An ecosystem is all the living and non-living things occurring together and the interelationships between them; the biotic and abiotic factors of an environment.
BIOTIC FACTORS = living things (predators, food, humans)
ABIOTIC FACTORS = non-living things (temperature, water availability, oxygen levels)
Ecosystems are dynamic systems - they’re always changing. The components of an ecosystem are:
- HABITAT - where an organism lives
- POPULATION - all the organisms of one species that live in the same space, at the same time, and can breed together.
- COMMUNITY - all the populations of different species who live in the same place, at the same time and can interact with each other.
A niche is the role each species plays in an ecosystem and is almost impossible to define, it’s different for every species - it’s impossible for two different species to share the same niche. Things that define a species niche would include what it eats, how it eats, what it excretes etc. (great detail on everything an organism does that would somehow effect its ecosystem).
The main way energy enters the ecosystem is photosynthesis when a plant converts light energy into a form that can be used by other organisms (although in sea ecosystems, bacteria use chemicals from deep sea vents as an energy source). Plants are hence called producers; they produce energy for the ecosystem.
Energy is transferred through the living organisms of an ecosystem when one organism eats another. These organisms are the consumers; they consume other organisms. Depending on what trophic level (a trophic level is a stage of a food chain occupied by a particular group of organisms) of the food chain the organism is, it is either a primary, secondary, or tertiary consumer.
So it goes:
PRODUCER —> PRIMARY CONSUMER —> SECONDARY CONS. —> TERTIARY CONS.
LETTUCE —> SLUG —> HEDGEHOG —> FOX
The arrows of a food chain show the transfer of energy from one trophic level to the next. A food chain show simple lines of this energy transfer, food webs show how lots of food chains in an ecosystem overlap.
Energy ‘locked up’ in things that can’t be eaten (eg. bones, faeces) get recycled back into the ecosystem by decomposers which break down dead or undigested organic material. Examples of decomposers are fungi and bacteria.