Lectures 4-8

Question 1

What is genetic drift?

Answer 1

Random change in allele frequencies due to chance events, especially strong in small populations.

Question 2

Why does population size matter in genetic drift?

Answer 2

Smaller populations experience larger random fluctuations in allele frequencies, so drift has stronger effects.

Question 3

What is allele fixation?

Answer 3

When an allele reaches frequency of 1.0 and is the only allele at that locus in the population.

Question 4

What is allele loss?

Answer 4

When an allele’s frequency goes to 0 and it disappears from the population.

Question 5

How does genetic drift affect genetic variation within populations?

Answer 5

It decreases genetic variation within populations.

Question 6

How does genetic drift affect variation among populations?

Answer 6

It increases genetic differences among populations.

Question 7

What is the founder effect?

Answer 7

Genetic drift that occurs when a small group colonizes a new area and carries only a subset of the original genetic variation.

Question 8

What is a bottleneck effect?

Answer 8

A sharp reduction in population size leading to loss of genetic diversity due to drift.

Question 9

What is gene flow?

Answer 9

Movement of alleles between populations via migration of individuals or gametes.

Question 10

How can gene flow increase variation within a population?

Answer 10

By introducing new alleles.

Question 11

How does gene flow affect differences among populations?

Answer 11

It reduces genetic differences among populations.

Question 12

What is “swamping” in gene flow?

Answer 12

When high gene flow overwhelms local adaptation by introducing maladaptive alleles.

Question 13

How can gene flow increase fitness?

Answer 13

By spreading beneficial alleles and increasing genetic variation.

Question 14

What is natural selection?

Answer 14

Differential survival and reproduction of individuals due to heritable trait differences.

Question 15

What roles do chance and sorting play in natural selection?

Answer 15

Mutations arise by chance; natural selection sorts beneficial alleles.

Question 16

What is relative fitness?

Answer 16

A genotype’s reproductive success compared to others.

Question 17

What is directional selection?

Answer 17

Favors individuals at one extreme of a phenotype.

Question 18

What is disruptive selection?

Answer 18

Favors individuals at both extremes.

Question 19

What is stabilizing selection?

Answer 19

Favors intermediate phenotypes and selects against extremes.

Question 20

What is sexual selection?

Answer 20

Selection for traits that improve mating success.

Question 21

What is sexual dimorphism?

Answer 21

Distinct differences between sexes in secondary sexual traits.

Question 22

What is intrasexual selection?

Answer 22

Competition within the same sex for mates.

Question 23

What is intersexual selection?

Answer 23

Mate choice (often female choice).

Question 24

What is balancing selection?

Answer 24

Selection that maintains multiple alleles in a population.

Question 25

What is heterozygote advantage?

Answer 25

When heterozygotes have higher fitness than both homozygotes.

Question 26

What is frequency-dependent selection?

Answer 26

When fitness depends on how common a phenotype is.

Question 27

What is speciation?

Answer 27

Formation of new species from existing ones.

Question 28

What is the biological species concept?

Answer 28

Defines species by ability to interbreed and produce fertile offspring.

Question 29

What is reproductive isolation?

Answer 29

Barriers that prevent gene flow between species.

Question 30

What are prezygotic barriers?

Answer 30

Barriers that prevent mating or fertilization.

Question 31

What are postzygotic barriers?

Answer 31

Barriers after fertilization (e.g., sterile hybrids).

Question 32

What is allopatric speciation?

Answer 32

Speciation due to geographic isolation.

Question 33

What is sympatric speciation?

Answer 33

Speciation without geographic separation.

Question 34

What is polyploidy?

Answer 34

Having extra chromosome sets due to cell division errors.

Question 35

Difference between autopolyploid and allopolyploid?

Answer 35

Auto = same species duplication; Allo = hybridization between species.

Question 36

What is habitat differentiation?

Answer 36

Speciation driven by using different habitats in the same area.

Question 37

What is adaptive radiation?

Answer 37

Rapid diversification into many species from one ancestor.

Question 38

What is a hybrid zone?

Answer 38

Region where different species mate and produce hybrids.

Question 39

What can hybrid zones reveal?

Answer 39

Strength and order of reproductive barriers.

Question 40

What is reinforcement?

Answer 40

Selection that strengthens reproductive barriers to avoid hybridization.

Question 41

What is reproductive character displacement?

Answer 41

Greater trait divergence in sympatry than allopatry.

Question 42

What is fusion?

Answer 42

Breakdown of barriers leading species to merge.

Question 43

What is stability in hybrid zones?

Answer 43

Continued hybrid formation without species merging.

Question 44

Why is hybrid speciation common in plants?

Answer 44

Due to polyploidy and tolerance for genome duplication.

Question 45

What is admixture?

Answer 45

Mixing of gene pools between species.

Question 46

Can hybridization lead to new species?

Answer 46

Yes, especially in plants.

Question 47

What is phylogeny?

Answer 47

Evolutionary history of a species or group.

Question 48

What is systematics?

Answer 48

Study of classifying organisms and their evolutionary relationships.

Question 49

What data are used to infer phylogenies?

Answer 49

Fossils, molecular data, and genetic data.

Question 50

What are the Linnaean levels of classification?

Answer 50

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Question 51

What is binomial nomenclature?

Answer 51

Two-part scientific naming (Genus + species).

Question 52

What does a branch point in a tree represent?

Answer 52

Divergence from a common ancestor.

Question 53

What are sister taxa?

Answer 53

Groups sharing an immediate common ancestor.

Question 54

Can branches be rotated on a tree?

Answer 54

Yes, without changing relationships.

Question 55

Do phylogenetic trees show time or amount of change?

Answer 55

Not necessarily.

Question 56

What is homology?

Answer 56

Similarity due to shared ancestry.

Question 57

What is analogy?

Answer 57

Similarity due to convergent evolution.

Question 58

What is convergent evolution?

Answer 58

Independent evolution of similar traits due to similar pressures.

Question 59

What is homoplasy?

Answer 59

Similarity not due to shared ancestry (includes convergence and reversals).

Question 60

How can homology vs analogy be distinguished?

Answer 60

Fossil evidence and complexity; more complex similarity is more likely homologous.