Question

FOR THIS ESSAY IT IS ABOUT 1,200 WORDS.

DARWIN WAS NOT THE FIRST TO CONSIDER EVOLUTION AS A PROCESS BUT HE DID COME UP WITH THE FIRST EFFECTIVE EXPLANATION FOR HOW IT HAPPENS. DESCRIBE DARWIN'S THEORY OF EVOLUTION BY NATURAL SELECTIONS. EXPLAIN HOW THIS THEORY WAS A MAJOR ADVANCE OVER PRIOR IDEAS AS TO HOW ORGANISMS CHANGED OVERTIME. GIVE EVIDENCE IN SUPPORT OF EVOLUTION AND DESCRIBE THE DRIVING FORCES FR EVOLUTIONARY CHANGE.

Answer 1

Darwin proposed that species can change over time, that new species come from pre-existing species, and that all species share a common ancestor. In this model, each species has its own unique set of heritable (genetic) differences from the common ancestor, which have accumulated gradually over very long time periods. Repeated branching events, in which new species split off from a common ancestor, produce a multi-level "tree" that links all living organisms.

Darwin referred to this process, in which groups of organisms change in their heritable traits over generations, as “descent with modification." Today, we call it evolution. Darwin's sketch above illustrates his idea, showing how one species can branch into two over time, and how this process can repeat multiple times in the "family tree" of a group of related species.

Importantly, Darwin didn't just propose that organisms evolved. If that had been the beginning and end of his theory, he wouldn't be in as many textbooks as he is today! Instead, Darwin also proposed a mechanism for evolution: natural selection. This mechanism was elegant and logical, and it explained how populations could evolve (undergo descent with modification) in such a way that they became better suited to their environments over time.

Darwin's concept of natural selection was based on several key observations:

• Traits are often heritable. In living organisms, many characteristics are inherited, or passed from parent to offspring. (Darwin knew this was the case, even though he did not know that traits were inherited via genes.)

• More offspring are produced than can survive. Organisms are capable of producing more offspring than their environments can support. Thus, there is competition for limited resources in each generation.

• Offspring vary in their heritable traits. The offspring in any generation will be slightly different from one another in their traits (color, size, shape, etc.), and many of these features will be heritable.

Based on these simple observations, Darwin concluded the following:

Darwin's model of evolution by natural selection allowed him to explain the patterns he had seen during his travels. For instance, if the Galápagos finch species shared a 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 doesn't favor traits that are somehow inherently superior. Instead, it favors traits that are beneficial (that is, help an organism survive and reproduce more effectively than its peers) in a specific environment. Traits that are helpful in one environment might actually be harmful in another.

In the example of Darwin's finches, we saw 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 favor 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.

various evidences are given in order to prove the evolution which includes - homology, embryology, fossils, connecting links etc.Among these are some are direct evidences and some are indirect.

• In a population, some individuals will have inherited traits that help them survive and reproduce (given the conditions of the environment, such as the predators and food sources present). The individuals with the helpful traits will leave more offspring in the next generation than their peers, since the traits make them more effective at surviving and reproducing.

• Because the helpful traits are heritable, and because organisms with these traits leave more offspring, the traits will tend to become more common (present in a larger fraction of the population) in the next generation.

• Over generations, the population will become adapted to its environment (as individuals with traits helpful in that environment have consistently greater reproductive success than their peers).