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Abiogenesis is the natural process by which ... For example, a cell, whether the LUCA or in a modern organism, copies its DNA with the DNA polymerase enzyme, which is ...
Spontaneous generation, the first naturalistic theory of abiogenesis, goes back to Aristotle and ancient Greek philosophy, and continued to have support in Western scholarship until the 19th century. [15] The theory held that "lower" animals are generated by decaying organic substances.
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 ...
Unsolved problems relating to the behaviour of animals include: Homing. A satisfactory explanation for the neurobiological mechanisms that allow homing in animals has yet to be found. Flocking (behavior). How flocks of birds and bats coordinate their movements so quickly is not fully understood.
A scenario is a set of related concepts pertinent to the origin of life (abiogenesis), such as the iron-sulfur world. Many alternative abiogenesis scenarios have been proposed by scientists in a variety of fields from the 1950s onwards in an attempt to explain how the complex mechanisms of life could have come into existence. These include ...
The History of Animals contains many accurate eye-witness observations, in particular of the marine biology around the island of Lesbos, such as that the octopus had colour-changing abilities and a sperm-transferring tentacle, that the young of a dogfish grow inside their mother's body, or that the male of a river catfish guards the eggs after ...
The timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth. Dates in this article are consensus estimates based on scientific evidence , mainly fossils .
Biologists can study life at multiple levels of organization, [1] from the molecular biology of a cell to the anatomy and physiology of plants and animals, and the evolution of populations. [ 1 ] [ 6 ] Hence, there are multiple subdisciplines within biology , each defined by the nature of their research questions and the tools that they use.