Levels of organisation
An ecosystemThe living organisms in a particular area, together with the non-living components of the environment. is the interaction between a communityAll the organisms that live in a habitat (plants and animals). of living organisms and their environment. A community is two or more populationAll of the members of a single species that live within a geographical area. of organisms. An ecosystem is the interaction of two or more populations of organisms in their environment.
Producers and consumers
Feeding relationships show what organisms eat or are eaten by others and through this the levels of organisation in an ecosystem. These can be shown in food chainA sequence (usually shown as a diagram) of feeding relationships between organisms, showing which organisms eat what and the movement of energy through trophic levels., which add together to make food webA network of food chains, showing how they all link together. for a habitatA place where plants, animals and microorganisms live..
A simple example of a food chain is:
grass 鈫 rabbits 鈫 foxes
At the base of almost every food chain is a producerPlants that begin food chains by making energy from carbon dioxide and water.. These are plants or algae, which photosynthesisA chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic.. This means they convert energy from the sun into glucose during photosynthesis producing biomassThe dry mass of an organism.. It is this which feeds the rest of the food chain.
All animals above the producer are called consumers. The first is the primary consumerThe name given to an organism that eats a producer. A herbivore., the next is the secondary consumerAn organism that obtains its energy by eating the primary consumer.. Animals that hunt and kill others are called predatorAn animal that hunts, kills and eats other animals for food., and those that are hunted and killed are called preyOrganisms that predators kill for food.. The top animal in the feeding relationship is called the apex predator.
Decomposers
decomposerAn organism which eats dead organisms, fallen leaves, animal droppings, etc, and breaks them down into simpler materials. are bacteria and fungi, which break down dead organisms in a process called decomposition or rotting. They do this by releasing enzymeA protein which catalyses or speeds up a chemical reaction. onto the dead matter and afterwards, consume the broken down substances. They form a vital role in the recycling of matter. When organisms die and decomposeIf a substance decomposes, it breaks down into simpler compounds or elements. plants absorb the broken down nutrients through their roots.