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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 [1] It was repealed by a joint act of Congress on 21 May 1838.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]
Edward Hitchcock's fold-out paleontological chart in his 1840 Elementary Geology. Although tree-like diagrams have long been used to organise knowledge, and although branching diagrams known as claves ("keys") were omnipresent in eighteenth-century natural history, it appears that the earliest tree diagram of natural order was the 1801 "Arbre botanique" (Botanical Tree) of the French ...
LD 350-1 is now considered the earliest known specimen of the genus Homo, dating to 2.75–2.8 Ma, found in the Ledi-Geraru site in the Afar Region of Ethiopia. It is currently unassigned to a species, and it is unclear if it represents the ancestor to H. habilis and H. rudolfensis, which are estimated to have evolved around 2.4 Ma. [36]
Hard money policies support a specie standard, usually gold or silver, typically implemented with representative money. In 1836, when President Andrew Jackson 's veto of the recharter of the Second Bank of the United States took effect, he issued the Specie Circular , an executive order that all public lands had to be purchased with hard money.
[2] [3] Estimates on the number of Earth's current species range from 10 million to 14 million, [4] with about 1.2 million or 14% documented, the rest not yet described. [5] However, a 2016 report estimates an additional 1 trillion microbial species, with only 0.001% described. [6]
This tree diagram, used to show the divergence of species, is the only illustration in the Origin of Species. Darwin proposes sexual selection , driven by competition between males for mates, to explain sexually dimorphic features such as lion manes, deer antlers, peacock tails, bird songs, and the bright plumage of some male birds. [ 129 ]
Controversy exists as to whether Charles Darwin recognized a true geographical-based model of speciation in his publication On the Origin of Species. [5] In chapter 11, "Geographical Distribution", Darwin discusses geographic barriers to migration, stating for example that "barriers of any kind, or obstacles to free migration, are related in a close and important manner to the differences ...
The biologist Ernst Mayr championed the concept of ring species, stating that it unequivocally demonstrated the process of speciation. [10] A ring species is an alternative model to allopatric speciation, "illustrating how new species can arise through 'circular overlap', without interruption of gene flow through intervening populations…"