The primary source of all energy for all living things comes from the

I'm pretty sure all living things get their energy primarily from sunlight. Hope this helps! ^-^

•there must be variation for the particular trait within a population.

•the variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).

•individuals with one version of the trait must produce more offspring than those with a different version of the trait.good

explanation:

the tricuspid valve is present between right atrium and right ventricle