Some fishes in the twilight zone have enlarged eyes, enabling them to see in the very dim light, as well as light-emitting organs that attract mates and prey.
Adaptation via natural selection results from the interactions of organisms with their environments, which brings us back to our definition of ecology. Thus, events that occur in the short term, during the course of an individual's lifetime, may translate into effects over a longer scale of time.
Many lakes and ponds are affected by large inputs of nitrogen and phosphorus from sewage and runoff from fertilized lawns and farms. These nutrients often produce heavy growth of algae, which reduces light penetration. When the algae die and decompose, a pond or lake can suffer serious oxygen depletion, killing fish that are adapted to high-oxygen conditions.
The equator receives the greatest intensity of solar radiation and thus has the highest temperatures, which in turn evaporates water from Earth's surface. As this warm, moist air rises, it cools, diminishing its ability to hold moisture. The water vapor condenses into clouds, and rain falls