Biodiversity is the variety of life on Earth. It describes the variety of types of life forms as well as the variety within a kingdom, phylum or even a species. The number and types of species has varied throughout Earth's 4.5-billion year history. Scientists estimate that life on Earth began about 3.5 billion years ago when primitive life forms lacking a nucleus and organelles began using nutrients in water. These life forms are probably the ancestors of modern bacteria and other species of the Kingdom Monera. Blue-green bacteria may have produced oxygen as a waste product of photosynthesis. As oxygen built up in the atmosphere, new life forms that use oxygen began to appear in the fossil record.

Throughout Earth's history, biodiversity has changed with species appearing for a time in the fossil record then disappearing forever. There have been mass extinctions found in the fossil record when many species disappeared from the Earth never to reappear. Extinction occurs when there are no breeding pairs left to produce another generation of a species. Species become threatened or endangered when their numbers decline to the point that the breeding population could die out in one generation.

Climate change seems to be the major force for changes in global biodiversity. Humans in modern times have had a significant impact on biodiversity through habitat loss, introduction of alien species, pollution, population growth, and overconsumption.

Earth's history is divided in to Eons, Eras, Periods, and Epochs. Each era is defined by a geological event that marked its beginning and end. Frequently, these era changes are also accompanied by a dramatic change in biodiversity. Eras are divided into periods. Periods usually have a set of indicator fossils that are clue to the climate of the time. Periods can be further divided into epochs. Fossils of the modern era are the best studied and easiest to delineate into epochs.

Habitat loss can change local and global biodiversity particularly when a particular region is the only known habitat of a species. Animals that are food specialists such as the panda and koala are especially vulnerable to habitat loss since their main food source may be lost. Habitat loss affects migratory animals such as songbirds that rely on deep forest interiors for breeding. The fragmentation of forests with the subsequent creation of edges threatens the survival of songbird species. Not only do the songbirds lose breeding territory, they become more subject to predation by edge species whose population growth is favored by the increase in edge space.

Introduced species, both plant and animal, may have a survival advantage over native species, especially if there are no predators or diseases in the new habitat. Rabbits introduced into Australia dig burrows and consume vegetation speeding up desertification in Australia. In the New Jersey highlands, Japanese wine grass is more salt tolerant than native grasses and has been able to crowd out native species along roadways that are salted in the winter.

Pollution may be a significant factor in climate change. The exact effect of carbon dioxide emissions on the Ozone layer is still being studied. An increase in average global temperatures has been recorded along with a decrease in glacial ice thickness. What this will mean for the short-term and long-term future is uncertain. A well-documented case of biodiversity change was reported by Dr. Kettlewell in England during the Industrial Revolution. Dr. Kettlewell noticed a change in the peppered moth population that could be attributed to the deposition of carbon soot on tree trunks. When coal was no longer used as a fuel, the peppered moth population changed in response to the new environmental conditions.

Population growth worldwide has placed a strain on the environment and in some respects is the root cause behind habitat loss, introduced species, pollution and overconsumption.

Overconsumption is the use of resources beyond what is sustainable. Sustainability means the use of resources so that the needs of the present generation may be met without endangering the ability of future generations to meet their needs. The Florida Everglades is a good example of how human consumption has altered biodiversity.

FROGS!

Learn more about a real problem in Minnesota by visiting Frogs. Middle school students noticed that there were deformed frogs in the pond they were studying. They alerted scientists who are investigating a variety of possible causes. It's a real application of the scientific method you must see to believe. There's even a frogcam in the lab! (It's only on when the lab lights are on. Try catching the frogs right after school to see how their doing in the experimental tank.)

Explore Your Ecoregion

Find out more about your ecoregion by visiting National Geographic Wildworld. Select the link to the "Terrestrial Ecoregions of the World" then type in your zip code to find your ecoregion. Be patient. It takes a little trial and error to explore the site for information, but it's worth the trouble.

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