Food chains and Food webs

FOOD CHAINS and FOOD WEBS
There are two types of feeding relationships: autotrophic and heterotrophic.
Autotrophic organisms make their own food by the process of photosynthesis e.g. plants.
Heterotrophic organisms cannot make their own food (i.e. cannot carry out photosynthesis), therefore must eat other organisms to get their nutrients e.g. animals.
A food chain is the feeding relationship among organisms or the series of living organisms that eat each other.
A food chain shows the transfer of energy from one organism to another. In drawing a food chain, we use arrows (means 'eaten by') to show the direction in which food (energy) passes from one organism to another.
ALL food chains start with a plant. Plants provide food for ALL organisms, either directly or in directly (directly - animals eat plants or indirectly - animals eat other organisms which ate plants).
The position an organism occupies in a food chain is called a trophic level e.g. producer, primary or secondary consumer.

A SIMPLE FOOD CHAIN plant → animal eats plant → animal eats animal
(producer) (primary consumer) (secondary consumer)

E.g. cabbage → caterpillar → bird
(producer) (primary consumer) (secondary consumer)
(producer) (herbivore) (carnivore) Green plants produce or manufacture food and are therefore called PRODUCERS.
Animals that feed on other organisms and are called CONSUMERS. There are various trophic levels of consumers.
A primary consumer is the first animal in the food chain and feeds directly on the green plants.
A secondary consumer is the second animal in the food chain and feeds on the first animal in the food chain.
A herbivore is a an animal that eats plants only e.g. rabbit, cow.
A carnivore is an animal that eats animals only e.g. lion, hawk.
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