The 4 key points of the Theory of Evolution by Natural selection?

Question

I will pick the best answer to the 1st person who explains it to me...thanks!!

Answer 1

In biology, evolution is the process of change with time in the inherited characteristics, or traits, of a population of organisms. Heritable traits are encoded in the genetic material of an organism (usually DNA). Evolution results from changes in this genetic material (mutation) and the subsequent spread of these changes in the population, and explains the observed changes over time in the fossil record.
Natural selection, one of the processes that drives evolution, results from improved reproductive success by individuals best adapted to survive and reproduce in a given environment. These successful survivors and reproducers pass their beneficial, heritable traits to the next generation. If these traits increase the evolutionary fitness of an organism, they will be more likely to survive and reproduce than other organisms in the population. In doing so, they pass more copies of those (heritable) traits on to the next generation, causing advantageous traits to become more common in each generation; the corresponding decrease in fitness for deleterious traits results in their becoming rarer. In time, this results in adaptation: the gradual accumulation of new beneficial traits and the preservation of existing ones results in a population of organisms becoming better suited to its environment and ecological niche.
Though natural selection is decidedly non-random in its manner of action, other more capricious forces have a strong hand in the process of evolution. Genetic drift results in heritable traits becoming more or less common simply due to random chance. This aimless process may overwhelm the effects of natural selection in certain situations (especially in small populations).
Differences in environment, and the element of chance in what mutations happen to arise and which ones survive, can cause different populations (or parts of populations) to develop in divergent directions. With enough divergence, two populations can become sufficiently distinct that they may be considered separate species, in particular if the capacity for interbreeding between the two populations is lost. Evidence such as the wide distribution of the canonical genetic code indicates that all known cellular organisms are ultimately descended from a common ancestral population.
While the idea of evolution (as opposed to the fixity of species) is ancient, the modern concept of evolution by natural selection was first set out by Alfred Wallace and Charles Darwin in a joint paper to the Linnean Society, followed by the publication of Darwin's 1859 book, On the Origin of Species. In the 1930s, the modern evolutionary synthesis combined Darwin's natural selection with Gregor Mendel's genetics. As more and more evidence was collected and understanding of the processes of evolution improved, evolution became the central organising principle of biology.

Answer 2

There are two points, not four:
- Variation occurs. Due to radiation, chemical damage, or other causes, the genetic heritage of an organism may differ from that of its parents. This is called a mutation.
- Natural selection occurs. A mutated organism may be better suited to its environmental conditions than an unmutated one, and will survive preferably. Sexual reproduction insures that well-suited genes will be disseminated rapidly.
These points are both known to be valid, and since the theory of evolution contains these points and no others, it is proven to be correct.