Lecture 19

Question 1

In population genetics,evolutionis defined as ?

Answer 1

a change in the frequency ofallelesin a population over time.

Question 2

Population?

Answer 2

all the individuals of 1 species living in a specific area, that have the potential to breed

Question 3

Individual: Genotype
Population: __?

Answer 3

Gene pool

Question 4

Gene pool?

Answer 4

All the alleles present in a population

Question 5

Micro-Evolution: change in __

Answer 5

gene pool

MICROEVOLVED: SAME SPECIES

Question 6

Microevolution

Answer 6

Selective pressures act on individuals

BUT

Changes (evolution) seen in a POPULATION over TIME: see changes in the frequency of certain (not all) alleles ie changes in the gene pool

Same species, just change in allele frequency in gene pool

Question 7

Hardy-Weinberg Principle used to see if a population is micro-evolving?

Answer 7

For a population that is not evolving ie is at genetic equilibrium:

the frequencies of alleles and genotypes in a population’s gene pool remain constant from generation to generation

Question 8

Hardy-Weinberg Principle?
A sexually reproducing population will be at genetic equilibrium (not evolving) if all 5 conditions to genetic equilibrium are met

Answer 8

natural selection not occurring
mating is random
no net mutations
large population (avoid genetic drift)
no migration between populations

If any of these are NOT met, evolution can occur

Note: even if only 1 gene out of the thousands is evolving, then that population is said to be evolving

Question 9

the frequencies of what is observed for a microevolution? (Genotypes, Alleles, Phenotypes)

Answer 9

only genotypes and alleles. If constant

NO Evolution occurring

Question 10

Why isn’t phenotype observed in the microevolution?

Answer 10

Because Aa and AA give the same phenotype (complete dominance), no change in phenotype. Phenotypes can be effected by the environment as well.

Question 11

Hardy-Weinberg Principle null and alternative hypothesis?

Answer 11

Null hypothesis: the population is in Hardy–Weinberg proportions (the population is not evolving).
Alternative hypothesis: the population is not in Hardy–Weinberg proportions (the population is micro-evolving).

Question 12

what p value is acceptable?

Answer 12

less than 0.05

Question 13

Fitness (in evolution)

Answer 13

includes its ability to survive, find a mate, produce offspring—& ultimately leave its genes in the next generation.

Question 14

Natural selection relies on __, __ & __

Answer 14

survival, mate-finding & reproduction

Question 15

Natural selection causes changes in allele frequencies leading to __

Answer 15

adaptive evolutionary change

Question 16

3 modes of selection of phenotypes

Answer 16

1. Stabilizing: favors intermediate variants.
2. Directional: favors one phenotypic extreme
3. Disruptive: favors individuals at both extremes of the phenotypic range. Ex birds with big beaks eat big seeds, little beaks small holes in trees, birds with medium beaks die out

Question 17

Sexual selection

Answer 17

non-random mating that is an example of natural selection

Can result in stabilizing selection, directional selection, or disruptive selection

Question 18

Non-adaptive factors leading to evolution

Answer 18

1. Non-random mating that’s not adaptive
2. Genetic mutations
3. Genetic drift: Bottleneck, founder effect
4. Gene flow

Question 19

Non-adaptive factors leading to evolution:

1) Non-random mating that’s not adaptive

Answer 19

Inbreeding, which occurs when individuals with similar genotypes are more likely to mate with each other rather than with individuals with different genotypes.
inbreeding can lead to a reduction in genetic variation in the population

Question 20

frequencies of random mating b/w AA, Aa, aa individuals

Answer 20

The combined genotype frequencies of the offspring for the 6 crosses above will be AA 25%, Aa 50%, aa 25%

Question 21

Non-adaptive factors leading to evolution:

2) Genetic mutations

Answer 21

• Genetic mutations are random
• Most mutations occur in somatic cells & are therefore lost with the death of the individual
• Only mutations in gametes can be passed on to offspring
• Mutation rates low in animals & plants
• Microorganisms: more generations/time period, so accumulate mutations faster

Question 22

Point mutation vs Chromosomal mutation

Answer 22

Point mutation = one nucleotide base change: Rarely increases reproductive success
Chromosomal mutation: deletion, duplication: Usually harmful

Question 23

__ and __ produce the variation that makes evolution possible

Answer 23

Mutation & sexual recombination

Mutations in DNA sequence rare in plants & animals, important for asexually-reproducing organisms
Sexual recombination much more important

Question 24

Non-adaptive factors leading to evolution:

3) Genetic drift

Answer 24

Occurs when changes in allele frequencies from 1 generation to another occur because of random events that occur in small populations

• Bottleneck
• Founder effect
  Both cause a reduction in the genetic variation of the population

Question 25

Bottleneck?

Answer 25

A sudden decrease in population size caused by adverse environmental factors
Resulting in a reduction in genetic diversity

Question 26

Founder effect

Answer 26

Individuals leave  the original population & start a new population(s).
New population (founders) has less genetic variation than original (parent) population

Question 27

Small populations are __ susceptible to genetic drift

Answer 27

more
Allele frequencies more likely to change by random fluctuations (genetic drift) than in a large population.

Example: in a population of only a few individuals, an allele at low frequency could be completely lost by chance.

Question 28

Factors leading to evolution:

4) Gene Flow

Answer 28

• Transfer of alleles b/w populations, of same species
• Populations: recipient pop. gains alleles donor pop. may lose alleles
• Results from the movement of fertile individuals or gametes: alleles move too

Usually ↑ genetic variation in recipient population

Question 29

Horizontal gene transfer

Answer 29

Movement of genetic material between different species

Question 30

Selective pressures leading to evolution: (Darwin) Natural selection:

Answer 30

(Darwin) Natural selection: Environment must change to select new phenotype or organism migrates to a different environment

Question 31

Selective pressures leading to evolution: (Beyond Darwin) Other selective pressures:

Answer 31

(Beyond Darwin) Other selective pressures: These are not adaptive: genetic drift, gene flow between populations of the same species, horizontal gene flow

Question 32

why sexual selection is considered to be an example of natural selection

Answer 32

Natural selection (adaptive: adapting to the environment)
Includes sexual selection (adaptive non-random mating)