What causes variety in the characteristics between organisms of the same species?

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important

Scenario #2 in 2001, a population of 2,500 poison dart frogs lived in the amazon rain forest. due to increased deforestation, the population dwindled to 25 frogs in 2019. new government regulations were enacted in 2022, successfully putting an end to the deforestation of the amazon rain forest. once deforestation was stopped, the poison dart frog population was able to recover. by 2050, the population reached 8,000 frogs, of that population, 20 are homozygous recessive for being spotted (ss genotype). q2- ? q- p- p2- 2pq-

Plsss > .< compare and contrast the characteristics of flatworms rounds worms and earthworms