Extinctions occur at a great pace and species that we did not even know existed become extinct all the time. Scientists say that of all the species that existed on this Earth, 99.9 per cent are extinct now. It is predicted that a species becomes extinct every 20 minutes. This is an enormous 72 species lost in one day and about 26, 000 species every year. We are losing more and more species each year and scientists say this is partly our own fault.
A species that is still living is classified as extant. A species that is in danger of becoming extinct but it is still an extant species is called an endangered species. Endangered species are protected by law in many countries and it is a crime to hunt or intentionally kill these species.
Sometimes, humans deliberately make a species extinct for the benefit of humankind. This is called planned extinction. Many scientists are working on a pesticide that will contaminate and absolutely terminate the entire population of the malaria causing mosquitoes also known as the anopheles mosquito. Olivia Judson claims that she has found a specicide (a contaminating pesticide) which will knockout these mosquitoes by causing mutation and bringing out only the recessive genes. This will weaken the mosquito and cause it to die. She justifies this by saying that making this species extinct she can save over one million lives a year and so it is a humanitarian cause.
Fossils help us gain evidence for extinction. Bones and DNA of animals and plants have been discovered that is unlike any bones or DNA in the current time. Fossils can give us an almost accurate account of what the species was like, what it ate, where it lived and what caused it to become extinct.
There are numerous causes for a species to become extinct. The most common reason that causes a species to become extinct is if it is unable to reproduce or survive in its current environment and unable to go to another environment where it can survive and eventually reproduce becomes an extinct species.
Charles Darwin's Theory of Natural selection also plays an important role in extinction. He said that a species with favorable traits in a particular environment is more likely to survive than a species without these traits. We can relate this to extinction because a primary reason for extinction is that some animals that compete against newer and better adapted organisms for habitat or food become extinct. The one that is able to catch more food and find safer habitat is the one that will survive and the other will become extinct. Every year, three species of birds become extinct like this. Some scientists also express fears that we someday could develop intelligent' technology or cause a sudden and major climate change which could lead to the instantaneous or eventual extinction of humans.
The degradation or destruction of a species habitat can make it unfit to survive and reproduce. Habitat degrading may be caused by a direct or indirect effect. Toxicity, for example, is a direct effect on the environment and on the species health. The toxic chemicals can cause contamination which can totally wipe out the species or infertility (sterilization) in the species. This means they will no longer be able to reproduce and therefore become certainly extinct. This is the Sumatran Tiger who is now extinct due to its habitat being destroyed.
PREDATION, COMPETITION AND DISEASE
The introduction of a species can have devastating effects on the local population and can certainly cause extinction. When a more powerful...