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Food in ecosystems
In any ecosystems, food is vital. Food contains the matter and energy required by living organisms. To understand how ecosystems function, it is important to understand the feeding relationships between organisms. Ecologists consider that each organism performs a role in the ecosystem. The organisms do not know they have a role, or that it will support the ecosystem. They are simply trying to survive. However, their interactions result in a balanced system.
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Producers
Every community must have a source of food, which is made by organisms called producers. Most producers are green plants. Producers are essential for the community. Without them there would be no life, because other organisms such as animals and fungi cannot make their own food.
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All the organisms that require a ready-made source of food are called consumers. Even humans cannot produce food without the help of plants. All the food people make comes from plant or animal products. For example, bread comes from wheat seeds. Many animals that we eat are raised on
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Almost all producers, apart from some bacteria, make food my photosynthesis. This is a chemical process that takes place inside cells containing a green pigment called chlorophyll. Photosynthesis is a complicated process of many chemical reactions.
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Food Chains and webs
In communities, there are sequences, or chains, of organisms feeding on each other. A food chain is a sequence of organisms feeding on each other. Organisms are classified according to their position in food chains. A herbivore is always referred as first order consumer. An animal feeding on the herbivore is a second-order consumer. An animal feeding on a second-order consumer is a third-order consumer, and so on. An animal that eats another animal is also referred to as a carnivore. Food chains help you see that all organisms in a food chain depends on the producer.
There are many food chains and they are all interconnected. All the connected food chains are known as a food web. Food webs are usually more complex than food chains. |
Energy flow in ecosystems
To understand how energy flows through ecosystems, think about what you eat. You eat food for two reasons:
- to build new cells needed for growth and repair
- to provide energy for movement and internal processes.
Biodiversity
Biodiversity refers to the range of different species in a community. High biodiversity means a large number of different species in an ecosystem. An ecosystem with many different species is less likely to be disrupted by environmental changes.
There are many reasons why biodiversity enables an ecosystem to remain stable and continue to function. Consider the invasion of an ecosystem by species from other countries, such as weeds invading an area of Australian bush.
Food webs with few species are very susceptible to changes in any one of the species. that one species may have been supporting a large part of the food web. In a food web with more species, if one source of food is lost, there will be others available.
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Biodiversity also helps stabalize the ecosystem when physical conditions change. If there is a change in the weather leading to an unusually heavy flowing of eucalyptus then there may be an increase in the number of bees. This is because more food is available and so more bees can survive. If the number of bees increases, then there is more food for honey eaters, rainbow birds etc.
So the numbers of a predator and its prey tend to change as they affect each other. A rise in prey numbers is followed by a rise in predator numbers. As the predator numbers increase to high levels, the prey numbers decrease. The predators seem to control the numbers of its prey.
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