Microevolution

define population

A group of organisms that live near and interbreed with eachother

population genetics goal

to determine the variety of alleles in a population and how they change over time

4 genetic variations factors

1. Random mutations

2. Mate selection

3. reconbination of chromosomes in meiosis

4. freuqnecy of reproduction

3 types of random mutations

1. Substitution

2. Insertion

3. Deletion

Subsiution mutations

one nucleotide is changed in a gene which can result in, at most, a change in one amino acid in the protein it codes for

Insertion and deletion mutations

One nucleotide is gained or lost

• results in a frameshift which disrupts the codons of mRNA transcribed from a gene

In order for a mutation to appear in the next generation, what cell types would the mutation need to occur in

1. Egg and sperm cells

2. Zygotes

3. Germline stem cells

Mate selection

breeding can potentially occur between any opposite sex members of the population which influences which alleles are passed to the next generation

recombination of chromosomes in meiosis

Crossing over

frequency of reproduction

The faster a population reproduces the more opportunities for mutation and new allele combinations. Therefor higher genetic variation

Microevolution

when the freuqnecy of certain alleles change

• can occur in just a few generations or even in one

• 5 factors

5 factors that contribute to microevolution

1. Natural selection

2. genetic dift

3. founder effect

4. bottleneck effect

5. gene flow

Natural selection in microevolution

Some organisms in a population may have traits that help them survive and reproduce more effectively than others. These selected organisms have a higher likelihood of reproducing and passing their traits to the next generations. Therefor those traits become higher in frequency

Genetic drift

random natural events can influence the allele frequency in a population. Usually involves mass death in a population where the survivors dictate the alleles frequency

This has nothing to do with reproductive success

Founder effect

Sometimes individuals of a population venture off and form their own population. The allelle frequency of the new population is now determined by the founding members

Bottleneck effect

When mass population loss ocurs leaving only a few members to try and rebuild the population. The few last survivors dictate allele frequency in the following generations. Loss of habitat is a key driver of the bottleneck effect

• Type of genetic drift but specifically refers to drastic decrease in population numbers

Three directions in which allele freuqnecy can change in repsponse to the envoirment

1. Directional

2. Disruptive

3. stabilizing

Gene flow

Members of a population sometimes join other populations. Likewise, populations can gain members from other popualtions. In both cases allele freqnecy can be altered

Super simple definition of microevolution

A change in allele frequency

Directional selection

Allele and trait frequency shifts towards one the extremes

(bell curve moving left or right)

Disrupuptive selection

Allele and trait frequency shifts towards both of the extremes

• one mountains becomes two smaller mountains with a gap in the middle (kinda like the grand canon)

Stabilizing selection

Allele and trait frequency shifts away from both of the extremes

• Becomes a super skinny tall mountain