7. the origin of species

Question 1

true or false:

-mutations always have a negative effect

Answer 1

false

sometimes mutations don’t even have an effect

Question 2

define gene flow

Answer 2

the movement of genes between populations

Question 3

give an example of gene flow

Answer 3

bees & flowers:

bees and other insects transfer gametes from one population to another

Question 4

define genetic drift

Answer 4

chance alterations in a populations allele frequency

Question 5

what are the two causes of genetic drift

Answer 5

founder effect

genetic bottleneck

Question 6

what is genetic bottleneck

Answer 6

an event led to only a few individuals surviving, significantly reducing variation in the gene pool

Question 7

what is founder effect

Answer 7

colonisation of a new large area, eg Galapagos. the few individuals become the founders of a new isolated population

Question 8

give an example of where founder effect has had negative impact

Answer 8

dutch migrated to South Africa, these individuals had high frequency of alleles for Huntington’s disease, these alleles became prominent in the population

Question 9

what are the three modes of natural selection

Answer 9

stabilising selection
directional selection
diversifying selection

Question 10

describe stabilising selection

Answer 10

favours average, extremes are disadvantaged

Question 11

describe directional selection

Answer 11

one side of outliers Is favoured

Question 12

describe diversifying selection

Answer 12

extremes are advantaged. average is disadvantaged

Question 13

why does selection occur at high density populations

Answer 13

adaptations are favoured that enable reproduction with fewer resources

Question 14

why does selection occur at low density populations

Answer 14

selection favours traits that promote rapid reproduction

Question 15

what are the two types of speciation

Answer 15

allopatric

sympatric

Question 16

define allopatric speciation

Answer 16

this is where a population forms a new species whilst geographically separated from its parent population
some alleles may be lost

Question 17

define sympatric speciation

Answer 17

occurs in geographically overlapping populations

gene flow is reduced

Question 18

what are the two types of reproductive barriers

Answer 18

pre-zygotic

post-zygotic

Question 19

what is pre-zygotic

Answer 19

impeded mating or fertilisation of ova

Question 20

what is post-zygotic

Answer 20

prevents an ovum fertilised by another species from developing into a viable fertile adult

Question 21

give an example of prezygotic

Answer 21

habitat isolation

mechanical- not physically possible

Question 22

what are the two theories for rates of evolution

Answer 22

gradualism

punctuated equilibrium

Question 23

what is gradualism

Answer 23

gradual evolutionary change- slow but constant over long periods of time

Question 24

what is punctuated equilibrium theory

Answer 24

appearance of new characteristics give rise to new species quickly- then stay the same for a long time
(equilibrium)