Beyond the Sun: Energy Sources for Life Quiz

If radioactive decay produces heat that drives volcanic activity, and if that volcanic activity releases chemicals that support chemosynthesis, then radioactive heat is a valid starting point for an energy chain.

If moons like Europa have internal heat and chemicals but no light, and if Mars had water and sun in the past, and if Venus has extreme heat, then these are valid scientific observations about energy.

If humans only discovered the diverse ecosystems around deep-sea vents in 1977, and if we knew about plants and sunlight for thousands of years, then chemical-based life is indeed a more recent discovery.

If light intensity follows the inverse-square law, then doubling the distance from a star reduces the light to one-fourth; if the light is reduced, then organisms have less energy available for photosynthesis.

If an animal eats a plant, it uses some of that energy to move and grow, but a large portion is released into the environment as a waste product of work; if that waste is felt as warmth, then it is heat.

If plants take in carbon dioxide and water to make sugar using light, and if the extra atoms not used for the sugar are released into the air, then that byproduct is oxygen.

If life needs to extract power to do work, then light (solar), heat (geothermal), and chemical bonds (glucose/minerals) are usable sources; however, gravity and a vacuum do not provide fuel for life.

If vision requires light to hit the eye and be processed by the brain, and if this process is essential for the survival of most animals, then vision is a life process linked to sunlight.

If autotrophs are "self-feeders" that make food from light or chemicals, and if animals cannot do this, then they must belong to the group that gets energy by consuming others, known as heterotrophs.

If an autotroph is an organism that creates its own food, and if "chemo-" refers to using chemicals, then the specific name for these organisms is chemoautotrophs.

If most plants on the surface require light to produce their own food, and if almost all animals depend on those plants for survival, then sunlight is the primary energy source for surface life.

If life requires energy to repair cells and grow, and if food is the way energy is stored, then the goal of any biological energy process must be to create that food or fuel.

If photosynthesis requires sunlight, then plants like trees and grass, as well as algae like kelp and certain bacteria like cyanobacteria, qualify; however, tube worms rely on chemical-eating bacteria.

If bacteria at hydrothermal vents need a specific chemical to break down for energy, and if that chemical is a common volcanic gas that smells like rotten eggs, then it is hydrogen sulfide.

If a plant needs to capture light energy to start photosynthesis, and if chlorophyll is the specific pigment that absorbs sunlight, then chlorophyll is the essential molecule for this process.

If some ecosystems are powered entirely by the Earth's internal chemical heat (chemosynthesis) without any light, then not all biological energy originates from the Sun.

If sunlight cannot penetrate the deep ocean, and if large communities of animals are found living near volcanic vents, then those vents must be providing an alternative energy source through chemical heat and minerals.

If an organism lives at the bottom of the ocean where no light reaches, and if it uses the energy stored in chemical bonds to make food, then that process is defined as chemosynthesis.

If photosynthesis requires energy from light to function, and if chemosynthesis uses energy from chemical reactions instead of light, then chemosynthesis is the only one that can occur in dark environments like the deep ocean.

If photosynthesis is the process of converting light into chemical energy, and if the inputs for this process are water and carbon dioxide, then the resulting output must be sugar (glucose).