Patterns of inheritance ( Part 2 )

Question 1

What are the factors affecting evolution ?

Answer 1

• Selection pressure / change in environment
• Mutations
• Genetic drift
• Genetic bottleneck
• Founder effect

Question 2

Define genetics bottleneck ?

Answer 2

The reduction in the gene pool of a population due to a significant decrease in population size

Question 3

What is the effect of genetic bottleneck ?

Answer 3

• Significant decrease in population means many allles are lost
• Modern population descended from small gene pooole / few survivors

Question 4

Define genetic drift ?

Answer 4

The gradual change in the allele frequencies of a small population due to chance/ mutations and not natural selection

Question 5

What are the effects of genetic drift ?

Answer 5

• One individual / allele has proportionally greater effect on small population
• More likely alleles will be lost from population/ more vulnerable to chnages in their environment

Question 6

Define flounder effect ?

Answer 6

When the allele frequency of the newly isolated small population changes in a different direction in comparison to the large parent population due to chance/ mutations

Question 7

What are the conditions for the Hardy-Weinberg principle ?

Answer 7

• Organisms are diploid
• Organisms reproduce by sexual reproduction only
• There is no overlap between generations, i.e. parents do not mate with offspring
• Mating is random
• The population is large
• There is no migration, mutation, or selection
• The Allele frequencies are equal in both sexes

Question 8

What is the equation that represents the frequency of alleles in a population ?

Answer 8

• P = frequency of dominant allele
• Q = frequency of the recessive allele

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

Question 9

Define ‘Genetic isolation’ ?

Answer 9

Genetic Isolation : When two populations of the same species become reproductively isolated and genetically isolated from one another

Question 10

Explain what occurs as a result of genetic isolation ?

Answer 10

• Two populations of the same species no longer reproduce and exchange genes with each other
• Populations experience different selection pressure and evolve independently of each other
• Mutations/ change in allele frequency occurs in each population
• Populations are no longer a let to breed with one an other due to different gene pool / allele frequency
• They are now different species / speciation occurs

Question 11

Define ‘speciation’ ?

Answer 11

Speciation : The formation of new species from a pre-existing species over time due to change in gene pool/ allele frequency over time

Question 12

What are the requirements for speciation ?

Answer 12

• Mutations
• Natural selection
• Time
• Different selection pressures

Question 13

What are the two types of speciation ?

Answer 13

• Allopatric speciation
• sympatric speciation

Question 14

What causes allopatric speciation ?

Answer 14

When two populations of the same species are isolated from one another due to a geographical barrier

Question 15

Explain what happens during allopatric speciation ?

Answer 15

• Species become separated from each other by geographical barriers
• Two populations are reproductively isolated from one another and cannot exchanges alleles during reproduction
• MUTATIONS OCCUR WITHIN POPULLATIONS
• Populations experience different selection pressures causing change in gene pool/ allele frequency within both populations over time
• Directional selection
• They can no longer breed with one another and are different species

Question 16

When does sympathise speciation occur ?

Answer 16

• Sympatric speciation takes place with no geographical barrier
• Something has to happen that splits or separates the two populations

Question 17

What are the two types of separation that cause sympathetic speciation to occur ?

Answer 17

• Ecological separation
• Behavioural separation

Question 18

Define ‘Ecological separation’ ?

Answer 18

Ecological separation: Populations are separated because they live in different environments within the same area

Question 19

Define ‘Behavioural separation’ ?

Answer 19

Behavioural separation: Populations are separated because they have different behaviours ( eg. Courting rituals, feeding behaviours )

Question 20

Explain what occurs during sympathetic speciation ( eg. Fish ) ?

Answer 20

• Some individuals within the population feed on the bottom while others remain higher up in the open water
• The different feeding behaviours separates the population into different environments
• MUTATIONS OCCUR WITHIN POPULLATIONS
• The separated groups experience different selection pressures
• Over time natural selection causes allele frequency/ gene pool of the populations to change and evolve different COURTSHIP DISPLAY / MATING RITUALS
• DIRECTIONAL SELECTION
• They can no longer interbreed; they are now considered separate species

Question 21

Define ‘Artificial selection’ ?

Answer 21

Artificial selection : Artificial selection is the process by which humans choose organisms with desirable traits and selectively breed them together to produce offspring with desirable traits over many generations generations

Question 22

Explain how selective breeding occurs ?

Answer 22

• The population shows phenotypic variation / has genetic variation
• Individuals with the desired phenotype/ displaying extreme trait are selected and bred together
• The offspring produced reach maturity and are then tested for the desirable trait
• Offspring that display desired phenotype to the greatest degree/ most extremely are selected for further breeding
• Repeated over several generations, increasing allele frequency coding for desired trait within popullation

Question 23

Why is selective breeding conducted in animals ?

Answer 23

• Cows, goats and sheep that produce a higher yield of milk or meat
• Chickens that lay large eggs
• Domestic dogs that have a gentle nature
• Sheep with good quality wool

Question 24

Why is selective breeding conducted in plants ?

Answer 24

• Disease resistance in food crops
• Increased crop yield
• Hardiness to weather conditions (eg. drought tolerance)
• Better tasting fruits
• Large or unusual flowers

Question 25

Explain the importance of maintaining a resource of genetic material for use in selective breeding ?

Answer 25

- Ensures that the gene pool for a particular species doesn't become too small - Prevents inbreeding depression - Allows introduction of new traits - Source of replacement if cultivated population is in danger - Reduce genetic variation and makes population more susceptible to changes in their environment/ will not be able to adapt

Question 26

What are the effects of inbreeding individuals ?

Answer 26

- Reduces genetic diversity - More likely to inherit homozygous recessive alleles that are harmful - Desired extreme trait may be linked to harmful gene/ allele which causes X condition