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​:
Nitrogen makes up approximately 78% of dry air and is not a greenhouse gas.

All other gases when present in the air enhance the greenhouse effect to cause global warming. (Choices A, B and C)

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:
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​:
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:
Negative feedback is a regulatory mechanism in which the body responds to a change in order to return the homeostatic variable back to within its set points. For example, if blood pH increases above the set point, negative feedback mechanisms will occur to bring blood pH back down. Statement I is therefore true and Statement II is therefore false. Choices B and D are not correct.

While the nervous system plays a significant role in many feedback mechanisms, it is not the only system involved. The endocrine system, which releases hormones into the bloodstream also plays a crucial role in feedback control. Statement III is therefore false, meaning Choice B is incorrect, and Choice A is the correct response to the question.

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 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​:
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​:
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 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​:
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​:
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​:
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:
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​:
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 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​:
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​:
The largest area in the pie charts showing sources of methane and nitrogen oxides is agricultural production.

Land use and biomass burning (Choice A) are a source of both methane and nitrous oxide but the area in the pie charts is less than agricultural production.

Industrial use (Choice B) releases mainly nitrous oxide.

Residential sources (Choice C) also release both methane and nitrous oxide but in lesser amounts than agricultural production.

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​:
mRNA, also known as messenger RNA, carries the genetic information needed for protein synthesis (Choice B).

Ribosomal RNA is found in ribosomes. This RNA contributes to the structure of the ribosome and does not code for proteins (Choice A).

ATP (Choice C) is a molecule made out of a nucleotide (adenosine tri-phosphate), while nucleic acid is made out of many nucleotides.

tRNA (Choice D), also known as transfer RNA, brings amino acids to the ribosomes and does not code for proteins.

Explanation​:

Taq polymerase was isolated from bacteria found in the hot springs at Yellowstone National Park, USA. This enzyme is able to withstand high temperatures used for PCR assays.
All other choices (Choice A, C and D) describe bacteria living in colder locations compared to hot springs which strongly suggests that enzymes present in these bacteria would not be adapted to higher temperatures.

Explanation​:
Statement III is not true, as homologous chromosomes often have different alleles (forms of genes), so are generally not identical to each other.

Statements I and II are true, as homologous chromosomes are pairs of chromosomes that have their centromeres and genes at the same positions. Therefore, Choice C is correct.

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 nuclear envelope is the membrane that separates the nucleus from the cytoplasm. For mitosis to proceed it must be broken down in the first stage of mitosis which is prophase so that the spindle fibres are able to attach to the centromeres. Choice A is correct.

Metaphase (Choice B), Anaphase (Choice C) and Telophase (Choice D) all follow Prophase (Choice A) in the sequence of mitosis and do not involve the breakdown of the nuclear envelope.