Darwin ´s 4 Postulates
Variation, Inheritance, Differential Survival and Extinction
Individuals are Variables
Darwin already knew that each organism carried their own set of unique traits. Each variable or unique organism seemed to carry a different combination of genes which was driving Charles Darwin a bit confuse. He did´nt knew that each organism seem to have genetic differences which made them unique. In order to have a variation of genes, the animal or individual needs to adapt to a certain mutation. This mutation alters their genes creating new alleles that arise new DNA replications. This DNA replication is what makes that family or expand or grow more. In Variation, existing genes alter, making the DNA damage repair during cell division. In other words, Variation is not only involved with mutations but also during sexual reproduction were new DNA combinations are created making the variable stronger or weaker.
Some Variations are Passed Down
Way back in 1856, our world was This statement was a truly unique portion of Darwin's theory. In 1856, he did not know about DNA. He did not know about recombination events. He did not even know about genes. He merely understood that for selection to occur, variations must be transmittable from parent to offspring. We now know, that variation is caused by differences in genes and genes are passed on to offspring. More importantly, different genes are passed on to offspring independently of each other (independent assortment) and intact.
More offspring are produced than can survive
In most generations, more offspring are born than can survive to reproductive age given selection pressures such as predation and limited food supply. For example, many fish lay hundreds or even thousands of eggs at once, yet most of the young will be eaten or will starve before they can produce young of their own and pass down their genes (and the genes of their parents).
Reproduction and survival are not random
Since more offspring are produced than can survive, some must die. Those that survive are those that have the greatest fitness. A trait that increases an individual's fitness is called an adaptation. Those individuals with the genes that convey traits that are best adapted to the environment in which the organism lives (those with high fitness) are more likely to survive and reproduce than those that are less adapted to their environment (those with low fitness).