food chain. it tells how different organism feed on in a linear way. if we mix more than 2 food chains it will become food web.
Natural selection is a theory developed by Charles Darwin. It is believed that animal species evolve by nature "selecting" the ones that are fit to live in specific environments. For example, if an animal lacks a trait that is needed for a certain environment, it is likely to die. The animals that have the needed traits are more likely to live and procreate, which will pass on the trait to its offspring. Hope this helped!