The answer is An endangered species is a type of organism that is threatened with extinction. Species are becoming endangered for two main reasons: habitat loss and loss of genetic variation.
Habitat loss can occur naturally. The dinosaurs, for example, lost their habitat about 65 million years ago. The hot, dry Cretaceous climate changed very quickly, most likely due to an asteroid impact on Earth. The asteroid's impact threw debris high into the atmosphere and reduced the amount of heat and light reaching Earth's surface. The dinosaurs could not adapt to this new, cooler habitat. The dinosaurs were threatened with extinction and then died out.
Human activities can also contribute to habitat loss. The development of settlements, industry and agriculture reduces the habitat of native organisms. This can be done in a number of ways.
Development may directly remove native habitats and species. In the Amazon rainforest in South America, developers have cleared hundreds of thousands of hectares. Clearing a piece of land means removing all trees and vegetation. The Amazon rainforest is being cleared for ranching, logging and urban use. That means the habitat can support fewer cougars. However, since large parts of the Sierra Nevada, Rocky and Cascade mountain ranges remain undeveloped, cougars are not in danger.
