Topic 7: Populations And Evolution

Question 1

What is a species?

Answer 1

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

Question 2

What is a population?

Answer 2

A group of organisms of the same species living in a particular area at a particular time, so they have the potential to breed

Question 3

What is the gene pool?

Answer 3

Is the complete range of alleles present in a pop, how often an allele occurs in pop called allele frequency

Question 4

What is the Hardy-Weinberg principle?

Answer 4

Mathematical model that predicts the freq of alleles in a pop won’t change from one generation to the next

Question 5

What are the two conditions that hardy-Weinberg principle is only true under what conditions?

Answer 5

It has to be a large population where there’s no immigration, emigration, mutations or natural selection
There needs to be random mating, all possible genotypes can breed with all others

Question 6

What is the equation for allele frequency, in terms of hardy-Weinberg principle?

Answer 6

P + q = 1

Question 7

What is the equation for genotype frequency, in terms of hardy-Weinberg principle?

Answer 7

P2 + 2pq + q2 = 1

Question 8

What is the total freq of all possible genotypes for one characteristic in a certain pop?

Answer 8

1.0

Question 9

What are the 5 ways to use hardy Weinberg principle?

Answer 9

Predicting allele freq
Predicting genotype freq
Predicting phenotype freq
Predicting the % of a pop that has a certain genotype
Showing if any external factors are affecting allele freq

Question 10

What is variation?

Answer 10

The difference that exists between individuals

Question 11

What is intraspecific variation?

Answer 11

Variation between a species, meaning that individuals in a pop can show a wide range of diff phenotypes

Question 12

What is intraspecific variation cause by?

Answer 12

Genetic and/or environmental factors

Question 13

Name 4 ways genetic variation occurs?

Answer 13

Same genes different alleles
Mutations
Random fertilisation
Meiosis

Question 14

What is evolution?

Answer 14

Frequency of an allele in a pop changes over time

Question 15

What is evolution caused by?

Answer 15

Genetic drift

Question 16

Name 3 selecting pressures?

Answer 16

Predication, disease and competition

Question 17

What are the 3 types of selection?

Answer 17

Stabilising, directional and disruptive selection

Question 18

What is stabilising selection?

Answer 18

This is where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
Occurring when the environment isn’t changing, and it reduces the range of possible phenotypes

Question 19

What is directional selection?

Answer 19

This is where individuals with alleles for single extreme phenotypes are more likely to survive and reproduce, this could be a response to an environmental change

Question 20

What is disruptive selection?

Answer 20

Where individuals with alleles for extreme phenotypes are more likely to survive no reproduce
It is the opposite of stabilising selecting as characteristics towards the middle of the range are lost
Occurring when the environment favours more than one phenotype

Question 21

What is speciation?

Answer 21

The development of a new species from an existing species

Question 22

When does speciation occur?

Answer 22

When populations of the same species become reproductively isolated, changes in allele frequency cause changes in phenotype, which man they can no longer interbreed to produce fertile offspring

Question 23

When can reproductive isolation occur and what does it cause to happen?

Answer 23

When a physical barrier e.g flood divides a population of a species causing some individuals to become separated from the main population

Question 24

What is geographical isolation?

Answer 24

When a physical event e.g. flood divides a population of a species causing some individuals to become separated from the main population

Question 25

If there is so gene flow between the 2 populations what can it lead to?

Answer 25

Allopathic speciation

Question 26

When does sympathetic speciation occur?

Answer 26

When a pop comes reproductively isolated without any physical separation

Question 27

What will populations that are geographically separated experience ?

Answer 27

Experience slightly different conditions

Question 28

In allopathic speciation, how do different changes in allele frequencies occur?

Answer 28

Different alleles will be more advantageous in different populations, so natural selection occurs. Directional selection will then act an the alleles for the key characteristics (fur length), increasing the freq of the allele for longer fur length
Allele freq will also change as mutations will occur independently in each population
Genetic drift may also affect the allele frequencies in one or both populations
Overtime leading to speciation

Question 29

In allopathic speciation, what an changes in allele freq lead to?

Answer 29

Differences accumulating in the gene poos of the separated populations, causing change in phenotype frequencies
Eventually individuals from the different pop will have changed so much that they wont be able to breed with one another

Question 30

When can sympatric speciation occur?

Answer 30

When random mutations within a pop prevent individuals that carry the mutation from breeding with other members of the population that don’t carry the mutation, it doesn’t involve geographical isolation

Question 31

Name the 3 changes that can cause reproductive isolation?

Answer 31

Seasonal, mechanical and behavioural changes

Question 32

What can selection pressures change?

Answer 32

Allele freq of a pop over time

Question 33

How does genetic drift occur?

Answer 33

Individuals within a pop show variation in their genotypes
By chance, the allele for one genotype is passed on to more offspring than the others so the number of individuals with the allele increases
If by chance the same alleles is passed on more often again and again, it can lead o evolution as the allele becomes more common in the pop

Question 34

What can genetic drift lead to?

Answer 34

Differences in allele freq, between to isolated populations
If enough differences in allele freq build up over time this could eventually lead to reproduction isolation and speciation

Question 35

Which has a larger influence on smaller populations, evolution by genetic drift or pop size

Answer 35

Evolution