Many genetic studies, particularly those of recessive traits, have focused on small isolated human populations, such as those on islands. Which are major advantages that isolated populations might provide for the study of recessive traits? Some recessive traits that are rare in most large populations may be relatively common in some small populations. Geneticists are more likely to be able to control mating choices in small populations. Autosomal dominant traits will be more likely to be found in such populations. Small populations likely will experience a high mutation rate and thus produce more genetic variation for study. Inbreeding, which is more common in small populations, will tend to increase the frequency of recessive phenotypes.

Hunting in the darksome fish rely on senses beyond sight. in the darkness of the marianas trench, a fish called the rattail has an extremely sensitive sense of smell. the fish uses scent, rather than sight, to steer toward food. once it's near food, the rattail uses a special organ on the bottom of its chin to guide itself by feel.marine snowone staple of the deep sea diet is "marine snow," flakes of organic, edible substances that sink down from the upper ocean. animals at the ocean's bottom find sustenance in everything from the bodies of dead creatures to fecal matter. marine snow is diverse enough to support numerous species. for instance, several species of snails and worms feed exclusively on deceased whales.microorganismsthe deep sea is an intricate ecosystem, and even the ocean floor itself plays a part. hydrothermal vents are cracks in the sea floor where erupting magma mixes with ocean water to produce plumes of hot, sulfur-rich chemicals. some microbes can use these chemicals for energy, sustaining their existence and that of the animals who depend on their roles in the deep sea food chain.