Charles Darwin theory

Answer 1

Darwin's Theory of Evolution is the widely held notion that all life is related and has descended from a common ancestor: the birds and the bananas, the fishes and the flowers -- all related. Darwin's general theory presumes the development of life from non-life and stresses a purely naturalistic (undirected) "descent with modification". That is, complex creatures evolve from more simplistic ancestors naturally over time. In a nutshell, as random genetic mutations occur within an organism's genetic code, the beneficial mutations are preserved because they aid survival -- a process known as "natural selection." These beneficial mutations are passed on to the next generation. Over time, beneficial mutations accumulate and the result is an entirely different organism (not just a variation of the original, but an entirely different creature).

Answer 2

The idea that organisms could change with time pre-existed Charles Darwin. However, it was Darwin himself who gathered the first major evidence into the definitive book on the subject The Origin of Species. Darwin's addition to the concept of change of organisms across time was the concept of selection. There are three types of selection: Artificial Selection, Sexual Selection and Natural Selection. He used Artificial Selection to back up the hypothesis that organisms harbour within themselves the capacity to change from common ancestors. Artificial Selection is obvious, as should be the notion that life derives from common ancestry. Chihuahuas, Alsations, Dachshunds etcetera have all been artificially selected and derive from the Canis lupus common ancestor. Birmingham Rollers and many other breeds of pigeon (Darwin bred pigeons so would know what he was talking about) derive from the Columba livia common ancestor. Artificial Selection is simply an illustration. It seems Natural Selection should be the true ruler of Selection in the wild undomesticated world. Natural Selection states that whatever has a morphology or biochemistry or behaviour that does not allow it to survive and reproduce, will not do so. Desert animals do not have thick coats. Ptarmigans are not black in winter. Birds have airsacks in addition to lungs. Gazelles have eyes on the sides of their heads and as a result are better able to scan for predators.

In other words, from predarwinian change-thoughts, a mechanism for that change had been added by Darwin, that whatever is around today is the result of Natural Selection.

But Natural Selection is simply the selector of what change survives and what doesn't. The change itself is brought about by genetics. Mendel's Genetics knowledge came too late for Darwin to add into his own work. DNA was only discovered by Watson and Crick in 1953. The story of Darwin ended and modern genetics took over, explaining where change comes from. DNA replicates prior to gametogenesis and errors are made by the enzymatic processes that replicate the DNA. During meiosis, DNA is randomly segregated, splitting maternal and paternal chromosomes into separate and randomly assorted gametes, giving high possibility that the offspring should differ slightly from their parents. Now, the picture is even more complex; chromosomal rearrangements during meiosis may reproductively isolate the offspring of a pairing. See articles on chromosomal rearrangement in muntjaks and many rodents for more information.

There is also a fossil component, displaying past evolution. Darwin predicted that there should be transitional forms between major taxa, and he was right. Archaeopteryx (discovered 1859) is transitional between coelurosaurs and birds. Tiktaalik, Ichthyostega and Acanthostega show the evolution of the amphibian leg from the fish's fin. Mammal-like reptiles of the Permian show the evolution of the mammal jaw. There are many australopithecine and Homo intermediates between early apes and Homo sapiens. There are many species of extinct elephant and horse and giraffe and seal and Ambulocetus and Rodhocetus show the evolution of the whale.

Thus I would phrase The Theory of (Darwinian) Evolution by Means of Natural Selection as a theory of how life comes to be as it is, via change, at any moment of time. It is documented by the fossil record which shows how past life evolved to the present life we see now. Genetics and cytogenetics show how new species arose (past) and arise (present) and how the change itself occurs. Natural Selection explains how the change that emerges genetically is either 'selected' or 'not selected'; in other words how the survival of what morphologies and behaviours can survive, do survive, whereas the morphologies and behaviours that fail when faced with the environment, do not survive. And central to the theory, all life proceeds by common ancestry.

Answer 3

That through time, a species of animal, plant, bacterium can change.

When a life form reproduces, one of its"babies" may be different from its parents because of genetic mutation. Sometime, this mutation may give it an advantage over other individuals of its specie. (e.g.: A giraffe has a higher neck and can search food on high trees.) Because of this advantage, the life form that is different (we will call it A) can live longer and has better chances to reproduce. The life form that has not this advantage (we will call it B) will live less longer and will have less chances to reproduce. Because of that, the population of "A" will increase and the population of "B"will decrease. In the end, there will only be "A".

Answer 4

The theory of Natural selection. Basically, any trait that makes an animal more responsive to change will allow it to survive longer, giving it more opportunity for it to mate, and therefore pass on it's genes.

Answer 5

Charles Robert Darwin, established that all species of life have descended over time from common ancestry.

Answer 6

The origin of species by natural selection/the theory of evolution

Answer 7

The theory of evolution by natural selection.