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The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
Sexual reproduction may have increased the rate of evolution. [52] By 1000 Ma First non-marine eukaryotes move onto land. They were photosynthetic and multicellular, indicating that plants evolved much earlier than originally thought. [53] 750 Ma Beginning of animal evolution. [54] [55] 720–630 Ma
Carcinisation (American English: carcinization) is a form of convergent evolution in which non-crab crustaceans evolve a crab-like body plan. The term was introduced into evolutionary biology by L. A. Borradaile, who described it as "the many attempts of Nature to evolve a crab". [2]
All of these facts, the types of plants and animals found on oceanic islands, the large number of endemic species found on oceanic islands, and the relationship of such species to those living on the nearest continents, are most easily explained if the islands were colonized by species from nearby continents that evolved into the endemic ...
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
He also argued that the first human of the form known today must have been the child of a different type of animal (probably a fish), because man needs prolonged nursing to live. [8] [9] [7] In the late nineteenth century, Anaximander was hailed as the "first Darwinist", but this characterization is no longer commonly agreed. [10]
Squids are shrinking, birds are migrating and lizards are getting blown away by hurricanes. The signs are everywhere; animals are changing because of climate change. We asked biologist Thor Hanson ...
The result of four billion years of evolution is the diversity of life around us, with an estimated 1.75 million different species in existence today. [71] [72] Usually the process of speciation is slow, occurring over very long time spans; thus direct observations within human life-spans are rare.