SCSA Human Biology Science Inquiry Skills

Initial allelic frequencies were B 0.55 and b 0.45.
Allelic frequencies after 20 generations were B 0.3 and b 0.7.
B decreased (from 0.55 to 0.3) and b increased (from 0.45 to 0.7).
This selection pressure was in favour of white rabbits as both genotype and allelic frequencies shifted toward the white phenotype and the white allele.

Frequency (a) = $[(2 \times 226) + 60] / 600$
$= 0.85$
Frequency (A) = $[(2 \times 14) + 60] / 600$
$= 0.15$

Allele frequencies remained relatively constant in forest X over the 10-year period, with a slight increase in allele A over time. This suggests genetic drift is occurring and the changes are likely due to chance rather than the environment favouring a particular phenotype.
This contrasts with forest Y, where the frequency of allele A increases significantly over time after it first appears in 2016. The allele may have been introduced to forest Y due to migration (mice moving in from a neighbouring forest) or mutation. Either way, it is evident that the allele A provided a selective advantage to mice in forest Y, resulting in its frequency increasing over time.

Species richness is higher in areas with low invasive species cover (seven different species compared to two).

The presence of the invasive species has a negative effect on biodiversity. While the same number of species were observed in the area when invasive species cover was 0–60% (7, as indicated by species richness), the SDI decreased from 0.83 to 0.3 as percentage cover increased. This indicates that overall, biodiversity decreased as percentage cover increased.

Species richness indicates the number of species that can coexist in the area; however, it doesn’t account for the abundance of each species, so one or two species may be dominating. SDI considers the number of species and their relative abundance (evenness), but the number of species is not obvious from the index.
Having both values is more informative because it allows the researcher to identify the number of species in the area (7) and infer evenness from the SDI. For example, the same number of species was present for 0–60% coverage (7), but the evenness was not the same, as the SDI decreased as % coverage got higher.

Species richness is five times higher in zone D than zone A. Zone A has two different species, whereas zone D has 10.

As organic matter increased from 1% to 30%, the pH decreased from 8.4 to 6. This suggests that organic matter lowers soil pH.

Zone D. Zone D is the oldest dune and has the highest species richness. This suggests it may be further along in succession. The number of K-selected species tends to increase as succession progresses.

Genetic drift causes a decrease in genetic diversity.

Suitable explanations included:

• It is a random change in allele frequency and is more pronounced in small, isolated populations.
• Genetic drift may cause an allele of a particular gene to disappear altogether purely by chance OR may lead to a bottleneck in future populations.

Genetic diversity is maintained as birds bred in captivity have different genetic diversity. When gene flow occurs between the populations, these differences enter the wild population.

A consequences-based approach places central importance on the consideration of the consequences of an action, with the aim to maximise the positive outcomes and minimise the negative effects.

As part of their response, students were required to consider possible positive outcomes and negative effects of the work by Zoos Victoria in preventing the extinction of the helmeted honeyeater.

Positive outcomes Zoos Victoria may have sought to maximise included an increase in the total number of birds OR an increase in genetic diversity in the wild which may prevent extinction.

Negative effects Zoos Victoria may have sought to minimise included not having a negative effect on the bird's health OR not enough food available OR space for nesting.

To produce the genetically modified (GM) mosquitoes, it is necessary to transfer the SERPINE 1 gene from a human to the mosquito using recombinant DNA technology. Restriction enzymes are used to cut the SERPINE 1 gene from a human cell chromosome. A bacterial plasmid (circular DNA) is opened using the same restriction enzymes and the SERPINE 1 gene is inserted and attached using DNA ligase. The bacteria then reproduce, producing multiple copies of the SERPINE 1 gene. The gene can then be delivered into the mosquitos. This can be done by micro-injection into mosquito egg cells, so that the mosquito which develop from the egg will contain the SERPINE 1 gene, which will allow the mosquito to express PAI-1.

In recombinant DNA technology, selected genes can be cut and pasted from one organism into another using, for example, ligase enzymes. The human insulin producing gene has been transferred into bacteria, allowing for increased production of insulin, benefitting sufferers of diabetes, who can access insulin more readily and cheaply. This means that diabetes patients have a greater life span.

Genetic technologies such as CRISPR can be used for controlling pest populations including insects that cause diseases in both humans and other animals. By controlling the number of disease causing insects eg mosquitoes that cause dengue fever, we can significantly reduce the incidence of the vector-borne diseases. This would result in healthier populations and reduced stress on the health care system.

These technologies have largely been beneficial to society, improving access to drugs, the life expectancy and quality of life for many people.

Gene mutations only affect one gene (loci), whereas chromosomal mutations affect more than one gene.

It occurred in the cells that produce the gamete, and only mutations produced in these cells can be inherited.

Mutagens are substances that are known to increase the rate of changes to DNA, such as ionising radiation, mustard gas, or formaldehyde.

During DNA replication, errors during the process can alter the DNA code, which can be deleting, duplicating, insertions, or frameshifts of DNA.

During cell division, errors during the process can alter the genes or chromosomes in the daughter cells formed, such as be non-disjunction, translocation, or inversions of DNA.

For example: Individuals with the DEC2 gene will sleep less hours a night.

Individuals without the DEC2 gene act as a comparison to the experimental group.

Mutations introduce new alleles into the population. These alleles may produce traits favourable to survival. Favourable alleles are then passed to offspring, and favourable traits will increase in number within the gene pool.