Threatened categories have different thresholds for these criteria. As the population and range of the species decreases, the species becomes more threatened. Urbanzoos, located in large cities, still resemble the smaller zoos that were popular 200 years ago. Often, these zoos sit in the middle of cities, making expansion difficult. There is little room for urbanzoos to grow, and many of the zoo’s buildings are historic landmarks that cannot be destroyed or redesigned.

Deforestation - National Geographic Society Deforestation - National Geographic Society

A species is classified as critically endangered when there are fewer than 250 mature individuals. A species is also classified as critically endangered when the number of mature individuals declines by at least 25 percent within three years or one generation, whichever is longer. Discover rare and unusual species, brilliant bears, fierce felines, awesome reptiles and incredible marine life, just to name a few. Biodiversity is a term used to describe the enormous variety of life on Earth. It can be used more specifically to refer to all of the species in one region or ecosystem. Bio diversity refers to every living thing, including plants, bacteria, animals, and humans. Scientists have estimated that there are around 8.7 million species of plants and animals in existence. However, only around 1.2 million species have been identified and described so far, most of which are insects. This means that millions of other organisms remain a complete mystery. Deforestation is the purposeful clearing of forested land. Throughout history and into modern times, forests have been razed to make space for agriculture and animal grazing, and to obtain wood for fuel, manufacturing, and construction.Classifying a species as endangered has to do with its range and habitat, as well as its actual population. For this reason, a species can be of least concern in one area and endangered in another. The gray whale, for instance, has a healthy population in the eastern Pacific Ocean, along the coast of North and South America. The population in the western Pacific, however, is critically endangered. Probability of extinction in the wild is at least 50 percent within 10 years or three generations, whichever is longer. During this time, people started wanting to study animals for scientific reasons. Scientists wanted to research animal behavior and anatomy. To do this, scientists and zookeepers had to keep animals in places that were close to, or resembled, the animals’ natural habitats.

Zoo - National Geographic Society Zoo - National Geographic Society

Species with fewer than 10,000 mature individuals are vulnerable. The species is also vulnerable if that population declines by at least 10 percent within 10 years or three generations, whichever is longer.The Ethiopian banana frog ( Afrixalus enseticola) is a small frog native to high- altitude areas of southern Ethiopia. It is a vulnerable species because its area of occupancy is less than 2,000 square kilometers (772 square miles). The extent and quality of its forest habitat are in decline. Threats to this habitat include forest clearance, mostly for housing and agriculture. However, the snaggletooth shark is a vulnerable species because of a severe population reduction rate. Its population has fallen more than 10 percent over 10 years. The number of sharks is declining due to fisheries, especially in the Java Sea and Gulf of Thailand. The snaggletooth shark’s flesh, fins, and liver are considered high-quality foods. They are sold in commercial fish markets, as well as restaurants.