Iridium is a chemical element in the periodic table that has the symbol Ir and atomic number 77. A dense, very hard, brittle, silvery-white transition metal of the platinum family, iridium is used in ... > more
Fossils are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. The totality of fossils and their placement in fossiliferous ... > more
This timeline of the evolution of life outlines the major events in the development of life on the planet Earth. Dates given are estimates based on scientific evidence.
In biology, evolution is the ... > more
The cetaceans (whales, dolphins and porpoises) are descendants of land-living mammals, and remnants of their terrestrial origins can be found in the fact that they must breathe air from the surface; ... > more
In biology and ecology, extinction is the cessation of existence of a species or group of taxa, reducing biodiversity. The moment of extinction is generally considered to be the death of the last ... > more
The timeline of human evolution outlines the major events in the development of humans species and the evolution of human's ancestors. It begins with the time of the origin of life and presents a ... > more
The Stone Age is a broad prehistoric time period during which humans widely used stone for toolmaking. Stone tools were made from a variety of different kinds of stone. For example, flint and chert ... > more
Rodentia is an order of mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must be kept short by gnawing.
Forty-percent of mammal ... > more
Birds are bipedal, warm-blooded, oviparous vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. Birds range in size from the tiny hummingbirds to the huge ... > more