Biodiversity

Biodiversity is the degree of variation of life. It is a measure of the variety of organisms present in different ecosystems.

This can refer to genetic variation, ecosystem variation, or species variation (number of species) within an area, Biome, or planet. Terrestrial biodiversity tends to be highest near the equator, which seems to be the result of the warm climate and high primary productivity.

Biodiversity is not distributed evenly on Earth. It is the richest in the tropics. Marine biodiversity tends to be highest along coasts in the Western Pacific, where sea surface temperature is highest and in the mid-latitudinal band in all oceans.

There are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time but will be likely to slow in the future.

Biodiversity is the result of 3.5 billion years of evolution. Until approximately 600 million years ago, all life consisted of archaea, bacteria, protozoans and similar single-celled organisms.

The history of biodiversity during the Phanerozoic (the last 540 million years), starts with rapid growth during the Cambrian Explosion — a period during which nearly every phylum of multicellular organisms first appeared.

Over the next 400 million years or so, invertebrate diversity showed little overall trend, and vertebrate diversity shows an overall exponential trend.

This dramatic rise in diversity was marked by periodic, massive losses of diversity classified as mass extinction events.

A significant loss occurred when rainforests collapsed in the carboniferous. The worst was the Permo-Triassic Extinction, 251 million years ago. Vertebrates took 30 million years to recover from this event.