Biodiversity Biodiversity refers to the number and variety of species on Earth. The number of known species on Earth is about 8.7 million, 6.5 million on land, 2.2 million in the ocean, most of which are insects. This is different from the actual number of species on Earth, which may be closer to 100 million.

Importance of Biodiversity Biodiversity provides: a variety of products and resources a livable planet for us and for all other species. Biodiversity helps: maintain the atmosphere keep the soil fertile purify water

Loss of Biodiversity We share the environment with other organisms in a complex network. Each species has a role or niche to play in its ecosystem. If one species disappears from an ecosystem, the ecosystem changes. Keystone species are species that are so important to the functioning of an ecosystem that if they disappear, the ecosystem falls apart.

An Example in Texas: Black-tailed Prairie Dogs Black-tailed prairie dogs once roamed the western mid-west. Now cover less than 1% of their original territory. Digging aerates and promotes soil formation. Clip back brush maintaining the short grass prairie. Provide food and shelter for as many as 170 different animals.

• Habitat loss • Introduced species • Population growth • Pollution Main Threats to Biodiversity • Habitat loss • Introduced species • Population growth • Pollution

Habitat Loss the destruction of habitats is the number one cause of species extinction.

Turn and Talk How does habitat loss affect biodiversity in an ecosystem?

Introduced Species Nonnative or Exotic species that are not native to a particular region. Fire ants from South America entered the U.S. through Mobile, Alabama, probably in soil used for ships' ballasts. They were accidentally introduced around the 1930's and have been spreading ever since.

Turn and Talk How do introduced species affect biodiversity in an ecosystem?

Population Growth There are 7 billion humans living on Earth. Earth’s population of human beings is increasing at a rate of about 222,000 people each day. Humans take up more space and deplete more resources than any other species.

Pollution Can be an oil spill, acid rain, trash or insecticides that can cause reproductive failure in fish, birds, and mammals (like DDT).

Turn and Talk How does pollution affect biodiversity in an ecosystem?

Extinction Extinction occurs when the last individual of a species dies. San Marcos Gambusia, Texas, 1983 Texas red wolf, Oklahoma, Texas, 1970 Texas gray wolf, New Mexico, Texas, 1942

Mass Extinction The extinction of many species during a relatively short period of time. Often caused by a change in climate. Many scientists believe that we are living in a mass extinction, and that by the year 2100, 25% or more of all species of plants and animals that were on Earth in 1900 will have become extinct.

Turn and Talk How will this mass extinction affect Earth?