Evolution may lead to speciation 2

Question 1

what results in natural selection

Answer 1

competition for resources and impact of disease and predators

Question 2

why is there a large range of variation in phenotype in a population

Answer 2

genetic and environmental factors

Question 3

sources of genetic variation

Answer 3

mutation

meiosis

random fusion of gametes

Question 4

what results in a selection pressure

Answer 4

predation disease and competition

Question 5

if have favourable phenotype

Answer 5

1- selective advantage
2- more likely to survive
3- more likely to produce offspring
4- pass on favourable alleles
5- to next generation
5- results in a change in allele frequency - evolution

Question 6

evolution definition

Answer 6

change in allele frequency in a population

Question 7

change in allele frequency in a gene pool called

Answer 7

differential reproductive success

Question 8

3 types of selection

Answer 8

1- stabilising
2- directional
3- disruptive

Question 9

disruptive selection graph

Answer 9

red- before
blue= after

Question 10

stabilising selection graph

Answer 10

red- before
blue= after

Question 11

directional selectrion graph

Answer 11

red- before
blue= after

Question 12

Disruptive selection is

Answer 12

when individuals which contain the alleles coding for either extreme trait are more likely to survive and pass on their alleles.

allele frequency changes as more individuals possess the alleles for the extreme traits

the middling trait allele becomes less frequent.

Question 13

continued disruptive selection can lead to

Answer 13

speciation

Question 14

stabilising selection is

Answer 14

is that the range of alleles decreases and most individuals have the modal trait.

Question 15

directional selection is

Answer 15

that the allele frequency changes and more of one of the extreme trait’s alleles become more frequent.

Question 16

What type of selection results in speciation

Answer 16

disruptive

Question 17

Describe disruptive selection

Answer 17

Population experiances two different selection pressures
Two phenotypes are advantageous and both become more common
Speciation occurs

Question 18

Explain stabilising selectio

Answer 18

Mean phenotypes best adapted to survivie in unchanging enviroment

Selection against extreme phenotypes in favour of mean phenotypes

Range and standard deviation reduced

Question 19

Example of stabilising selection

Answer 19

birth weight in humans

Question 20

Explain directional selection and give an example

Answer 20

Extreme phenotype is best adapted to survive in unchanging enviroment

Selection against mean phenotypes in favour of extreme phenotypes

Range and standard deviation reduced

Question 21

Example of directional selection

Answer 21

Antibiotic resistance in rats

Question 22

speciation

Answer 22

results in the creation of new species

Question 23

Regarding natural selection, and evolution, what are the primary and secondary causes of variation

Answer 23

Mutations primary
Meiosis secondary
Random fertilisation of gametes secondary

Question 24

speciation can occur..

Answer 24

1- one original population of the same species becomes reproductively isolated.

2- now two populations of the same species

3- but they cannot breed together (no gene flow).

4- result in the accumulation of differences in their gene pools

5- two populations unable to interbreed to make fertile offspring

6- classed as two different species.

Question 25

two different ways that populations can become reproductively isolated

Answer 25

geographically (allopatric) or because of changes in reproductive mechanisms (sympatric).

Question 26

Describe and explain the process of allopatric speciation

Answer 26

1- Two populations become reproductivly isolated geographically 2- No gene flow between populations 3- Each population experiances different selection pressures 4- Variation occurs in each population, due to mutation 5- DIfferent alleles are advanatageous, so different alleles are passed on 6- Change in frequency of alleles 7- Disruptive selection 8- Eventually, populations **cannot interbreed to produce fertile offspring **

Question 27

Describe and explain the process of sympatric speciation

Answer 27

1- Two populations become reproductivly isolated in the same habitat 2- No gene flow between populations 3- Each population experiances different selection pressures 4- Variation occurs in each population, due to mutation 5- DIfferent alleles are advanatageous, so different alleles are passed on 6- Change in frequency of alleles 7- Disruptive selection 8- Eventually, populations cannot interbreed to produce fertile offspring

Question 28

Define allopatric speciation

Answer 28

Formation of new species from different populations, that are reproductivly isolated georgraphically

Question 29

Define sympatric speciation

Answer 29

Formation of new species from a population that are reproductivly isolated, but not geographically isolated (in the same habitat)

Question 30

Genetic drift

Answer 30

change in the allele frequency within a population between generations.

Question 31

What does genetic drift cause

Answer 31

Change in allele frequencies

Question 32

Effect on gene pools in a smaller population

Answer 32

Smaller populations have smaller gene pools

Question 33

The smaller a population,

Answer 33

the bigger the impact allele frequency changes evolution happens more rapidly

Question 34

Describe how the behaviour of female guppies could result in sympatric speciation.

Answer 34

1- Not geographically isolate 2. Leading to reproductive isolation 3- Gene pools kept separate; 4-. Changes in allele frequencies; 5. Cannot breed to produce fertile offspring;

Question 35

One hypothesis for LP in humans suggests that the selective pressure was related to some human populations farming cattle as a source of milk. Describe how farming cattle as a source of milk could have led to an increase in LP.

Answer 35

1- LP due to mutation 2. Milk provides named nutrient e.g. proteins 3. Individuals with LP more likely to survive and reproduce 4- Individuals with advantageous allele more likely to survive and reproduce; 5- Directional selection; 6 . Frequency of allele increases in next generation

Question 36

Use the information provided to explain why the number of people showing LP would rapidly increase once selection for this condition had been established.

Answer 36

1- Dominant allele; 2. Always expressed when present in phenotype 3- Expressed when only one dominant allele present;

Question 37

Lord Howe Island in the Tasman Sea possesses two species of palm tree which have arisen via sympatric speciation. The two species diverged from each other after the island was formed 6.5 million years ago. The flowering times of the two species are different. Using this information, suggest how these two species of palm tree arose by sympatric speciation. (5)

Answer 37

1- Occurs in the same habitat and not genetically isolated 2. Mutation/s cause different flowering times; 3. Reproductive isolation 4- No gene flow 5- Gene pools remain separate; 6- Different allele/s passed on 7- Change in frequency of allele/s 8. Disruptive (natural) selection; 9. Eventually different species cannot interbreed to produce fertile offspring

Question 38

There was a time lag between the introduction of Bt crops and the appearance of the first insect species that was resistant to the Bt toxin. Explain why there was a time lag.

Answer 38

1- Initially few insects with favourable mutation / allele; 2. Individuals with (favourable) mutation / allele will have more 3. Takes many generations for (favourable) mutation / allele to become the most common allele (of this gene).

Question 39

There are nine subspecies of giraffe. These subspecies evolved when populations of giraffe were separated for long time periods. Each subspecies has distinct coloured skin markings. Some biologists have suggested that up to six of these subspecies should be classified as different species. (a) Explain how different subspecies of giraffe may have evolved from a common ancestor. Use information from the passage in your answer. (5)

Answer 39

1- No interbreeding 2- gene pools are separate 3-geographical isolation 4- Mutation linked to colours; 5. survival linked to (different) markings/colours; 6. Adapted organisms breed / differential reproductive success; 7- . Change in allele frequency

Question 40

Biologists compared the mitochondrial DNA of the different subspecies of giraffe. They used the results from comparing this DNA to conclude that six of the nine subspecies are separate species. Suggest how they came to this conclusion

Answer 40

1- compare base sequence 2- different in different species

Question 41

One farmer stated that the increase in the use of Bt crop plants had caused a mutation in one of the insect species and that this mutation had spread to other species of insect. Was he correct? Explain your answer.

Answer 41

1- Mutations are random; 2. Only the rate of mutation is affected by environment; 3. Different species do not interbreed / do not produce fertile offspring; 4. So allele cannot be passed from one species to another.