🩶 3.4 Topic 4 - 3.4.4 Genetic diversity and adaptation

Question 1

What does natural selection increase in a population?

Answer 1

Advantageous alleles.

Question 2

What is natural selection?

Answer 2

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

Question 3

How does natural selection work?

Answer 3

1) Individuals that have an allele that increases their chance of survival are more likely to survive, reproduce and pass on their genes (including the beneficial alleles), than individuals with different alleles.
2) A greater proportion of the next generation inherits the beneficial allele.
3) More likely to survive, reproduce and pass on their genes.
4) Frequency increases of the beneficial allele from generation to generation.
5) Over generations this leads to evolution as the advantageous allele becomes more common in the population.

Question 4

What are two key factors in evolution?

Answer 4

Adaptation and selection.

Question 5

Evolution definition.

Answer 5

The gradual change in species over time.

Question 6

give the definition for genetic diversity

Answer 6

the total number of different alleles of genes in a species or population.

Question 7

give the definition for a population

Answer 7

a population is a group of organisms of the same species that live in the same habitat and can interbreed.

Question 8

Give 2 factors in which genetic diversity is increased by.

Answer 8

Mutation in the DNA - forming new alleles.
Different alleles being introduced into a population when individuals from another population migrate into them and reproduce - known as GENE FLOW.

Question 9

What does genetic diversity allow to happen?

Answer 9

Natural selection.

Question 10

What reduces genetic biodiversity?

Answer 10

Genetic bottlenecks.

Question 11

What is a genetic bottleneck?

Answer 11

It is an event that causes a big reduction in a population. E.g. when a large number of organisms within a population die before reproducing.
- This reduces the number of different alleles in the gene pool and therefore reduces genetic diversity. The surviving alleles reproduce and a larger population is created from a few individuals.

Question 12

Give a definition for a gene pool.

Answer 12

The complete range of alleles in a population.

Question 13

Give an arrow diagram of a genetic bottleneck.

Answer 13

Original population - large number of population die - reduced population - reproduction - new population with reduced genetic diversity.

Question 14

What does natural selection lead to?

Answer 14

Populations becoming better adapted to their environment to help them survive.

Question 15

What are the three types of adaptations cause by natural selection?

Answer 15

Behavioural, physiological and anatomical.

Question 16

What are behavioural adaptations caused by natural selection?

Answer 16

Ways an organism acts that increase its chance of survival and reproduction.

Question 17

What are physiological adaptations caused by natural selection?

Answer 17

Processes inside an organism’s body that increase its chance of survival.

Question 18

What are anatomical adaptations caused by natural selection?

Answer 18

Structural features of an organism’s body that increase its chance of survival.

Question 19

What do different types of natural selection lead to?

Answer 19

Different frequency patterns.

Question 20

What are two types of natural selection that affect allele frequency in different ways?

Answer 20

Stabilising and directional.

Question 21

Directional selection definition.

Answer 21

Where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.

Question 22

What type of selection could be in response to an environmental change?

Answer 22

Directional selection.

Question 23

State an example of directional selection.

Answer 23

Antibiotic resistance - bacteria evolving antibiotic resistance.
If bacteria are exposed to antibiotics = most of the population will not be resistant to its effects = not survive.
if a mutation evolved that confers resistance = selection will strongly favour bacteria with the resistant phenotype.
– the extreme, resistant phenotype is favoured.

Question 24

Directional selection simple definition + what environment does it take place in?

Answer 24

Where natural selection favours one extreme phenotype, the selection pressures in directional selection select against all other phenotypes.
+ takes place after an environment has experienced change.

Question 25

What does directional selection result in?

Answer 25

Phenotypes at one extreme of the population being selected for and those at the other extreme being selected against.

Question 26

Stabilising selection definition:

Answer 26

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

Question 27

What type of selection occurs when the environment is not changing?

Answer 27

Stabilising selection.

Question 28

State an example which shows stabilising selection.

Answer 28

Human birth weight.
If a baby has a below average weight = unlikely to survive.
if a baby has an above average weight = more likely to encounter difficulties during birth.
– stabilising selection selects for an phenotype within the average weight range.

Question 29

Stabilising selection simple definition + what environment does it take place in?

Answer 29

Where natural selection favours an average phenotype, the selection pressures in stabilising selection select against the extreme phenotypes.
+ takes place in environments which do NOT change.

Question 30

What does stabalising selection result in?

Answer 30

Phenotypes around the mean of the population being selected for and those at both extremes being selected against.

Question 31

Differences between the reproductive success of individuals affects allele frequency in populations. How does this process work like?

Answer 31

• within any population or a species there will be a gene pool containing a wide variety of alleles.
• random mutation of alleles within this gene pool may result in a new allele of a gene which in most cases will be harmful.
• however in certain environments. the new allele or a gene might give its possessor an advantage over other individuals in the population.
• these individuals will be better adapted and therefore more likely to survive in their competition with others.
• these individuals are more likely to obtain the available resources and so grow more rapidly and live longer. As a result, they will
  have a better chance of breeding successfully and producing more offspring.
• Only those individuals that reproduce successfully will pass on their alleles to the next generation.
• therefore it is the new allele that gave the parents an advantage in the competition for survival that is most likely to be passed on to
  the next generation.
• as these new individuals also have the new, ‘advantageous’ allele, they in turn are more likely to survive, and so reproduce successfully.
• over many generations, the number of individuals with the new, ‘advantageous’ allele will increase at the expense of the individuals with the ‘less advantageous’ alleles.
• over time, the frequency of the new, ‘advantageous’ allele in the population increases while that of the ‘non advantageous’ ones decreases.

Question 32

How does natural selection act on an individual?

Answer 32

By imposing a selection pressure.

Question 33

What are aseptic techniques used to prevent?

Answer 33

Contamination of cultures by unwanted microorganisms.

Question 34

Why do you want to use aseptic techniques when carrying out practical work?

Answer 34

To avoid contamination as this can affect the growth of the microorganism that are working with. Also to avoid contamination with disease-causing microbes that could make you ill.

Question 35

List 5 aseptic techniques.

Answer 35

1) disinfecting work surfaces regularly (don’t put utensils on the work surface and instead put contaminated utensils in a beaker of disinfectant).
2)Use sterile equipment and discard safely after use (pre-sterilised plastic instruments are used once, then discarded).
3) Work near a bunsen flame, hot air rises so microbes in the air should be drawn away from your culture.
4) Minimise the time spent with the lid off the agar plate (reduces the chance of airborne microorganisms contaminating the culture).
5) Briefly flame the neck of the glass container of the broth just after opened and just before it is closed (causes air to move out of the container, preventing unwanted organisms from failing in).