5.5 Kingdoms can be used to classify organisms 5.6 Animals that have no skeleton

5.5

Kingdoms can be used to classify organisms

Learning intentions

By the end of this topic, you will be able to: • explain how living things have been classified into different kingdoms • describe how classification of organisms changes as new information becomes available.

Interactive 5.5 Kingdoms

multicellular consisting of two or more cells unicellular consisting of only one cell; an example is bacteria taxonomist a scientist who classi es living things into groups nucleus a membrane-bound structure in cells that contains most of the cell's genetic material cell wall a structure that provides support around the cell in some organisms, such as plants and fungi

Key ideas

• Taxonomists are scientists that classify living things. • New information that compares genetic material may change the five kingdoms. • The nature of science is to change and develop as new evidence becomes available.

Building blocks of life Kingdom Animalia

All organisms in this kingdom are multicellular. Each cell stores its genetic material in a nucleus but does not have a cell wall. Animals gain energy from other living things. We belong in this kingdom. Zoologists are the scientists who study animals. Cells are often called the building blocks of life. Think of the way bricks are used to build a house. Cells build living things in a similar way. However, there are usually many more cells in living things than bricks in a house. Any living thing with more than one cell is multicellular (Figures 1a and 1b). Many living things, such as bacteria, consist of only one cell. These are single-celled or unicellular organisms (Figure 1c). Parts of a cell Taxonomists ask three questions when they are trying to classify the cells of an organism: 1 Does the cell keep all of its genetic material (called DNA) inside a nucleus ? The nucleus protects the DNA that carries all the instructions for living and reproducing. 2 Does the cell have a cell wall around it for extra support? 3 Does the cell use sunlight to make its own nutrients (autotroph)? Plant cells can do this, DRAFT but fungi (like mushrooms) need to absorb their nutrients from other living things (heterotrophs). These three features are used to divide all living things into big groups called kingdoms.

a b c

Figure 2 Kingdom Animalia: the proboscis monkey (Nasalis larvatus)

Figure 1 a Simple animal cell, b plant cell, and c bacterial cell

Kingdom Plantae

Plants include trees, vines, bushes, ferns, mosses, weeds and grasses (Figure 3). They all gain energy by converting the energy from sunlight into food (autotrophs). They are multicellular and their cells are surrounded by a cell wall. There is a nucleus inside each cell. Botanists are the scientists who study the plant kingdom.

a

break down rubbish and wastes produced by animals (especially humans). Without bacteria, Kingdom Fungi we would be surrounded by mountains of smelly rubbish. Bacteria have been put to Kingdom Fungi includes mushrooms, toadstools, use by humans to make food, such as cheese yeasts, puffballs, moulds and truf es (Figure 4). and yoghurt (Figure 5). Microbiologists are Some fungi grow in wood and soil, and develop the scientists who study micro-organisms in from tiny spores. Fungi store their genetic Kingdoms Monera and Protista. material in a nucleus and do not make their own food. Instead, they feed on the remains of Kingdom Protista dead animals and plants. Some fungi can cause diseases, such as tinea (athlete’s foot). Mycologists There are approximately 55 000 species of are the scientists who study Kingdom Fungi. protists. Their cell structure is more complex than that of the Monera. Often, organisms that Kingdom Monera do not t into any other kingdom will belong in Protista. Protists may range in size from single Kingdom Monera is made up of the simplest celled organisms to much larger ones, such as and smallest living things. There are kelp (seaweed). They all have one feature in approximately 75 000 different organisms in common: they store their genetic material in a Kingdom Monera, and they are all unicellular nucleus. Plankton , the tiny sea creatures eaten and have a cell wall but no nucleus. Bacteria in their millions by whales, are part of this are the most common in this kingdom. Many kingdom. Amoeba , microscopic organisms people think of bacteria as harmful to humans, that change their shape to trap their food, also but this is not always true. Bacteria in the soil belong to this group (Figure 6).

Figure 3 Kingdom Plantae: the smelliest plant, the Rafflesia , is found in South-East Asia (its flower Figure 4 Kingdom Fungi: mushrooms can measure up to 90 cm across and weigh about 11 kg, and it gives off a rotten meat odour when it blossoms to attract insects). a bDRAFT

b

bacteria unicellular organisms that have a cell wall but no nucleus

plankton microscopic organisms that oat in fresh or salt water

amoeba a type of single-celled organism belonging to the Protista kingdom

Figure 5 Kingdom Monera, as seen under a microscope: Lactobacillus casei , a helpful bacteria used to make some dairy foods

Figure 6 Kingdom Protista, as seen under a microscope: amoeba

5.5 Check your learning

Retrieve

1 Identify where a plant cell stores its genetic material (DNA). 2 Name four features of Kingdom Fungi. 3 De ne the term ‘multicellular’. 4 Name an organism made up of just one cell.

Analyse

5 Contrast a protist with a bacterium. 6 Compare the cells in Kingdom Plantae with those in Kingdom Fungi. Apply

7 Discuss why the invention of the microscope was important to our understanding of living things.

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