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In evolutionary biology, the term cellularization (cellularisation) has been used in theories to explain the evolution of cells, for instance in the pre-cell theory, [1] [2] [3] dealing with the evolution of the first cells on this planet, and in the syncytial theory [4] attempting to explain the origin of Metazoa from unicellular organisms.
From these conclusions about plants and animals, two of the three tenets of cell theory were postulated. 1. All living organisms are composed of one or more cells 2. The cell is the most basic unit of life. Schleiden's theory of free cell formation through crystallization was refuted in the 1850s by Robert Remak, Rudolf Virchow, and Albert ...
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 .
The Specie Circular is a United States presidential executive order issued by President Andrew Jackson on 11 July 1836 pursuant to the Coinage Act of 1834. It required payment for government land to be in gold and silver (specie). [1] It was repealed by a joint act of Congress on 21 May 1838. [2]
Image from his textbook The Cell in Development and Inheritance, second edition, 1900. Edmund Beecher Wilson (October 19, 1856 – March 3, 1939) [2] was a pioneering American zoologist and geneticist. He wrote one of the most influential textbooks in modern biology, The Cell. [3] [4] He discovered the chromosomal XY sex-determination system in ...
A phylogenetic tree, phylogeny or evolutionary tree is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time. [ 1 ] [ 2 ] In other words, it is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon ...
The evolutionary history of species has been described as a "tree" with many branches arising from a single trunk. While Haeckel's tree is outdated, it illustrates clearly the principles that more complex and accurate modern reconstructions can obscure.
Objections to evolution have been raised since evolutionary ideas came to prominence in the 19th century. When Charles Darwin published his 1859 book On the Origin of Species, his theory of evolution (the idea that species arose through descent with modification from a single common ancestor in a process driven by natural selection) initially met opposition from scientists with different ...