Explanation​:
Nucleotides are linked together by condensation reactions to form molecules of DNA (Choice B). The formation of DNA requires the removal of water for the joining of smaller molecules to form a larger molecule.

The joining of nucleotides together can also be classified as an anabolic reaction but not as a catabolic reaction (Choice C). Catabolism is the breaking down of a large molecule into a smaller molecule. An example of catabolism is hydrolysis which is a reaction that breaks down a large molecule into a smaller molecule by adding water (Choice A).

Translation is a process which follows the transcription of DNA (Choice D). It is where mRNA is used as a template by ribosomes to synthesize polypeptides.

Explanation​:
Choice D is correct because the three domains of organisms are Archaea, Eubacteria and Eukaryota. Choice A is incorrect because prokaryote is not the name of one of the domains. Choice B is incorrect because Protista and prokaryota are not the names of domains. Choice C is incorrect because Protista is not one of the domains.

Explanation​:
Choice A - Excretion is the process wherein waste and excess water in the organism are removed. Paramecia expel waste products such as carbon dioxide through the process of diffusion.

Choice B - Homeostasis pertains to the ability of living things to maintain a stable internal environment. Paramecia maintain a stable internal condition by expelling excess water using the contractile vacuole.

Choice C - Reproduction is the biological process by which organisms produce offspring that are biologically similar to themselves. Paramecia can reproduce sexually through meiosis and asexually through mitosis.

Choice D - Metabolism refers to all the chemical reactions in organisms such as anabolic and catabolic reactions. Paramecia produce enzymes that catalyse different catabolic and anabolic reactions in the cell.

Explanation​:
Louis Pasteur's experiments where he boiled nutrient broth in swan-necked flasks disproved spontaneous generation. Choice B is correct.

Miller and Urey's (Choice A) experiments proved that organic compounds could be produced in Earth’s early atmosphere. Rosalind Franklin’s (Choice C) work was instrumental in the discovery of the structure of DNA. Meselson and Stahl (Choice D) proved that DNA replication is semi-conservative.

Explanation:
The resolution is the ability to distinguish between two objects. Choice B is correct.

Choices A and D are incorrect because a photograph taken using an electron microscope would allow the ultrastructure of the cells (fine detail of cells, such as organelles) to be observed. Choice C is incorrect because these photographs are magnified at the same power.

Explanation​:
Choice B is correct because X labels the core histone proteins which help package the DNA into nucleosomes through coiling.

Choice A is incorrect because X is not linker DNA which extends from one nucleosome to the next, connecting nucleosomes with one another. Choice C is incorrect because enzymes carry out DNA replication, not histone proteins. Choice D is incorrect because DNA carries genetic material, not the core histone proteins.

Explanation​:
DNA molecule is made up of two antiparallel strands of nucleotides. Antiparallel means that both strands are geometrically parallel but oriented in opposite directions (Option II). One of the strands is in the direction of 5' to 3', whereas the other strand is in the direction of 3' to 5'. The backbones, made of alternating sugar and phosphate groups, are held together by covalent phosphodiester bonds (Option III). Both of these strands are joined together by the hydrogen bonds between the complementary base pairs.

DNA strands are not symmetrical (Option I) because symmetrical would mean that they are a mirror image of each other.

Explanation​:
Choice D is correct because organisms placed in the same group share common ancestry. Choice A and Choice B are incorrect because morphology and anatomical characteristics are used to describe the structures of organisms which are used to primarily group them together. Choice C is incorrect because modes of nutrition are used to describe organisms but not to classify organisms.

Explanation:
DNA molecules consist of four nitrogenous bases: adenine (A), cytosine (C), guanine (G) and thymine (T). In DNA molecules, adenine always pairs with thymine and cytosine always pairs with guanine. This is known as complementary base pairing.

Sequences I and III both follow base-pairing rules correctly. Statement II is incorrect because it shows T paired with G and A paired with C.

Explanation​:
The chromosomes of eukaryotes are linear, and the DNA is coiled around histone proteins (Choice C). Choice A is incorrect because eukaryotic DNA molecules are not circular. Choice B is incorrect because eukaryotic cells do not have looped DNA in the nucleus. Choice D is incorrect because the linear DNA molecules in eukaryotic cells are coiled around histone proteins.

Explanation​:
Eukaryotic cells contain mitochondria but prokaryotic cells do not. Choice A is correct.

Choices B and D are incorrect as the cell is not prokaryotic; it has a nucleus. Choice C is incorrect because the cell has a nucleus.

Explanation​:
Gravity is responsible for holding water on Earth and is a fundamental factor in water retention within the planet's atmosphere and surface. Choice D is, therefore, correct.

Choice A is incorrect, as although rainfall is a part of the water cycle and is responsible for distributing water, it does not directly contribute to the retention of water on Earth.

Choice B is incorrect, as the moon's gravitational force regulates the tides of large bodies of water but does not directly contribute to water retention on Earth. Choice C is incorrect as water is lost from bodies of water on the surface of the Earth and evaporates into the atmosphere, which doesn't directly address water retention.

Explanation:
Statement I is true because all cells have cytoplasm enclosed by the plasma membrane.

Statement II is also true because the invention of the microscope made viewing structures within the cell easier.

Statement III is false because all cells have genetic material. Eukaryotic cells have their genetic material inside of the nucleus, while prokaryotes have their genetic material in the nucleoid region.

Explanation​:
Uracil and thymine are nitrogenous bases found in two types of nucleic acids: DNA and RNA.

Uracil is found in RNA, whereas thymine is found in DNA. (Choice B)

Uracil pairs with adenine in RNA and thymine pairs with adenine in DNA (Choice D).

In both DNA and RNA, these nitrogenous bases are joined to a five-carbon sugar, also called a pentose sugar which has a ring structure, so Choice A is incorrect.

Both uracil and thymine are pyrimidines which are single-ring structures (Choice C). Adenine and guanine are purines which consist of two rings.

Explanation​:
Choice D is correct. The DNA sequence (Statement I) and amino acid sequence (Statement II) are the usual, present way of determining members of the same clade, however, physical appearance (Statement III) was previously, but is now rarely, used.

Explanation​:
The number of organisms found via the fossil record for any era is much lower compared to the number of organisms found on Earth now and those that continue to be found, so Choice B is correct. Choice A is incorrect as changing levels of atmospheric carbon dioxide provide evidence for humans' impact on carbon dioxide levels. Choices C and D are incorrect as evidence suggests that the rate of evolution and speciation are increasing, which provides evidence for increasing biodiversity.

Explanation​:
RNA is believed to be a potential candidate for the first genetic material due to its ability to form spontaneously from nucleotides (Statement I). Miller's famous experiment demonstrated that simple organic molecules, including nucleotides, could be produced from a mixture of gases under conditions that simulated early Earth (Statement III). This experiment suggested that nucleotides could have formed spontaneously on a prebiotic Earth, providing a plausible scenario for the emergence of RNA as the first genetic material. Therefore Choice B is correct.

Choice A only included Statement I and not II, so it is incorrect. While it is true that RNA contains ribose as its sugar component (Statement II), the presence of ribose is not a primary reason for RNA being considered the first genetic material. Both RNA and DNA contain sugars in their structures, but the key point in favour of RNA as the first genetic material is its ability to form spontaneously. Choices C and D included Statement II and so are incorrect.

Explanation​:
Vesicles are formed from a phospholipid bilayer. This phospholipid bilayer forms spontaneously because the phosphate heads are hydrophilic (‘water loving’), and the fatty acid tails are hydrophobic (‘water hating’). Therefore Choice B is correct.

The membrane around the vesicle is not a single layer (Choices A and C) of phospholipids due to the hydrophilic phosphate heads naturally pointing outwards and inwards into the aqueous environments, and the hydrophobic fatty acid tails aligning in the centre to minimise their exposure to water. Vesicles are not induced to form in cells (Choices C and D) as the amphipathic nature of the phospholipids means that the vesicles form through self-assembly.

Explanation​:
Prokaryotic cells do not contain mitochondria but eukaryotic cells do. Choice D is correct.

Choice A is incorrect as eukaryotes (as well as Archae) contain 80S ribosomes. Choice B is incorrect as both eukaryotic and prokaryotic cells contain a plasma membrane. Choice C is incorrect as eukaryotic cells contain a nucleus but prokaryotic cells do not.

Explanation​:
Isotopes with long half-lives (Choice C), such as uranium and potassium isotopes, are often used in absolute dating because they decay slowly and are suitable for dating older fossils.

Stable isotopes (Choice A) are not used for fossil dating because they do not undergo radioactive decay. Absolute dating relies on the measurement of the decay of radioactive isotopes into stable daughter isotopes to determine the age of a sample. Isotopes with short half-lives (Choice B) are typically used for dating more recent events, not older fossils. Isotopes with no half-lives (Choice D) cannot be used for fossil dating using the methods based on radioactive decay. Isotopes without half-lives do not undergo radioactive decay, so it is impossible to establish a chronology or estimate the age of a fossil using these isotopes.

Explanation​:
Choice D is correct because homologous structures refer to structures inherited from a common ancestor which are similar but often used for different functions.

Choice A is incorrect, as ancestral structures refer to structures present in an ancestor species, not structures found in present day species. Choice B is incorrect as convergent structures are not a term used in biology. Convergent evolution, on the other hand, leads to analogous structures. Choice C is incorrect as analogous structures refer to structures used for the same function, which are significantly different when closely inspected. Analogous structures also have different evolutionary origins.

Explanation​:
Choices A, B and D are incorrect as they all have a single membrane.

Explanation​:
Species that share a recent common ancestor, such as humans and chimpanzees, are more likely to have similar base sequences. Over time, as species diverge and evolve, mutations accumulate in their base sequences. The longer two species have been separated from their common ancestor, the more mutations will have accumulated in their genomes. Therefore, species that are closely related have fewer accumulated mutations and more similar base sequences (Choice B).

Choice A is incorrect because genome size is not necessarily proportional to the size of the species. The genome size can vary significantly even among organisms of similar size, and organisms with similar-sized genomes, such as the horse and mouse vary greatly in size. Choice C is incorrect because it is possible to have a larger genome size with a comparable, or even smaller, number of genes, depending on the amount of non-coding DNA and repetitive sequences present in the genome. Humans have a larger genome but a similar number of genes to the chimpanzee, mouse and horse. Choice D is incorrect because although the nucleotide base sequence in the table for humans and chimpanzees is the same it does not mean that their whole genome is the same.

Explanation​:
Choice B is the correct definition for a clade, a group of organisms that share a common ancestor. Choice A and C are incorrect as they do not feature the idea of a common ancestor. Choice D is incorrect because organisms within a clade do share a common ancestor.

Explanation:
Hydrophilic (Choice C) substances dissolve in water through the formation of hydrogen bonds with water.
Non-polar (Choice D) substances are not attracted to water molecules and do not form bonds with them. These substances are hydrophobic (Choice B), making them insoluble (Choice A) in water.