Explanation:
Choice A is correct because the medulla is the inner region of the kidney.

Choice B is incorrect because the outer region of the kidney is the cortex.

Choice C is incorrect because it is the renal artery.

Choice D is incorrect because it is the ureter.

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 B is correct because human males have one X chromosome and one Y chromosome. Choice A shows the sex chromosomes of a female. Choice D only shows the Y chromosome, which is incorrect because males have an X and a Y chromosome. Choice D only shows the X chromosome, which is incorrect because males have an X and a Y chromosome.

Explanation:
Choice A is correct because meiosis happens in the anther and ovule of flowers, it does not happen in the cells of the shoot apex. Choice B, Choice C and Choice D are incorrect because mitosis and cell elongation happen in the shoot apex to produce new cells and allow for primary growth (plant lengthening).

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:
Choice B is not true. Not all genes are expressed in each cell. Only the necessary genes are expressed based on the specialised function of the cell. All other statements are true.

Explanation:
Choice A is correct because when there are fewer copies of a given strand of mRNA in the cytoplasm, ribosomes have fewer copies to bind to and thus the rate polypeptides are synthesised based on this strand will decrease, not increase (Choice B).

Choices C and D are incorrect because if the rate mRNA is degraded decreases, there will be more copies of this strand of mRNA resulting in an increase in the rate ribosomes bind to these strands and synthesise polypeptides.

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:
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 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:
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:
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:
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:
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:
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:
The four stages of mitosis are prophase, where chromosomes supercoil and become visible; Metaphase, where chromosomes line up at the equator of the cell; anaphase, where sister chromatids are pulled apart and telophase, where the nuclear envelope reforms and two new daughter nuclei are formed.

Statement I is incorrect as sister chromatids are not pulled apart during metaphase. They are pulled apart during anaphase.
Choice B is incorrect as both statements II and III are correct and should be included.

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:
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:
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 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:
The bond formed between two glucose molecules to form maltose is an alpha 1-4 linkage. This is a covalent bond between two alpha glucose molecules, where the carbon #1 of one of the glucose molecules forms a bond with the carbon #4 of the other glucose molecule. Choice C is correct.

A hydrogen bond (Choice A) is a weak electrostatic attraction between a hydrogen atom that is covalently bonded to a highly electronegative atom and another electronegative atom in a different molecule or region of the same molecule. For example, between two water molecules. Peptide bonds (Choice B) are covenant bonds that hold amino acids together in polypeptide chains, and phosphodiester bonds (Choice D) are covalent bonds between the ribose sugars and phosphate groups, forming the backbone of DNA and RNA. Choices A, B and D are incorrect.

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:
The graph shows an overall positive correlation, as maternal age increases, the incidence of non-disjunction increases (Choice A). Choice B is incorrect because there is a positive correlation not a negative correlation. Choice C is incorrect because there is a correlation. Choice D is incorrect because non-disjunction does occur below 35 years, but the incidence is lower when compared to above 35 years.

Explanation:
A base substitution is when one nucleotide randomly replaces another in a sequence causing a single nucleotide polymorphism. This can result in a shorter polypeptide being translated (Statement I) due to the base change causing a stop codon to appear earlier in the DNA/mRNA sequence. It can also cause an altered polypeptide chain to be translated (Statement II) if the base substitution causes a different amino acid to be translated. It can also have no effect on the polypeptide that is translated (Statement III), as the genetic code is degenerate, meaning many codons code for the same amino acid. Choice D is therefore correct.

Choices A, B and C are incorrect, as they do not include all three statements.

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)