Microevolution: Cap 23

Question 1

What mechanism can cause the evolution of population (cause change in allele frequencies)

Answer 1

• Natural selection
• genetic drift
• gene flow

Question 2

Micro evolution

Answer 2

Evolution on its smallest scale. A change in the allele frequencies in a population over generations.

Question 3

Phenotypic traits

Answer 3

Individuals within spices vary in phenotypic traits, such as facial features, heigh and voice.

Question 4

Genetic variation

Answer 4

Differences amoung individuals in their composition of theirs genes or other DNA sequences

Question 5

Gene variability

Answer 5

Average percentage of loci that are heterozygous.

Question 6

Mutation

Answer 6

New alleles can arise by mutation. A change in the nucleotide sequence of an organism DNA. Caused by errors in DNA replication, exposure to UV light and other high energy form of radiation, and exposure to chemicals.

Question 7

Point mutation

Answer 7

A mutation caused by a little as one change of a base in the nucleotide. Can cause a significant impact on the phenotype, as in sickle cell.

Question 8

Hetrozygote protection

Answer 8

A harmful allele that are recessive can be hidden from selection. In a heterozygous individuals (where the harmful effect can be masked by the dominant favorable allele)

Question 9

Natural variation

Answer 9

Point mutations in non encoding regions. Differences in DNA sequences that does not confer a selective advantage or disadvantage.

Question 10

Population

Answer 10

A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.

Question 11

Gene pool

Answer 11

Consist of every copies of every type of allele at every locus in all members of a population.

Question 12

Hardy-Weinberg principle

Answer 12

Gene pool of a population that is not evolving. Only fictional

Question 13

Hardy-Weinberg equilibrium

Answer 13

The frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles that are at work

Question 14

Hardy-Weinberg equation

Answer 14

p^2 + 2pq + q^2

p+q=100

Question 15

Conditions for hardy Weinberg equilibrium

Answer 15

• Random mating
• No mutation
• No natural selection
• No gene flow
• Extremely large population

Question 16

Hardy-Weinberg No mutation

Answer 16

The gene pool is modified if mutations alter alleles or if entire genes are deleted or duplicated

Question 17

Hardy-Weinberg Random mating

Answer 17

If individuals mate preferentially within a subset in the population such as their close relatives (interbreed), random mixing of gametes does not occur and genotype frequencies change

Question 18

Hardy Weinberg: No natural selection

Answer 18

Differences in the survival and reproductive success of individuals carrying different genotypes can alter allele frequencies

Question 19

Hardy weinberg: Extremelt large populations

Answer 19

The smaller the populations, the more likely is that the allele frequencies will fluctuate by change from one generation to the next (genetic drift)

Question 20

Hardy Weinberg no gene flow

Answer 20

By moving alleles into or out of populations, gene flow can alter allele frequencies

Question 21

Why is the hardy Weinberg equilibrium used?

Answer 21

As an initial test of whether evolution is occurring in a population

Also has medical applications, such as estimating the precentage of a population carrying the allele for an inherited disease

Question 22

Natural selection

Answer 22

Individuals in a population exhibit variations in their heritable traits. And those traits that are better suited to the environment tend to produce more offsprings, than those who does not have this heritable trait.

Question 23

Adaptive evolution

Answer 23

Traits that enhance survival or reproduction tend to increase in frequencies over time

Question 24

Genetic drift- key points

Answer 24

Chance events can cause allele frequencies to fluctuate unpredictably from one generation to next

1. Significant in small populations.
2. Can cause allele frequencies to change at random
3. Leads to a loss of genetic variations within the population
4. Cause harmful alleles to become fixed

Question 25

Founder effect : genetic drift

Answer 25

Few individuals become isolated from a large population, this smaller group may establish a new population whose gene pool differs from the source population . Accounts for the relative high frequencies of certain inherited disorders amoung isolated human populations.

Question 26

Bottleneck effect : genetic drift

Answer 26

Sudden change in environment that may drastically reduce the size of population (floods, fire) Severe drop in population size Alleles may be: overrepresented, underrepresented or absent.

Question 27

Genetic drift: significant in smalle populations

Answer 27

Chance events can cause an allele to be disproportionately over or underrepresented in the next generation. Although chance events occur in population of all sizes, they tend to have a bigger effect in allele frequencies in smaller populations

Question 28

Generic drift: Allele frequencies to change at random

Answer 28

An allele may increase in frequency one year, then decrease the next. The change from year to year is not predictable. Thus, unlike natural selection which a given environment consist of favoring some alleles over others. Genetic drift cause allele frequencies to change at random over time

Question 29

Genetic drift: loss of genetic variations within populations

Answer 29

By causing allele frequencies to fluctuate randomly over time, genetic drift can eliminate alleles from a population. Because evolution depend on genetic variations, such losses can influence how effectively a population can adapt to a change in the environment.

Question 30

Genetic drift: cause harmful alleles to become fixed

Answer 30

Alleles that are neither harmful nor beneficial can be lost or become fixed entirely by chance though genetic drift. In very small populations, genetic drift can cause alleles that are slightly harmful to become fixed. When this occurs, the populations survival can be threatened.

Question 31

Gene flow

Answer 31

The transfer of alleles into or out of a population due to the movement of fertile individuals of their gametes.

Question 32

Relative fitness

Answer 32

Contribution an invidual makes to the gene pool of the next generation relative to the constribution of other inviduals.

Question 33

3 modes of selection

Answer 33

Directional, disruptive, stabilizing

Question 34

Directional selection

Answer 34

Occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, shifting a populations frequency curve for the phenotypic in one direction of the other Common when a population enviorment change or when a member og a population migrate to a new and different habitat

Question 35

Disruptive selection

Answer 35

Occurs when conditions favor individuals at both extremes of a phenotypic range over individuals with intermedia phenotype

Question 36

Stabilizing selection

Answer 36

Acts against both extreme phenotypes and favors intermediate variants Reduces variations and tends to maintain the status quo for a particular phenotypic character

Question 37

Sexual selection

Answer 37

Form of selection in which individuals with certain inherited characteristics are more likely than other inviduals to obtain mates

Question 38

Sexual dismopphis

Answer 38

Sexual selection can lead to. difference between the 2 sexes in secundary sexual characteristics. Size, color, behavior

Question 39

Intrasexual selection

Answer 39

Selection within the same sex, individuals of one sec compete directly for mates of the opposite sex

Question 40

Intersexual selection

Answer 40

Mate choice Common is females Individuals of one sex are choosy in selecting their mates from the other sex Females choice depends on the showiness of the males apperance or behavior

Question 41

Natural variations

Answer 41

Differences in DNA sequences that do not confer a selective advantage or disadvantage

Question 42

Diploidy

Answer 42

Genetic variations hidden in recessive alleles in hetrozygotes

Question 43

Balancing selections

Answer 43

Occur when natural selection maintains 2 or more forms in a population

Question 44

Hetrozygote advantage

Answer 44

Individuals who are heterozygous at a particular locus have greater fitness than those with homoxygous