Evolution Unit

Question 1

What is considered evidence that Darwin found for common ancestry?

Answer 1

Similar species were found close together geographically

Question 2

What is common ancestry?

Answer 2

ancestral species give rise to descendant species and create a lineage

Question 3

What are homologies?

Answer 3

-evidence of evolution and common ancestry
-structures that have deep underlying similarities between species and likely were preserved through time from a common ancestor
ex: vertebral column, 4 limbs

Question 4

What is the evidence that there is one common ancestor of all life forms?

Answer 4

1. DNA/RNA molecules made of the same nucleotides
2. same 20 amino acids
3. cells use ATP
4. structures such as ribosomes are well preserved
   5.genetic sequencing showing conserved genes in all species

Question 5

What is a polymorphic population?

Answer 5

a population with changing genetic mutation

Question 6

What is a fixed varient?

Answer 6

a genetic mutation that holds high frequency throughout time

Question 7

What is a paraphyletic group on a phylogenetic tree?

Answer 7

has a common ancestor but does not include all descendant lineages (not a clade)

Question 8

What is a monophyletic group on a phylogenetic tree?

Answer 8

a common ancestor and all its descendant lineages (IS a clade)

Question 9

What are the endpoints called at the end of a phylogenetic tree?

Answer 9

taxon

Question 10

What are the 3 things defined at the node on a phylogenetic tree?

Answer 10

-last common ancestor
-when descendant lineages become geographically isolated from one another
- splitting of ancestral lineage populations

Question 11

Where can switches be made in a phylogenetic tree?

Answer 11

Within a clade

Question 12

What is the principle of parsimony?

Answer 12

the most likely hypothesis to describe a set of events or a change is the one that makes the least amount of assumptions

Question 13

What is an internode?

Answer 13

a set of local populations linked together through gene flow that they tend to remain genetically similar

Question 14

How can we define an evolutionary change in this class?

Answer 14

a change in the frequency of alleles

Question 15

What is a continuous trait?

Answer 15

has a range of values and is controlled by multiple alleles, is on a bell curve distribution

Question 16

How do you calculate allele frequencies in diploid organisms?

Answer 16

heterogenous/2 + homozygous dominant divided by population (this will give you the dominant allele requency)

Question 17

What is the Hardy-Weinburg equation?

Answer 17

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

Question 18

What does p^2 represent?

Answer 18

homozygous dominent frequency

Question 19

What does 2pq represent?

Answer 19

heterozygous frequency

Question 20

What does q^2 represent?

Answer 20

homozygous recessive frequency

Question 21

What is directional selection?

Answer 21

acts on continuous traits, favors an increase in one allele’s frequency, that allele enhances the fitness of the genotype that carries it

Question 22

What is the result of directional selection?

Answer 22

• one allele goes to fixation
• the other allele goes to extinction

Question 23

Does it matter if an allele is dominant or recessive for directional selection?

Answer 23

yes, directional selection works slower on recessive traits

Question 24

How does directional selection act on continuous traits?

Answer 24

It changes the mean to be higher or lower than the previous mean

Question 25

What does directional selection do to genetic variation?

Answer 25

it reduces genetic variation

Question 26

How is genetic variation added back to populations?

Answer 26

mutation

Question 27

What are the 3 factors that change allele frequency?

Answer 27

-genetic drift
-selection
-mutation

Question 28

How can we predict the fixation or the extinction of an allele if there is no directional selection?

Answer 28

yes based off of the starting frequency: if its .1 starting frequency, the allele has a 10% chance of fixation and a 90% chance of extinction

Question 29

How does population affect genetic drift?

Answer 29

genetic drift has a more dramatic affect in smaller populations compared to larger populations

Question 30

What is overdominant selection?

Answer 30

the heterozygote is more fit than either of the homozygotes

Question 31

What is the result of overdominant selection?

Answer 31

balanced polymorphism: where both traits retain frequency in the population

Question 32

What is the breeders equation? And what do the variables represent?

Answer 32

r = h^2s
r is the real response in continuous trait mean
h^2 is the proportion of variance in the population that is due to genetics
s is the maximum amount of change possible without heritability

Question 33

When does trait evolution happen?

Answer 33

On branches, not on nodes

Question 34

What are classifications based on?

Answer 34

relatedness not similarites

Question 35

What is convergent evolution?

Answer 35

Traits become similar but do not come from the same evolutionary origin

Question 36

What are homologies?

Answer 36

Traits that are similar because they come from the same evolutionary origin

Question 37

What is the result of less genetic variation?

Answer 37

a population is more susceptible to environmental pressures and pathogens

Question 38

What are the two theories for the evolution of mitochondria?

Answer 38

-endosymbiotic theory (procaryote engulfed by eukaryote)
-autogenous theory (evolved from the nucleus and then did not form linear dna organization)