Genetic variation due to mutation

Question 1

petri dish inhibition zone exp.

work under a lit bunsen burner

Answer 1

create an updraft to prevent microbes from the air landing in your petri dishe

Question 2

petri inhibition practical

Flame the neck of the flask containing your batch culture

Answer 2

Heats the air at the neck of the flask so it expands. This creates a higher pressure in the bottle than outside

Question 3

petri practical

Clean surfaces thoroughly before carrying out experiment

Answer 3

Kills microbes on surfaces so they cannot contaminating your petri dish

Question 4

Wear gloves (two reasons)

Answer 4

Prevent bacteria from hands contaminating experiment

Prevent bacteria from expt being transferred to you

Question 5

Only partially lift the lid of the petri dish

Answer 5

Prevent bacteria from the air contaminating your petri dish

Question 6

Incubate at 25C rather than 35C

Answer 6

So it is not the right temperature for human pathogens (which would grow at approx. human body temp).
This reduces the chances of human pathogens growing.

Question 8

Give 2 factors other than cost that should be considered when selecting an antibiotic to treat a bacterial disease: (2)

Answer 8

• side effects
• interaction with other drugs
• how much resistance the bacteria have built up

Question 9

A student made a 1 in 100 dilution.
Then used it to make a 1 in 1000 dilution.
Suggest why she didn’t use a 1 in 100 dilution. (2)

Answer 9

• 1 in 100 is too concentrated
• too many bacterial cells
• so too many colonies would form and overlap
• count may be innacurate and unreliable

Question 10

Frequent treatment with AB vancomycin can lead to AB resistanct strains of bacteria. Explain: (6)

Answer 10

• random mutations create new alleles of genes
• so there’s existing variation betw/ bacteria in population and how resistant they are to AB
• bacteria with allele that makes them resistant to VM have selective advantage
• so they survive and reproduce MORE than the OTHER bacteria
• and pass on advantageous alleles for AB resistance to next generation
• so frequency of allele for resistance increases in population

Question 11

mnemonic for genetic diversity through mutation

Answer 11

• Mutation
• Variation
• Selective advantage
• Survive
• Reproduce MORE than …
• Advantageous alleles for..
  (to)
• Generations
• Frequency of allele for …. increases in the population

my very slimy snail ran away (to) grandmas farm

Question 12

AB resistance is a type of:

Answer 12

directional selection

an extreme phenotype is favoured

Question 13

How can AB kil bateria:

Answer 13

• stop / break down cell wall (formation)
• target bacterial ribosomes
• target enzymes involved in DNA replication

Question 14

Why should we care about biodiversity? (9)

Answer 14

Ethical
* prevent extinction
* prevent loss of habitats
* save organisms for future generation
* we are animals, ecosystem part of our habitat

Economical
* medical / pharmaceutical
* commercial products
* tourism
* agriculture
* saving local forest communities

Question 15

what is genetic diversity?

Answer 15

the number of different alleles of genes in a population

Question 16

genotype

Answer 16

the combination of alleles that an organism has

Question 17

phenotype

Answer 17

characteristics that are expressed
* depends on genotype and phenotype

Question 18

directional selection

Answer 18

• selection that may vary in one direction from the mean of the population
• an extreme phenotype has a selective advantage
• this changes the characteristics of the population over time
• modal trait changes
• occurs when there’s a change in environment

Question 19

Describe a method to find out abundance of clover in a field (6)

Answer 19

• Create a grid on the field using measuring tapes as an x and y axis
• Use a calculator to generate random numbers which are used as coordinates
• Place the quadrat at the intersect of the coordinates
• Estimate the abundance of clover plants in the quadrat (e.g. using % cover)
• Repeat many times so that the mean abundance calculated per quadrat is reliable
• Multiply the number of plants per quadrat BY the number of times the quadrat fits into the total area of the field in order to work out the population in the whole field

Question 20

How would you use systematic sampling to estimate how the number of clover plants change as you move away from the tree (4)

Answer 20

• lay a tape measurement perpendicular to the tree to create a transect
• place a quadrant at regular intervals along the transect
• count the frequency of clover plants in the quadrant
• repeat the transect many times

Question 21

what is a species (2)

Answer 21

• similar organisms
• that produce fertile offspring

Question 22

how does sound help ensure female only mates with male fruitfly (2)

Answer 22

• to recognise correct species
• to continue courtship behaviour

Question 23

rules for classification: (3)

Answer 23

• Organisms w/ common characteristics go together.
• No overlap between groups.
• Be hierarchial.

Question 24

What is phylogenetic groups? (1)

Answer 24

Phylogenetic groups are formed of organisms who share an evolutionary history and common ancestry.

Question 25

How can we work out the relationship between organisms? (5)

Answer 25

1. Comparing observable characteristics
2. looking at the sequences of amino acid sequence in proteins
3. looking at the base sequences in DNA for the same gene in different organisms
4. Looking at the base sequence in mRNA for the same gene in different organisms
5. using immunology.

Question 26

what is a sign stimulus? (1)

Answer 26

• the essential feature of a stimulus
• which is necessary to elicit a response

Question 27

what assumptions are made for mark recapture to work? (5)

Answer 27

• time for marked individuals mix at random back into the population
• по immigration or emigration;
• Few/no deaths AND few/no births
• not lost or worn off
• The proportion of marked to unmarked individuals in the second sample is the same proportion as in the whole population

Question 28

Ecologists studied a community of fish in a lake.
The ecologists could have used the mark-release-recapture method to estimate the number of one species of fish in the lake.
Describe how. [4]

Answer 28

1. Capture sample, mark, count it and release;
2. Leave time for the sample to disperse and mix with the rest of the population
3. Take second sample, count total number and count marked organisms;
4. Use equation to estimate population size
5. Appropriate method of marking suggested / method of marking does not harm fish;

Question 29

Give two ways in which courtship behaviour increases probability of successful mating: (2)

Answer 29

Recognition of same species;

Stimulates release of gametes;

Recognition of mate / opposite gender;

Indication of sexual maturity / fertility;

Question 30

Scientists studied two species of North American seahorse. They thought that these two species are closely related. Describe how comparisons of biological molecules in these two species could be used to find out if they are closely related. (6)

Answer 30

• (Compare) DNA;
• Sequence of bases / nucleotides;
• Compare same / named protein;
• Sequence of amino acids / primary structure;
• …
  Immunological evidence
• Inject (seahorse) protein / serum into animal;
• (Obtain) antibodies / serum;
• Add protein / serum / plasma from other (seahorse) species;
• Amount of precipitate indicates relationship;

Question 31

in mutation questions:

Answer 31

mention the type of selection

Question 32

stabilising selection describe:

Answer 32

• Modal traits has the selective advantage
• Occurs when there is no change in the environment
• the modal trait remains the same.
• Standard deviation decreases; individuals w/ extreme traits decrease.

Question 33

The peppers must have two forms, a dark and light, prior to the Industrial Revolution, the majority of the moth population were light.
However, after the industrial revolution, there was a buildup of soot on tree bark.
Explain how the proportion of dark moths in the population increased. (4)

Answer 33

• Random mutations cause dark and light alleles for colour to be present in the population.
• This creates variation
• The Industrial Revolution occurs and the dark moths have a selective advantage.
• So they are more likely to survive and reproduce because they are less likely to be eaten by predators
• and pass on their advantages allele, which makes them darker colour to the next generation.
• So frequency of allele for dark colour increases in population.

make sure to use context from the question: eg. industrial revolution

Question 34

Definition of stabilising selection: (2)

Answer 34

• selection that favours average individuals
• preserves characteristics of a population