Two organisms that are mostly related

the first option

Explanation:

As the soil gets darker, brown beetles become easily recognised by predators (like birds) and will be eaten. Black beetles however, are better camouflaged and will less likely be spotted by the birds. Black beetles will survive and interbreed, allowing the recessive allele to be passed on to upcoming generations.

Selective pressure is what makes the genetic pool shift toward a particular genotype with a particular phenotype (recessive black in this case) that gives the new generations a selective advantage. They're more likely to survive and reproduce. Survival of the fittest.

Genotype- the genetic makeup of an organism (eg: the recessive gene for black; bb)

Phenotype- physical feature of an organism as determined by the genotype (the colour black)