Explanation:
Okapi is a herbivore (II) because it only eats plants. Okapi is a species (III) since it can interbreed and produce fertile offspring.

They are not a hybrid of a giraffe and a zebra (I), even though they look like one.

Explanation:
Neurotransmitters travel freely without energy from an area of high concentration at the presynaptic membrane to a low concentration at the postsynaptic membrane via simple diffusion, Choice C is correct.

Choice A is incorrect, as neurotransmitters do not use a channel to diffuse across the synapse. Choice B is incorrect, as neurotransmitters do not travel against the concentration gradient using energy across the synapse. Choice D is incorrect as although neurotransmitters are released from the presynaptic membrane via exocytosis, they do not travel across the synapse using this method.

Explanation:
Enclosed greenhouse experiments allow for wavelengths of light to be controlled by exposing the plants to different colours of light. By adjusting the spectrum of light, researchers can investigate the isolated effects of distinct wavelengths on plant responses to elevated carbon dioxide levels. Such control is typically unattainable in open-air experiments like the free-air carbon dioxide enrichment (FACE) system, where natural light conditions predominate. Choice A is correct.

Choice B is incorrect as an enclosed greenhouse space does not mimic a natural ecosystem as it is a man-made enclosed structure. Choice C is incorrect, as large trees cannot fit or grow freely in a greenhouse. Choice D is incorrect as in an enclosed greenhouse, water can be controlled, mimicking rainfall.

Explanation:
Invasive species are introduced deliberately or accidentally to new areas outside of their native range, and so have no natural predators. An example would be the zebra mussel which originates from the lakes of Russia and Ukraine. It was accidentally introduced to the Great Lakes of the US through the discharge of a contaminated cargo ship's ballast water. Invasive species have been recognised as a major threat to biodiversity and ecosystems worldwide. They can disrupt native ecosystems, outcompete native species for resources, and lead to declines in native populations. Therefore Choice C is correct. While it is true that some invasive species have evolved and adapted to specific conditions (Choice A) in their native range, this characteristic is also true of native species. Invasive species often have a native region (Choice B), as do native species. Also, some invasive species have a broad native distribution, and when they are introduced to new areas, they can spread widely. Invasive species can be influenced by environmental changes (Choice D), but native species can also be affected by environmental changes, and vulnerability to these changes can vary widely among both invasive and native species.

Explanation:
The data collected for recording the presence and absence of two plants can be used in a chi-squared test to determine if the two plants are associated. This is a relevant statistical method.

The biodiversity found in an area (Choice A) is usually determined by using Simpson’s Diversity Index or other similar calculations. The chi-squared test cannot be used to find the range (Choice B) for heights of trees or predict the probability of finding certain plants (Choice C) in an area.

Explanation:
Photosynthesis is the production of carbon compounds such as glucose using light energy. Oxygen is produced as a waste product which then diffuses out of the cell. Plants use smaller molecules such as carbon dioxide and water to build larger molecules like glucose. Hence, photosynthesis is an anabolic reaction. An anabolic reaction requires energy to build larger molecules. Photosynthesis takes in energy so is known as an endothermic reaction.

Cell respiration (Choices B and D) is the production of ATP, carbon dioxide and water using glucose and oxygen. Glucose is broken down to form smaller molecules so it is categorized as a catabolic reaction. A catabolic reaction releases energy when larger molecules are broken down to form smaller molecules. Reactions that release energy are known as exothermic reactions.

Explanation:
Choice A – Catabolic reactions involve the breakdown of large molecules into smaller molecules.

Choice B – Fermentation refers to anaerobic respiration which occurs in the cytoplasm.

Choice C - Anabolic reactions build complex compounds from simpler molecules. In the case of photosynthesis, the reactants carbon dioxide and water are turned into glucose and oxygen gas.

Choice D – Hydrolysis is an example of a catabolic reaction which involves the splitting of water.

Explanation:
Almost all enzymes are globular proteins and differ from fibrous proteins in that they are sensitive to pH and temperature and are mostly water soluble.

Fibrous proteins (Choice A), unlike globular proteins, are long and narrow, less sensitive to changes in pH and temperature and are generally insoluble in water. Enzymes are not lipids (Choices B, D). Enzymes tend to be hydrophilic, not hydrophobic since they are mostly soluble in water.

Explanation:
Glycolysis occurs in the cytoplasm of the cell. Then, in aerobic respiration, the product of glycolysis (pyruvate), then is transported into the mitochondrion, where it enters the link reaction. The link reaction takes place in the fluid part of the mitochondrion, the matrix. The product of the link reaction then enters the Krebs cycle, which also occurs in the matrix. The final stage, the electron transport chain, occurs in the membranes of the cristae. Choice B is, therefore, correct.

Choices A, C and D are incorrect as they give one or more incorrect locations.

Explanation:
ATP from cell respiration is an immediate source of energy for metabolic processes.

Neurons transmit information in the form of electrical impulses (Statement I). This transmission can only happen when there is a difference in concentrations of Na

and K

ions across the axonal membrane of a neuron. Energy in the form of ATP is required for the Na

/K

pump to restore the ionic balance after the voltage-gated response.

Osmosis (Statement II) does not require ATP. It is a passive transport process where water can move through a partially permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

The condensation reaction of a polypeptide (Statement III) is the joining of amino acids together to form a polypeptide. It is an anabolic reaction where ATP is required to join amino acids together to form a peptide bond, and water is produced.

Explanation:
Heat and pressure from the Earth’s crust decompose the remains of dead plants and animals over millions of years to form oil, natural gas or coal (fossil fuels).

Respiration (Choice B) takes place in a relatively short time as does photosynthesis which requires light to synthesize organic compounds (Choice C). Forest fires (Choice D) often occur naturally and release carbon dioxide into the atmosphere. Global warming has increased the number of wildfires.

Explanation:
The length of food chains tends to be shorter than 6 organisms, even including parasites and detritivores. When energy is passed from one organism to the next, most of the energy is generally lost as heat which means that less and less energy is available to higher trophic levels.

All other statements are true.

Explanation:
The digestion of starch is a catabolic reaction where starch molecules are broken down into maltose by hydrolysis.

Peptide formation from amino acids (Choice A), starch synthesis from glucose (Choice B), and DNA synthesis from nucleotides (Choice D) are all examples of anabolic reactions.

Explanation:
Choice A is correct because zoonotic diseases are diseases that can be transmitted from one species to another, such as from chickens to humans. Choice B is incorrect because zoonotic diseases do not only affect domesticated animals. Choice C is incorrect because zoonotic diseases are not only caused by viruses. Choice D is incorrect because zoonotic diseases do not only affect humans.

Explanation:
The endocrine system (Statement II) is involved in the fight or flight response through the release of hormones from endocrine glands, such as adrenaline (epinephrine), from the adrenal glands. Adrenaline (epinephrine) is released into the bloodstream and travels throughout the body to target organs and tissues, preparing the body for immediate action. When adrenaline (epinephrine) reaches its target tissues it binds to specific transmembrane receptors on the surface of cells (Statement I). This binding triggers a cascade of intracellular events that ultimately lead to physiological changes associated with the fight or flight response, such as increased heart rate and dilated airways. The autonomic nervous system (Statement III) plays a central role in the fight or flight response. In a frightening situation, the nervous system is activated, leading to the release of adrenaline (epinephrine), increased heart rate, increased blood flow to muscles, and other physiological changes that prepare the body for a rapid response. Choice D is therefore correct.

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

Explanation:
Autotrophs are producers and form the base of food chains. They carry out photosynthesis and get their energy from the Sun.

The most abundant organisms (Choice A) are usually the producers but there are exceptions. Energy always enters the food chain via the autotrophs, not consumers (Choice C).

The flow of energy (Choice D) is from producers to primary to secondary to tertiary consumers.

Explanation:
A community is a group of populations living and interacting in a shared habitat (biotic factors). The abiotic factors for this community have not been described but could be the depth of the water, light intensity and the nutrients available for phytoplankton.

A population (Choice A) is a group of organisms of the same species living in the same area at the same time which can interbreed. A habitat (Choice C) refers to the environment in which a species normally lives. An ecosystem (Choice D) is a group of populations living and interacting in a common habitat and includes both biotic and abiotic factors.

Explanation:
Choice C is correct because antigens are chemicals that stimulate the production of antibodies. Choice A is incorrect because B lymphocytes produce antibodies, not antigens. Choice B is a description of antibodies, which binds to antigens so is incorrect. Choice D is incorrect because hybridoma cells produce antibodies, not antigens.

Explanation:
Choice A is correct because all statements are true. Plasma cells are clones of B lymphocytes, produce large numbers of antibodies and have extensive rough endoplasmic reticulum.

Individuals of the same species competing for resources (Choice B) is ‘intraspecific Competition.’ Choice A refers to predator-prey interactions and is not any type of competition. Individuals of different species cooperating for limited resources (Choice D) describes a mutualistic relationship, not a competitive one.

Explanation:
All the statements above are true. In most ecosystems, light energy from the Sun is captured by producers via photosynthesis and transferred to consumers through feeding. As organisms respire, they lose energy in the form of heat which cannot be reused by organisms. There is a constant input of energy from the Sun.

Explanation:
Choice A is incorrect as it describes how neurotransmitters are released from the presynaptic cleft. Choice C is incorrect as neurotransmitters do not require energy to move across the synaptic cleft. Choice D is incorrect as channels are not present in the synaptic cleft. They are only present in the membranes of neurons.

Explanation:
Choice D is correct because the gland X is the pineal gland and it produces melatonin. Choice A is incorrect because leptin is produced by adipose tissue. Choice B is incorrect because thyroxine is produced by the thyroid gland. Choice C is incorrect because progesterone is produced by ovaries.

Explanation:
Choice B is correct because insect-pollinated flowers have coloured petals (Statement II) to attract pollinators and a nectary (Statement I) to reward them, whereas all flowers have a stigma (Statement III). Choice A is incorrect because both statements I and II are correct. Choices C and D are incorrect because the stigma is not adapted for a mutualistic relationship with insects. Only the flower benefits from the presence of a stigma.

Explanation:
Cells are the basic structural and functional units of life. They are the fundamental building blocks of all living organisms. Tissues are groups of specialised cells that work together to perform a specific function. Different types of tissues combine to form organs. Organs are composed of multiple tissues that work together to carry out complex functions. Organs have specific roles within the body. Organ systems are groups of organs that collaborate to perform broader functions necessary for the survival of the organism. Organism refers to the complete living individual made up of various organ systems working together. Therefore Choice B is correct.

Choices A, C and D are all in the incorrect order.