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

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

3. 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

4. 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.

5. 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.

6. 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.

7. 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

8. Genetic Variation

9. 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.

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

11. 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

12. 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

13. Genetic Drift

14. 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

15. 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.

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

17. 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.