Which of the following is TRUE? Species on Earth today are just a fraction of all species that ever lived. The number of species existing at one time has decreased throughout history. Until recent history, extinctions have always happened gradually and on a small scale. Most organisms present early in Earth's prehistory were more complex than modern organisms. Natural selection always favors complexity and a larger body size

Until recent history,extinctions have always happened gradually and on a small scale.

Explanation:

Extinction occur when environmental factors like natural disaster,habitat fragmentation,over exploitation,global change don't favor the survival of species thus gradually leads to extinction of species.

Some times human activity becomes the major problem for extinction.More over,poor reproduction,decline in population number and genetic inbreeding also leads to extinction.

99% of all species that exist on earth become disappeared.

Evolution leas to speciation which leas to formation of new species but species become extinct when they are unable to survive against competition.

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