What are the five main items used to support the theory of evolution?

Answer 1

I don't know about there being five things used in favour of evolution, but there are many nonetheless. Below are some supports for Darwin's Theory of Evolution.

Comparative anatomy: The bones of vertebrate forelimbs are 'homologous'. They have common ancestry. You can identify the same bones in the hand of a bat as there are in the hand of a human, the leg of a horse, the flipper of a whale or the paw of a cat. Evolution does not start from scratch all the time but adapts what is already present. Thus once evolution was equipped with forelimb bones, it simply stretched them to support a wing (in bats), strengthened them for beating down water (in whales) or warped their agility to the gripping ability of a human hand.

There are also 'vestigial' anatomical structures which are seen as very convincing of evolution. Whales evolved from hoofed terrestrial herbivores. Whales have foreflippers but not hindflippers. There are however vestigial bones in the hindquarters, which are the left overs of the ancestral terrestrial artiodactyl. Pythons are snakes (thus legless) but evolved from limbed lizards (varanids may be the closest lizard relatives to snakes). Pythons have vestigial hindlimb bones too.

Comparative genetics: Modern science can, incredibly, sequence whole sections of an organism's genome or indeed the whole genome. The genome is composed of DNA, and what is 'sequenced' are the bases of that DNA. DNA bases are abbreviated A, T, C and G. Say you select a frog, a snake and a dog as representatives of amphibians, reptiles and mammals. Now you sequence a gene that each of them share and compare the sequences.

Hypothetical sequences:

Dog: AAAGCGGGGTAG

Snake: AAAGCCGGGTAC

Frog: AAGCCCCGGAAC

You would expect the sequences to show a pattern like the one above, where the most sequence differences are between most distantly related organisms. Evolution would predict that a dog is more closely related to a snake than to a frog. If you come up with a sequence like the above, there are a greater number of AGCT (base) differences between the dog and the frog than between the dog and the snake. This would confirm the idea that snakes and dogs are more closely related than frogs and dogs. Such sequencing has been done and the results have confirmed all of the Theory of Evolutions's predictions.

The fossil record: The fossil record provides many extinct transitions between major taxa. Archaeopteryxrepresent a reptilian-avian transition. Tiktaalik and Icthyostega and relatives give clues as to the sarcopterygian-amphibian transition. Early hominid skulls are representations of transitions from Australopithecus and early Homo to our present species Homo sapiens.

There are also modern (extant) animals and plants that give clues as to transitions. These extant examples are remnants of lineages of ancient organisms that have survived to the present. Platypuses show the reptilian-mammalian transition. Some plants like Welwitschia and other gnetophytes give clues to gymnosperm-angiosperms transitions.

Additionally there is a lot of molecular and chromosomal work done. Origins of species are sometimes demonstrated by this investigation. Apparently an single species of Aethomys mouse was investigated and it was found that the sperm cells of one group were incompatible with the egg cells of another. The two groups were sympatrically and reproductively isolated and were thus separate species.

Chromosomes can fuse together. This reproductively isolates populations and thus promotes speciation. Chromosomes fused somewhere in the lineage between the Chimpanzee-Human common ancestor and modern Homo sapiens. Chromosomes fuse and split all over the place across the animal kingdom. Plant chromosomes merge due to imperfect meiosis probably and produce nondiploid polyploid individuals. All of this promotes reproductive isolation and thus speciation and speciation is the way evolution makes progress.