Charles Darwin was a British naturalist who proposed the theory of biological evolution by natural selection. Darwin defined evolution as “descent with modification,” the idea that species change over time, give rise to new species, and share a common ancestor.
In order for natural selection to occur, three conditions must be met: There must be variation for the particular trait within a population. The variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).
Darwin’s theory of evolution, also called Darwinism, can be further divided into 5 parts: “evolution as such”, common descent, gradualism, population speciation, and natural selection.
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual’s ability to compete, survive, and reproduce.
Natural selection is an inevitable outcome of three principles: most characteristics are inherited, more offspring are produced than are able to survive, and offspring with more favorable characteristics will survive and have more offspring than those individuals with less favorable traits.
The essence of Darwin’s theory is that natural selection will occur if three conditions are met. These conditions, highlighted in bold above, are a struggle for existence, variation and inheritance. These are said to be the necessary and sufficient conditions for natural selection to occur.
Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the
So main theories of evolution are: (II) Darwinism or Theory of Natural Selection. (III) Mutation theory of De Vries. (IV) Neo- Darwinism or Modern concept or Synthetic theory of evolution.
Branching descent and natural selection are the two key concepts of Darwinian Theory of Evolution.
Groups of species undergo various kinds of natural selection and, over time, may engage in several patterns of evolution: convergent evolution, divergent evolution, parallel evolution, and coevolution.
The four key points of Darwin’s Theory of Evolution are: individuals of a species are not identical; traits are passed from generation to generation; more offspring are born than can survive; and only the survivors of the competition for resources will reproduce.
According to the scientific method, a “ theory ” is an explanation grounded in a large amount of evidence. Among scientists, evolution is considered a very solid, well-trusted idea, and one of the most fundamental laws of nature. In fact, evolution is a theory just like thermodynamics and gravity.
Five types of evidence for evolution are discussed in this section: ancient organism remains, fossil layers, similarities among organisms alive today, similarities in DNA, and similarities of embryos.