Evolution is the change in allele frequency over time in a population of organisms. Mutation and natural selection, the nonrandom survival and reproduction of randomly varying organisms, are the main drivers of evolution. Genetic drift, a sampling error and gene flow between populations of the same species also can cause evolution, but, generally, in small populations.
Evolution occurs because biological organisms reproduce with variation, and variants reproduce at different rates.
Genetic variation is the result of genetic mechanisms such as reproductive recombination and spontaneous mutation. These mechanisms ensure that each offspring is a unique combination of alleles. Alleles are "rival" variants of genes with a specific "function". For many genes, having one allele rather than another will result in some difference in expression, resulting in turn in a difference in phenotype, which might result in a behavioural difference, a difference in appearance, or a difference in metabolic rate, for instance.
It stands to reason then, that it is possible that different variants react to circumstances differently. A variant with slightly longer intestines might find it easier to process certain foods, opening up a new niche for itself and its offspring. A variant with slightly longer fur might find it easier to venture into colder areas to gather food, again giving it and its offspring access to a new niche.
If the circumstances are thus that a particular trait or combination of traits makes it likely that a variant has a higher average number of offspring than its rival variants, then this will result in an increase of the number of alleles representing this variation in the next generation. This trend can, if these circumstances remain the same, persist until the great majority of the population possesses these successful traits.
Together, the emergence of new traits through reproductive variation, the spreading of successful traits and the decline of less successful traits through reproductive differential success, are called evolution, and the mechanisms behind these trends are the reason that evolution happens.
yes.
Because adaptations are an observed effect of evolution. They could not happen if evolution did not occur.
Organisms are required for evolution to occur. Evolution is defined as something that happens when organisms reproduce.
Evolution occurs in population not in an individual.
Yes. Evolution ocurred in all geologic periods.
You do not allow evolution to occur, for you are evolution in selective breeding.
The more variation there is in a group of specimens, the more evolution can occur between them.
Down Syndrome is a the addition of an extra chromosome and not really related to evolution. It is more of a genetic mutation that causes this event to occur.
For a mutation to affect evolution it must occur in the dominant allele. This allele is what is passed on.
During evolution, chromosomal cariation in structure cannot occur due to
Selective Breeding of course!
It already has in some instances