What is a protective layer around all cells that controls the movement of materials into and out of the cell

How does an angiosperm prevent self pollination

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-

Tom wants to conduct a scientific study but he needs to finish by the end of the school year. what practical way could tom work around this limitation and be successful in his study?