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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 eukaryotic cell seems to have evolved from a symbiotic community of prokaryotic cells. DNA-bearing organelles like mitochondria and chloroplasts are remnants of ancient symbiotic oxygen-breathing bacteria and cyanobacteria, respectively, where at least part of the rest of the cell may have been derived from an ancestral archaean prokaryote ...
Coalescent theory – Model for tracing the history of genetic variation; Variation Genetic variation – Difference in DNA among individuals or populations Genetic diversity – Total number of genetic characteristics in a species; Gene frequency – The relative frequency of a variant of a gene at a particular locus in a population
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 While Haeckel's tree is outdated, it illustrates clearly the principles that more complex and accurate modern reconstructions can obscure.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 ...
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 [1] It was repealed by a joint act of Congress on 21 May 1838.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]
The frontispiece to Erasmus Darwin's evolution -themed poem The Temple of Nature shows a goddess pulling back the veil from nature (in the person of Artemis). Allegory and metaphor have often played an important role in the history of biology. Part of a series on Biology Index Outline Glossary History (timeline) Key components Cell theory Ecosystem Evolution Phylogeny Properties of life ...