TOPIC 4 - Genetic diversity and adaption

Question 1

Define genetic diversity

Answer 1

The number of different alleles of a gene in a species/ population

Question 2

Why is genetic diversity important?

Answer 2

-If a population has a low genetic diversity it may not be able to adapt to changes in the environment and the whole population could be wiped out by a single event such as disease

Question 3

Which factors increase genetic diversity?

Answer 3

-Mutations in the DNA forming new alleles- can be advantageous/ disadvantageous (point mutations and frameshifts
-Different alleles being introduced into a population migrate into it and reproduce (gene flow)
-Crossing over
-Independent segregation
-Random combination of gametes
-Non disjunction
-Homologous chromosomes in A1
-Sister chromatids in A2
-Sister chromatids in mitosis
-Allele interactions

Question 4

What is a genetic bottleneck?

Answer 4

-An event that causes a big reduction in a population

Question 5

Give an example of a genetic bottleneck

Answer 5

-When a large number of organisations die within a population before being able to reproduce

Question 6

Why do genetic bottlenecks reduce genetic diversity?

Answer 6

-Reduces the number of different alleles in the gene pool

Question 7

What is the founder effect?

Answer 7

-Describes what happens when just a few organisms from a population start a new colony and there is only a small amount of different alleles in the initial gene pool
-This frequency of each allele in the new colony might be very different to the frequency of those alleles in the original population

Question 8

What does the founder effect lead to?

Answer 8

-High rates of genetic disease

Question 9

How does the founder effect occur?

Answer 9

-As a result of migration leading to geographical separation or if a new colony is separated from the original population for a reason such as religion

Question 10

What is natural selection?

Answer 10

-When the allele codes for a characteristic that increases the chances of an organism surviving, its frequency within the population can increase

Question 11

What is differential reproductive success?

Answer 11

-Individuals that have an allele that increases their chance of survival are more likely to survive, reproduce and pass on their genes however the individuals with less advantageous alleles are less likely to survive

Question 12

Explain the steps of natural selection

Answer 12

1. Differential reproductive success
2. DFS means that a greater proportion of the next generation inherits the beneficial allele
3. They are more likely to survive, reproduce and pass on their genes
4. The frequency of the beneficial allele in the population increases from generation to generation
5. Over generations this leads to evolution as the advantageous alleles become more common in the population

Question 13

Define evolution

Answer 13

-The gradual change in species over time

Question 14

What are adaptions?

Answer 14

-Features that help organisms to survive in their environment

Question 15

What are the three types of adaptions?

Answer 15

-Behavioural
-physiological
-Anatomical (structural)

Question 16

What are behavioural adaptions?

Answer 16

-These are ways an organism acts that increase it’s chance of survival

Question 17

Give 2 examples of behavioural adaptations

Answer 17

-Possums- play dead to escape attack
-Scorpians- dance before mating- makes sure they attract a mate of the same species

Question 18

What are physiological adaptions?

Answer 18

-Processes inside an organisms body that increase it’s chance of survival

Question 19

Give 2 examples of physiological adaptions

Answer 19

-Brown bears hibernate- Lower their metabolism to conserve energy
-Some bacteria produce antibiotics- kill other species of bacteria, less competition

Question 20

What are anatomical adaptions?

Answer 20

-Structural features of an organisms body that increase chance of survival

Question 21

Give 2 examples of anatomical adaptions

Answer 21

-Otters- streamlined, easier to catch, increase their chance of survival
-Whales- have a thick layer of blubber, increases chances of survival in the places where their food is found

Question 22

What is directional selection?

Answer 22

-Individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce

Question 23

What could directional selection be a response to?

Answer 23

-Environmental change

Question 24

What is stabilising selection?

Answer 24

-Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce

Question 25

When does stabilising selection occur?

Answer 25

-When the environment isn’t changing

Question 26

What does stabilising selection reduce?

Answer 26

-The range of possible characteristics

Question 27

What factors decrease diversity?

Answer 27

-Natural selection/artificial
-Selective breeding
-Selection pressure
-(All environmental)

Question 28

What are selection pressures?

Answer 28

-A factor which causes selection within a population
by exerting environmental resistance

Question 28

Draw a flow diagram for natural selection

Answer 28

-Mutations
-Variation
-Adaptations
-Survive
-Reproduce (differential success)
-Alleles passed on
-Change in allele frequency

Question 29

Give some examples of selection pressures

Answer 29

-Competition
-Predation
-Limited light, oxygen,water and other abiotic factors
-Variation in temp (global warming)
-Disease
-Human influence- pollution,overuse of antibiotics, pesticides and poisons

Question 30

How would you apply natural selction?

Answer 30

-Random mutation may result in a new allele of a gene
-The new allele may provide the possessor with an advantage/adaptation
-This individuals will be better adapted to source resources, compete and survive
-As a result of being successful they will be more likely to attract a mate, reproduce and pass on their alleles onto the next generation
-As their offspring will have the new, advantageous allele they are more likely to survive
-Over time the frequency of the new allele will increase in the population

Question 31

What is a dominant (S) allele?

Answer 31

-The allele that is always expressed even if only one copy (of the two) is present

Question 32

What is a recessive (s) allele?

Answer 32

-Trait is only produced if there is 2 copies of the allele

Question 33

What is allele frequency?

Answer 33

-How common an allele is in a population