population genetics

Question 1

hardy weinberg equation

Answer 1

can be used to predict allele frequencies in the population.

Question 2

gene pool

Answer 2

all of the alleles of all genes within the population at one time.

Question 3

population

Answer 3

all individuals of the same species in the same area at one time.

Question 4

allele frequency

Answer 4

proportion of an allele within the gene pool.

Question 5

speci

Question 6

genetic factors- mutations

Answer 6

sudden changes in gene or chromosomes
main source of variation
may or may not be passed onto next generations

Question 7

genetic factors- meiosis

Answer 7

crossing over and independent segregation
nuclear divions
new combinations of alleles before they go into gametes.

Question 8

genetic factors- random fertilisation

Answer 8

random fusion of gametes
sexual production- new combinations of alleles- genetic variation among offspring.

Question 9

enirovnmental factors

Answer 9

influences organism’s expression of genes.
genes set limit but environment determines where within these limits organisms can survive e.g.
food availability
pH
soil conditions.

Question 10

human environmental factors

Answer 10

height and mass
polygenes

e.g. height would produce a normal distribution curve.

Question 11

what is genetic diversity?

Answer 11

total number of different allles of a gene in a population

Question 12

what is required for natural selection to occur?

Answer 12

natural selection can only occur when there is genetic diversity within the population.

Question 13

what does natural selection lead to?

Answer 13

evolution- change in allele frequency over many generations within a population.

Question 14

what are the 3 types of adaptations?

Answer 14

anatomical
physiological
behavioural

Question 15

evolution via natural selection

Answer 15

mutations produce a new allele
in certian environmental conditions, organisms with this allele have a selective advantage and are more likely to survive and reproduce
this allele is inherited by their offspring.
over many generations, the frequency of this allele increases in the population.

Question 16

directional selection

Answer 16

organisms with extreme phenotype have selective advantage
modal/most common trait changes
occurs when there is an environmental change.
e.g. antiobiotic resistance in bacteria.

Question 17

stabilising selection

Answer 17

modal/most common trait remains the same
occurs when there is no environmental change
standard deviation/range decreases as number with extreme phenotype decreases
e.g. birth weight of babies.

Question 18

what is differential reproductive success?

Answer 18

all organisms are not as likely to reproduce which leads to changes in allele frequency within the gene pool.

Question 19

disruptive selection

Answer 19

individuals with alleles for either extreme phenotype have a selective advantage/are more likely to surive and reproduction

frequency of middling trait decreases
more individuals with extreme alleles

continuous disruptive selection ultimately leads to speciation.

Question 20

2 ways that populations can become reproductively isolated

Answer 20

geographic barrier- allopatric
changes in reproductive mechanisms- sympatric.

Question 21

allopatric speciation

Answer 21

reproductive isolation due to geographical barrier e.g. mountain ranges or bodies of water separating land masses

2 populations accumulate different beneficial mutations to survive in their environment.
their DNA differences become so siginificant that they can no longer interbred to produce fertile offspring- so there are now 2 different species.

Question 22

allopatric speciation

Answer 22

reproductive isolation due to geographic barrier e.g. mountain ranges or bodies of water separating land masses.
2 populations accumulate different beneficial mutations to enable them to survive in their environment.
DNA differenes are so significant over time that organisms cannot interbred to produce fertile offspring- 2 different species.

Question 23

sympatric speciation

Answer 23

-may not be a geographic barrier, but organisms are unable to interbreed
-random mutation could cause changes in courtship behaviour e.g. fertile at different times of year/different courtship rituals.

over time, reproductively isolated populations accumulate different mutations- can no longer interbreed to produce fertile offspring.

Question 24

genetic drift

Answer 24

genetic drift is the changes in allele frequency between generations within a population

genetic drift will always occur between generations but continual, substantial genetic drift will lead to evolution

evolution occurs more rapidly in smaller populations as they are more affected by changes in allele frequency.