3.7.2 Population and Evolution

Question 1

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

What is continuous variation ?

Answer 4

when the individuals vary in a range so there are no distinct categories

Question 5

What is discontinuous variation ?

Answer 5

When there are two or more distinct categories and each individual falls into only one category

Question 6

Answer 6

Question 7

Give examples of continuous variation

Answer 7

Question 8

Give examples of discontinuous variation

Answer 8

Question 9

What causes variation in phenotypes?

Answer 9

The organisms genotypes and the environment

Question 10

name 3 sources of genetic variaion

Answer 10

Mutation, meiosis (independenet assortment and crossing over) and random fusion of gametes

Question 11

How does the use of Hardy Weinberg equation allow us to see if evolution has occurred?

Answer 11

Identify changes in the allele frequency over time, if allele frequency has changed then selection has occurred. Also if you do the maths and either of the HW equations doesn’t add to 1 then this suggest evolution

Question 12

Answer 12

Question 13

What is a gene pool?

Answer 13

All the alleles of all the genes in a population at a certain time

Question 14

How can looking at phenotype help to measure genetic diversity of a species?

Answer 14

Different phenotypes are coded for by different alleles, so the larger the number of different phenotypes, the greater the diversity of alleles so the greater the genetic diversity

Question 15

How can looking at genotype help to measure genetic diversity of a species?

Answer 15

Analyse the sequence of base pairs in DNA samples of organisms. The order of bases in different alleles is slightly different. By sequencing the DNA of individuals of the same species, you can look at similarities and differences in the alleles. The larger the number of dif alleles the greater the genetic diversity

Question 16

Answer 16

Question 17

Define ‘selection pressure’

Answer 17

environmental factors that limit the population of a species

Question 18

Define ‘directional selection’

Answer 18

When individuals away from the mean are selected for. One extreme is selected in favour of the other so the normal distribution shifts in one direction

Question 19

Define ‘disruptive selection’

Answer 19

When individuals away from the mean are selected for. Individuals at both extremes are selected in favour of those near the mean so the normal distribution becomes ‘squashed’ in the middle

Question 20

Draw the effects of 3 types of selection pressure on this curve

Answer 20

insert pic

Question 21

scroll through all pictures

Answer 21

2 answers

Question 22

Explain how natural selection has lead to antibiotic resistance

Answer 22

Chance mutation, new allele, selection pressure, bacteria with resistance survive and pass on allele, increase in allele frequency,

Question 23

What happens to individuals with the advantageous alleles?

Answer 23

They are more likely to survive, reproduce and pass on their advantageous alleles to their offspring

Question 24

Answer 24

Question 25

what is speciation

Answer 25

The evolution of new species from existing ones.

Question 26

Answer 26

Question 27

What are the two types of speciation

Answer 27

Allopatric - when populations become geographically separated. Sympatric - speciation that occurs in the same geographic area

Question 28

What is reproductive isolation?

Answer 28

When changes in the alleles and phenotypes of the populations prevent them from successfully breeding together

Question 29

Answer 29

Question 30

what is hybrid sterility and give an exampe

Answer 30

when two different species can breed but their offspring are infertile (eg tiger + lion = liger)

Question 31

Why might a population become reproductively isolated?

Answer 31

Due to geographical isolation or random mutations

Question 32

How does geographical isolation lead to speciation?

Answer 32

Conditions on either side of the barrier are slightly different. Different characteristics will be advantageous on each side so the allele frequencies change in each population. Mutations occur independently in each population, also changing the allele frequencies. The changes in allele frequencies lead to changes in phenotype frequencies. Eventually, the different populations become genetically distinct and are reproductively isolated

Question 33

What does it mean when organisms are reproductively isolated?

Answer 33

The individuals from the different populations will have changed so much that they won't be able to successfully breed with each other to produce fertile offspring

Question 34

Answer 34

Question 35

What is adaptive radiation

Answer 35

A population of organisms spreads to many new habitats. In each new habitat different selection pressures exist that result in the formation of multiple new species from one ancestor (eg Darwin's finches)

Question 36

What is genetic drift

Answer 36

When allele frequencies (especially in small populations) change over time due to random changes and random mating

Question 37

What is a genetic bottleneck

Answer 37

When allele frequencies in a population can change if a population decreases drastically in number (eg due to a natural disaster) and then repopulates

Question 38

Define allele frequency

Answer 38

How often an allele occurs in a population

Question 39

Under what conditions is the Hardy Weinberg principle true?

Answer 39

Large population, random mating, no natural selection, no mutations, no immigration or emigration

Question 40

what are the two hardy weinberg equations

Answer 40

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

Question 41

What does p stand for in p + q = 1?

Answer 41

the frequency of the dominant allele

Question 42

What does q stand for in p + q = 1?

Answer 42

the frequency of the recessive allele

Question 43

what does p^2 stand for in p^2 + 2pq + q^2 = 1?

Answer 43

the frequency of the homozygous dominant genotype

Question 44

what does 2pq stand for in p^2 + 2pq + q^2 = 1?

Answer 44

the frequency of the heterozygous genotype

Question 45

what does q^2 stand for in p^2 + 2pq + q^2 = 1?

Answer 45

the frequency of the homozygous recessive genotype

Question 46

Answer 46

Question 47

Define evolution

Answer 47

When frequency of an allele in a population changes over time

Question 48

What is allopatric speciation

Answer 48

Formation of a new species due to geographical isolation

Question 49

Define speciation

Answer 49

When a new species develops because populations of the same species become reproductively isolated, reducing gene flow between the two populations

Question 50

What is sympatric speciation

Answer 50

The formation of a new species without geographical isolation due to random mutations which produce changes in phenotype