Question

Most people tend to think that if the sun ever stopped emitting light, all animal life on Earth would soon end. Populations of hydrothermal-vent animals might continue to exist for thousands of years, however. Explain.

Short answer

Most animal life on Earth relies on sunlight for energy, either directly or indirectly. However, hydrothermal-vent animals live in complete darkness and obtain their energy from chemosynthesis, a process that relies on chemicals from deep-sea vents instead of sunlight. Hence, they could potentially survive for thousands of years without sunlight.

Step-by-step solution

Define the Dependency

Identify how and why most animal life on Earth is dependent on sunlight. These mechanisms may include photosynthesis enabling the food chain, vitamin D production, temperature regulation, and regulation of circadian rhythms.

Discuss hydrothermal-vent life

Hydrothermal-vent animals live in the deep sea, near underwater volcanic vents. They do not require sunlight as they exist in a completely dark environment. These animals get their energy from chemicals spewing out of the hydrothermal vents, in a process known as chemosynthesis. Chemosynthesis occurs without sunlight and supplies the basis of the food chain for these creatures.

Explain the Survival

The reason they could continue to exist for thousands of years without the sun is that the energy source for these animals is independent of sunlight, and is instead dependent upon the geothermal activity on the Earth.

Key concepts

Chemosynthesis

In the dark depths of the ocean, life finds a way through a process called chemosynthesis. Unlike photosynthesis, which relies on sunlight to convert carbon dioxide and water into glucose and oxygen, chemosynthesis does not need any sunlight. Instead, it uses chemical reactions to produce food.
Hydrothermal-vent animals, such as tube worms and giant clams, thrive near underwater volcanic vents. These vents release chemicals like hydrogen sulfide, which bacteria use to produce energy. The bacteria convert these chemicals into organic molecules that can be consumed by vent animals.
This remarkable process of creating energy independent of sunlight allows organisms in these ecosystems to thrive, even in complete darkness. Chemosynthesis forms the base of the food web in these isolated environments, supporting a diverse range of life without the need for solar input.

Sunlight Dependency

Most life on Earth relies on sunlight either directly or indirectly to survive. Photosynthesis is the primary mechanism through which sunlight is converted into energy. Plants, algae, and some bacteria use sunlight to synthesize foods with carbon dioxide and water.
This process forms the basis of the food chain, as plants and other producers serve as food for herbivores. In turn, herbivores become food for carnivores, creating a chain where energy from the sun powers almost all life forms. Beyond food production, sunlight also regulates temperature and biological rhythms, like the circadian cycles in many animals.
If sunlight were to disappear, most ecosystems and life forms would indeed face dire consequences, leading to a collapse of the traditional food chains and energy cycles that sustain life. However, this dependency is not universal, as shown by the unique adaptations of deep-sea ecosystems.

Deep Sea Ecosystems

Deep-sea ecosystems present a fascinating exception to the norm of sunlight dependency. In these profound underwater environments, particularly around hydrothermal vents, life prospers without the need for sunlight. Here, geothermal energy from the Earth's interior takes center stage.
The hydrothermal vents spew out hot, mineral-rich water, providing the perfect conditions for chemosynthesis to take place. This unique environment harbors diverse species ranging from hardy bacteria to colorful fish. In a sense, these ecosystems create an entire world that operates independently from the sun, relying solely on the Earth’s internal heat and chemistry for survival.
The ability of these ecosystems to thrive in total darkness highlights the resilience and adaptability of life, showcasing how organisms can exploit even the most extreme environments for energy and sustenance. These ecosystems could continue existing for millennia even if sunlight were to vanish, thanks to their unique energy source.