Theory of Evolution

Nicholas steno is credited as the father of paleontology and fossils. His theory proposed structure of quartz crystals, suggested that fossils were the remains of ancient organisms, and that the study of the earth's strata could provide a history of the planet.

Buffon's idea that species change over time has become the cornerstone of the modern of evolutionary theory. His technique of comparing similar structures across different species, called comparative anatomy, is used today in the study of evolution and is discussed in evidence of evolution.

Thomas Robert Malthus argued that, left unchecked, a population will outgrow its resources. He discussed two ways to 'check' a population: preventive checks, like the moral restraint of postponing marriage, or positive checks, like famine, disease and warfare.

Lamarck believed that living things evolved in a continuously upward direction, from dead matter, through simple to more complex forms, toward human "perfection." Species didn't die out in extinctions, Lamarck claimed. The law of use and disuse, which states that when certain organs become specially developed as a result of some environmental need, then that state of development is hereditary and can be passed on to progeny.

Georges Cuvier developed his theory of catastrophes. Accordingly, fossils show that animal and plant species are destroyed time and again by deluges and other natural cataclysms, and that new species evolve only after that.

He influenced Darwin so deeply that Darwin envisioned evolution as a sort of biological uniformitarianism. Evolution took place from one generation to the next before our very eyes, he argued, but it worked too slowly for us to perceive. Lyell also gave influential explanations of earthquakes and developed the theory of gradual "backed up-building" of volcanoes.

Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits. date shows his work with the pea plants

Both men believed that species descend from common ancestors, and they determined that species evolve through their 'struggle for existence'. More individuals are produced each generation that can survive. Phenotypic variation exists among individuals and the variation is heritable. Those individuals with heritable traits better suited to the environment will survive.

Known as "population genetics," their approach revealed how mutations arise and, if they are favored by natural selection, can spread through a population. Even a slight advantage can let an allele spread rapidly through a group of animals or plants and drive other forms extinct. Evolution, these population geneticists argued, is carried out mainly by small mutations, since drastic mutations would almost always be harmful rather than helpful.

Punctuated equilibrium is a theory in evolutionary biology which proposes that once a species appears in the fossil record the population will become stable, showing little evolutionary change for most of its geological history. This state of little or no morphological change is called stasis.