Chapter 23

Question 1

Microevolution

Answer 1

Evolution at its smallest scale

Focus on the change in allelic frequencies

Question 2

3 Mechanisms that cause change in allele freqencies

Answer 2

Genetic Drift- Random change in a population
Gene Flow- Transfer of Alleles between different populations
Natural Selection- Favoring of beneficial trait

Question 3

Discrete Characters

Answer 3

Characteristics that can be distinctly chosen. Often determined by a single gene locus with different alleles

Question 4

Quantitative Characters

Answer 4

Characteristics that vary along a continuum. Results from the influence of two or more genes on a phenotypic characteristic

Question 5

Measuring Genetic Variation

Answer 5

• Measure it through the whole gene level (gene variability)

- Molecular level of DNA through nucleotide variability

Question 6

Cline

Answer 6

This is a variation of a characteristic across a region. Provides an example of natural selection because organisms living in different environments have to adapt differently

Question 7

Source of New Alleles

Answer 7

Mutation

Question 8

Point Mutation

Answer 8

A mutation in which only one base is changed. Often point mutations have no effect is they don’t change the shape/function of amino acids

Question 9

Translocation

Answer 9

When part of a chromosome is taken and placed on another chromosome. Results in the linking of new DNA

Question 10

Gene duplication

Answer 10

This occurs when errors happen such as DNA replication slipping, unequal crossing during meiosis.
Duplication of large portions of the chromosome are often harmul, but this allows for this duplication in many future generations, increased genome more loci, more mutations more functions

Question 11

Mixing of Alleles

Answer 11

-Independant assortment of chromosomes, crossing over, and fertilization
homologous chromosomes cross some of their DNA to eachother
Alleles randomly distributed into different gametes
-Organisms with different alleles mate with eachother

Question 12

Population

Answer 12

A group of individuals that are the same species, live in the same region, interbreed and produce viable offspring

Question 13

Gene Pool

Answer 13

A collection of all the alleles from all the loci from all the individuals in the population

Question 14

Fixed Allele

Answer 14

When there is only one allele that exists for a locus in a population. All individuals are homozygous for this allele

Question 15

Hardy Weinberg Principle

Answer 15

If the frequency of alleles remains constant through many generations then the population is not evolving. Only in the case of Mendelian segregation and recombination

Question 16

Conditions for the Hardy Weinberg Principle

Answer 16

1. No mutations- they modify the gene pool
2. Random Mating- If there is preferential mating, the allele frequencies change
3. No Natural Selection- Makes one allele favorable over the other
4. Extremely Large Population- Small populations increase chance of genetic drift
5. No gene Flow- Migration causes fluctuating allel frequencies

Question 17

Hardy- Weinberg Equation

Answer 17

p^2+ 2pq + q^2
p- Dominant Allele
q- Recessive allele

Question 18

Natural Selection

Answer 18

Natural selection changes the allele frequency because it favors the alleles that help the organism survive. Increases favorable allele

Question 19

Genetic Drift

Answer 19

The process of a chance event that causes alleles to fluctuate unpredictably

Question 20

Gene Flow

Answer 20

The flowing of alleles into and out of the population. Makes populations more similar

Question 21

Founder Effect

Answer 21

When a small group of a larger population becomes isolated and forms a new population. This causes a different gene pool from original population- One form of genetic drift

Question 22

Bottleneck Effect

Answer 22

When a severe drop in the population occurs. This allows one allele frequency to increase, or to be completely taken out of the population. Then there is little genetic variation in future generation- Genetic Drift

Question 23

Relative Fitness

Answer 23

the contribution an individual mkaes to the genepool to the next generation- The number of beneficial alleles the organism has to pass down to the next generation

Question 24

Stabilizing Selection

Answer 24

When extreme alleles are unfavorable and so their frequencies decreased while the intermediate is found more favorable. - Narrowed Bellcurve

Question 25

Directional Selection

Answer 25

This is when an extreme allele is found favorable and the whole population then moves to have this allele and the bell curve is shifted over

Question 26

Disruptive Selection

Answer 26

This is when two different alleles on extremes of the continuum are found favorable and the frequencies of both alleles increase, while the intermediate decreases- Through this speciation can occur

Question 27

Sexual Dimorphism

Answer 27

Effect if sexual selection

Where the male and female physical appearances look increasingly different (size color behavior)

Question 28

Intrasexual Selection

Answer 28

This is competition of individuals within the same sex

A male might guard a females from other males, thus preventing other males from mating with them

Question 29

Intersexual Selection

Answer 29

Females are able to pick which males they mate with and they choose the ones with the healthiest genes

Question 30

Preservation of Genetic Variation

Answer 30

• Natural selection does not eliminate variation because there are two mates that form an individual and many recessive alleles are hidden and therefore not eliminated from natural selection
• Balancing selection also preserves variety, when two alleles are thought to be advantageous

Question 31

Heterozygous Advantage

Answer 31

This is where gene loci have greater advantage in heterozygous individuals than homozygous individuals

Question 32

4 Reasons why Natural Selection Does Not Produce Perfect Organisms

Answer 32

1. Natural selection can only make certain alleles more favorable than others. CANNOT CREATE ALLELES
2. Natural selection can only work on the population body structure, cannot form new structure
3. Adaptations are only compromises between different factors, not perfect solution
4. Genetic Drift, Genetic flow and changing environments are constantly affecting natural selection