Mechanism of evolution

What is a population?

A group of organisms of the same species, living together in a particular place at a particular time.

What is a gene?

A section of DNA that codes for a particular protein or trait.

What is an allele?

Alternate forms of a gene.

What is a trait?

The specific characteristic that is determined by the genes present in the organism.

What is allele frequency?

How often each allele occurs in a gene pool.

What is a gene pool?

The sum of all the different alleles that exist in a population.

What is genetic diversity?

The measure of the number of different alleles present within a gene pool.

What is variation?

The measure of the different traits in an individual.

What is a species?

A group of individuals that share characteristics and can breed to produce fertile offspring.

What is evolution?

The process by which living organisms change over time through changes in the genome.

What are the four primary factors that cause changes in allele frequency?

Mutations, differing selection pressures, random genetic drift, and changes in gene flow between adjoining groups.

What is gene flow?

The movement of alleles between two populations via migration (immigration or emigration) or interbreeding.

How does immigration affect a gene pool?

It introduces new alleles into a population, increasing its allele frequency and genetic diversity.

How does emigration affect a gene pool?

It removes existing alleles from a population, decreasing its allele frequency and genetic diversity.

What are geographical/physical barriers?

Physical obstacles like oceans, mountain ranges, ice sheets, and deserts that restrict populations from crossing and interbreeding.

What are cultural/social barriers?

Differences in religion, language, education, or economic status that cause people to choose not to interbreed.

What is random genetic drift?

Random, non-directional changes to allele frequency between generations due to chance events, which is highly significant in small populations.

What is the primary effect of genetic drift on a population's diversity?

It decreases genetic diversity within the population and often results in alleles being lost (0%) or fixed (100%).

What is the difference between gene flow and genetic drift regarding diversity between populations?

Gene flow decreases differences between populations, whereas genetic drift increases differences between populations.

What is the founder effect?

When a few individuals isolate themselves to start a new, unpopulated area, carrying only a fraction of the original gene pool by chance.

Why is genetic drift unlikely to have a significant effect on a large population?

Large populations are cushioned by size; random mating and chance deaths do not drastically shift overall allele percentages.

Identify four effects a small population has on a gene pool that can reduce the chance of species survival.

Reduced genetic diversity/less variation,

increased chance of random genetic drift,

reduced instance of new mutations,

and increased likelihood of inbreeding.

Explain how the high incidence of Tay-Sachs within the Ashkenazi Jewish community in Australia is an example of the founder effect.

A small original population migrated to Australia with individuals carrying the allele; cultural isolation restricted breeding within the gene pool, causing the allele frequency to increase over time.

What is natural selection?

When environmental factors confer a selective advantage on specific phenotypes, allowing individuals to enhance survival, reproduce, and pass on their alleles.

What are the 6 steps of natural selection?

1. Variation, 2. Overproduction, 3. Struggle for existence, 4. Survival of the fittest, 5. Reproduction, 6. Generational change.

What happens during the "struggle for existence" stage of natural selection?

More offspring are produced than can survive due to limited resources, leading to high competition among the species.

What happens during "generational change" in natural selection?

Over many generations, those better adapted pass on favorable alleles, increasing their frequency and creating directional change in the gene pool.