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Question 1

Topic: 7.2

(a) Fig. 1.1 is a diagram of the digestive system.

(i) State the letter from Fig. 1.1 that represents:

where salivary amylase is produced
where insulin is produced
the liver
where protease acts.

(ii) State one function of the hydrochloric acid in the stomach.

(b) Amylase is an enzyme.

(i) Describe the function of amylase.

(ii) Define the term enzyme.

▶️ Answer/Explanation

Solution

(a)(i)

1. A (where salivary amylase is produced – the salivary glands)

2. C (where insulin is produced – the pancreas)

3. G (the liver)

4. E (where protease acts – the stomach)

Explanation: The digestive system diagram would show these structures clearly. Salivary amylase is produced in the salivary glands (A), insulin is produced in the pancreas (C), the liver (G) is a large organ with multiple functions, and protease enzymes act in the stomach (E) to break down proteins.

(a)(ii)

Kills/destroys harmful microorganisms OR provides an optimum acidic pH for pepsin/protease enzyme activity.

Explanation: Hydrochloric acid in the stomach serves two main purposes. First, it creates a highly acidic environment that kills most pathogens entering with food. Second, it provides the ideal pH (around pH 2) for pepsin, the protease enzyme that breaks down proteins, to function most effectively.

(b)(i)

Amylase breaks down starch into simpler sugars (like maltose).

Explanation: Amylase is a digestive enzyme that specifically targets starch molecules. It catalyzes the hydrolysis of starch (a polysaccharide) into smaller carbohydrate units, primarily maltose (a disaccharide). This process begins in the mouth (salivary amylase) and continues in the small intestine (pancreatic amylase).

(b)(ii)

An enzyme is a protein that acts as a biological catalyst, speeding up chemical reactions without being used up in the process.

Explanation: Enzymes are protein molecules that play crucial roles in biological systems. They work by lowering the activation energy needed for chemical reactions to occur, thereby accelerating these reactions. Importantly, they remain unchanged after the reaction, allowing them to be reused. Each enzyme is specific to particular substrates and reactions.

Question 2

Topic: 6.1

A student investigated photosynthesis in a variegated leaf. A variegated leaf has a green part that contains a green pigment and a white part that does not contain the green pigment.

Fig. 2.1 is a photograph of some variegated leaves.

(a) State where the green pigment is found in a plant cell.

(b) A student investigated a variegated leaf from a plant that had been kept in the light for 24 hours. The student prepared the leaf by boiling it and then placing it in ethanol to remove the green pigment. The student then tested the leaf with iodine solution. Table 2.1 shows the results.

Explain the results shown in Table 2.1 for the white part of the leaf.

(c) This investigation was repeated with a plant that was kept for 24 hours in an environment where all the carbon dioxide was removed. Complete Table 2.2 to predict the results.

(d) (i) The boxes on the left show the names of some substances that are made in plants. The boxes on the right show uses of these substances in plants. Draw lines to link each substance with its correct use in plants. Draw three lines.

(ii) List the chemical elements contained in carbohydrates.

▶️ Answer/Explanation

Solution

(a) Chloroplast.

Explanation: The green pigment in plant cells is chlorophyll, which is found in the chloroplasts. These organelles are responsible for photosynthesis and give plants their green color. The white parts of variegated leaves lack chloroplasts, which is why they appear white.

(b) The white part of the leaf cannot photosynthesize because it lacks chlorophyll. No glucose is produced in this region, and therefore no starch is stored. Iodine solution remains yellow-brown in the absence of starch, indicating a negative result for starch presence.

Explanation: The white parts of the leaf don’t contain chlorophyll, which is essential for photosynthesis. Without photosynthesis, no glucose (and subsequently no starch) is produced. Iodine turns blue-black in the presence of starch, but remains yellow-brown when starch is absent, which explains the result for the white part of the leaf.

(c)

part of the leaf	colour with iodine solution
green	yellow-brown
white	yellow-brown

Explanation: Even though the green part contains chlorophyll, photosynthesis cannot occur without carbon dioxide, which is a key reactant in the process. Therefore, no starch would be produced in either part of the leaf, resulting in a negative iodine test (yellow-brown color) throughout the entire leaf.

(d) (i)

Explanation: Cellulose is a structural polysaccharide that forms plant cell walls. Nectar is a sweet liquid produced by flowers to attract pollinators like insects. Sucrose is the main form of sugar transported through the phloem in plants.

(ii) Carbon, hydrogen, oxygen.

Explanation: Carbohydrates are organic compounds composed of these three elements, typically in a ratio of 1:2:1 (CH₂O). This basic composition applies to all carbohydrates, from simple sugars like glucose to complex polysaccharides like starch and cellulose.

Question 3

Topic: 9.2

(a) Fig. 3.1 is a diagram of a cross-section of a human heart.

(i) Draw an X on Fig. 3.1 to identify the position of the left atrium.

(ii) On Fig. 3.1, label with a label line and the correct name a structure that ensures the one-way flow of blood.

(iii) State two letters that identify arteries in Fig. 3.1.

(iv) State the name of the part that separates the left and right sides of the heart.

(v) State the name of the main tissue the wall of the heart is made from.

(b) In one country, the percentages of males and females with coronary heart disease (CHD) in different age groups were recorded.

Fig. 3.2 shows these data.

(i) Using the information in Fig. 3.2, describe the similarities and differences between the percentages of males and females with CHD. [3]

(ii) State three risk factors for CHD not identified in Fig. 3.2.

▶️ Answer/Explanation

Solution

(a)(i) X should be drawn in the left atrium only, with a label line ending in left atrium.

Explanation: The left atrium is the upper chamber on the left side of the heart that receives oxygenated blood from the lungs. It’s important to place the X specifically in this chamber and not confuse it with the right atrium.

(a)(ii) Valve; valve identified with label line.

Explanation: The heart contains several valves (tricuspid, bicuspid/mitral, pulmonary, and aortic) that ensure one-way blood flow. Any one of these can be labeled. The valves prevent backflow of blood, maintaining the correct circulation direction.

(a)(iii) B and C (either order).

Explanation: Arteries carry blood away from the heart. In the diagram, B and C represent major arteries – likely the aorta and pulmonary artery. These have thick, muscular walls to withstand high blood pressure.

(a)(iv) Septum.

Explanation: The septum is the muscular wall that completely separates the left and right sides of the heart. This separation is crucial to prevent mixing of oxygenated and deoxygenated blood.

(a)(v) Muscle.

Explanation: The heart wall is primarily composed of cardiac muscle tissue (myocardium). This specialized muscle can contract rhythmically without tiring, enabling the heart to pump continuously throughout life.

(b)(i) Any three from:
– CHD increases with age for both males and females
– In age group 0-34 there’s no CHD in males or females
– More males than females overall have CHD
– Greatest difference between genders is in age group 75-84
– (Any valid comparative data quote between males and females)

Explanation: The data shows that while both genders see increased CHD with age, males are consistently more affected, particularly in older age groups. The complete absence in young people suggests CHD develops over time. The gender difference may relate to hormonal or lifestyle factors.

(b)(ii) Any three from:
– Unhealthy diet (high in saturated fats/cholesterol)
– Lack of exercise/physical inactivity
– Smoking
– High blood pressure
– Stress
– Genetic predisposition
– Obesity
– Diabetes

Explanation: While age and gender are shown in the data, many other modifiable risk factors contribute to CHD. Poor diet can lead to atherosclerosis, while smoking damages blood vessels. Lack of exercise weakens the cardiovascular system. These factors often interact, compounding risk.

Question 4

Topic: 19.2

(a) Fig. 4.1 shows a marine food web.

(i) Place ticks (✓) in the boxes to show the correct descriptions for the organisms shown in Fig. 4.1.

(ii) Construct one food chain from Fig. 4.1 that contains four organisms including the octopus.

(iii) Identify one organism in Fig. 4.1 that feeds at the second and third trophic levels.

(b) State the name of the type of organism that gets its energy from dead organic material.

(d) Outline ways humans can directly impact food webs.

▶️ Answer/Explanation

Solution

(a)(i)

Explanation: Algae are producers as they perform photosynthesis. Zooplankton are herbivores as they feed on phytoplankton (producers). Sharks are both carnivores (as they eat other animals) and tertiary consumers (as they are at the top of the food chain).

(a)(ii) algae → limpet → octopus → shark or phytoplankton → mussel → octopus → shark

Explanation: Both food chains are correct as they show the flow of energy from producer (algae/phytoplankton) to primary consumer (limpet/mussel) to secondary consumer (octopus) to tertiary consumer (shark). The arrows must point in the direction of energy flow.

(a)(iii) sardine

Explanation: Sardines feed at both the second trophic level (as herbivores eating phytoplankton) and the third trophic level (as carnivores eating zooplankton), making them omnivores in this food web.

(b) decomposer

Explanation: Decomposers like bacteria and fungi break down dead organic material, recycling nutrients back into the ecosystem. They play a crucial role in nutrient cycles by converting complex organic compounds into simpler inorganic forms.

(c) the Sun

Explanation: The Sun is the ultimate source of energy for nearly all biological systems. Through photosynthesis, producers convert solar energy into chemical energy stored in glucose, which then flows through the food web.

(d) Humans can impact food webs through:

Overharvesting of species (e.g., overfishing), which can disrupt predator-prey relationships
Pollution (e.g., oil spills, pesticides) that can poison organisms at various trophic levels
Habitat destruction (e.g., deforestation, coral reef damage) that removes key species from the web
Introduction of invasive species that can outcompete native species
Climate change altering species distributions and interactions

Explanation: Human activities can have cascading effects on food webs by removing key species, altering habitats, or introducing new elements that disrupt the delicate balance of energy flow and species interactions in ecosystems.

Question 5

Topic: 15.1

(a) Antibiotics are a type of drug.

The box on the left contains the beginning of a sentence.

The boxes on the right show some sentence endings.

Draw lines to link the phrase ‘Antibiotic drugs’ on the left to three boxes on the right to make three correct sentences.

(b) Fig. 5.1 shows the number of antibiotic doses given per 1000 people per day in six different countries.

(i) Calculate the difference in the number of antibiotic doses given per 1000 people per day between country A and country F in Fig. 5.1.

number of antibiotic doses given per 1000 people per day in country A

number of antibiotic doses given per 1000 people per day in country F

(ii) Using the information in Fig. 5.1, state the two countries that gave the same number of antibiotic doses per 1000 people per day.

▶️ Answer/Explanation

Solution

(a)

Explanation: Antibiotics are specifically designed to target bacteria, not viruses. They work by interfering with bacterial cell processes (chemical reactions) like cell wall synthesis or protein production. Overuse can lead to antibiotic resistance, making them less effective. They are not used for coronary heart disease (which requires different medications) and are not the cause of rickets (a vitamin D deficiency condition).

(b)(i)

From the graph:

Country A = 42 doses
Country F = 22 doses
Difference = 42 – 22 = 20 doses

Explanation: The calculation involves reading the values from the bar graph for countries A and F, then finding the arithmetic difference between them. This shows country A uses nearly twice as many antibiotics per capita as country F.

(b)(ii)

Countries D and E gave the same number of antibiotic doses.

Explanation: By examining the graph, we can see that both countries D and E have bars of equal height, indicating they administer the same quantity of antibiotics per 1000 people daily. This visual comparison is key to identifying matching values in bar graphs.

Question 6

Topic: 8.2

(a) Fig. 6.1 is a diagram showing the pathway of water into a plant. The arrows show the direction of water movement.

(i) State the name of the cell labelled A in Fig. 6.1.

(ii) State the name of cell B and describe how it is adapted for absorption of water.

(iii) State the name of the process by which cell B absorbs water.

(b) State two uses of water in plants.

▶️ Answer/Explanation

Solution

(a)(i) (root) cortex (cell)

Explanation: The cell labelled A is part of the root cortex, which is the region of parenchyma cells between the epidermis and vascular tissue in plant roots. These cells store starch and help in the movement of water and minerals from the epidermis to the vascular tissue.

(a)(ii) root hair (cell); large surface area / elongated shape

Explanation: Cell B is a root hair cell, which is specialized for water absorption. Its key adaptation is its elongated shape that creates a large surface area to maximize absorption of water and minerals from the soil. The thin cell wall also facilitates this absorption process.

(a)(iii) osmosis

Explanation: Root hair cells absorb water through osmosis, which is the passive movement of water molecules from an area of higher water potential (soil) to an area of lower water potential (root hair cell) across a partially permeable membrane.

(b) Any two from: photosynthesis / metabolic processes; support; solvent; transport; germination

Explanation: Water has multiple crucial roles in plants. It’s essential for photosynthesis as a raw material and maintains turgor pressure for support. As a universal solvent, it transports minerals and nutrients. Water is also vital for metabolic processes and is required for seed germination.

(c) Any two from: wind(speed); temperature; humidity; light intensity

Explanation: Environmental factors significantly affect transpiration rates. Wind increases water loss by removing humid air around leaves. Higher temperatures accelerate evaporation. Low humidity creates a steeper water potential gradient. Light intensity affects stomatal opening, thus influencing transpiration.

Question 7

Topic: 16.4

(a) Fig. 7.1 is a diagram of the female reproductive system in humans.

Table 7.1 shows the name, letter and function of some of the parts in Fig. 7.1.

Complete Table 7.1.

(b) This list shows some specialised animal and plant cells.

ciliated cell
guard cell
neurone
palisade mesophyll cell
red blood cell
white blood cell

Choose words from the list to state the names of:

two specialised plant cells
the cell that transports oxygen
the cell found in the trachea that moves mucus

(d) Fig. 7.2 is a drawing of another specialised cell.

(i) Label three cell structures in Fig. 7.2 with label lines and the correct names.

(ii) State the name of the cell shown in Fig. 7.2.

▶️ Answer/Explanation

Solution

(a)

Explanation: The uterus (A) is where the fetus develops during pregnancy. The oviduct (E), also called fallopian tube, is where fertilisation typically occurs when sperm meets egg. The ovary (D) produces and releases egg cells (ova) and also secretes female sex hormones.

(b)

Two specialised plant cells: guard cell and palisade mesophyll cell
Cell that transports oxygen: red blood cell
Cell in trachea that moves mucus: ciliated cell

Explanation: Guard cells control stomatal opening in leaves, while palisade mesophyll cells contain chloroplasts for photosynthesis. Red blood cells contain hemoglobin to carry oxygen. Ciliated cells in the trachea have hair-like projections that sweep mucus and trapped particles upward.

(c) When (existing) cells divide.

Explanation: New cells are produced through the process of cell division, either mitosis (for growth and repair) or meiosis (for gamete production). This is a fundamental process in all living organisms.

(d)(i) Three structures to label:

Acrosome (contains enzymes to penetrate egg)
Nucleus (contains genetic material)
Mitochondria (provides energy for movement)

(d)(ii) Sperm cell

Explanation: The diagram shows a sperm cell, which is the male gamete. Its streamlined shape and flagellum enable movement, while the acrosome contains enzymes needed to penetrate the egg during fertilisation. The mid-piece contains many mitochondria to provide energy for swimming.

Question 8

Topic: 1.2

(a) All living organisms can be classified into groups by the features they share.

(i) Complete the sentences about classifying organisms.

A species is a group of organisms that reproduce to produce …… offspring.

All species are named using an internationally agreed system called the …… system.

Fish, mammals, reptiles and amphibians are vertebrate groups. The other vertebrate group is …… . All vertebrates belong to the …… kingdom.

One feature that is used to identify vertebrates is a …… .

(ii) Draw a (circle) around the characteristic shared by all living organisms.

egestion

nutrition

sexual reproduction

transpiration

(b) Scientists measured the length of a sample of one species of fish.

Fig. 8.1 shows where the scientists took their measurements to determine the length of each fish.

Table 8.1 shows the results.

(i) Use the information in Table 8.1 to calculate the total number of fish the scientists measured.

(ii) State the most frequent length shown in Table 8.1.

(iii) State the type of variation shown by the data in Table 8.1.

▶️ Answer/Explanation

Solution

(a)(i)

fertile ; binomial ; birds ; animal ; backbone / AW ;

Explanation: A species is defined as a group of organisms that can interbreed to produce fertile offspring. The binomial system (Genus species) is the international naming convention. The five vertebrate groups are fish, mammals, reptiles, amphibians, and birds. All vertebrates belong to the animal kingdom and share the characteristic of having a backbone (or vertebral column).

(a)(ii)

nutrition circled ;

Explanation: Nutrition is the fundamental characteristic shared by all living organisms as they all require energy and nutrients for survival. While egestion, sexual reproduction, and transpiration are important biological processes, they are not universal to all life forms (e.g., some organisms reproduce asexually, and transpiration is specific to plants).

(b)(i)

3365 (fish) ;

Explanation: The total number of fish is calculated by summing all the values in the “number of fish” column: 8 + 162 + 1710 + 1350 + 130 + 5 = 3365. This represents the sample size of the study.

(b)(ii)

40-59 (cm) ;

Explanation: The most frequent length group is identified by finding the highest value in the “number of fish” column. The 40-59 cm range has 1710 fish, which is significantly higher than any other group, making it the modal class.

(b)(iii)

continuous ;

Explanation: The data shows continuous variation because the length measurements can take any value within a range (from 0-119 cm in this case) and the data forms a normal distribution pattern with most fish clustered around the middle values.

(c)

second row ticked: variation is the differences between individuals of the same species ;

Explanation: Variation refers to the observable differences between individuals within a species. The first option describes an allele, the third describes a specific genetic scenario, and the fourth describes heredity rather than variation itself. The correct definition focuses on the phenotypic and genotypic differences among organisms of the same species.

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