Explanation:
At fertilisation, two gametes, which are haploid, fuse together to produce a diploid cell. Gametes of a fruit fly have a haploid number of 4, so fertilisation produces a cell with 8 chromosomes (choice A). Choice B is incorrect because 4 is the haploid number. Choice C is incorrect because fruit fly somatic cells have 8 chromosomes and fertilised egg cells have 8 chromosomes. Choice D is incorrect because 16 is twice the diploid number of fruit flies.

Explanation​:
Choice A is correct because high blood glucose concentration is detected by the beta cells in the pancreas and they respond by releasing insulin. Choice B is incorrect because alpha cells produce glucagon and not insulin. Choice C is incorrect because the release of insulin is triggered by high blood glucose concentration and not low blood glucose concentration. Choice D is incorrect because low blood glucose concentration does not cause the release of insulin and insulin is not secreted by alpha cells.

Explanation​:
Choices B, C and D are incorrect because as the trees get darker, the camouflage of the peppered moth will be less effective, meaning it is more visible to predators and therefore more likely to be eaten.

Explanation​:
Telophase is the last phase of mitosis and does not cause mutations (Choice C). Single base substitutions cause a change in the base sequence of DNA, which is a mutation (Choice A). Carcinogens (Choice B) and high energy radiation (Choice D) are mutagens which means they can cause changes in the base sequence of DNA.

Explanation​:
Statement I (Choices A and D) is incorrect as learned behaviours are changes that occur during a lifetime, and so do not affect the genetic code and cannot be passed on. Statement III (Choices C and D) is incorrect as natural selection increases the frequency of characteristics that make individuals better adapted.

Explanation​:
Photosynthesis (Choice B) is the process by which carbon dioxide in the air is converted to carbon compounds in green plants.

Respiration releases carbon dioxide (Choice A), and decomposition by decomposers (Choice C) also releases carbon dioxide. Transpiration is the process by which water is drawn up the stem of a plant to the leaves where it evaporates (Choice D) and is not involved directly in the carbon cycle.

Explanation:
Choice C is correct because the transfer of seeds away from the parent plant is dispersal. Choice A is incorrect because the fusion of a male and female gamete is fertilization. Choice B is incorrect because the transfer of pollen from an anther to a stigma is pollination. Choice D is incorrect because pollen transfer involves the movement of pollen, not seeds.

Explanation​:
Choice C is a correct definition of a gene. Chromosomes are made of DNA and protein (Choice A), while genes are only made of DNA. When DNA is at various levels of supercoiling, it is wrapped around histone proteins. However, the presence of histones is not part of the definition of a gene (Choice B). Genes control some characteristics, but some characteristics are also affected by the environment (Choice D).

Explanation:
Facilitated diffusion and osmosis are both passive means of transport and therefore do not require energy.

Active transport (Choice A) requires energy expenditure. Facilitated diffusion is a passive form of transport but active transport requires energy (Choice B). Facilitated diffusion (Choice D) does not require energy expenditure but this answer choice does not include osmosis.

Explanation​:
Choice C is correct, as the 9th nucleotide in the sequence (C) has been deleted from the original sequence.

Choice A is incorrect as it is the exact same sequence as the original sequence. Choice B is incorrect as it represents an insertion mutation, an adenine has been inserted in the 7th position. Choice D is incorrect as it represents a base substitution mutation, as G has replaced a T in the 14th position.

Explanation​:
Choice A is correct because if the heart were placed in a hypotonic solution (as opposed to isotonic) water would diffuse into the cardiac muscles.

Choice B is incorrect because there would be no net movement into the tissues of the heart in an isotonic solution, not a hypotonic or hypertonic solution. Choice C is incorrect because even if it is placed in a solution other than an isotonic solution, it cannot dry out as it is still bathed in a watery solution. Choice D is incorrect as the tonicity of the solution the heart is stored in has no effect on whether the recipient’s immune system identifies the heart as foreign which would lead to rejection of the heart by the immune system.

Explanation​:
Choice A is incorrect as autosomes are chromosomes that are not the sex chromosomes and so do not determine biological sex. Choice B is incorrect as linked genes are genes that are found on the same chromosome. Choice C is incorrect as a gene locus is the position of a gene on a chromosome.

Explanation​:
The question states that heterozygous individuals have the banded pattern on their hairs, which means that the agouti trait is dominant. Two heterozygous parents will produce offspring with the dominant and recessive characteristics in the ratio of 3:1 (Choice B). The offspring of a heterozygous individual and a homozygous agouti individual will all receive at least one dominant allele, so they would all be agouti (Choice A). The offspring of at least one parent that is homozygous for agouti will all have the agouti characteristic (Choices C and D).

Explanation​:
Sweat (Choice B) is a coolant and helps to cool the body.
Tears (Choice A), urine (Choice C) and saliva (Choice D) do not lower or raise the body temperature.

Explanation​:
Choice D is correct because low blood glucose concentration is detected by the alpha cells in the pancreas and they respond by releasing glucagon. Choice A is incorrect because high blood concentration does not cause the secretion of glucagon and it is not secreted by beta cells. Choice B is incorrect because high blood concentration does not cause the secretion of glucagon, it causes the release of insulin. Choice C is incorrect because glucagon is not secreted by beta cells.

Explanation:
Choice D is correct because food is stored in the cotyledon(s). Choice A is incorrect because the function of the radicle is to develop into the root of the seedling. Choice B is incorrect because the function of the plumule is to develop into the shoot of the seedling. Choice C is incorrect because the testa is the outer covering of the seed.

Explanation:
Choice A is correct because during metaphase I homologous chromosomes align at the equator and are subject to random orientation. Choice B is incorrect as, during Prophase I, homologous chromosomes condense and crossing over occurs. Choice C is incorrect as, during Metaphase II, chromosomes align on the cell's equator, and there is random orientation of the sister chromatids and not homologous chromosomes. Choice D is incorrect as, during Prophase II, chromosomes align on the cell's equator.

Explanation​:
Choice B is correct because there are pairs of homologous chromosomes lined up on the equator, and each chromosome is attached to only one pole. Choice A is incorrect because in metaphase II, chromosomes are not in homologous pairs. Each chromosome, composed of sister chromatids, is attached to both poles. Choice C is incorrect because in anaphase I, homologous chromosomes are separated, and one chromosome from each pair is pulled to one pole. Choice D is incorrect because in telophase I, there are two sets of chromosomes that are already separated.

Explanation:
Down syndrome is not caused by a trisomy of sex chromosomes (choice B). The other statements are correct. Down syndrome is caused by trisomy 21 (choice A). It is caused by a trisomy of autosomes (choice C) because chromosome 21 is an autosome. Down syndrome is caused by an incorrect number of chromosomes (choice D).

Explanation​:
Choice A is correct because in both selective breeding and natural selection, favourable characteristics are “selected”, by either the environment (natural selection) or humans (selective breeding). Choice B is incorrect because natural selection doesn’t increase variation, it influences the proportion of existing variants. Choices C and D are incorrect because natural selection is not controlled by humans and does not contribute to the domestication of animals.

Explanation:
A greenhouse gas is a gas that contributes to the greenhouse effect. Greenhouse gases absorb the long wave infrared radiation (heat energy) emitted from Earth’s surface and can reradiate it back to Earth’s surface. So, one factor that determines whether a gas acts as a greenhouse gas is its ability to absorb long wave radiation: gases that are better able to absorb long wave radiation are more likely to act as greenhouse gases. A second factor that qualifies carbon dioxide as a greenhouse gas of concern is its relatively high concentration in the atmosphere: gases that are in higher concentration in the atmosphere have a larger effect on Earth’s temperature.

Explanation​:
Haemoglobin is a globular protein which is responsible for transporting oxygen around the body (Choice A). Choice B is incorrect as collagen is a fibrous protein. Choice C is incorrect as haemoglobin is not a fibrous protein and does not provide structural support. Choice D is incorrect as collagen does not transport oxygen.

Explanation​:
Protein pumps are membrane proteins that carry out active transport. They require the energy to pump molecules up their concentration gradient.

Protein channels (Choice A), protein carriers (Choice C), and aquaporins (Choice D) all conduct passive transport.

Explanation​:
Mitosis forms two genetically identical daughter cells with the same number of diploid chromosomes as the parent cell.

18 (Choice B) is incorrect as it is the haploid number of chromosomes. 72 (Choice C) is incorrect as it is twice the diploid number of chromosomes. 9 (Choice D) is incorrect as it is a quarter of the diploid number and an odd number.

Explanation​:
A mRNA strand contains four nitrogenous bases: adenine (A), cytosine (C), guanine (G) and uracil (U). It does not contain thymine (T) (Choice C and Choice D).

Most mRNA strands which code for polypeptides begin with the $\text{‘}$START$\text{’}$ codon AUG and end with a `STOP$\text{’}$ codon, UAG, UAA or UGA (Choice A). Choice B has a $\text{‘}$STOP$\text{’}$ codon at the beginning which would terminate translation before it begins.