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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 ...
However, viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon. Major extinctions in terrestrial vertebrates and large amphibians. Earliest examples of armoured dinosaurs. 195 Ma First pterosaurs with specialized feeding (Dorygnathus). First sauropod dinosaurs.
The largest unanswered question in evolution is how simple protocells first arose and differed in reproductive contribution to the following generation, thus initiating the evolution of life. The lipid world theory postulates that the first self-replicating object was lipid -like.
The diversity of life forms did not increase significantly because of a series of mass extinctions that define widespread biostratigraphic units called biomeres. [159] After each extinction pulse, the continental shelf regions were repopulated by similar life forms that may have been evolving slowly elsewhere. [ 160 ]
The basic idea was that life was continuously created as a result of chance events. [17] In the 17th century, people began to question spontaneous generation, in works like Thomas Browne's Pseudodoxia Epidemica. His contemporary, Alexander Ross, erroneously rebutted him. [18] [19] In 1665, Robert Hooke published the first drawings of a ...
Other important Andean cultures include the Moche, whose ceramics depict many aspects of daily life, and the Nazca, who created animal-shaped designs in the desert called Nazca lines. [112] The Olmecs of Mesoamerica developed by about 1200 BCE [ 113 ] and are known for the colossal stone heads that they carved from basalt . [ 114 ]
[1] [2] [3] The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago. [4] [5] [6] Evolution does not attempt to explain the origin of life (covered instead by abiogenesis), but it does explain how early lifeforms evolved into the complex ecosystem that we see today. [7]
Evolutionary thought, the recognition that species change over time and the perceived understanding of how such processes work, has roots in antiquity. With the beginnings of modern biological taxonomy in the late 17th century, two opposed ideas influenced Western biological thinking: essentialism, the belief that every species has essential characteristics that are unalterable, a concept ...