(a) Aquatic ecosystems are rich in diversity. The life inside water is largely influenced by various abiotic factors. The abiotic factors are the chemical and physical components of an environment that affect the organisms living there. The primary abiotic factors that affect the life underwater are temperature, light and availability of oxygen.
(b) Oxygen available to the aquatic organisms is a detrimental factor. If less oxygen is available underwater aquatic animals will not be able to respire and die.
Light is also an important abiotic factor for underwater organisms especially for the aquatic plants. the aquatic plants underwater will not be able to make their food by photosynthesis if proper light is not available.
Temperature also plays an important role. Too low or too high temperature affects the metabolic activities of the organisms.
Depth of water body affects the availability of light and oxygen to the aquatic organisms. Shallow water bodies have light available to more aquatic organisms.
A mass extinction event occurs when a species disappears far more quickly than it is replaced. This is typically understood as the loss of around 75% of all species over a "short" period of geological time, or fewer than 2.8 million years.
An enormous number of species were wiped out by a harsh, worldwide, swift, and selective event is mass extinction. According to marine fossils, at least 75% of all species are thought to have become extinct. The most recent mass extinction is the Cretaceous-Paleogene extinction event, which is also the only one that can be proven to have been caused by a significant asteroid impact. All non-avian dinosaur species, making up about 76 percent of all species on the earth, perished during mass extinction. The Chicxulub asteroid impact in what is now Mexico, which occurred 66 million years ago, caused an ecosystem collapse that resulted in the extinction of the dinosaurs and >75% of all land and sea species as well as the macroevolution of mammals.
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Genetic Change in Viruses. Viruses are continuously changing as a result of genetic selection. They undergo subtle genetic changes through mutation and major genetic changes through recombination. Mutation occurs when an error is incorporated in the viral genome
Answer:
The crust is thinner and less dense than the mantle.
