Search results
Results from the WOW.Com Content Network
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.
The evolution of fishes took place over a timeline which spans the Cambrian to the Cenozoic, including during that time in particular the Devonian, which has been dubbed the "age of fishes" for the many changes during that period. The Late Devonian extinctions played a crucial role in shaping the evolution of fish, or vertebrates in general. [1]
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 .
A cyclic model (or oscillating model) is any of several cosmological models in which the universe follows infinite, or indefinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a Big Bang and ending with a Big Crunch; in the interim, the ...
The transition from fins to limbs occurred once an endoskeleton entered the base of the fin, as seen in today's lungfish. [21] This is thought to have originated in the group Sarcopterygians , including osteolipiforms like Eusthenopteron , due to the homology of the tetrapod forelimb and the osteolepiform fin endoskeleton.
The chronology of the universe describes the history and future of the universe according to Big Bang cosmology.. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level.
Main page; Contents; Current events; Random article; About Wikipedia; Contact us
The book The Five Ages of the Universe discusses the history, present state, and probable future of the universe, according to cosmologists' current understanding. The book divides the timeline of the universe into five eras: the Primordial Era, the Stelliferous Era, the Degenerate Era, the Black Hole Era and the Dark Era.