ESTRUCTURA ORGANICA FUNCIONAL

Environment and ecosystems

Living places of animals and plants

Food relationships between plants, animals and the environment

Aims and learning objectives

• To develop knowledge of the environment and to show how animals and plants are adapted to a range of different environments

• To understand the feeding relationships between groups of organisms—food chains and food webs. • To understand that changing one part of a food web can affect the other parts.

Background information

What is an environment? An environment can be defined as the conditions that act upon an animal or a plant. It includes all the physical conditions such as the amount of water, sunlight, temperature, and type of soil. These are called the abiotic factors. An environment also includes all the populations and communities of living things within the area. These contribute to the biotic factors.

There are various kinds of environments. Not all environments have the same temperature, rainfall, or sunlight. Biologists have divided environments into at least six types. These are large areas or regions called ‘biomes’. A biome covers a large area or region of the Earth and contains many communities with many populations. The physical conditions such as the amount of rain, sunlight, temperature, and soil are similar throughout most of the biome’s territory, making it possible for certain animals and plants to live there.

The major biomes on land are: Arctic-tundra area, coniferous-evergreen area, deciduous forest, grassland or savannah, desert and tropical rain forest. These environments do not go from one extreme to another. Some environments present on the edges of two distinct areas blend together. The animals and plants that live in boundary areas are adapted to both environments. For example, ponds and woods often appear together as do grasses and trees.

Unit introduction

Display a large chart with the word ‘ecology’ printed on it. Ask the students if they know what it means. Discuss what ecology means. ‘Eco’ comes from the Greek word oikos which means household, ‘ology’ means the study of something. Together it means the study of households in nature. Nature is our environment or our surroundings. Explain that ecology is the study of animals and plants in their natural surroundings and scientists who study ecology are called ecologists.

Teaching procedure

Ask the students: where do lions and zebras live? Where do cockroaches live? Where do rabbits live? Why do

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Explain that animals have their own niche or territory in an environment. A niche is a special place to live that belongs to a population of animals. When there is a large variety of plants and animals living in a biome, such as in a jungle, there tends to be less competition for food. The great diversity allows each animal to have its own niche or territory to live in. Animals in a jungle rarely need to compete for the same food.

Adaptations

Show the students pictures of different animals and plants and discuss the special features each one has to protect itself from its enemies. Discuss the adaptive features of these organisms.

Adaptation means that a plant or an animal changes itself to fit into its environment so it can survive. What do the students think would happen if an animal or plant could not adapt to its environment? How do they think animals in zoos adapt to their environment?

Discuss the consequences if an animal or plant cannot change and adapt to its environment. Ask the students: why are there no more dinosaurs on Earth?

Explain that they could not adapt to environmental changes: plant or animal species that do not adapt, die and might become extinct. The more versatile and flexible a plant or animal is with its growth, the more likely it is to survive.

Additional activity 1

Name the animal that has the following adaptation: Animal adaptation claws hoofs shell sharp teeth horns sharp beak spines scaly skin Food chains and webs

Ask the students: what did you eat today? Where do you think it came from?

Explain that green plants are called producers. They produce their own food supply from the Sun’s energy. Green plants provide food or energy for animals. Animals cannot produce their own food. All animals are dependent on plants even if they do not eat plants directly. If it were not for green plants, the herbivores or plant-eating animals would not grow up to be the food for the carnivores or meat-eating animals. Meat-eating animals consume other animals for food. Energy flows from the Sun (as light) to plants, then to plant-eating animals, and then to flesh-eating animals. This energy flow forms a food chain. Consumers often eat more than one kind of food, and so several food chains are connected to form a food web.

A food web is a complex system in which animals can be part of more than one food chain. The food chains are interlocked and interwoven like a spider web. If one small chain in the food web breaks, not a lot of damage is done. But the shape of the food web might change slightly. If a major part of the chain is broken, a lot of damage can occur. The whole food web could collapse.

Additional activity 2

Have the students cut out pictures of plants and animals from magazines that could make a possible food chain. Ask them what the first picture would have to be.

All animals need food. Most living things eventually become food for other animals or for bacteria and fungi when they rot or decompose.

Explain the terms carnivore, herbivore, and omnivore. Which category do most human beings belong to? Can the students name some other animals that are omnivores?

Additional activity 3

Ask the students to collect pictures of different kinds of animals. Have them sort the pictures into piles according to the food the animals eat—carnivores, herbivores, and omnivores.

Help them to become aware that carnivores do not restrict themselves to eating just one kind of animal, for example, foxes and hawks can eat rabbits, squirrels, mice and birds.

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The predator-prey relationship

The animal eaten by another animal is called its prey. The animal that does the eating is called a predator. Predators attack other animals and control the population of the prey. If foxes and hawks did not eat rabbits, there would be too many rabbits. The rabbits would destroy the balance of the biome by eating too many green plants. This would mean that other animals would not have enough to eat. Encourage the students to watch National Geographic programmes on television about food relationships between animals.

Food cycle

All life depends on energy. Green plants absorb light energy from the Sun and store it in the food materials that they produce. Other living things, such as non-green plants and animals, use these food materials to gain the energy that their bodies need. In animals most of this energy is utilized in the different activities of the body. The rest of it is given off as heat. Bacteria and fungi get their energy from dead plants and animals by using them as food materials.

Endangered species

Show the students pictures of oil-soaked beaches and animals, polluted waters and dead fish. Ask them to commet on what they see. Discuss the effects of pollution on the environment.

Poisons in food chains have led some animals to the verge of extinction. Such animals are called endangered species. Have the students find out what animals in their biome are endangered and how they are important to the food web. What measures can be taken to conserve them. Information about endangered species can be obtained from WWF or Green Peace Organization.

Additional activity 4

Ask students to use the Internet or reference books to answer the following questions. What would happen to an ecosystem if:

• excess fertilizer ran off a field into a woodland?

• pesticide was accidentally sprayed onto the edge of a woodland? • part of a woodland was burnt to the ground?

Answers

The environment: p 64

1. Environment is a scientific term or word for surroundings.

2. The physical or the non-living parts of the environment are called the abiotic factors. For example, air, water, temperature, etc.

The biotic factors are the living things in an environment. For example, plants, animals, human beings, etc.

3. a), b) c) Answers depend on the students.

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bacteria & fungi