Section 2 Introduction
Completion requirements
Targets
At the end of this Unit you should be able to answer the following questions
2. What are the roles of various organisms in a food web?
2.1 Who are the producers, consumers, and decomposers in a wetlands habitat?
2.2 What are food chains and food webs?
Interactions among plants and animals are important in any ecosystem as well as in a wetland. To survive and grow, animals must eat or be eaten. Each plant or animal has an important role in a wetland food chain.
A food chain shows the way organisms are related and dependent on each other so that all can be fed. They are usually represented by simple diagrams using arrows that show which is providing energy—often by being eaten!
This simple food chain shows that energy from the Sun moves to the plant and up the food chain as each organism is eaten. Eventually, it reaches the pelican at the top of the food chain. Several food chains might be connected to form a food
web.
Figure 1: Food Web
Figure 1 shows a food web for a pond ecosystem.
Members of a food web are classified as producers, consumers, or decomposers. The role of an organism is very important to the balance of the entire ecosystem.
As you go through this part of the unit, focus on these questions:
Members of a food web are classified as producers, consumers, or decomposers. The role of an organism is very important to the balance of the entire ecosystem.
As you go through this part of the unit, focus on these questions:
- What is a food chain?
- How is a food chain different from a food web?
- Do food chains exist in wetlands only?
- Do you belong to a food chain?
- What do food chains have to do with survival in wetlands?
Environmental Connection
Humans are at the top of most food chains. This means that, in addition to eating plants, we also eat animals that have eaten plants and/or other animals. This can be a health concern for humans when there is a build-up of toxins (poisons) in the environment. Certain types of fish may contain low levels of mercury (a heavy metal that is toxic to living things). These levels are not high enough to be toxic to the fish, but for organisms higher up in the food chain such as people or certain birds, eating large quantities of these fish can lead to dangerous levels of mercury in their bodies. Bioaccumulation results in increasing concentrations of a harmful chemical at each higher level of a food chain.