Evolution

-
Evolution
Evolution, in biology, complex process by which the characteristics of living organisms change over many generations as traits are passed from one generation to the next. The science of evolution seeks to understand the biological forces that caused ancient organisms to develop into the tremendous and ever-changing variety of life seen on Earth today. It addresses how, over the course of time, various plant and animal species branch off to become entirely new species, and how different species are related through complicated family trees that span millions of years.

Evolution provides an essential framework for studying the ongoing history of life on Earth. A central, and historically controversial, component of evolutionary theory is that all living organisms, from microscopic bacteria to plants, insects, birds, and mammals, share a common ancestor. Species that are closely related share a recent common ancestor, while distantly related species have a common ancestor further in the past. The animal most closely related to humans, for example, is the chimpanzee. The common ancestor of humans and chimpanzees is believed to have lived approximately 6 million to 7 million years ago (see Human Evolution). On the other hand, an ancestor common to humans and reptiles lived some 300 million years ago. And the common ancestor to even more distantly related forms lived even further in the past. Evolutionary biologists attempt to determine the history of lineages as they diverge and how differences in characteristics developed over time.

Comments

Post a Comment

Popular posts from this blog

The Animal Kingdom

-
Image
. Kingdom Animalia includes more than one million living species, grouped into more than 30 phyla. Vertebrates, members of the phylum Chordata, comprise only one percent of these organisms. Phylum Arthropoda is more successful in sheer numbers, total mass, and distribution than all other groups of animals combined. The remaining animal phyla are composed of mostly marine-dwelling organisms. THE MAJOR PHYLA : Acanthocephala (Spiny-Headed Worm) Annelida (Annelids) Arthropoda (Arthropods)-> subphyla: Chelicerata, Crustacea, and Unirama Brachiopoda (Lampshell) Chaetognatha (Arrowworm) Chordata (Chordates)-> subphyla: Cephalochordata, Tunicata , Vertebrata ( fishes , amphibians , reptiles , birds , and mammals ) Cnidaria (Cnidarians) Ctenophora (Comb Jellies) Cycliophora (Symbion) Echinodermata (Echinoderms)-> Subphyla: Pelmatozoa, Eleutherozoa Echiura (Spoonworm) Ectoprocta (Moss Animals) or Bryozoa Entoprocta (Entoprocts) Gastrotricha (Gastrotrich) Gnathostomulida
Read more

Land Habitats

-
On land, animal habitats are strongly influenced by climate, the combination of precipitation and temperature conditions experienced in a region. At or near the equator, year-round moisture and warmth generates a constant supply of food. Further north or south, seasonal changes become much more pronounced, shaping the type of animals that live in different habitats and their strategies for survival (see Animal Distribution ). Tropical and subtropical forests are home to by far the largest number of animal species on land. These animals include the majority of the world's insects, most of its primates, and a large proportion of its birds. Tropical forests have existed longer than any other forests on earth and their plants and animals have evolved an elaborate web of interrelationships. Much of the animal life of tropical forests is still poorly known, and new species are constantly being discovered. The majority of these newly identified animals are invertebrates, but larger anima
Read more

Chimpanzee

-
Chimpanzee, an ape, genus Pan, of the equatorial forests of central and W Africa. The common chimpanzee, Pan troglodytes, lives N of the Congo River. Full-grown animals of this species are up to 5 ft (1.5 m) tall and weigh about 150 lb (68 kg); they have an arm spread of up to 9 ft (2.7 m) and are much stronger than humans. They are covered with long, black hair over most of the body and have naked faces ranging in color from nearly white to nearly black. The pygmy chimpanzee, P. paniscus, now usually called the bonobo, lives south of the Congo. It is a bit smaller and more slenderly built, with a black face. Chimpanzees spend much time on the ground, where they walk on all fours, using the soles of the feet and the knuckles of the hands; they can also stand on two legs and sometimes walk this way for short distances. They climb trees in pursuit of food and for nesting and can swing by their hands from branch to branch. Their diet consists largely of fruit and other plant matter, but
Read more