Explanation:
Sexual reproduction results in variation as it is the fusion of genetically distinct gametes from two genetically different individuals. Mutation results in variation as it produces new alleles. Meiosis results in variation as it produces new combinations of alleles. Choice C is correct.

Choices A, B and D are incorrect as they all include either mitosis, asexual reproduction or binary fission, which all produce genetically identical cells.

Explanation​:
Peptide bonds form between amino acids as a result of condensation reactions. Statement II (Choice C) is correct because dipeptides are composed of two amino acids held together by a peptide bond and proteins (Statement III) are composed of one or more polypeptides, which are chains of amino acids held together by peptide bonds. Choice A, B and D are incorrect as individual amino acids (Statement I) do not possess peptide bonds.

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​:
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​:
Choice B is correct because pollination is the transfer of pollen from an anther to a stigma. Choice A is incorrect because the fusion of a male and female gamete is fertilization. Choice C is incorrect because the transfer of seeds away from the parent plant is dispersal. Choice D is incorrect because pollination can occur without a pollinator. Some plants are wind-pollinated.

Explanation​:
PCR is used to amplify samples of DNA so they can be used for analysis.

PCR replicates DNA but does not show that replication is semi-conservative (Choice A).

PCR does not determine the base sequence of DNA. It produces copies of short sections of DNA that can then be further analyzed (Choice B).

Taq polymerase is an enzyme used in PCR but no Taq DNA is incorporated. (Choice D).

Explanation​:
Choice D is correct because transpiration is the loss of water from the stomata of a plant, it is not a stage of plant reproduction. Choices A, C and D are incorrect because pollination, fertilisation and seed dispersal are all stages of plant reproduction.

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 B is incorrect as it describes unlinked genes. Choice C is incorrect as all genes can be recombined during crossing over. However, the frequency of recombination due to crossing over is much lower in linked genes, depending on how close they are. Choice D is incorrect as it describes alleles.

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:
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​:
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​:
If there are two alleles for a gene, but there are three possible phenotypes, this could suggest incomplete dominance (Choice C). This is when the dominant allele doesn’t completely suppress the effects of the recessive allele. Choice A is incorrect because if one allele was completely dominant over the other, then there would only be two possible phenotypes. Choice B is incorrect because if the alleles were codominant, then we would see both expressed in the phenotype. In this case, some petals would be white and others red, instead of the flower being pink. Choice D is incorrect because sex-linkage does not create an additional phenotype.

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​:
When the environmental temperature drops, your body responds by trying to conserve heat. Reducing sweat production means there is less sweat to evaporate from the skin's surface, so less heat is lost. Vasoconstriction of the blood vessels reduces the volume of blood reaching the surface of the heat, so less heat is lost by radiation. Contraction of the erector pili muscles makes the hairs of the skin stand up, trapping an insulating layer of air next to the skin, again reducing heat loss by radiation and also by convection. Choice B is, therefore, the correct answer.

Choices A, C and D are incorrect as they have one or more factors wrong.

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​:
Choice A is correct because pollen is produced by the anther and the ovum (plural: ova) is produced by the ovule, found inside the ovary. Choice B is incorrect because the stigma is where pollen lands. Choice C is incorrect because the filament supports the anther and does not produce pollen. Choice D is incorrect because the filament supports the anther and the style is the part of the flower that the pollen passes through.

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:
The fossil record provides evidence of evolution, as the sequence in which fossils appear matches the sequence that they would be expected to evolve. Homologous structures provide evidence of evolution as they provide evidence that organisms shared a common ancestor. Speciation provides evidence of evolution as when populations become reproductively isolated, then natural selection can act differently on those populations, resulting in the formation of new species. Choice C is correct. Choices A and D are incorrect as the organisms becoming more complex does not necessarily correlate with evolution. Choice B is incorrect, as the increasing size of organisms does not necessarily correlate with evolution.

Explanation​:
Choice C is correct because meiosis halves the number of chromosomes, mitosis maintains the diploid number and fertilisation restores the diploid number.

Choice A is incorrect because meiosis separates pairs of alleles and produces nuclei with one allele for each gene.

Choice B is incorrect because mitosis produces genetically identical cells that have two alleles for each gene.

Choice D is incorrect because, in fertilisation, two gametes fuse, and each gamete has one allele for each gene.

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​:
Choice A, B, and D – These statements are true.

Choice C -This statement is false. In eukaryotic cells, translation takes place in the cytoplasm. Prokaryotic cells do not have a nucleus.

Explanation​:
The solution used to bathe organs to be used in a transplant should have an osmolarity equal to that of the organ to be transplanted and so the solution is isotonic compared to the organ’s tissues.

A solution with an osmolarity higher than that of the organ to be transplanted (Choice A) would cause tissue cells to shrivel, while a solution with an osmolarity lower than that of the organ to be transplanted (Choice B) would cause organ cells to burst. There are no described protocols that indicate that the solution should be mixed with cells from the organ to be transplanted (Choice D).

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 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.