Acacia Evelyn and Madison Garcia EOC Review Project Benchmark 15.13 Acacia Evelyn and Madison Garcia

This Powerpoint will Contain the Following Topics: Natural Selection Genetic Drift Genetic Variation

Natural Selection Variation Overproduction Adaptation Natural selection is a mechanism where individuals that have beneficial adaptions for survival their environment, pass these traits onto their offspring. This theory was created by Charles Darwin. A scientist who is known for proposing a theory on evolution, which also included this topic. There are four main principals to the theory of natural selection: Variation Overproduction Adaptation Descent with Modification

Heritable differences that exist within every population. Variation Heritable differences that exist within every population. This is the basis for natural selection. Variation can result from genetic mutations in the individual or it's inherited from a parent.

Overproduction It is useful because having many offspring will help the chances of some surviving But the downside to this is that overproduction also results in competition between the offspring for resources.

Adaptation This is when a certain variation in an individual allows a better chance of survival over others. This causes more 'naturally selected' individuals to live longer and produce more offspring that have this adaptation.

Descent with Modification Natural selection will cause adaptions within a species to trickle down to the offspring. This pattern will continue with each generation, where beneficial adaptations to the environment of the species will be passed on More individuals will have the trait with each following generation as long as the environmental conditions continue to be beneficial for that trait

Genetic Variation

Gene Pool and Allele Frequency A gene pool is the genetic variation stored in a population An allele frequency is a measure of how common a certain allele is.

Genetic Variation Comes from two Main Sources These are....: Mutations and Recombination

Mutation A mutation is a random change in the DNA of a gene, and this change can form a new allele Mutations in reproductive cells can be passed on to the offspring and this increases genetic variation in the gene pool

This process creates new allele combinations in offspring Recombination This process creates new allele combinations in offspring Most recombination occurs during meiosis, which is a type of cell division needed for sexual reproduction The rearranging of the parent's alleles, create many different genetic combinations

Genetic Drift

Genetic Drift Genetic drift causes a loss of genetic diversity in a population. Two processes commonly causes populations to become small enough for genetic drift to occur, these are: The Bottleneck Effect and The Founder Effect

Bottleneck Effect The bottleneck effect is a genetic drift that occurs after an event greatly reduces the size of a population This is caused by the effect destructive event that leaves only a few survivors in a population. One example of this is the overhunting of elephant seals during the 1800s.

Founder Effect The Founder effect is genetic drift that occurs after a small number of individuals colonize a new area.

The Effects of Genetic Drift Genetic drift can cause several problems for populations. One is that the population loses genetic variation, and with little genetic variation a population is less likely to be able to adapt to a changing environment. Another problem is that alleles that are lethal in homozygous individuals will be carried on through heterozygous individuals, and thus become more common in the gene pool.