How many SCSA Human Biology questions cover Gene pools?

AusGrader has 77 SCSA Human Biology questions on Gene pools, all with instant AI grading and detailed marking feedback.

SCSA Human Biology Gene pools

5 sample questions with marking guides and sample answers · Avg. score: 49.1%

Q13

2021

SCSA

1 mark

Q13

1 mark

Which of the following are all selection pressures which could reduce genetic variation in a population?

disease, increased competition and climate change

increased food availability, disease and climate change

increased competition, reduced environmental pollutants and disease

reduced land availability, increased food availability and climate change

Q20

2022

SCSA

1 mark

Q20

1 mark

Natural selection is often referred to as 'survival of the fittest'. Which of the following is the best definition for 'fittest' as used in this statement?

the ability of an organism to survive and reproduce

adaptations that produce favourable traits

selective breeding to promote favourable traits

heritable traits that will be passed on to offspring

Q36

2022

SCSA

13 marks

Q36

The occurrence of atavism provides a possible piece of evidence for evolution. Atavism involves the reappearance of an ancestral genetic trait that has been lost over many generations of evolutionary change. One example in humans is a ‘caudal appendage’, where babies are born with a posterior tail made of cartilage and additional vertebrae.

The caudal appendage is an exterior extension of the coccyx. The coccyx itself is often considered an example of a vestigial organ.

Q36b

Human colour blindness is considered another possible example of atavism in modern humans. It is believed that the colour blindness trait may have originated in early humans as a survival advantage. It is possible that the inability to distinguish some colours can improve the ability to view different textures and shades, providing a visual advantage in some habitats.

Q36c

Consider the following hypothetical situation: An isolated island had a population of 300 people, 10 of which were colour blind. After 150 years, the island had a population of 400 people, none of whom were colour blind.

Q36a (i)

1 mark

Identify one other vestigial organ of the human body.

Examples include (any 1 of the following):

appendix/male nipples/muscles to move ears/nictitating membrane/pointed canines/wisdom teeth/hair on body

Marking Criteria

Descriptor	Marks
appendix/male nipples/muscles to move ears/nictitating membrane/pointed canines/wisdom teeth/hair on body	1

Q36a (ii)

3 marks

Explain how vestigial organs provide evidence for evolution.

Vestigial structures are structures that have a benefit in some species, but are present but not functional in other species. This indicates shared common ancestry.

Marking Criteria

Descriptor	Marks
Describes them as structures that have a benefit or normal function in some species	1
States they are present but not functional in other species	1
Explains that this indicates shared common ancestry or that at one point both species shared an ancestor who had the structure	1

Q36b

5 marks

If colour blindness did provide a survival advantage, using the theory of natural selection, explain how colour blindness would have been maintained in early human populations.

Some individuals possess the colour blindness trait. Competition exists in the population, and those with colour blindness are more suited to the environment. They are more likely to survive to reproduce, so the allele is maintained or increased in the gene pool.

Marking Criteria

Descriptor	Marks
States that some individuals possess the colour blindness trait, the allele for colour blindness is present in the population, or there is variation in the population	1
Identifies that competition exists in the population, there is a struggle to survive, or limited resources are present	1
Explains that those with colour blindness are more suited to the environment or have better vision so are able to see predators better	1
States that they are more likely to survive to reproduce or more likely to pass alleles onto offspring	1
Concludes that the allele is maintained or increased in the gene pool	1

Q36c (i)

1 mark

If colour blindness did provide a survival advantage to this population, identify the name of the process that would provide the best explanation for the change in the population over time.

Descriptor	Marks
(Random) genetic drift	1

Q36c (ii)

3 marks

Justify your response to part (c)(i).

This is due to the small size making it more likely to occur, and there is no gene flow evident with other populations. It must be a chance event, because if it does have a survival advantage it would be selected for in the population.

Marking Criteria

Descriptor	Marks
1 mark for each correct point (any 3 of): States it is more likely to occur due to small size Identifies that there is no gene flow evident with other populations States it must be a chance event Explains that if it does have a survival advantage it would be selected for, maintained, or increased in the population	3

Q40

2025

SCSA

20 marks

Q40

The Pacific Islands are made up of small, widely spread islands. Although migration between them has occurred, vast distances have historically made travel difficult for the inhabitants. As a result, genetic studies have shown that some of the island populations have distinctly unique gene pools.

Q40a

8 marks

Identify and explain the evolutionary mechanism that would have led to the populations in the Pacific Island countries being genetically different when compared to the original population from which they migrated.

The evolutionary mechanism is the founder effect/genetic drift.

The original population contains variation and a wide variety of phenotypes.

A small group of individuals moves to a new area and establishes a new population. This new group is not genetically representative and has a different allele frequency to the original population, resulting in decreased genetic variation in the new population.

There is no breeding between populations as the populations are isolated from each other. Over many generations, the ratio of allele frequency will differ to that of the original population, and these changes in allele frequency are non-directional or by chance.

Marking Criteria

Evolutionary mechanism

Descriptor	Marks
Identifies the evolutionary mechanism as the founder effect/genetic drift	1

Explanation

Descriptor	Marks
States that the original population contains variation/wide variety of phenotypes	1
Describes that a small group of individuals moves to a new area and establishes a new population	1
Explains that the new group is not genetically representative/has a different allele frequency to the original population	1
States that this results in decreased genetic variation in the new population	1
Identifies that there is no breeding between populations/populations are isolated from each other	1
Explains that over many generations, the ratio of phenotypes/allele frequency will differ to that of the original population	1
States that changes in allele frequency are non-directional/by chance	1

Q40b

4 marks

Define comparative genomics and explain how it is used to compare the genomes of different species.

Comparative genomics involves comparing the genome sequence of different species to determine relatedness.

DNA is sequenced to determine the order of nucleotides or bases. Over time, populations accumulate more and more differences in their genome. More similar DNA suggests species are more closely related and have a more recent common ancestor.

Marking Criteria

Descriptor	Marks
Defines comparative genomics as comparing the genome sequence of different species to determine relatedness	1
States that DNA is sequenced to determine the order of nucleotides or bases	1
Explains that over time, populations or species accumulate more and more differences in their DNA or genome	1
Explains that more similar DNA suggests species are more closely related or have a more recent common ancestor	1

Q40c

8 marks

Compare how nuclear DNA and mitochondrial DNA are used to provide evidence for evolution and migration.

Nuclear DNA is found in the nuclei of cells and is inherited from both parents. Due to recombination, migration is difficult to track; hence, it is used to trace evolutionary relationships between species.

Mitochondrial DNA (mtDNA) is found in the mitochondria and is only inherited from the mother. It has a high mutation rate; hence, it is used to trace migration routes between populations within a species.

Marking Criteria

Nuclear DNA

Descriptor	Marks
States that nuclear DNA is found in the nuclei of cells	1
States that it is inherited from both parents	1
Explains that due to recombination, migration is difficult to track	1
Concludes that it is used to trace evolutionary relationships between species	1

Mitochondrial DNA

Descriptor	Marks
States that mitochondrial DNA (mtDNA) is found in the mitochondria	1
States that mtDNA is only inherited from the mother	1
Identifies that mtDNA has a high mutation rate	1
Concludes that it is used to trace migration routes between populations within a species	1

Q39

2023

SCSA

20 marks

Q39

A mutation is a permanent change in the DNA code. Lactase persistence is the ability to digest lactose (the sugar found in milk) in adults. This ability is attributed to a mutation that became present in various gene pools between 2000 and 20 000 years ago. Only about 35% of the world's adults possess the mutation today and can effectively digest lactose.

Q39a

5 marks

Identify and describe the type of mutation that would be responsible for lactase persistence, considering that it has been maintained within the gene pool. Compare this type of mutation to mutations that are not passed to future generations.

Germ-line mutation.

This type of mutation is not somatic, found in the gametes and not body cells. Germ-line mutation is involved with the formation of offspring, and is not removed from the gene pool when the individual dies

Marking Criteria

Descriptor	Marks
germ-line mutation	1
not somatic	1
found in the gametes not body cells	1
involved with production of the zygote/formation of offspring	1
not removed from the gene pool when the individual dies	1

Q39b

6 marks

Point mutations can alter the DNA code in a number of ways, one of these being a frameshift mutation. Explain what a frameshift mutation is and describe two other ways point mutations can alter the DNA code.

A frameshift mutation occurs when nucleotides are added or removed from a section of code, which results in new codons.

Other types of mutations include silent mutations, where the codon still codes for the same amino acid, and can be caused by the insertion of a new nucleotide.

Missense mutations occur when the code is changed to a different amino acid, caused by the substitution of one nucleotide being replaced by a new nucleotide.

Marking Criteria

Frameshift

Descriptor	Marks
States that a frameshift occurs when nucleotides are added or removed from a section of code	1
States that it results in new codons/codes for different amino acids	1

Other types of mutations 1

Marking Bands

Descriptor	Marks
Describes a mutation type (silent, missense, or nonsense) and its cause/effect	2
Identifies a mutation type or describes its cause/effect only	1
None of the above	0

Other types of mutations 2

Marking Bands

Descriptor	Marks
Describes a second mutation type (silent, missense, or nonsense) and its cause/effect	2
Identifies a second mutation type or describes its cause/effect only	1
None of the above	0

Q39c

9 marks

In farming populations, the allele frequency for lactase persistence can be as high as 96% whereas in non-farming populations the frequency is only 20%. Explain how natural selection could be responsible for this difference in allele frequency.

Lactase persistence mutation became present, causing variation in the gene pool in populations that used milk as an energy source.

Those that had the lactase persistence mutation had a better chance of survival, somore individuals with the lactase persistence allele survive to reproduce. So more offspring is born with the mutation present. Thus, allele frequency of the mutation increases over time.

In populations without a milk diet there would be no difference in survival rate, so allele frequency of mutation remains unchanged

Marking Criteria

Descriptor	Marks
lactase persistence mutation became present	1
causing variation in the gene pool	1
in populations that used milk as an energy source	1
those that had the lactase persistence mutation had a better chance of survival	1
more individuals with the lactase persistence allele reach adulthood/survive to reproduce	1
more offspring born with the mutation present	1
allele frequency of the mutation increases over time	1
in populations without a milk diet there would be no difference in survival rate/selection advantage	1
allele frequency of mutation remains unchanged	1

SCSA Human Biology Gene pools

Evolutionary mechanism

Explanation

Nuclear DNA

Mitochondrial DNA

Frameshift

Other types of mutations 1

Other types of mutations 2

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