the female reproductive cells. Ovules are attached to the placenta in the ovary through a stalk-like structure known as a funiculus. Ovules consists of three parts: 1. Integument: An integument is a protective cell layer surrounding the ovule. The integuments develop into the seed coat when the ovule matures after fertilisation.

2. Nucellus: It is the central portion of the ovule in which the embryo sac develops.

3. Female gametophyte: The female gametophyte is specifically termed a megagametophyte or the embryo sac in angiosperms. The embryo sac produces an egg cell for fertilisation.

Cross-section through Ovule Chalaza Antipodals Secondary nucleus Embryo sac

Egg Synergids Inner integument Micropyle

Outer integument Funiculus

Fig. 6.10 Structure of ovule

Structure of embryo sac: A typical embryo sac consists of three parts: 1. Egg apparatus: The egg apparatus consists of a middle larger egg cell or female gamete, and the two lateral ones are called synergids. Synergids are short-lived (one of them degenerates with the entry of the pollen tube and the second after the entry of the pollen tube into the embryo sac).

2. Central cell: The central cell consists of two polar nuclei, which fuse to form the single diploid secondary nucleus.

3. Antipodals: Antipodals are the smallest cells of all and are the vegetative cells of embryosac.

They degenerate before or after fertilisation.

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Antipodals

Polar cell Central cell Egg Synergids Filiform apparatus

Fig. 6.11 Structure of embryo sac

6.4.3 Pollination The transfer of pollen grains from another to the stigma or the ovule is called pollination.

This process of pollination occurs before fertilisation in gymnosperms and angiosperms.

Types of pollination: Pollination is of two types, namely: 1. Self-pollination 2. Cross-pollination 1. Self-pollination (autogamy)

The transfer of pollen grains from the anther to the stigma of the same flower is called autogamy or self-pollination. It occurs in plants with bisexual flowers.

Advantages of self-pollination • It maintains the parental character in the offspring.

• The plants do not need to produce a large number of pollen grains.

• Flowers need not to attract insect pollinators.

• It ensures seed production.

• Self-pollination eliminates recessive characters.

Disadvantages of self-pollination • Vigour and vitality of the race decrease with prolonged self-pollination.

• Reduction in immunity to diseases.

• Variability and adaptability of the plant offspring is reduced.

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2. Cross-pollination

It is the transfer of pollen grains from the anther of one flower to the stigma of another flower on a different individual of the same species.

Pollination Pollinator Pollen

Pollen

Pollen

Pollen

Pollen grains

Stigma

Ovule Ovary a) Self-pollination

b) Cross-pollination Fig. 6.12 Pollination

Advantages of cross-pollination •

Cross-pollination introduces genetic recombination and variations in the progeny.

•

ross-pollination increases the adaptability of the offspring towards changes in the C environment.

•

Plants produced are usually larger and the offspring have better characteristics than the parents.

•

New and more useful varieties can be produced through cross-pollination.

Agents for cross-pollination Plants use two abiotic (wind and water) and one biotic (animal) agent to achieve pollination. The majority of plants use biotic agents for pollination.

1. Wind pollination (anemophily): It is an abiotic means of pollination by wind and is nondirectional. Pollination by wind (anemophily) is more common amongst abiotic pollinations. The pollen would reach the right stigma through the wind. The wind pollination is quite common in grasses.

2. Water pollination (hydrophily): The mode of pollination through the agency of water is not very common and occurs only in a few aquatic plants, especially submerged ones, like Vallisneria and Zostera. In a majority of aquatic plants, such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind.

3. Zoophily: It is animal-mediated pollination. Most flowering plants use a range of animals as pollinating agents (zoophily). Bees, butterflies, flies, beetles, wasps, ants, moths (entomophily-

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pollination by insects), sunbirds and hummingbirds (ornithophily-pollination by birds), and bats (chiropterophily) are the common pollinating agents. Among the animals, insects, particularly bees, are the dominant biotic pollinating agents. Even larger animals, such as some squirrels (therophily), primates (lemurs), arboreal (tree-dwelling) rodents, or even reptiles (snakes-ophiophily; Gecko lizard and garden lizard) have also been reported as pollinators in some species. In some plants, snails are the pollinators, and this type of pollination is called malacophily.

6.5 POLLEN GERMINATION AND FERTILISATION The pollen grains, after falling on the stigma, start germination in the presence of moisture and nutrients available on the stigma. A pollen tube emerges from the intine of the pollen. It produces enzymes that digest the tissues of the stigma and the style. In plants that shed pollen in the threecelled condition, pollen tubes carry the two male gametes from the beginning. The pollen tube finally enters the ovule through its micropyle and embryo sac through one of the synergids. Later on, the two male gametes are discharged into the embryo sac.

Pollen grains Stigma Sperm nuclei Tube nucleus

Pollen tube Style Embryo sac

Sperm nuclei Egg cell

Polar nuclei Ovary Micropyle

Fig. 6.13 Development of the pollen tube

6.5.1 Fertilisation •

Syngamy or generative fertilisation: The fusion of one male gamete with the egg to form a zygote (2n) is called syngamy or generative fertilisation. It was discovered by Strasburger.

•

Triple fusion or vegetative fertilisation: The fusion of a second male gamete with two polar nuclei or secondary nuclei of the central cell to form a triploid primary endosperm nucleus (PEN) is known as triple fusion or vegetative fertilisation. It was discovered by S.G.

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Nawaschin. The central cell, after triple fusion, becomes the primary endospermic cell (PEC) and develops into an embryo.

•

Double fertilisation: The simultaneous occurrence of syngamy and triple fusion in the embryosac of angiosperms is called double fertilisation. Double fertilisation was first reported

by S.G. Nawaschin (1898) in Fritillaria and Lilium. It is unique to angiosperms. The zygote develops into an embryo, and the primary endosperm cell develops into the endosperm.

Antipodals Egg cells

Pollar nuclei

Synergids Release of Sperm cells

Endosperm (3n)

Zygote (2n) Double fertilisation Fig. 6.14 Process of fertilisation

6.6 POST-FERTILISATION PHASE The events of endosperm and embryo development, maturation of ovules into seeds and ovary into fruit, are collectively termed post-fertilisation events.

6.6.1 Endosperm •

Endosperm development precedes embryo development.

•

Endosperm accumulates food reserves and functions as the nutritive tissue for the developing embryo.

6.6.2 Embryo In most flowering plants, the zygote divides and develops as an embryo. A mature dicotyledonous embryo has two cotyledons and an embryonal axis. The cotyledons are fleshy, storing food materials.

The plumule and radicle of an embryo develop as a shoot system and root system, respectively.

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Scutellum Plumule

Coleoptile

Cotyledons

Shoot apex

Hypocotyl

Epiblast

Radicle Root cap (a)(a) Dicot embryo

Radicle Root cap Coleorhiza (b) Monocot (b) embryo

Fig. 6.15 Endosperm

6.6.3 Seed In angiosperms, the seed is the final product of sexual reproduction. Seeds are formed inside the fruit. A seed consists of a seed coat, cotyledon, and embryonal axis. The ovules, after fertilisation, develop into seeds.

Structure of a dicotyledonous seed

The outermost covering of a seed is the seed coat. It has two layers, the outer testa and the inner tegmen. Outer integument forms the testa, and the tegmen develops from the inner integument.

The funiculus forms the stalk of the seed. Ultimately, the stalk withers and leaves a minute scar called hilum. Above the hilum is a small pore called the micropyle (seed pore). This facilitates the entry of oxygen and water into the seed during germination.

Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons. The cotyledons are connected to the node of the embryonal axis, known as the tigellum. The part of the tigellum above the cotyledons is the epicotyl, which terminates with the plumule, while that below is the hypocotyl, which terminates with the radicle. The root tip is covered with a root cap.

In some seeds such as castor, the endosperm is a food-storing tissue. In plants, such as beans, gram, and peas, the endosperm is not present in mature seeds, which are called non-endospermic. In nonendospermic seeds, cotyledons are fleshy and store food materials.

Seed coat Epicotyl Hypocotyl Embryo Radicle

Cotyledons (Stored Fig. 6.16 Structure food) of a dicot seed

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Structure of a monocotyledonous seed

Generally, monocotyledonous seeds are endospermic, but some, as in orchids, are non-endospermic.

In the seeds of cereals such as maize, the seed coat is membranous and generally fused with the fruit wall. The endosperm is bulky and stores food. The outer covering of the endosperm separates the embryo by a proteinous layer called the aleurone layer. The embryo is small and situated in a groove at one end of the endosperm. It consists of one large and shield-shaped cotyledon known as a scutellum and a short axis with a plumule and a radicle. The plumule and radicle are enclosed in sheaths, which are called coleoptile and coleorhiza, respectively.

Seed coat & fruit-wall

Endosperm

Aleurone layer

Scutellum Coleoptile

Endosperm

Plumule

Embryo

Radicle Coleorhiza

Fig. 6.17 Structure of a monocot seed

6.6.4 Fruits The fruit may be defined as a ripened ovary containing one or more seeds. The ovary undergoes two important changes immediately after fertilisation. Ovules develop into seeds. The wall of the ovary thickens and ripens into the pericarp (fruit wall). The fruit protects the seed inside it.

There are some fruits that do not contain seeds. These fruits are formed without fertilisation of the ovary. These fruits are called parthenocarpic fruits.

Fruit False Fruit (Fruit develops other than ovary) Apple, Cashew

True Fruit (Fruit develops from ovary) Mango, Neem

Edible food

Epicarp Mesocarp Seed Endocarp Mango

Pedicel

Pericarp Core (ovary) Coconut

Cashew nut (False fruit)

Seeds Apple

Cashew

Fig. 6.18 Fruits

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Before Fertilisation

After Fertilisation

1) Calyx, Corolla, Androecium, style stigma

Wither

2) Ovary

Fruit

3) Ovule

Seed

4) Integuments

Seed coats

5) Outer integument

Testa (outer seed coat)

6) Inner integument

Tegmen (inner seed coat)

7) Micropyle

Micropyle (seed pore)

8) Funicle

Stalk of seed

9) Nucellus

Consumed (if persistent, is called perisperm)

10) Egg cell

Zygote (oospore)

11) Synergids and antipodals

Disintegrate and disappear

12) Hilum

Scar of the seed Table 6.1 Transformation of parts of a flower

6.7 GERMINATION OF SEEDS Seed germination is the process through which a new plant emerges from a seed. Once the seed has formed, it enters a dormant state, awaiting suitable conditions for germination. When provided with adequate water and temperature, germination begins, leading to the development of a seedling.

Initially, the seedling relies on nutrients from the seed until it matures enough to produce its food through photosynthesis.

There are two primary types of seed germination: 6.7.1 Epigeal germination In this type, the cotyledons emerge above the soil surface. The cotyledons turn green and function like leaves to conduct photosynthesis. Examples include beans, castor, onions, and papaya.

6.7.2 Hypogeal germination In this type, the cotyledons remain below the soil surface and do not contribute to photosynthesis.

Examples include peas and maize.

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1. Epigeal (Bean)

Epicotyl Cotyledon

Cotyledon

Hypocotyl

Hypocotyl

2. Hypogeal (Pea) Epicotyl Hypocotyl Cotyledon

Root Seed Radicle 1

2

Seed coat 3

Hypocotyl 4

Seed

5

Radicle 1

2

Seed coat 3

Root 4

5

Hypocotyl

(1) Epigeal seed germination (2) Hypogeal seed germination Fig. 6.19 Germination of seeds

QUICK REVIEW • Reproduction is vital for the continuity of plant species, involving both sexual and asexual methods.

• There are lower plants that reproduce via asexual processes such as spore formation.

• Male gametes (pollen) develop in the anther.

• Female gametes (ovules) develop in the ovary.

• Flowers are the reproductive organs in angiosperms that have essential parts, such as the stamen and carpel, and non-essential parts, such as sepals and petals.

• The male part of the plant is the stamen, which consist of the anther and the filament.

• The female parts of the plant are pistil or carpel, which consist of style, stigma, and ovary.

• Pollination is the transfer of pollen from anther to stigma. It can be by wind, insects, or other pollinating agents.

• Fertilisation occurs when a pollen grain reaches the ovule in the ovary.

• Fusion of male and female gametes forms a zygote.

• The zygote develops into an embryo within the ovule.

• The ovule transforms into a seed containing the embryo.

• The ovary develops into a fruit, protecting and aiding in seed dispersal.

• Seeds are of two types: monocot and dicot.

• Seed germination is the process through which a new plant emerges from a seed.

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WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Asexual reproduction in plants, flowers 1. The 'eyes' of the potato tuber are a. Root buds

b. Flower buds

c. Shoot buds

d. Axillary buds

c. Sucker

d. Runner

2. Vegetative propagation in mint occurs by a. Stolon

b. Rhizome

3. What aspects do biologists consider flowers to be objects of? a. Morphological marvels

b. Embryological marvels

c. Sites of sexual reproduction

d. All of the above

4. Which one among the following represents the pollen grain? a. Zygote

b. Megaspore

c. Female gametophyte

d. Male gamete

5. Which of the following represents the whorl of stamens in a flower? a. Gynoecium

b. Androecium

c. Calyx

d. Corolla

6. Which of the following represents the whorl of the carpel in a flower? a. Gynoecium

b. Androecium

c. Calyx

d. Corolla

7. What are the components or elements that constitute stamens? a. Filament

b. Style, stigma

c. Anther

8. Identify the parts A to I in this figure.

B C E D F G

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A I H

d. Both (a) & (c)

IL Foundation Series Class 8

a. A: Ovary, B: Anther, C: Filament, D: Nectariferous area, E: Sepal, F: Stigma, G: Style, H: Ovule, I: Petal b. A: Anther, B: Ovule, C: Stigma, D: Anther, E: Petal, F: Filament, G: Sepal, H: Nectariferous area, I: Ovary c. A: Ovary, B: Ovule, C: Nectariferous area, D: Sepal, E: Filament, F: Petal, G: Anther, H: Stigma, I: Style d. A: Style, B: Stigma, C: Anther, D: Petal, E: Filament, F: Sepal, G: Nectariferous area, H: Ovule, I: Ovary 9. The pollen grain is related to the embryosac as a. Male gametophyte is to the egg

b. Male gametophyte is to the female gametophyte

c. Sperm is to the egg

d. Sperm is to the female gametophyte

10. Which one is the female gamete in the embryo sac? a. Egg cell

b. Antipodal cell

c. Placenta

d. Synergids

b. Style

c. Ovary

d. None of them

c. Egg apparatus

d. None of them

11. Bulged basal part pistil is a. Stigma

12. The cells located at chalazal ends are called a. Synergids

b. Antipodals

13. The central cell a. Contains two haploid nuclei

b. Has two polar nuclei

c. Located in the centre of the embryo sac

d. All are correct

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14. Match Column I with Column II and select the correct option.

Column-I

Column-II

A. Funicle

i. Mass of cells within ovule with more food

B. Hilum

ii. The basal part of the ovule

C. Integument

iii. One or two protective layers of ovule

D. Chalaza

iv. The region where the body of the ovule fuses with funicle

E. Nucleus

v. Stalk of ovule

a. A-i, B-ii, C-iii, D-iv, E-v

b. A-v, B-iv, C-iii, D-ii, E-i

c. A-iv, B-ii, C-i, D-iii, E-v

d. A-i, B-iii, C-v, D-ii, E-iv

15. Identify A to E in this figure.

E

D C B A

a. A: Synergids, B: Egg, C: Central cell, D: Polar nuclei, E: Antipodals b. A: Antipodals, B: Synergids, C: Central cell, D: Egg, E: Polar nuclei c. A: Synergids, B: Central cell, C: Polar nuclei, D: Anrtipodals, E: Egg d. A: Egg, B: Polar nuclei, C: Antipodals, D: Central cell, E: Synergids II. Pollination and its types

1. When the pollen of a flower is transferred to the stigma of another flower of the same plant, the pollination is referred to as:

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a. Autogamy

b. Self-pollination

c. Cross-pollination

d. None of these

IL Foundation Series Class 8

2. Pollination by snails and slugs is known as a. Ornithophilous

b. Chiropterophilous

c. Entomophilous

d. Melacophilous

3. Chiropterophily means a. Pollination by snails

b. Pollination by bats

c. Pollination by wind

d. Pollination by insects

4. If the pollen of a flower falls on the stigma of another flower belonging to the same plant, it is a. Ecologically cross-pollination b. Genetically and ecologically cross-pollination c. Genetically self-pollination and ecologically cross-pollination d. None of these 5. Statement-I: Insects visit flowers to gather honey.

Statement-II: The attraction of flowers prevents the insects from damaging other parts of the plant. a. Both statements are true b. Both statements are false c. Statement-I is true, Statement-II is false d. Statement-I is false, Statement-II is true III. Double fertilisation

1. Food material in the exalbuminous seed is mainly stored in a. Nucellus

b. Testa

c. Endosperm

d. Embryo

2. The total number of nuclei involved in double fertilisation in angiosperms is a. Two

b. Three

c. Four

d. Five

3. Which one forms the endosperm? a. Antipodals

b. Synergids

c. Secondary nucleus

d. Oosphere 147

REPRODUCTION IN PLANTS

4. Commonly in a mature fertilised ovule n, 2n and 3n condition are respectively found in a. Antipodals, synergids, and integuments

b. Egg, nucellus, and endosperm

c. Egg, antipodals, and nucellus

d. Synergids, embryo, and endosperm

5. The fusion of one male gamete with the egg cell and the fusion of another male gamete with a secondary nucleus is called a. Fertilisation

b. Double fertilisation

c. Triple fertilisation

d. Karyogamy

6. Double fertilisation involves a. Fertilisation of the egg by two male gametes b. Fertilisation of two eggs in the same embryo sac by two sperms brought by one pollen tube c. Fertilisation of the egg and the central cell by two sperms brought by different pollen tubes d. Fertilisation of the egg and the central cell by two sperms brought by the same pollen tube IV. Post-fertilisation events and seed germination

1. The formation of fruits without fertilisation is known as a. Parthenocarpy

b. Parthenogenesis

c. Polyembryony

d. Polygamy

2. Parthenocarpy is not desirable in a. Tomato

b. Pomegranate

c. Banana

d. Potato

3. Testa of seed is produced from a. Ovary wall

b. Hilum

c. Outer integument of ovule

d. Funicle

4. Seed is a. Fertilised ovule

b. Fertilised endosperm

c. Modification of integument

d. Formed from pericarp

5. Seedless banana is

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a. Parthenocarpic fruit

b. Multiple fruit

c. Drupe fruit

d. True fruit

IL Foundation Series Class 8

6. Select the false statement. a. Hard seed coat protects the young embryo. b. Generally, seeds are the product of sexual reproduction, so they generate new genetic combinations, leading to variation. c. Seeds have better adaptive strategies for dispersal to a new habitat and help the species to colonise in other areas. d. Pollination and fertilisation in angiosperm depend on water.

7. Which of the following statements is false? a. The storage tissue of rice and other cereal grains is endosperm. b. The outermost layer of the endosperm of maize is triploid. c. The aleurone layer of maize gram is especially rich in proteins. d. The transformation of ovules into seeds and ovary into fruit does not proceed simultaneously.

8. Statement-I: A true fruit is a ripened ovule.

Statement-II: Scutellum is a cotyledon of monocot seed. a. Both statements are true b. Both statements are false c. Statement-I is true, Statement-II is false d. Statement-I is false, Statement-II is true 9. Statement-I: Embryos of monocotyledons possess only one cotyledon.

Statement-II: In the grass family, the cotyledon is called scutellum. a. Both statements are true b. Both statements are false c. Statement- I is true, Statement -II is false d. Statement-I is false, Statement-II is true

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10. Which of the following events is not involved in post-fertilisation events? a. Endosperms and embryo development

b. Maturation of ovules into seed

c. Maturation of ovary into fruit

d. Degeneration of the nucleus

11. What is the primary trigger for seed germination? a. Light

b. Temperature

c. Water

d. Soil nutrients

12. Which part of the seed absorbs water during germination? a. Cotyledon

b. Epicotyl

c. Radicle

d. Plumule

13. What term describes the emergence of the seedling above the soil surface? a. Emergence

b. Exhumation

c. Hypogeal germination

d. Epigeal germination

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER [AIPMT 2015]

1. In ginger, vegetative propagation occurs through: a. Rhizome

b. Offsets

c. Bulbils

2. The product of sexual reproduction generally generates

d. Runners [NEET 2013]

a. Longer viability of seeds b. Prolonged dormancy c. New genetic combination leading to variation d. Large biomass 3. Which of the following parts represents the whorl of petals in a flower? a. Gynoecium

b. Androecium

c. Calyx

d. Corolla

4. Which of the following represents the whorl of sepals in a flower? a. Androecium

b. Style, stigma

c. Calyx

d. Corolla

5. Which is the most logical sequence with reference to the life cycle of angiosperms? a. Germination, endosperm formation, seed dispersal, double fertilisation b. Cleavage, fertilisation, grafting, fruit formation c. Pollination, fertilisation, seed formation, germination d. Maturation, mitosis, differentiation, fertilisation 150

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6. The egg apparatus of angiosperm comprises a. An egg cell and two antipodals

b. An egg cell and two synergids

c. An egg cell and two polar nuclei

d. An egg cell and the central cell

7. The elongated slender part of the pistil is a. Stigma

b. Style

c. Ovary

d. None of them

8. Which of the following components makes up the egg apparatus? a. Two synergids

b. Two antipodal

c. Egg cell

d. Both (a) and (c)

9. What are A, B, C, and D in this figure?

A B

C D

a. A: Thalamus, B: Style, C: Ovary, D: Stigma b. A: Style, B: Ovary, C: Stigma, D: Thalamus c. A: Stigma, B: Style, C: Ovary, D: Thalamus d. A: Ovary, B Stigma, C: Thalamus, D: Style 10. The most common abiotic pollinating agent for plants is a. Anemophily

b. Hydrophily

c. Pollination by bees

d. Pollination by ants

11. What is the term for the transfer of pollen from one flower of the same plant to another? a. Cross-pollination

b. Self-pollination

c. Wind pollination

d. Animal pollination

12. What is the role of the stigma in pollination? a. Producing pollen

b. Receiving pollen

c. Nourishing the ovule

d. Attracting pollinators

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13. What is the purpose of the colourful petals in the flower? a. Attracting pollinators

b. Protecting the ovary

c. Storing nutrients

d. Enhancing photosynthesis

14. Wind pollination is common in a. Legumes

b. Lilies

c. Grasses

d. Orchids

15. In which type of pollination does water play a significant role? a. Entomophily

b. Anemophily

c. Hydrophily

d. Zoophily

16. What is the term for the transfer of pollen from anther to stigma in the same flower? a. Cross-pollination

b. Self-pollination

c. Cross-fertilisation

d. Self-fertilisation

17. In entomophily, pollination occurs through: a. Wind

b. Insects

c. Water

d. Birds

18. Regarding cross-pollination, which of the following statements is incorrect? a. Plants use two abiotic and one biotic agent. b. The majority of plants use abiotic agents for pollination. c. Production of enormous amounts of pollen grains is concerned with compensating uncertainty and loss of pollens. d. Pollination by wind is more common among abiotic pollinations.

19. The role of double fertilisation in angiosperms is to produce a. Cotyledons

b. Endocarp

c. Endosperm

d. Hormones

20. The fusion of male gamete with polar nuclei in the embryo sac is known as a. Double fertilisation

b. Embryogenic

c. Pollination

d. Triple fusion

21. In a fertilised ovule, n, 2n, and 3n conditions occur respectively in a. Antipodals, egg, and endosperm

b. Egg, nucellus, and endosperm

c. Endosperm, nucellus, and egg

d. Antipodals, synergids, and integuments

22. Endosperm is formed during double fertilisation by

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a. Two polar nuclei and one male gamete

b. One polar nuclei and one male gamete

c. Ovum and male gamete

d. Two polar nuclei and two male gametes

IL Foundation Series Class 8

23. Orchid seeds are a. Light and dry

b. Small and sticky

c. Large and heavy

d. Dry and heavy

24. The wheat grain has an embryo with one large shield-shaped cotyledon known as a. Scutellum

b. Coleoptile

c. Epiblast

d. Coleorhiza

25. Scutellum is a. The protective covering of the monocot root

b. The protective covering of the monocot shoot

c. The leftover cotyledon in the monocots

d. The coleoptile of the monocot stem

26. Which of the following statements is not correct? a. As the seed matures, its water content is reduced, and seeds become relatively dry (10% --15% moisture by mass). b. The seed dormancy is the internal or innate inhibition of the generation of normal viable seeds. c. Embryo in dormant seed shows a higher rate of general metabolic rate. d. Because of dormancy, seeds remain viable for a longer period and can be stored.

27. Seeds are called products of sexual reproduction because they a. Give rise to new plants

b. Are formed by the fusion of gametes

c. Can be stored for a longer time

d. Are formed by the fusion of pollen tubes

28. Statement-I: Parthenocarpic fruits are seedless.

Statement-II: Parthenocarpic fruits develop without fertilisation. a. Both statements are true b. Both statements are false c. Statement-I is true, Statement-II is false d. Statement-I is false, Statement-II is true 29. A small flap-like outgrowth considered a second cotyledon seen in a few monocot embryos is called a. Scutellum

b. Epiblast

c. Coleoptile

d. Epicotyl

30. Which environmental factor is crucial for breaking seed dormancy and initiating germination? a. Humidity

b. Light intensity

c. Oxygen concentration

d. Water availability 153

REPRODUCTION IN PLANTS

31. What is the purpose of the seed coat during germination? a. Nutrient storage

b. Protection

c. Photosynthesis

d. Water absorption

32. Which hormone is often associated with promoting seed germination? a. Auxin

b. Gibberellin

c. Ethylene

d. Cytokinins

33. What is the first visible structure during seed germination? a. Root

b. Shoot

c. Cotyledon

d. Hypocotyl

34. In which direction does the radicle grow during seed germination? a. Towards light

b. Away from gravity

c. Towards gravity

d. Laterally [AIPMT 2011]

35. Which of the following pollinations is autogamous? a. Geitonogamy

b. Xenogamy

c. Chasmogamy

d. Cleistogamy [AIPMT 2006]

36. Egg apparatus consists of a. Egg and two synergids

b. Egg and antipodal cells

c. Egg and central cell

d. Egg and one synergid

37. Double fertilisation is:

[NEET 2018]

a. Fusion of two male gametes of a pollen tube with two different eggs b. Fusion of one male gamete with two polar nuclei c. Fusion of two male gametes with one egg d. Syngamy and triple fusion 38. What is the fate of the male gametes discharged in the synergid? a. One fuses with the egg, and the other(s) degenerate(s) in the synergid. b. All fuse with the egg. c. One fuse with the egg, and the other(s) fuse(s) with synergid nucellus. d. One fuses with the egg, and the other fuses with central cell nuclei.

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[NEET 2019]

7

REACHING THE AGE OF ADOLESCENCE

7.1 INTRODUCTION The transitional stage of human development, during which a juvenile matures into an adult, is known as adolescence. It is a stage of psychological and social transition from childhood to maturity, during which time children undergo more subtle bodily changes.

Adolescence is defined by the World Health Organization (WHO) as the age between 10 and 19 years. This stage of human development, which falls between childhood and adulthood during adolescence, is known as the 'child-to-adult transition' and is marked by a variety of physical and psychological changes related to the reproductive system's development. The adolescent body experiences various transformations. Puberty, or the start of the body's transition to adulthood, is indicated by several changes.

7.2 CHANGES AT PUBERTY The stage of life known as puberty is when a boy or girl who is sexually immature matures and can reproduce. It occurs when males are 13 to 16 years old, and females are 11 to 13 years old. This time frame differs from person to person. When a teenager reaches reproductive maturity, puberty comes to an end. When males reach puberty, their testes begin to produce sperm and release the male hormone testosterone. The female ovaries begin to release eggs and produce progesterone and estrogen, the female hormones.

Boys and girls go through similar changes when they reach puberty. They are as follows: 1. Increase in height 2. Changes in body shape 3. Voice change 4. Increased activity of sweat and sebaceous glands 5. Maturation of sex organs 6. Mental, intellectual, and emotional maturity 7. Development of secondary sexual characters

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7.2.1 Increase in height During puberty, there is a sudden increase in height due to the growth of the long bones in the legs and arms. Initially, girls grow faster than boys. At the age of 18, both boys and girls reach their maximum height. The rate of growth varies in different sexes (i.e., in boys and girls) and also in different individuals.

7.2.2 Change in body shape During puberty, boys and girls begin to look different as their bodies go through specific changes.

• For boys, their muscles grow and become more noticeable. Their shoulders become broader, and their chest widens. This makes their body appear more muscular.

• In girls, the area below their waist becomes wider, and they develop breasts, which grow and increase in size. Inside these breasts, special glands called mammary glands develop. These glands are responsible for producing milk.

7.2.3 Voice change During puberty, a part of the throat, called the voice box or larynx, starts to grow.

• In boys, it becomes more noticeable and sticks out, creating what is commonly known as an Adam's apple.

• In girls, the larynx is smaller and not easily seen from the outside. Boys develop a deeper and sometimes raspy voice, while girls develop a higher, sweeter voice.

Sometimes, in some boys going through puberty, the muscles in the growing voice box may not fully cooperate, causing the voice to become hoarse and rough. However, this is only temporary, and the voice eventually becomes normal after some time.

Larynx Adam’s apple

Fig. 7.1 Adam’s apple

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7.2.4 Increased activity of sweat and sebaceous glands During puberty, the sweat glands and sebaceous glands on the face become more active. This can lead to the appearance of acne and pimples on the face. To avoid this issue, it is helpful to reduce the consumption of fatty foods and keep the face clean by washing it properly and frequently.

Sweat glands are responsible for regulating body temperature and getting rid of waste by releasing water, salts such as sodium, and waste products like urea onto the skin surface. The main substances in sweat are sodium and chloride. Sweat itself doesn't have an odour, but it can develop a smell when it mixes with bacteria present on our skin.

7.2.5 Maturation of sex organs During puberty, boys experience the full development of their male sex organs, such as the testes and penis. In girls, their ovaries start to grow, mature, and release eggs, which marks the beginning of their menstrual cycle.

7.2.6 Reaching mental, intellectual, and emotional maturity Adolescence is a stage in which changes happen in the brain and thinking ability. The nature of adolescence will differ as follows.

• When a person goes through adolescence, their way of thinking changes.

• Adolescents desire to become more independent.

• The mental and physical changes happening during adolescence can cause shifts in mood.

• They learn to identify and handle their emotions.

• Adolescents experience intellectual growth and spend a lot of time thinking. They become better at understanding other people's perspectives, exploring ideas, developing concepts, and improving their memory skills.

• As they mature, boys and girls become interested in the opposite sex.

• Sometimes, adolescents may feel unsure, self-conscious, or insecure while trying to adjust to the changes in their body and mind. This is a natural part of growing up that everyone goes through.

7.3 SECONDARY SEXUAL CHARACTERS Secondary sexual characteristics are specific traits that differentiate males from females. In males, these characteristics include an increase in height, a noticeable Adam's apple, a deeper voice, the growth of facial hair like beards and moustaches, as well as the development of pubic hair and hair on the chest, thighs, and armpits.

In females, the secondary sexual characteristics include an increase in height, although generally shorter than males, less facial hair, the growth of pubic hair and hair in the armpits, a 157

REACHING THEAND AGESALTS OF ADOLESCENCE ACIDS, BASES,

higher-pitched voice, and the development of breasts. Other features include a widening of the pelvis, the accumulation of fat around the hips, and smoother skin texture.

7.4 ROLE OF HORMONES IN INITIATING REPRODUCTIVE FUNCTION During adolescence, the development of secondary sexual characteristics is influenced by hormones.

These hormones are produced by the testes in boys and the ovaries in girls. In boys, the testes produce a hormone called testosterone, which brings about changes in their bodies. In girls, the ovaries produce a hormone called estrogen, which causes changes in their bodies.

The production of these hormones is controlled by the pituitary gland, which is often called the 'master endocrine gland'. The pituitary gland is located at the base of the brain and releases various hormones. The hormone released by the pituitary gland stimulates the testes in boys and the ovaries in girls to produce testosterone or estrogen, respectively. These hormones then travel to specific areas of the body, where they induce the development of secondary sexual characteristics.

7.5 REPRODUCTIVE PHASE OF LIFE IN HUMANS In females, the reproductive age starts during puberty and lasts until around 45 to 50 years of age.

Unlike males who continuously produce sperm, females go through a monthly cycle where one egg is released from the ovary, called ovulation. This cycle repeats every 28 to 30 days. During this cycle, the lining of the uterus becomes thicker to prepare for a fertilised egg. If the egg is fertilised by a sperm, it starts to develop, leading to pregnancy. However, if fertilisation doesn't occur, the lining of the uterus breaks down and is discharged from the vagina along with some blood and mucus. This is called menstruation or having a period that lasts for about 3 to 7 days. These cyclic changes in the ovaries and uterus, happening approximately every 28 days, make up the menstrual cycle. The first menstrual period is called menarche and occurs during puberty. When a woman reaches the age of around 45 to 50, the menstrual cycle stops, which is called menopause.

7.6 HOW IS THE SEX OF A BABY DETERMINED? The sex of a baby is determined by small structures called chromosomes found inside the cells.

Humans have 23 pairs of chromosomes, making a total of 46 chromosomes in each cell. Among these, two chromosomes are responsible for determining the sex of a person, and they are called sex chromosomes. They are named X and Y. Males have one X and one Y chromosome, while females have two X chromosomes. The egg and sperm, also called gametes, carry only one set of chromosomes, so they have 23 chromosomes each. Half of the male gametes, which are called sperm, carry an X chromosome, and the other half carry a Y chromosome. All female gametes, which 158

IL Foundation Series Class 8

are called eggs, carry only an X chromosome. When an egg with an X chromosome is fertilised by a sperm with an X chromosome, the resulting zygote (developing baby) will have two X chromosomes and will develop into a female child. When an egg with an X chromosome is fertilised by a sperm with a Y chromosome, the resulting zygote will have an X and a Y chromosome and will develop into a male child.

Sex

Chromosomes

Male

X, Y

Female

X, X

Table 7.1 Chromosomes in different sexes

7.7

HORMONES OTHER THAN SEX HORMONES (ENDOCRINE GLANDS)

Hypothalamus Pituitary gland Parathyroid gland Thyroid gland Thymus

Adrenal gland Pancreas Testis male Ovary (Female)

Fig. 7.2 Endocrine gland

Hormones are important for our growth and development. They are secreted by endocrine glands and released directly into our bloodstream. Unlike other glands, these endocrine glands do not have ducts, and their secretions go straight into the blood. That's why they are also known as ductless glands.

However, some glands, like sweat glands, salivary glands, and oil glands, release their secretions through ducts instead of directly into the blood.

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In the human body, there are important glands that make up the endocrine system. These include the hypothalamus, pituitary gland, thyroid gland, parathyroid gland, adrenal glands, pineal body, and reproductive organs (testes and ovaries). Each of these glands produces different hormones that have specific functions in our body.

7.7.1 Thyroid gland The thyroid gland is responsible for making a hormone called thyroxine. This hormone helps control how the body uses energy. When there is not enough thyroxine in the body, it can cause a condition called goitre, in which the thyroid gland becomes swollen.

7.7.2 Pancreas The pancreas is an organ that produces a hormone called insulin. Insulin helps control the amount of sugar in our blood. When there isn't enough insulin in the body, it can cause a disease called diabetes, in which the sugar level in the blood becomes too high.

7.7.3 Adrenal gland The adrenal gland is a gland that produces hormones to help our body function properly. One of the hormones it produces is called aldosterone, which helps keep the right balance of salt in our blood.

The adrenal gland also makes another hormone called adrenaline, which helps our body deal with stressful situations when we feel angry, embarrassed, or worried.

7.7.4 Pituitary gland The pituitary gland is an important gland in our body that makes different hormones. It controls things like how much water is in our body, our growth, and the release of other hormones. One of the hormones it makes is called growth hormone (GH), which helps us grow and develop. It also makes hormones like thyroid stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH).

Because it has an important role in controlling other glands in our body, it is often called the "master gland."

7.7.5 Testes The testes are organs in the male body that produce a hormone called testosterone. Testosterone helps in the growth and development of male secondary sexual characteristics. These characteristics include things like facial and body hair, a deeper voice, and muscle growth.

7.7.6 Ovaries The ovaries are organs in the female body that produce different hormones. These hormones include estrogen, progesterone, relaxin, and inhibin. Estrogen helps in the growth and development of female secondary sexual characteristics. These characteristics include things like breasts and wider hips. Progesterone helps in the growth of the uterus, which is important for pregnancy.

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7.8

ROLE OF HORMONES IN COMPLETING THE LIFE HISTORY OF INSECTS AND FROGS

In most animals, including humans, young ones grow directly into adults. However, some animals go through a process called metamorphosis, in which they change a lot before becoming adults. Metamorphosis is a series of changes that happen to these animals. Insects experience metamorphosis, or change, which is controlled by special chemicals called hormones. These hormones play an important role in their development and transformation. Similarly, in frogs, metamorphosis is also a part of their growth process. It is controlled by a hormone called thyroxine, which is produced by a gland in the body called the thyroid. To produce thyroxine, frogs need a certain substance called iodine, which is found in water. If the water in which the tadpoles (young frogs) are growing does not have enough iodine, they are unable to complete their metamorphosis and become adult frogs.

7.9 REPRODUCTIVE HEALTH Health means being completely physically, mentally, and socially well. You can say someone is healthy when they don't have any diseases, anxiety, or tension. To stay healthy, you need to eat a balanced diet, keep yourself clean, and exercise. During the teenage years, these things become even more important because your body is growing. If you get sick during this time, it can affect your growth.

7.9.1 Nutrition During adolescence, your body is growing fast, so you need to eat a balanced diet. This means eating different types of food that give you all the nutrients you need, like proteins, carbohydrates, fats, and vitamins.

7.9.2 Hygiene It is important to keep yourself clean, especially during the teenage years when sweat glands are more active. Taking a bath every day is important to stay clean and prevent infections. Girls should be extra careful about cleanliness during their menstrual period to avoid reproductive tract infections.

7.9.3 Physical exercise Taking walks and exercising is important for teenagers because it helps keep the body fit and healthy.

7.9.4 Saying no to drugs During adolescence, it's easy to feel unsure and influenced by others. It's important to avoid using drugs and alcohol because they are addictive and can harm your health and happiness in the long run.

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QUICK REVIEW • WHO defines adolescence as ages 10-19, marking the transition from childhood to adulthood.

• Puberty, occurring between 13-16 for boys and 11-13 for girls, involves physical and psychological changes.

• Both genders experience height increase, body shape changes, voice alterations, and increased gland activity.

• Sex organs mature, and secondary sexual characteristics develop.

• Adam's apple, deeper voice, facial, and body hair develop in males.

• Breast development, wider hips, and higher pitched voice develop in females.

• Hormones (testosterone in males, estrogen in females) control changes; the pituitary gland is crucial.

• Female reproductive age starts in puberty and lasts until menopause (45-50 years).

• The menstrual cycle involves ovulation, thickening of the uterus lining, and menstruation.

• Sex is determined by X and Y chromosomes; males have one of each, and females have two X. • Fertilisation outcomes determine the baby's sex (XX for females, XY for males).

• Endocrine glands (e.g., hypothalamus, pituitary, thyroid, adrenal, reproductive organs) release hormones.

• Hormones regulate growth, metabolism, sugar levels, stress response, and reproductive functions.

• Metamorphosis, in some animals, is controlled by hormones.

• Frogs undergo metamorphosis with thyroxine, requiring iodine from water.

WORKSHEET - 1 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER I. Changes at puberty 1. Which of the following is not a physical change that occurs during puberty in girls?

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a. Increase in height

b. Widening of hips

c. Beginning of menstruation

d. Development of oil and sweat glands

IL Foundation Series Class 8

2. Which statement is true about the growth patterns of boys and girls during puberty? a. Boys reach puberty at an earlier age than girls b. At about the age of 12, girls grow more rapidly than boys c. Between the ages of 4 and 12, girls grow faster than boys d. All of the above 3. What is the reason for girls growing faster than boys around the age of 12? a. Girls reach puberty earlier than boys b. Boys reach puberty earlier than girls c. Girls usually have a higher protein intake at the age of 12 d. Boys typically consume less food 4. Maximum height is reached a. At the end of adulthood

b. Before puberty

c. At the beginning of old age

d. At the beginning of adulthood

5. Which of the following changes generally occur during puberty in females? i. Ovulation ii. Enlargement of breasts iii. Broadening of hips a. (i) and (ii)

b. (ii) and (iii)

c. (i) and (iii)

d. (i), (ii), and (iii)

II. Secondary sexual characters

1. Which of the following is a secondary sexual characteristic that develops in boys during puberty? a. Growth of facial hair

b. Development of bones and muscles

c. Growth of pubic hair

d. All of the above

2. When do secondary sexual characteristics typically develop in girls? a. Between 9 to 11 years of age

b. Between 11 to 13 years of age

c. Between 15 to 18 years of age

d. Between 19 to 21 years of age

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REACHING THEAND AGESALTS OF ADOLESCENCE ACIDS, BASES,

3. What is Adam's apple? a. Mammary glands

b. Apple of Adam

c. An enlarged larynx

d. Thyroid gland

4. Which of the following is a secondary sexual characteristic in females? a. Adam's apple b. Increased muscle mass c. Widening of hips d. Enlargement of the Adam's apple III. Role of hormones in initiating reproductive function

1. What hormone is secreted by the testes during puberty? a. Thyroxine

b. Testosterone

c. Estrogen

d. Iodine

2. A hormone secreted only in the female body is a. Estrogen

b. Testosterone

c. Adrenaline

d. Thyroxine

3. The pituitary gland is found in a. Trachea

b. Gonad

c. Pancreas

d. Brain

IV. Reproductive phase of life in humans

1. In which of the following scenarios does menstruation not occur? a. When the ovum is released

b. After giving birth to a child

c. When hormones are produced

d. When fertilisation occurs

2. What changes occur during menopause? i. No more periods ii. No more development of new egg cells iii. The ovaries stop making estrogen

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a. (i) and (ii)

b. (ii) only

c. (i), (ii), and (iii)

d. (iii) only

IL Foundation Series Class 8

3. Which of the following is responsible for the changes that occur during puberty in females? a. Sex cells

b. Enzymes

c. Nutrients

d. Sex hormones

V. How is the sex of a baby determined?

1. How is the sex of a child determined? a. By the father's chromosomes

b. By the mother's chromosomes

c. By the Rh factor of the parents

d. By the blood group of the father

2. What are the chromosomes that determine the sex of an individual called? a. Autosomes

b. Allosomes

c. Plasmid

d. Giant chromosomes

3. What is the determining factor for the sex of a baby? a. The mother's diet during pregnancy b. The father's diet before conception c. A combination of genetic contributions from both parents d. The baby's position in the womb 4. Which of the following chromosomes is responsible for determining a baby's sex? a. N chromosome

b. Y chromosome

c. Z chromosome

d. W chromosome

5. In humans, if the father contributes a Y chromosome and the mother contributes an X chromosome, the baby's sex will be: a. Male

b. Female

c. Undetermined

d. Twins

VI. Hormones other than sex hormones (endocrine glands)

1. What are the glands that have ducts for releasing their secretions called? a. Endocrine glands

b. Exocrine glands

c. Heterocrine glands

d. Merocrine glands

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REACHING THEAND AGESALTS OF ADOLESCENCE ACIDS, BASES,

2. How are hormones transported from their place of origin to their target location? i. Through ducts ii. Through the blood iii. Through nerves a. Only (i)

b. Only (ii)

c. Only (iii)

d. (i), (ii), and (iii)

3. Which of the following is not a gland of the endocrine system? a. Adrenal

b. Thyroid

c. Penis

d. Ovary

4. Which gland is responsible for producing the growth hormone that plays a vital role in regulating growth and development? a. Thyroid gland

b. Pancreas

c. Adrenal gland

d. Pituitary gland

5. Which gland is responsible for producing insulin, a hormone involved in regulating blood sugar levels? a. Pancreas

b. Thyroid gland

c. Adrenal gland

d. Pituitary gland

VII. Reproductive health

1. Why is a diet rich in proteins important during puberty? a. To protect the body b. To support the formation of new cells for growth c. To promote the formation of strong bones and teeth d. To protect from diseases 2. What can happen if you don't take care of personal hygiene during your periods? a. Infections in the reproductive area b. Stomach pains c. Difficulty having children d. Getting pregnant

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IL Foundation Series Class 8

3. Which of the following is an example of a sexually transmitted infection (STI)? a. Ovarian cyst

b. Endometriosis

c. Syphilis

d. Polycystic ovary syndrome (PCOS)

WORKSHEET - 2 MULTIPLE CHOICE QUESTIONS WITH SINGLE CORRECT ANSWER 1. What is the term used to describe the release of a mature egg from the ovary around the 14th day of the menstrual cycle? a. Attraction

b. Menstruation

c. Fertilisation

d. Ovulation

2. Which of the following statements about the menstrual cycle is true? i. An unfertilised egg is released during menstruation ii. The lining of the uterus becomes thin immediately after menstruation iii. The fertile period is the period right after menstruation a. (i) and (ii)

b. (ii) and (iii)

c. (i) and (iii)

d. (i), (ii), and (iii)

3. Menstruation, the shedding of the uterine lining, is primarily triggered by the sudden decline in hormones that leads to the breakdown of the endometrial tissue. a. Reduction in cholecystokinin b. Reduction in progesterone c. Increase in adrenaline d. Increase in prolactin 4. Which one of the following events is correctly matched with the period in a normal menstrual cycle? a. Release of egg: 5th day b. Endometrium regenerates: 5 - 10 days c. Endometrium secretes nutrients for implantation: 11 - 18 days d. Rise in progesterone level: 1 - 15 days

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REACHING THEAND AGESALTS OF ADOLESCENCE ACIDS, BASES,

5. The deepening of the voice observed in males during puberty is a result of which anatomical change? a. Enlargement of the vocal cords

b. Widening of the nasal passages

c. Increase in lung capacity

d. Changes in the external nasal nares

6. Which hormone is primarily responsible for the development of secondary sexual characteristics in males? a. Estrogen

b. Testosterone

c. Progesterone

d. Follicle-stimulating hormone (FSH)

7. During adolescence, what is the primary endocrine hormone responsible for the significant growth spurt characterised by a rapid increase in height observed in males? a. Estrogen

b. Progesterone

c. Follicle-stimulating hormone (FSH)

d. Growth hormone

8. Rahul is about to face a challenging exam. During the first five minutes before the exam, he experiences restlessness, sweating, an increased heart rate, and respiration. Which group of hormones is primarily responsible for these physiological responses in Rahul's body? a. Estrogen and progesterone

b. Oxytocin and vasopressin

c. Adrenaline and non-adrenaline

d. Insulin and glucagons

9. Read the assertion and reason carefully and choose the correct option.

Assertion (A): The changes which occur during adolescence are controlled by hormones.

Reason (R): Hormones are chemical substances secreted from endocrine glands. a. Both assertion (A) and reason (R) are true, and reason (R) is the correct explanation of assertion (A) b. Both assertion (A) and reason (R) are true, and reason(R) is not the correct explanation of assertion (A) c. Assertion (A) is true, but reason (R) is false d. Both assertion (A) and reason (R) are false 10. Larynx is commonly known as:

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a. Noise box

b. Voice box

c. Magic box

d. Sound box

IL Foundation Series Class 8

11. Which of the following statements about the menstrual cycle are true? i. The body releases an unfertilised egg during menstruation. ii. The lining of the uterus becomes thin right after menstruation. iii. The fertile period is right after menstruation. a. (i) and (ii)

b. (ii) and (iii)

c. (i) and (iii)

d. (i), (ii), and (iii)

12. What happens when there is not enough insulin produced in the body? a. Myxoedema

b. Diabetes

c. Addison's disease

d. Cretinism

13. What causes the incomplete development of male secondary sexual characteristics? a. Estrogen

b. Adrenaline

c. Progesterone

d. Testosterone

14. What are the hormones produced by the pituitary gland? a. Hormones for growth b. Hormones that help absorb water c. Hormones that stimulate other glands in the body d. All of these 15. Arjun was experiencing weight loss despite eating regularly and feeling constantly thirsty.

The doctor found a high concentration of glucose in his urine. What is the disease that Arjun is likely suffering from? a. Swelling in the neck (goitre)

b. Cancer

c. Diabetes mellitus

d. Damage to the liver (cirrhosis of liver)

16. Assertion (A): Hormones have specific actions and chemical properties.

Reason (R): Hormones, like enzymes, are made of proteins and act as messengers in the body. a. Both assertion (A) and reason (R) are true, and reason (R) is the correct explanation of assertion (A). b. Both assertion (A) and reason (R) are true, and reason(R) is not the correct explanation of assertion (A). c. Assertion (A) is true, but reason (R) is false. d. Both assertion (A) and reason (R) are false 169

REACHING THEAND AGESALTS OF ADOLESCENCE ACIDS, BASES,

17. Assertion (A): The pituitary gland is known as the master gland.

Reason (R): The pituitary gland controls and influences the functioning of other glands in the body. a. Both assertion (A) and reason (R) are true, and reason (R) is the correct explanation of assertion (A) b. Both assertion (A) and reason (R) are true, and reason(R) is not the correct explanation of assertion (A) c. Assertion (A) is true, but reason (R) is false d. Both assertion (A) and reason (R) are false 18. What is the term for the transformation from a tadpole to an adult frog? a. Metamorphosis

b. Hatching

c. Mating

d. Reproduction

19. During which stage of the frog's life cycle is thyroxine production at its highest? a. Tadpole stage

b. Adult frog stage

c. Metamorphosis stage

d. Egg stage

20. Which gland is responsible for the production of thyroxine in frogs?

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a. Thyroid gland

b. Adrenal gland

c. Pituitary gland

d. Pancreas

ANSWER KEY 1: CROP PRODUCTION AND MANAGEMENT Worksheet 1 I. Agricultural practices 1. a 2. a 3. d 4. a 5. c 6. a II. Sowing 1. c 2. a 3. c III. Manure and fertilisers 1. c 2. a 3. c 4. a IV. Irrigation 1. b 2. b 3. d V. Preparation of soil 1. c 2. c 3. c VI. Protection from weeds 1. d VII. Storage 1. a 2. b VIII. Animal husbandry 1. a 2. c 3. d 4. a Worksheet 2 1. b 2. a 6. c 7. d 11. d 12. c 16. a 17. c 21. a 22. c

3. d 8. c 13. d 18. c 23. c

4. c 9. c 14. c 19. a

5. a 10. b 15. c 20. d

2: MICROORGANISMS: FRIEND AND FOE Worksheet 1 I. Microorganisms and us 1. d 2. a 3. b 4. a 5. c 6. c 7. b 8. c 9. c 10. a 11. d 12. a 13. d 14. c 15. b 17. d 18. b 19. b 20. a 16. a 22. d 23. b 24. d 21. d II. Harmful microorganisms 3. a 1. a 2. b 4. c 5. d 6. b 7. a 8. a 9. b III. Food spoilage and preservation 1. c 2. c 3. c 4. d 5. a 6. b IV. Nitrogen cycle 1. d 2. b 3. a 4. d 5. c 6. d 7. d

Worksheet 2 1. c 2. c 6. b 7. c 11. d 12. d 16. c 17. b 21. b 22. a 26. c 27. b 31. a 32. c

3. c 8. b 13. c 18. a 23. c 28. b 33. c

4. c 9. b 14. c 19. a 24. b 29. d 34. b

5. c 10. c 15. d 20. b 25. a 30. a 35. b

3: CELL – STRUCTURE AND FUNCTIONS Worksheet 1 I. Discovery of cell and cell theory 1. b 2. a 3. d 4. d 5. b 6. b 7. a II. Overview of cell 1. c 2. a 3. b 4. c III. Parts of the cell 1. d 2. a 3. a 4. b 5. d 6. c 7. b 8. d 9. b 10. d 11. c 12. a 13. c 14. d 15. b 16. c 17. a 18. d 19. b 20. a 21. d 22. a 23. c 24. a 25. c 26. a 27. b 28. d 29. c 30. d 31. c 32. b 33. c 34. d 35. b 36. a 37. a 38. c 39. a 40. c 41. b 42. d 43. a 44. b 45. d Worksheet 2 1. b 2. b 3. c 6. c 7. b 8. a 11.b 12. b 13. b 16. a 17. c 18. c 21. b 22. c 23. a 26. a 27. c

4. c 5. b 9. b 10. b 14. b 15. c 19. a 20. b 24. a 25. c

4: CONSERVATION OF PLANTS AND ANIMALS Worksheet 1 I. Conservation of plants and animals 1. d 2. d 3. c 4. a 5. c 6. a

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ANSWER KEY II. Deforestation – causes and consequences 1. c 2. a 3. d 4. a 5. b 6. c 7. d 8. d 9. d III. Reforestation 1. c 2. a 3. c IV. Conservation of forest and wildlife 1.d 2. c 3. a 4. c 5. b 6. b 7. a 8. a 9. c 10. b 11. b 12.d 13. b 14. c 15. c 16. a 17. d 18. c 19. c 20. a 21. c 22. d 23. b 24. b 25. c 26. b 27. b 28. b 29. b V. Red Data Book 1.d 2.b 3. b Worksheet 2 1. a 2. d 3. c 6. d 7. a 8. c 11. b 12. d 13. c 16. a 17. b 18. c 21. b 22. d 23. b 26. c 27.c 28. a 31. a 32. d 33. d 36. a 37.d 38. b 41. c 42. c 43. d 46. d 47. d 48. b

4. c 9. a 14. a 19. d 24. a 29. a 34.d 39. b 44. a 49. c

5. d 10. c 15. a 20. a 25. d 30. a 35. b 40. d 45. a 50. a

5: REPRODUCTION IN ANIMALS Worksheet 1 I. Introduction to reproduction in animals 1. d 2. b 3. b 4. a 5. a 6. a 7. b 8. a II. Asexual reproduction 1. c 2. c 3. d 4. d 5. a 6. c 7. a 8. d 9. a 10. c 11. c 12. a 13. b III. Story of Dolly, the clone 1. a 2. a 3. c 4. b 5. a 6. b IV. Male reproductive system 1. b 2. a 3. a 4. d 5. a 6. c 7. b 8. a 9. a V. Female reproductive system

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1. b 2. b 3. b 4. c 5. a 6. d 7. a 8. c 9. b VI. Development of embryo 1. a 2. b 3. b 4. a 5. a 6. b Worksheet 2 1. a 2. a 6. a 7. d 11. d 12. b 16. c 17. d 21. d 22. b 26. a 27. a 31. d 32. d 36. c 37. c 41. b 42. b 46. c 47. d

3. b 8. c 13. a 18. b 23. a 28. a 33. c 38. c 43. d 48. c

4. a 9. d 14. d 19. d 24. a 29. d 34. a 39. b 44. a 49. a

5. b 10. a 15. c 20. a 25. d 30. c 35. c 40. a 45. b 50. b

6: REPRODUCTION IN PLANTS Worksheet 1 I. Asexual reproduction in plants, flowers 1. d 2. c 3. d 4. d 5. b 6. a 7. d 8. d 9. b 10. a 11. c 12. b 13. d 14. b 15. a II. Pollination and its types 1. b 2. d 3. b 4. c 5. c III. Double fertilisation 1. d 2. c 3. c 4. d 5. b 6. d IV. Post-fertilisation events and seed germination 1. a 2. b 3. c 4. a 5. a 6. d 7. d 8. d 9. a 10. d 11. c 12. c 13. d Worksheet 2 1. a 2. c 6. b 7. b 11. b 12. b 16. b 17. b 21. b 22. a 26. c 27. b 31. b 32. b

3. d 8. d 13. a 18. b 23. a 28. a 33. a

4. c 9. c 14. c 19. c 24. a 29. b 34. c

5. c 10. a 15. c 20. d 25. c 30. d 35. d

ANSWER KEY 36. a

37. d

38. d

7: REACHING THE AGE OF ADOLESCENCE Worksheet 1 I. Changes at puberty 1. c 2. c 3. a 4. d 5. d II. Secondary sexual characters 1. d 2. b 3. c 4. c III. Role of hormones in initiating reproductive function 1. b 2. a 3. d IV. Reproductive phase of life in humans 1. d 2. c 3. d V. How is the sex of a baby determined?

1. a 2. b 3. c 4. b 5. a VI. Hormones other than sex hormones (endocrine glands) 1. b 2. b 3. c 4. d 5. a VII. Reproductive health 1. b 2. a 3. c Worksheet 2 1. d 2. a 6. b 7. d 11. b 12. b 16. a 17. a

3. b 8. c 13. d 18. a

4. c 9. a 14. d 19. c

5. a 10. b 15. c 20. a

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