A report on Natural selection and An Essay on the Principle of Population

Modern biology began in the nineteenth century with Charles Darwin's work on evolution by natural selection.

Title page of the original edition of 1798

Aristotle considered whether different forms could have appeared, only the useful ones surviving.

Part of Thomas Malthus's table of population growth in England 1780–1810, from his An Essay on the Principle of Population, 6th edition, 1826

Part of Thomas Malthus's table of population growth in England 1780–1810, from his Essay on the Principle of Population, 6th edition, 1826

Charles Darwin noted that pigeon fanciers had created many kinds of pigeon, such as Tumblers (1, 12), Fantails (13), and Pouters (14) by selective breeding.

Evolutionary developmental biology relates the evolution of form to the precise pattern of gene activity, here gap genes in the fruit fly, during embryonic development.

During the industrial revolution, pollution killed many lichens, leaving tree trunks dark. A dark (melanic) morph of the peppered moth largely replaced the formerly usual light morph (both shown here). Since the moths are subject to predation by birds hunting by sight, the colour change offers better camouflage against the changed background, suggesting natural selection at work.

1: directional selection: a single extreme phenotype favoured. 2, stabilizing selection: intermediate favoured over extremes. 3: disruptive selection: extremes favoured over intermediate. X-axis: phenotypic trait Y-axis: number of organisms Group A: original population Group B: after selection

Different types of selection act at each life cycle stage of a sexually reproducing organism.

The peacock's elaborate plumage is mentioned by Darwin as an example of sexual selection, and is a classic example of Fisherian runaway, driven to its conspicuous size and coloration through mate choice by females over many generations.

Selection in action: resistance to antibiotics grows though the survival of individuals less affected by the antibiotic. Their offspring inherit the resistance.

The book's 6th edition (1826) was independently cited as a key influence by both Charles Darwin and Alfred Russel Wallace in developing the theory of natural selection.

- An Essay on the Principle of Population

Darwin's ideas were inspired by the observations that he had made on the second voyage of HMS Beagle (1831–1836), and by the work of a political economist, Thomas Robert Malthus, who, in An Essay on the Principle of Population (1798), noted that population (if unchecked) increases exponentially, whereas the food supply grows only arithmetically; thus, inevitable limitations of resources would have demographic implications, leading to a "struggle for existence".

- Natural selection

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Alfred Russel Wallace

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British naturalist, explorer, geographer, anthropologist, biologist and illustrator.

Arenga pinnata sketched by Wallace on a visit to Celebes and later reworked by Walter Hood Fitch

A photograph from Wallace's autobiography shows the building Wallace and his brother John designed and built for the Neath Mechanics' Institute.

A map from The Malay Archipelago shows the physical geography of the archipelago and Wallace's travels around the area. The thin black lines indicate where Wallace travelled, and the red lines indicate chains of volcanoes.

An illustration from The Malay Archipelago depicts the flying frog Wallace discovered.

A photograph of Wallace taken in Singapore in 1862

Wallace's grave in Broadstone Cemetery, Broadstone, Dorset, which was restored by the A. R. Wallace Memorial Fund in 2000. It features a 7 ft tall fossil tree trunk from Portland mounted on a block of Purbeck limestone.

The Darwin–Wallace Medal was issued by the Linnean Society on the 50th anniversary of the reading of Darwin and Wallace's papers on natural selection. Wallace received the only gold example.

An illustration from the chapter on the application of natural selection to humans in Wallace's 1889 book Darwinism shows a chimpanzee.

A map of the world from The Geographical Distribution of Animals shows Wallace's six biogeographical regions.

The line separating the Indo-Malayan and the Austro-Malayan region in Wallace's On the Physical Geography of the Malay Archipelago (1863)

Spirit photograph taken by Frederick Hudson of Wallace and his late mother; he may have used double exposure.

Wallace and his signature on the frontispiece of Darwinism (1889)

Anthony Smith's statue of Wallace, looking up at a bronze model of a Wallace's golden birdwing butterfly. Natural History Museum, London, unveiled 7 November 2013

Alfred Russel Wallace, attributed to John William Beaufort (1864–1943), a portrait in the Central Hall of the Natural History Museum, London.

Corvus enca celebensis, Sula Islands, registered in 1861 at a forerunner of Naturalis Biodiversity Center

Toxorhamphus novaeguineae novaeguineae, Misool, Raja Ampat Islands, 1865

Pitohui ferrugineus leucorhynchus, Waigeo, West-Papua, no year

Nectarinia jugularis clementiae, Seram Island, 1865

Mino anais anais, South West Papua, 1863

He is best known for independently conceiving the theory of evolution through natural selection.

Wallace spent many hours at the library in Leicester: he read An Essay on the Principle of Population by Thomas Robert Malthus, and one evening he met the entomologist Henry Bates.

Darwin, c. undefined 1854, when he was preparing On the Origin of Species for publication

Charles Darwin

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English naturalist, geologist and biologist, best known for his contributions to evolutionary biology.

A chalk drawing of the seven-year-old Darwin in 1816, with a potted plant, by Ellen Sharples

Bicentennial portrait by Anthony Smith of Darwin as a student, in the courtyard at Christ's College, Cambridge where he had rooms.

The round-the-world voyage of the Beagle, 1831–1836

Darwin (right) on the Beagle's deck at Bahía Blanca in Argentina, with fossils; caricature by Augustus Earle, the initial ship's artist.

As HMS Beagle surveyed the coasts of South America, Darwin theorised about geology and the extinction of giant mammals. Watercolour by the ship's artist Conrad Martens, who replaced Augustus Earle, in Tierra del Fuego.

While still a young man, Darwin joined the scientific elite. Portrait by George Richmond.

In mid-July 1837 Darwin started his "B" notebook on Transmutation of Species, and on page 36 wrote "I think" above his first evolutionary tree.

Darwin chose to marry his cousin, Emma Wedgwood.

Darwin in 1842 with his eldest son, William Erasmus Darwin

Darwin's "sandwalk" at Down House was his usual "Thinking Path".

Darwin aged 46 in 1855, by then working towards publication of his theory of natural selection. He wrote to Joseph Hooker about this portrait, "if I really have as bad an expression, as my photograph gives me, how I can have one single friend is surprising."

During the Darwin family's 1868 holiday in her Isle of Wight cottage, Julia Margaret Cameron took portraits showing the bushy beard Darwin grew between 1862 and 1866.

An 1871 caricature following publication of The Descent of Man was typical of many showing Darwin with an ape body, identifying him in popular culture as the leading author of evolutionary theory.

By 1878, an increasingly famous Darwin had suffered years of illness.

The adjoining tombs of John Herschel and Charles Darwin in the nave of Westminster Abbey, London

In 1881 Darwin was an eminent figure, still working on his contributions to evolutionary thought that had an enormous effect on many fields of science. Copy of a portrait by John Collier in the National Portrait Gallery, London.

Unveiling of the Darwin Statue at the former Shrewsbury School building in 1897

In 1851 Darwin was devastated when his daughter Annie died. By then his faith in Christianity had dwindled, and he had stopped going to church.

A caricature of Darwin from a 1871 Vanity Fair

Statue of Darwin in the Natural History Museum, London

In a joint publication with Alfred Russel Wallace, he introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding.

Continuing his research in London, Darwin's wide reading now included the sixth edition of Malthus's An Essay on the Principle of Population.

On the Origin of Species

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Work of scientific literature by Charles Darwin that is considered to be the foundation of evolutionary biology.

Darwin pictured shortly before publication

Cuvier's 1799 paper on living and fossil elephants helped establish the reality of extinction.

Darwin researched how the skulls of different pigeon breeds varied, as shown in his Variation of Plants and Animals Under Domestication of 1868.

A photograph of Alfred Russel Wallace (1823–1913) taken in Singapore in 1862

On the Origin of Species by means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, 2nd edition. By Charles Darwin, John Murray, London, 1860. National Museum of Scotland

John Gould's illustration of Darwin's rhea was published in 1841. The existence of two rhea species with overlapping ranges influenced Darwin.

This tree diagram, used to show the divergence of species, is the only illustration in the Origin of Species.

In the 1870s, British caricatures of Darwin with a non-human ape body contributed to the identification of evolutionism with Darwinism.

Huxley used illustrations to show that humans and apes had the same basic skeletal structure.

Haeckel showed a main trunk leading to mankind with minor branches to various animals, unlike Darwin's branching evolutionary tree.

The liberal theologian Baden Powell defended evolutionary ideas by arguing that the introduction of new species should be considered a natural rather than a miraculous process.

A modern phylogenetic tree based on genome analysis shows the three-domain system.

Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection.

In late September 1838, he started reading Thomas Malthus's An Essay on the Principle of Population with its statistical argument that human populations, if unrestrained, breed beyond their means and struggle to survive.