The flow of energy through living systems can be modelers as food chains , food webs , or energy pirámide. The energy organisms need to live and grow first enters the ecosystem when which of the following occurs?

Photosynthesis
Explanation:
The energy organisms need to live and grow first enters the ecosystem through the process of photosynthesis when green plants manufacture their food.
Photosynthesis is the process in which green plants manufactures their foods in the presence of sunlight(solar energy) using water and carbon dioxide.
The sunlight synthesizes energy rich compounds in this process.
There is a transformation of solar energy to chemical energy.
Different organisms rely on this chemical energy for their own energy needs.

 the contribution an individual makes to the gene pool of the next generation relative to the contribution of another individual.

Explanation:

It is the ability for an organism to reproduce and create viable offspring (offspring live to maturity and which can reproduce themselves). Relative fitness is the survival rate relative to the maximum survival rate with other population.

For example if organism A ends up finding a mate and have babies and organism B does not this means that organism A has more fitness biologically than organism B