Topic 7B: Population and Evolution

Question 1

What is a species?

Answer 1

a group of similar organisms that produce 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

Question 3

What is a gene pool?

Answer 3

Complete range of alleles present in the population

Question 4

What is allele frequency?

Answer 4

How often an allele occurs in a population

Question 5

What does the Hardy-Weinberg principle predict?

Answer 5

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

Question 6

The Hardy-Weinberg prediction is only true under what conditions?

Answer 6

• large population
• no immigration/emigration
• no mutations
• no natural selection
• random mating

Question 7

What do the Hardy-Weinberg equations calculate?

Answer 7

-frequency of alleles

Question 8

What is the equation that calculates allele frequency?

Answer 8

p + q = 1

Question 9

What is the equation that calculates genotype/phenotype frequency?

Answer 9

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

Question 10

p is….

Answer 10

dominant

Question 11

q is….

Answer 11

recessive

Question 12

What is variation?

Answer 12

differences that exist between individuals

Question 13

What causes variation?

Answer 13

• genes
• the environment
• or both

Question 14

Variation within species means….

Answer 14

wide range of different phenotypes

Question 15

Although individuals of the same species have the same genes but

Answer 15

• they have different alleles

- this causes genetic variation

Question 16

What is the main source of genetic variation?

Answer 16

-mutation
BUT also 
-crossing over
-independent segregation
-random fertilisation

Question 17

What type of variation is caused within species most commonly?

Answer 17

a combination of genetic and environmental factors

Question 18

Only genetic variation causes….

Answer 18

evolution

Question 19

What is evolution?

Answer 19

A change in allele frequencies over time

Question 20

What is a method by which evolution occurs?

Answer 20

Natural selection

Question 21

Outline how evolution changes the allele frequency…

Answer 21

• Individuals of the same species vary between different alleles
• selection pressures create a struggle for survival
• organisms better adapted to the selection pressure survive/reproduce/pass onto offspring
• greater proportion inherit the beneficial alleles
• changes the frequency of alleles

Question 22

Name the three different types of selections?

Answer 22

• Directional
• Stabilising
• Disruptive

Question 23

What is stabilising selection?

Answer 23

• favours the middle of the range
• environment isnt changing
• reduces the range of possible phenotypes
• avoid extremes

Question 24

What is directional selections

Answer 24

• favours an extreme phenotype

- response to environmental change

Question 25

What is disruptive selection?

Answer 25

- favour BOTH extreme phenotypes - opposite to stabilising selection - middle range is lost - environment favours more than one phenotype

Question 26

Explain an example of stabilising selection

Answer 26

- fur length - fur at extremes reduced the chance of survival - because harder to maintain body temperature - so average fur length are most likely to survive and reproduce

Question 27

Explain an example of directional selection

Answer 27

- cheetahs run really fast - due to directional selection - individuals with increased speed more likely to catch prey - these compete with slower individuals and survive and reproduce etc

Question 28

Explain an example of disruptive selection

Answer 28

- range of beak sizes - birds with large beaks are designed to eat large seeds - birds with small beaks are designed to eat small seeds - birds with medium sized beaks have reduce chance of survival - pop of small and large beaks increases

Question 29

Name two types of speciation?

Answer 29

- Allopatric | - Sympatric

Question 30

What is speciation?

Answer 30

development of new species from an existing one

Question 31

How does speciation occur?

Answer 31

when population of the same species becomes reproductively isolated

Question 32

What does it mean being reproductively isolated?

Answer 32

when the species can no longer interbreed to produce fertile offspring

Question 33

What is reproductive isolation?

Answer 33

changes in allele frequency cause changes in the phenotypes

Question 34

What does geographical isolation lead to?

Answer 34

allopatric speciations

Question 35

Outline allopatric speciations

Answer 35

- population geographically isolated due to selection pressure OR genetic variation due to mutation - creates physical barrier - pop experience different selection pressures - different environmental conditions - changes in the alleles cause directional selection - causes differential reproductive success - changes in allele frequency/gene pool - they become reproductively isolated

Question 36

Examples of selection pressures

Answer 36

predatation, climate, disease

Question 37

What is sympatric speciation?

Answer 37

Random mutations that could occur within population, preventing members of that population breeding with other member of the species

Question 38

What is polyploidy?

Answer 38

When mutations can occur that increase the number of chromosomes

Question 39

Example of sympatric speciation?

Answer 39

- eukaryotic organisms are diploid - if they are polyploidy then reproduction can not happen sexually - polyploidy organism becomes reproductively isolated - if polyploidy organisms can reproduce asexually they new species could develop

Question 40

Is sympatric speciation more common in plants or animals?

Answer 40

Plants

Question 41

What in are the ways species can be reproductively isolated?

Answer 41

Changes in: seasonal mechanical behavioural

Question 42

What is a seasonal change?

Answer 42

-developing different flowering/mating seasons OR -becoming sexually active at different times of the year

Question 43

What is a mechanical change?

Answer 43

changes in the genitalia preventing successful mating

Question 44

What is a behaviour change?

Answer 44

a group of individuals developing courtship rituals that are not attractive to the main population

Question 45

What is genetic drift?

Answer 45

When chance rather than environment factors dictates which individuals survive breed and pass on their alleles.

Question 46

Example of genetic drift

Answer 46

- variation in genotype - by chance allele for one genoptype is passed on to offspring - allele frequency of that allele increases - reproductive isolation

Question 47

Evolution can occur by

Answer 47

- genetic drift | - natural selection

Question 48

When does genetic drift have a greater effect?

Answer 48

- When population size is smaller and so chance has a greater influence - in greater population the chance variation tends to even out

Question 49

Evolutionary changes causes..

Answer 49

greater diversity