Search results
Results from the WOW.Com Content Network
Species go extinct constantly as environments change, as organisms compete for environmental niches, and as genetic mutation leads to the rise of new species from older ones. At long irregular intervals, Earth's biosphere suffers a catastrophic die-off, a mass extinction , [ 9 ] often comprising an accumulation of smaller extinction events over ...
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 ...
There are numerous species of cichlids that demonstrate dramatic variations in morphology. Given the right circumstances, and enough time, evolution leads to the emergence of new species. Scientists have struggled to find a precise and all-inclusive definition of species. Ernst Mayr defined a species as a population or group of populations ...
In 1941, a committee chaired by Horace E. Wood II compiled a list of 19 "provincial ages" for North America, later called North American Land Mammal Ages (NMLAs). An example of an NMLA is the Rancholabrean, named after the Rancho La Brea fossil site. One of its characteristic fossils is the bison, which first appears in the Rancholabrean. [7]
On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (1st ed.). London: John Murray. ISBN 978-1-4353-9386-8. Darwin, Charles (1872). The Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (6th ed.). London: John Murray.
This species might be evolved some time before, up to c. 2 Ma ago. c. 1.7 Ma – Australopithecines go extinct. c. 1.8–0.8 Ma – colonisation of Eurasia by Homo erectus. c. 1.5 Ma – earliest possible evidence of the controlled use of fire by Homo erectus; c. 1.2 Ma – Homo antecessor evolves. Paranthropus dies out.
A towel on the floor means, 'Please replace.' Thank your for helping us conserve the Earth's vital resources." The card was decorated with the three green arrows that make up the recycling symbol.
Land plants evolved from a group of freshwater green algae, perhaps as early as 850 mya, [3] but algae-like plants might have evolved as early as 1 billion years ago. [2] The closest living relatives of land plants are the charophytes, specifically Charales; if modern Charales are similar to the distant ancestors they share with land plants, this means that the land plants evolved from a ...