Earth is richly supplied with different types of living organisms, including animals, plants, fungi, and bacteria. Various living organisms co-exist in their environments, forming complex, interrelated communities. Living organisms depend on one another for nutrients, shelter, and other benefits. The extinction of any one species can set off a chain reaction that affects many other species, partic…
The Endangered Species Act of 1973 (ESA) is generally considered one of the most far-reaching laws ever enacted by any nation for the preservation of wildlife. The passage of the ESA resulted from alarm at the decline of numerous species worldwide, as well as from recognition of the importance of preserving species diversity. The purpose of the ESA is to identify species that are either endangered…
The Endangered Species Act (ESA) is designed to protect plant and animal species in danger of extinction. During the 1990s there was a growing concern that traditional methods of species protection, which take a species-by-species approach, were ineffective. Many alternatives were proposed. One of the most popular was a method variously termed the "habitat," "ecosystem,"…
According to the U.S. Geological Survey in "How Much Water Is There on (and in) the Earth?" (http://ga.water.usgs.gov/edu/earthhowmuch.html), about 326 million trillion gallons of water make up the total water supply of the planet. This provides an enormous aquatic habitat for a wide variety and number of animal and plant species. The aquatic environment is threatened by many human a…
Marine mammals live in and around the ocean. They are warm-blooded, breathe air, have hair at some point in their lives, give birth to live young (as opposed to laying eggs), and nourish their young by secreting milk. Dolphins, whales, seals, sea lions, walruses, polar bears, manatees, and dugongs (manatee relatives) fall into this category. Historically marine mammals have garnered a high level o…
Fish, clams, snails, and crustaceans are aquatic creatures. Fish are vertebrates, meaning they have an internal skeleton made of bone or cartilage. Clams, snails, and crustaceans are invertebrates. …
Amphibians and reptiles are collectively known by biologists as herpetofauna. At present, there are over 5,000 described amphibian species and over 6,000 reptiles. New species in both these groups are being discovered every day, particularly in remote tropical regions that are only now being explored. Most of the herpetofauna native to the United States are found in wetlands and riparian habitat (…
Terrestrial animals are animals that inhabit the land. Mammals are warm-blooded, breathe air, have hair at some point in their lives, give birth to live young (as opposed to laying eggs), and nourish their young by secreting milk. The biggest cause of terrestrial mammalian decline and extinction in the twentieth-first century is habitat loss and degradation. As humans convert forests, grasslands, …
Birds belong to the class Aves, which contains dozens of orders. Birds are warm-blooded vertebrates with wings, feathers, and light hollow bones. The vast majority of birds are capable of flight. According to the U.S. Fish and Wildlife Service (FWS), more than 800 species of birds spend all or part of their lives in the United States; more than 9,000 species of birds have been identified around th…
Insects are members of the Animalia kingdom and belong to the phylum Arthropoda, along with crustaceans. There are many classes of arthropods, including the insects and arachnids. Both are invertebrates, but insects have six legs, while arachnids have eight legs. The arachnids include spiders, mites, ticks, scorpions, and harvestmen. Insects are the most diverse group in the animal kingdom. Scient…
Plants belong to the Plantae kingdom. Biologists estimate that there are up to 350,000 species making up this kingdom. In general, there are two types of land-growing plants—vascular and nonvascular. Vascular plants have specially developed organs similar to veins that move liquids through their systems. This category includes the trees, shrubs, flowers, and grasses. Nonvascular plants are …