The rate of extinction that has prevailed over one million years of evolutionary time claims that approximately one to three species go extinct every year. However, if humans start to change the pattern and cause species to go extinct the web of evolution may not support humans. Many people think that if animals and plants go extinct, they will be without food and sometimes clothing. To date, scientists have catalogued about 1.8 million species of animals, plants, fungi, bacteria, and other organisms. Most scientists believe that there are many more organisms that humans do not even no about, and that the numbers could be in the range of 4 million to 40 million.
Species can evolve and go extinct before they are even noticed in the world.
The single most species-rich group of organisms appears to be insects. Vertebrates combine for a total of about 50,000 species, and can be found in virtually all environments on Earth. Birds There are nearly 10,000 different species of birds that scientists know about. They also know more about birds than any other class of organisms on Earth. Some species that are extinct in the United States are phalacrocorax perspicillatus , found in Alaska, the laysan rail and the hawaiian rail , found in Hawaii, and the passenger pigeon , found in Illinois.