hd animal pictures 2013: Wild Animal Pictures

Saturday 30 November 2013

Wild Animal Pictures

Source Link:- google.com.pk

Wildlife traditionally refers to non-domesticated animal species, but has come to include all plants, fungi and other organisms which grow or live wild in an area without being introduced by humans. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative.
Wildlife can be found in all ecosystems. Deserts, forests, rain forests, plains, grasslands, and other areas including the most developed urban sites, all have distinct forms of wildlife. While the term in popular culture usually refers to animals that are untouched by human factors, most scientists agree that wildlife around is affected by human activities.
It is estimated that around 9 or 10 million species of animals inhabit the earth; the exact number is not known and all estimates are rough. Animals range in size from no more than a few cells to organisms weighing many tons, such as the giant squid. By far most species of animals are insects, with groups such as mollusks, crustaceans, and nematodes also being especially diverse. By this measure our own group, the vertebrates, is relatively inconsequential from a diversity perspective.
All animals are members of the Kingdom Animalia, also called Metazoa. This Kingdom does not contain prokaryotes (organisms made up of cells that lack a cell nucleus or any membrane-encased organelles, such as bacteria and blue-green algae) or protists (Kingdom Protista, which includes unicellular eukaryotic organisms). All members of Animalia are multicellular, and all are heterotrophs (i.e., they rely directly or indirectly on other organisms for their nourishment). Most ingest food and digest it in an internal cavity.
Animal cells lack the rigid cell walls that characterize plant cells. The bodies of most animals (all except sponges) are made up of cells organized into tissues, each tissue specialized to some degree to perform specific functions. In most, tissues are organized into even more specialized organs. Most animals are capable of complex and relatively rapid movement compared to plants and other organisms. Most reproduce sexually, by means of differentiated eggs and sperm. Most animals are diploid, meaning that the cells of adults contain two copies of the genetic material.
The development of most animals is characterized by distinctive stages, including a zygote, formed by the product of the first few divisions of cells following fertilization; a blastula, which is a hollow ball of cells formed by the developing zygote; and a gastrula, which is formed when the blastula folds in on itself to form a double-walled structure with an opening to the outside, the blastopore.