Population genetic basis of evolutionary change!

Question 1

What are the 2 processes of evolutionary change?

Answer 1

Transformation
Splitting/branching
I.e. anagenesis and cladogenesis

Question 2

What are branched evolutionary histories known as?

Answer 2

Phylogenies

Question 3

What is microevolution?

Answer 3

Evolution at the population level e.g. intraspecific evolution

Question 4

What is macroevolution?

Answer 4

Evolution at the species level and above

Question 5

What is a character?

Answer 5

Any measurable trait on an organism

Question 6

What is a character state?

Answer 6

Any variants of a character

Question 7

What is a single nucleotide polymorphism? SNP

Answer 7

a common type of genetic variation where a single nucleotide base changes within a DNA sequence - creates alleles

Question 8

Give an example of an extended phenotype

Answer 8

Nests

Question 9

What are the 2 types of phenotypic traits?

Answer 9

Continuous - many gene loci involved
Discontinuous - usually only a few gene loci involved

Question 10

What test would you do to compare something against other sampled?

Answer 10

T-test

Question 11

What 2 processes create genetic variation?

Answer 11

Mutations
Recombination

Question 12

Define genetic drift - what can it cause?

Answer 12

a random change in the frequency of gene variants (alleles) within a population over time due to chance events - can cause loss of heterozygosity

Question 13

Define bottleneck

Answer 13

a drastic reduction in the size of a population due to environmental events or human activities

Question 14

Effective population size is approximate to what?

Answer 14

Number of breeders

Question 15

Other than genetic drift, what else causes loss of heterozygosity?

Answer 15

Inbreeding

Question 16

What is linkage disequilibrium?

Answer 16

Non-Random association between loci
LD tells us whether certain combinations of alleles are found together more (or less) often than you’d expect by chance
Easiest definition to understand:
Linkage disequilibrium = When certain combinations of gene versions (alleles) show up together more often than expected by chance

Question 17

What is linkage equilibrium?

Answer 17

Random association between loci
a state where the frequency of haplotype combinations in a population matches what would be expected if genes at each locus were combined randomly

Question 18

Give an example of artificial, directed selection

Answer 18

Putting insecticides down - by humans
The insects with the mutation to survive will survive, the normal ones will not
Directed as it didn’t happen by chance
Artificial as humans caused the selection pressure
Predation would be natural selection

Question 19

Are all of an organism’s heritable phenotypic traits (or trait states) either
adaptive or ‘maladaptive’?

Answer 19

No, there are selectively neutral genes

Question 20

Why might neutral genes still correlate with selection pressures?

Answer 20

Neutral genes are known that ‘hitch-hike’ with (are linked to) genes that have an adaptive function.
*In which case they will be subject to selection

Question 21

Define pleiotropy

Answer 21

a single gene or genetic variant influences multiple phenotypic traits, meaning it has effects on more than one characteristic
The effect on one phenotypic trait can be adaptive (positive).
* While the effect on the other trait may be neutral, deleterious or positive

Question 22

What are the 3 kinds of selection?

Answer 22

Negative
Positive
Balancing

Question 23

Define negative (purifying) selection

Answer 23

Selection that removes harmful alleles, reducing genetic variation in the population.

Question 24

What is the phenotypic effect of negative selection?

Answer 24

Extreme phenotypes are selected against, narrowing the population distribution toward the mean.

Question 25

What is the genetic signature of negative selection?

Answer 25

Loss of variation around the selected region; rare harmful alleles disappear.

Question 26

Define positive selection

Answer 26

Selection that increases the frequency of beneficial alleles in the population.

Question 27

What is the phenotypic effect of positive selection?

Answer 27

A shift in the distribution toward a new advantageous trait.

Question 28

What is the genetic signature of positive selection?

Answer 28

A selective sweep: one haplotype increases rapidly in frequency, reducing variation nearby.

Question 29

Define balancing selection

Answer 29

A form of selection that maintains multiple alleles at a locus within a population.

Question 30

What is the phenotypic effect of balancing selection?

Answer 30

The population retains a diverse set of traits; heterozygotes may have a fitness advantage.

Question 31

What is the genetic signature of balancing selection?

Answer 31

Higher and stable genetic diversity; multiple alleles persist over time.

Question 32

What are the 3 kinds of constraint on evolutionary change?

Answer 32

i. Insufficient genetic variation exists in the gene pool. ii. No selection pressure operating. iii. Sufficient selection pressures, BUT there exist constraints upon changing the ‘blue print’ of an organism e.g. the size of a molting organism

Question 33

what is evolution

Answer 33

the process of temporal change when an organism comes to differ permanently from their ancestors with respect to heritable traits