Microevolution

Question 1

Microevolution?

Answer 1

Focus on evolutionary change in a population by changes in the allele frequencies that affects the genetic composition of populations.

Question 2

Forces?

Answer 2

Natural selection
Genetic drift
Gene flow

Question 3

The result?

Answer 3

A phenotype is the product of an inherited genotype and the environmental influences

Question 4

Mutations and heterozygote protection?

Answer 4

A harmful mutation can be hidden from selection and a recessive allele can be masked by heterozygote protection and there may be a pool of alleles that may not be favoured under present conditions but can shown if the environment changes.

Question 5

Key point?

Answer 5

Only mutations in cell lines that produces gametes can be passed to offspring

Question 6

Key potential sources of variations?

Answer 6

Translocation
Errors in meiosis - unequal crossover
Slippage during DNA replication
Transposable elements

Gene duplications that do not have severe effects can persist over generations and provide an accumulation of mutations = expanded genome.

Question 7

Sexual reproduction?

Answer 7

Homologous chromosomes 1 from each parent trade alleles by crossing over
Which are then distributed randomly into gametes
Fertilization typically brings together gametes that have different genetic background

Question 8

Gene pool?

Answer 8

A population genetic make up of all copies of every type of allele @ every locus in all members in the population

Question 9

Hardy-Weinberg?

Answer 9

In a population that is not evolving the allele and genotype frequencies will remain constant from generation to generation.

Only segregation and recombinations of alleles.

To asses if natural selection or other forces are causing evolution @ a particular locus, by determining what the genetic make up of a population would be if it were not evolving

Question 10

Gene duplication?

Answer 10

Where a similar gene gets copied and added to the same chromosome and can have different outcomes:

It can be inactivated
It can provide more gene product
It can specialize in another function, keeping the same function for the similar gene - neofunctionalisation or subfunctionalisation. Resulting in paralogs or orthologs.

Question 11

Allele frequency?

Answer 11

p and q and alleles can be either homo or heterozygous giving the equation:

p^2+2pq+q^2=1

Question 12

Key point Hardy-Weinberg?

Answer 12

Population is in eq only if the observed genotype frequencies are equal to one, indicated a non-evolving population

Question 13

Hardys big 5?

Answer 13

No mutations - gene pools cannot be modified
Big population - smaller are greater affected
No geneflow - no moving of alleles
Random mating - It describes an ideal situation in which all individuals on one sex are equally potential partners of all members of the opposite sex.
No natural selection - no difference in viability and fertility

Question 14

Natural selection?

Answer 14

Different succes in survival and reproduction and if some are better suited to their local environment will produce more offspring. By consistently favouring some alleles leading to adaptive evolution = trait that increases survival and reproduction tend to increase over time.

Question 15

Genetic drift?

Answer 15

Chance events that causes allele frequencies to change rapidly from 1 generation to next.

Founder effect - If few individuals become isolated can produce a gene pool that differs from the source population

Bottleneck - A sudden change in environment that drastically reduce the size of a population. By chance certain alleles may be overrepresented among survivors.

Question 16

Effects of genetic drift?

Answer 16

Affects smaller more than larger by alter allele frequencies
Can cause allele frequencies to change at random
Can lead to loss of genetic variation within populations
Can cause harmful alleles to become fixed, especially if the population is very small

Question 17

Gene flow?

Answer 17

Transfer of alleles in or out of a population due to movements of fertile gametes. Modifies the original poulations allele frequencies in the next generation so it tends to reduce the genetic differences between populations, and affect the adaptation to the local environment, both good or bad.

Question 18

Types of natural selection?

Answer 18

It increase the frequencies of alleles that provide higher fitness, and acts more on phenotype than on genotype.

Question 19

DDS?

Answer 19

Directional
Disruptive
Stabilizing

Question 20

Directional?

Answer 20

Resulting in a shift of the phenotypic curve to one extreme, usually as a result of environmental changes or when members of a population migrate to a new habitat. Does not affect the gene pool, just a shift.

Question 21

Disruptive?

Answer 21

Occurs when conditions favors both extremes and will result in a increase in allele frequency.

Question 22

Stabilizing?

Answer 22

Favors intermediate variants, and maintain the status quo for a particular character.

Question 23

Key points?

Answer 23

Adaptations can arise gradually over time as natural selection increases frequency of alleles that increases fitness.
Genetic drift and gene flow can increase frequencies of alleles that enhance survival or reproduction.

Question 24

Sexual selection?

Answer 24

Some inherited characteristics are more prone than others of the same sex to obtain mates.

Question 25

Sexual dimorphism?

Answer 25

Secondary sexual characteristic between male and female of the same species

Question 26

Intrasexual selection?

Answer 26

Same sex competes

Question 27

Intersexual selection?

Answer 27

Mate choice where 1 sex i choosy in selecting their mates from the other sex. Good genes hypothesis that provides an insight in the overall male health.

Question 28

Balancing selection?

Answer 28

Frequency dependent and heterozygote advantage

Question 29

Frequency dependant?

Answer 29

Fitness of a phenotype depends on how common it is in the population.

Question 30

Heterozygote advantage?

Answer 30

Higher fitness than the homozygotes.

Question 31

Evolution cannot create perfect organisms?

Answer 31

Selection acts only on excisting variations - may not be the most optimal
Evolution is limited by historical constraints - it operates on the traits an organism already has
Adaptations are often compromises - Cost/ benefit
Chance, natural selection and the environment interact - Send organisms to a new island not suited to the local environment, and theenvironment may change unpredicatably from year to year. That hinder individuals to be well-suited to the local environment.