Question

Basic logic of natural selection and how scientists test hypotheses of natural selection

Answer 1

Basic logic of Natural Selection :-

Natural Selection based on four characteristics of living systems.

1. Variation :- every organism has unique features that's the reason behind individuals in a population vary from one another.

2. Inheritance :- Traits (genotypes and phenotypes) can passes through one generation to next generation (like parents to offsprings)

3.Selection :- some variants reproduce more than others which makes them beneficial during Natural Selection.

Those organism reproduced most with the suitable traits which are favourable to environment ,survived most due to natural selection.The higher the reproduction rate of a population, the higher the competitive pressure is on an individual to survive. This pressure ensures that only the most suitable members survive while the weaker members perish.

Adaptation
A characteristic that is genetically controlled; increases an organisms chance of survival.

4.Time:- successful variations accumulate over many generations.

Darwin's model of evolution by natural selection allowed him to explain the patterns he had seen during his travels. For example, if the Galapagos finch species shared an common ancestor, it made sense that they should broadly resemble one another (and mainland finches, who likely shared that common ancestor). If groups of finches had been isolated on separate islands for many generations, however, each group would have been exposed to a different environment in which different heritable traits might have been favored, such as different sizes and shapes of beaks for using different food sources. These factors could have led to the formation of distinct species on each island.

Natural selection is a best example for explanation of how evolution happened and various examples prove that it is an important force controlling evolution.

Example :- polar bear. They hunt in the snowy arctic; they sneak up on their prey; and they are, after all, white. Thus they appear to be well adapted to their environment. White Polar bear survived easily in the snowy arctic region.

Many times of history of life mass extinction have occurred.

Such a mass extinction ended the 'dinosaurs' species at the end of the Cretaceous Period.Dinosaurs were large and dominated the world, whereas mammals were small and nocturnal, sneaking around in the dinosaurs' world. It was not until the dinosaurs went extinct that the mammals could take over and flourish. The mechanism that caused this extinction was a massive asteroid striking the Earth. This example shows that natural selection alone is not sufficient to explain the history of life. No matter how well adapted an animal is, it may not survive always.

Let's take a simple hypothetical example for understand the natural selection clearly.

A group of rabbits with heritable variation in fur color (white vs. grey) has just moved into a new area where the rocks are grey. This environment features hawks, which like to eat rabbits and can see the white ones more easily than the grey ones against the grey rock.
Because the hawks can see and catch the white rabbits more easily, a relatively large fraction of the white rabbits are eaten, while a much smaller fraction of the grey rabbits are eaten. The ratio of white to grey in the surviving ("not-eaten") group, it will be higher than in the starting population.Fur color is a heritable trait (one that can be passed from parent to child).

Survival of More number of grey rabbits tend to increase more number of grey rabbits in next generation.After several generations of selection, the population might be made up almost entirely of grey one. This is an example of natural selection during evolution.

Above examples concluded that , natural selection not favoured that inherited traits those are superior than others instead of it favoured those Traits which are beneficial for survival the organism and reproduced more .

In the example of Darwin's finches, observed that groups in a single population may become isolated from one another by geographical barriers, such as ocean surrounding islands, or by other mechanisms. Once isolated, the groups can no longer interbreed and are exposed to different environments. In each environment, natural selection is likely to favour different traits (and other evolutionary forces, such as random drift, may also operate separately on the groups). Over many generations, differences in heritable traits can accumulate between the groups, to the extent that they are considered separate species.

Based on various evidence, scientists think that this type of process has repeated frequently during the history of life on Earth. Evolution by natural selection and other mechanisms underlies the distinct diversity of present-day life forms, and the action of natural selection can explain the fit between present-time organisms and their environments.