Final answer:
Animals such as deep-sea chimaeras and anglerfish survive in the lower depths of the ocean by adapting their buoyancy to conserve energy and withstand high pressure, scarce food, and extreme temperatures. Buoyancy adjustments help them stay at the right depth for feeding and predator avoidance. Hydrothermal vent communities also show special adaptations to their unique environment.
Step-by-step explanation:
Animals survive at lower depths in the ocean through a range of adaptations that address the challenges of extreme pressure, scarce food, lack of sunlight, and temperature extremes. Adjusting buoyancy is essential for these animals because it allows them to conserve energy by floating at different depths without the need for constant swimming. An example of a marine animal with such an adaptation is the deep-sea chimaera, related to sharks. Chimaeras possess buoyancy adaptations that enable them to live thousands of feet under the ocean surface, where they navigate the dark, high-pressure environments in search of food.
It is beneficial for marine animals to adjust their buoyancy to respond to varying water pressures and to remain at depths suitable for feeding and avoiding predators. The hydrostatic equilibrium of the Earth's oceans means that as animals dive deeper, the pressure increases significantly, necessitating physiological adaptations to withstand these conditions.