Sun
The Sun is the principal source of energy input to biological systems.
Definitions
There are many terms you have to know in ecology. To start off, here are some of them:
[Supplementary] Definitions
Ecosystem
Ecosystem is defined as a unit containing all of the organisms and their environment, interacting together, in a given area, e.g. a lake.
Trophic Level
Trophic level is defined as the position of an organism in a food chain or food web.
Levels of Organisation
Based on the definitions mentioned earlier, here is an example of the different levels of organisation in an ecosystem.
The Food Web
You have seen how different organisms are linked via a food chain.
[Supplementary definition] The organisms each have their trophic level, which describes their position in the food chain or food web.
You must be able to write a simple food chain, identify producers and consumers in a food chain as well as identify between the different types of consumers.
Producers, primary consumers, secondary consumers, tertiary consumers and quaternary consumers are in different trophic levels in food webs and food chains.
Summing Up
Of the three different pyramids, only the pyramid of energy is always pyramidal in shape. The other two pyramids can deviate. This video here will help summarise ecological pyramids.
