18 populations and evolution

Question 1

what are the causes of variation in sexual reproduction?

Answer 1

mutation
meiosis
random fertilisation/fusion of gametes

Question 2

what is a mutation?

Answer 2

sudden change in base sequence of DNA

Question 3

any mutation could:

Answer 3

• confer a selective advantage
• be neutral
• confer a selective disadvantage

Question 4

how does the environment cause variation in phenotypes?

Answer 4

• climatic conditions
• abiotic factors
• biotic factors

Question 5

give an example of an abiotic factor

Answer 5

temperature
light intensity
soil pH
etc

Question 6

give an example of biotic factors

Answer 6

predators
food supply

Question 7

what kind of characteristics form a normal distribution curve?

Answer 7

characteristics that are polygenic

Question 8

what does a normal distribution curve look like?

Answer 8

bell shaped

Question 9

define selection

Answer 9

process where organisms that are better adapted to the environment survive and reproduce in greater numbers resulting in the increase of the frequency of advantageous alleles within the population

Question 10

what are the 4 types of selection?

Answer 10

stabilising
natural
directional
disruptive

Question 11

when does natural selection occur?

Answer 11

when variation exists

Question 12

describe natural selection

Answer 12

better adapted individuals more likely to survive and reproduce to pass on alleles
less well adapted individuals less likely to survive and reproduce to pass on alleles
organisms subject to selection pressure

Question 13

what does selection pressure do?

Answer 13

determines the spread of alleles within a gene pool

Question 14

when does stabilising selection occur?

Answer 14

when the environment is stable

Question 15

describe selection pressure

Answer 15

selection pressure at both ends of the distribution
favours the average and reduces variability

Question 16

when does directional selection occur?

Answer 16

when individuals one side of the mean survive better or reproduce more than those on the other

Question 17

describe directional selection

Answer 17

environmental change produces a new selection pressure which favours a new extreme
mean phenotype shifts

Question 18

when does disruptive selection occur?

Answer 18

when individuals of a mean phenotype are less fit than those of both higher and lower phenotype

Question 19

describe disruptive selection

Answer 19

opposite of stabilising
selection pressure favours 2 extremes and they dominate so the mean shifts to opposite ends

Question 20

define the term genetic drift

Answer 20

the random change in allelic frequency

Question 21

when is genetic drift important and why?

Answer 21

in small populations
loss of individuals with certain alleles results in a significant change in allelic frequency

Question 22

define the term gene flow

Answer 22

change in allele frequency due to the migration of fertile individuals

Question 23

give an example of genetic drift

Answer 23

volcano eruption
tsunami
earthquake

Question 24

give an example of gene flow

Answer 24

migration

Question 25

what is speciation?

Answer 25

the evolution of a new species from existing species

Question 26

what are the two types of speciation?

Answer 26

allopatric
sympatric

Question 27

what must 2 populations undergo to become genetically distinct?

Answer 27

reproductive isolation

Question 28

what is allopatric speciation?

Answer 28

1. physical barrier dividing the population
2. each isolated population subject to different selection pressures
3. mutations may occur
4. changes in genotype and phenotype may occur
5. when reunited- reproductively isolated as each population has become its own species

Question 29

what is sympatric speciation?

Answer 29

1. organisms in same area reproductively separated
2. (type of isolation)

Question 30

what are 6 types of isolation?

Answer 30

temporal
ecological
behavioural
mechanical
gametic
hybrid