Population and Evolution

Question 1

define species?

Answer 1

a group of similar organisms that can reproduce to give fertile offspring

Question 2

define population?

Answer 2

a group of organisms of same species living in particular area at particular time - have potential to interbreed

Question 3

define gene pool?

Answer 3

complete range of alleles present in population

Question 4

define allele frequency?

Answer 4

how often allele occurs in population

Question 5

what does the hardy weinberg principle predict?

Answer 5

that frequencies of alleles in population wont change from one generation to the next

Question 6

what is the hardy weinberg principle only true under?

Answer 6

HAS to be

• large population
• no immigration
• no emmigration
• no mutations
• no natural selection
• RANDOM mating

Question 7

what can the hardy weinberg principle be used to calculate?

Answer 7

frequency of particular alleles, genotypes and phenotypes within populations

Question 8

hardy weinberg equation used to predict allele frequency?

Answer 8

p + q = 1

p = frequency of one allele - dominant

q = frequency of one allele - recessive

Question 9

hardy weinberg equation to predict genotype and phenotype frequency?

Answer 9

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

p^2 = frequency of homo dominant

2pq = frequency of hetero genotype

q^2 = frequency of homo recessive

Question 10

define variation?

Answer 10

differences that exist between individuals

Question 11

variation within a species means…

Answer 11

individuals in pop show wide range of diff phenoypes

Question 12

what causes genetic variation within a species?

Answer 12

when same species have same genes but diff alleles

Question 13

what is the main source of genetic variation?

Answer 13

mutations

Question 14

how can genetic variation be introduced?

Answer 14

during MEIOSIS

• crossing over chromatids
• independent segregation
• random fertilisation of gametes

Question 15

what variation only results in evolution?

Answer 15

genetic

Question 16

define evolution?

Answer 16

frequency of allele in population which changes over time

Question 17

natural selection is one methof by which…

Answer 17

evolution occurs

Question 18

define selection pressure?

Answer 18

anything that affects an organisms chance of survival and reproduction

Question 19

stabilising selection?

Answer 19

individuals with alleles for characteristics towards MIDDLE range more likely to survive and reproduce

Question 20

when does stabilising selection occur?

Answer 20

when enviro not changing

• reduces range of phenotypes

Question 21

stabilising selection e.g.

Answer 21

RANGE OF FUR LENGTH

• in stable climate, having fur at extremes reduces chance of surviving and reproduction
• harder to maintain right body temp
• those with average fur length more likely to survive, reproduce & pass on alleles
• proportion of population with average fur length inc
• range of fur length dec

Question 22

directional selection?

Answer 22

individuals with alleles for single EXTREME phenotype more likely to survive and reproduce

Question 23

when directional selection occur?

Answer 23

in response to enviro change

Question 24

example of directional selection?

Answer 24

cheetahs - speed

Question 25

disruptive selection?

Answer 25

individuals with alleles for extreme phenotypes at either end of range are more likely to survive and reproduce.

Question 26

when does disruptive selection occur?

Answer 26

when enviro favours more than one phenotype (CAUSES EVOLUTION)

Question 27

example of disruptive selection?

Answer 27

beak sizes

Question 28

define speciation?

Answer 28

development of new species from existing species

Question 29

when does speciation occur?

Answer 29

when pop of same species = **reproductively isolated** - change in allele freq changes phenotype - no longer interbreed = fertile offspring

Question 30

# define geographical isolation? what does it lead to?

Answer 30

when a physical barrier divides a population of species, causing some individuals to = separated from main pop ALLOPATRIC SPECIATION

Question 31

define sympatric speciation?

Answer 31

when population becomes **reproductively isolated** without any physical separation

Question 32

allopatric speciation

Answer 32

1. geographical Isolation 2. environmental conditions vary between two habitats 3. different selection pressures 4. different alleles advantageous 5. survive, reproduce to = fertile offpsring - pass on advantageous allele 6. differences accumulating in gene pools - causes change in phentoype frequencies 7. = reproductively isolated

Question 33

sympatric speciation

Answer 33

1. new selection pressure occurs 2. populations remain in the same place 3. become reproductively isolated 4. both evolve because of selection pressure 5. can no longer interbreed successfully

Question 34

what is polyploidy?

Answer 34

when mutations occur that inc the number of chromosomes

Question 35

why does reproductive isolation occur?

Answer 35

- changes in alleles and phenotytpes - in some individuals prevent them from breeding successfully - with individuals without these changes

Question 36

what are the 3 main ways reproductive isolation occurs?

Answer 36

- seasonal - mechanical - behavioural

Question 37

seasonal

Answer 37

individuals with same population develop **diff flowering** / **mating seasons** / become **sexually active** at diff times of year

Question 38

mechanical

Answer 38

changes in **genitalia** prevent successful mating

Question 39

behavioural

Answer 39

group of individuals that develop **courtship rituals** that arent attractive to main pop

Question 40

what is evolution by natural selection?

Answer 40

when diff selection pressures can change allele frequencies in 2 geographically isolated species

Question 41

define genetic drift?

Answer 41

when **chance**, rather than enviro factors dictate which individuals survive, breed and pass on alleles

Question 42

genetic drift

Answer 42

- variation in genotypes of pop - by chance, allel for 1 genotype passed on to offspring **more often** than once - number of individuals with allele in - changes in allele frequency in 2 isolated pop leads to **reproductive isolation** and **speciation**

Question 43

what does evolution by genetic drift have a greater impact on?

Answer 43

pop with - smaller pop - chance has greater influence in larger pop - chance variations in allele frequency even out across whole pop

Question 44

suggest an explanation for the results in the figure?

Answer 44

- mutation produces KDR minus allele - DDT use provides selection pressure - KDR minus allele in pop inc - those with KDR minus survive, reproduce and pass on allele - frequency of KDR minus inc in pop

Question 45

Answer 45

- neurones remain depolarised - no AP

Question 46

Answer 46

- sodium ion channel protein changes shape - DDTs shape no longer complementary