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Question 1

Topic: 9.3

(a) Arteries are a type of blood vessel.
State two structural features of arteries.

(b) Capillaries are another type of blood vessel.
State one function of capillaries.

(d) Fig. 1.1 is a diagram of part of the human circulatory system.
The arrows show the direction of blood flow.

(i) On Fig. 1.1, draw arrows to show the direction of blood flow to and from the lungs. [1]

(ii) State the names of blood vessel X and organ Y in Fig. 1.1.

(e) State the name of the blood vessel that transports oxygenated blood to the kidney.

▶️ Answer/Explanation

Solution

(a) Any two from:
– Narrow lumen
– Thick wall
– Wall contains muscle layer
– Contains elastic fibers

Explanation: Arteries have specialized structures to withstand high blood pressure from the heart. Their thick walls contain elastic fibers that allow them to stretch and recoil, while the muscle layer helps regulate blood flow. The narrow lumen maintains high pressure as blood is transported away from the heart.

(b) Transfer of materials between blood and tissues / Transport materials to/from cells / Transport materials to/from blood.

Explanation: Capillaries are the smallest blood vessels with extremely thin walls (only one cell thick) that allow for efficient exchange of oxygen, carbon dioxide, nutrients, and waste products between the blood and surrounding tissues through diffusion.

(c) Valves

Explanation: Veins contain one-way valves that prevent the backflow of blood, especially important in limbs where blood must flow against gravity. These valves ensure blood moves in one direction toward the heart.

(d)(i) Arrows should be drawn from the pulmonary artery to the lungs (showing deoxygenated blood going to lungs) and from the lungs to the left atrium (showing oxygenated blood returning to heart).

(d)(ii)
X: Aorta
Y: Heart

Explanation: The aorta is the main artery carrying oxygenated blood from the heart to the body, while the heart is the central pumping organ of the circulatory system.

(e) Renal artery

Explanation: The renal artery branches from the abdominal aorta and delivers oxygen-rich blood to the kidneys for filtration and other kidney functions.

Question 2

Topic: 3.2

Water moves into and out of cells by osmosis.

(a) State two plant cell structures that water moves through to reach the cytoplasm.

(b) Potato plant tissue was used to investigate osmosis.

Potato cylinders were placed into different sucrose solutions for 30 minutes.

The masses of the potato cylinders were measured before and after being placed into the solutions.

The difference in mass was calculated for each potato cylinder.

Table 2.1 shows the results of the investigation.

(i) Using the information in Table 2.1, calculate the percentage change in mass for the potato cylinder in the 0.6 mol per dm³ sucrose solution.

Give your answer to two decimal places.

(ii) Describe the expected appearance of the potato cylinder that was placed in the 0.8 mol per dm³ sucrose solution for 30 minutes.

(iii) Using the results in Table 2.1, describe how the concentration of sucrose solution affects the percentage change in mass of the potato cylinders.

▶️ Answer/Explanation

Solution

(a) cell wall ; cell membrane

Explanation: Water moving into plant cells must pass through two key structures. First, it passes through the cell wall, which is a permeable outer layer that provides structural support. Then it moves through the cell membrane (also called plasma membrane), which is selectively permeable and controls what enters and leaves the cell. These two structures work together to regulate water movement while maintaining the cell’s structure.

(b)(i) (~)3.91(%)

Explanation: To calculate the percentage change in mass:
1. Identify the starting mass (2.30g) and final mass (2.21g)
2. Calculate the difference: 2.21 – 2.30 = -0.09g
3. Calculate percentage change: (difference/starting mass) × 100
= (-0.09/2.30) × 100 = -3.913%
4. Round to two decimal places: -3.91%
This negative value indicates the potato lost mass in this solution.

(b)(ii) smaller / shorter / shrunken

Explanation: In the 0.8 mol/dm³ sucrose solution, the potato cylinder would appear visibly smaller or shrunken. This happens because the solution is hypertonic compared to the potato cells – it has a higher solute concentration than the cell cytoplasm. Water moves out of the potato cells by osmosis, causing the cells to lose water and become flaccid. As many cells lose water, the entire cylinder shrinks in size.

(b)(iii) As the concentration of sucrose solution increases, the percentage change in mass decreases / the lower the concentration, the more percentage change in mass.

Explanation: The data shows a clear trend:
– In dilute solutions (0.0-0.4 mol/dm³), the percentage change is positive (potatoes gain mass) because water enters the cells by osmosis.
– In concentrated solutions (0.6-0.8 mol/dm³), the percentage change is negative (potatoes lose mass) because water leaves the cells.
– The higher the sucrose concentration, the greater the water loss (or less water gain), showing an inverse relationship between sucrose concentration and mass change.
This demonstrates how osmosis causes water to move from areas of low solute concentration to high solute concentration.

Question 3

Topic: 6.2

(a) Fig. 3.1 is a drawing of a leaf from an oak tree.

The oak leaf has a large surface area.

Explain why having a large surface area is an adaptation for photosynthesis.

(b) State the word equation for photosynthesis.

(i) State the letter in Fig. 3.2 which identifies the tissue that contains the highest density of chloroplasts.

(ii) In Fig. 3.2, the letter S labels a vascular bundle. State the names of two tissues found in the vascular bundle.

(iii) State the letter in Fig. 3.2 which identifies the cells that control gas exchange in the leaf and state their name.

(iv) State the name and one function of the layer labelled P in Fig. 3.2.

▶️ Answer/Explanation

Solution

(a) More light can be absorbed (for photosynthesis).

Explanation: The large surface area of oak leaves is an important adaptation for photosynthesis because it allows the leaf to capture more sunlight. Since sunlight is the energy source for photosynthesis, having more surface area means more chloroplasts can be exposed to light, increasing the rate of photosynthesis. This adaptation is particularly important in shaded environments where light intensity may be lower.

(b) Carbon dioxide + water → oxygen + glucose

Explanation: This word equation summarizes the process of photosynthesis where plants use carbon dioxide from the air and water from the soil, along with light energy, to produce oxygen (released into the atmosphere) and glucose (used as food for the plant). The actual chemical equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

(c)(i) R

Explanation: The palisade mesophyll tissue (labeled R in the diagram) contains the highest density of chloroplasts because it’s located near the top of the leaf where it can receive the most sunlight. These tightly packed, column-shaped cells are specialized for maximum light absorption.

(c)(ii) Xylem and phloem

Explanation: The vascular bundle contains two main transport tissues: xylem (which transports water and minerals from the roots to the leaves) and phloem (which transports sugars produced during photosynthesis to other parts of the plant). These tissues form the “plumbing system” of the plant.

(c)(iii) V; guard cell

Explanation: The letter V identifies the guard cells which control gas exchange in the leaf. These specialized kidney-shaped cells form stomata (pores) that can open and close to regulate the exchange of gases (CO₂ in, O₂ out) and water vapor (transpiration) between the leaf and the atmosphere.

(c)(iv) Cuticle; prevents water loss (from the leaf)

Explanation: The cuticle (labeled P) is a waxy, waterproof layer covering the epidermis of the leaf. Its primary function is to prevent excessive water loss through evaporation (transpiration), which is especially important in dry conditions. The cuticle also provides some protection against pathogens and physical damage.

Question 4

Topic: 11.1

(a) During inspiration air is taken into the lungs.

Table 4.1 shows the structures that air passes through during inspiration.

The structures are not in the correct order.

Identify the order of structures that air travels through during inspiration.

Write the letters from Table 4.1 in the boxes provided to show the correct order.

One has been done for you.

(b) The composition of inspired air is different from the composition of expired air.

Describe the differences in composition between inspired and expired air.

Fig. 4.1 shows the apparatus that was used.

The student breathed in and out, through the mouthpiece, for 15 seconds.

(i) State the name of the gas that can be identified using limewater.

(ii) Using the information in Fig. 4.1, predict what happened to the limewater in test-tube A and in test-tube B.

(d) The student exercised for five minutes.

Describe the effects of vigorous exercise on breathing.

▶️ Answer/Explanation

Solution

(a)

Explanation: During inspiration, air enters through the nose (E), then passes through the larynx (D), trachea (F), bronchi (B), bronchioles (C), and finally reaches the alveoli (A) where gas exchange occurs. This sequence represents the anatomical pathway of air from the external environment to the gas exchange surfaces in the lungs.

(b) Key differences between inspired and expired air:

1. Oxygen content: Inspired air has about 21% oxygen, while expired air has about 16% oxygen because some oxygen is absorbed in the lungs.

2. Carbon dioxide content: Inspired air has about 0.04% carbon dioxide, while expired air has about 4% as it carries waste CO₂ from respiration.

3. Water vapor: Expired air is more saturated with water vapor (about 6%) compared to inspired air which varies with humidity.

4. Temperature: Expired air is warmer (about 37°C) than inspired air which is at ambient temperature.

(c)(i) Carbon dioxide

Explanation: Limewater (calcium hydroxide solution) is used to test for carbon dioxide. When CO₂ is bubbled through limewater, it reacts to form calcium carbonate which makes the solution turn milky or cloudy.

(c)(ii)

Test-tube A: Remains clear/unchanged (as inspired air contains little CO₂)

Test-tube B: Turns cloudy/milky (as expired air contains CO₂)

Explanation: Test-tube A contains inspired air which has minimal CO₂, so the limewater remains clear. Test-tube B contains expired air rich in CO₂ from respiration, causing the limewater to turn milky due to formation of calcium carbonate.

(d) Effects of vigorous exercise on breathing:

1. Increased breathing rate (more breaths per minute) to supply more oxygen to working muscles.

2. Increased tidal volume (deeper breaths) to enhance gas exchange.

Explanation: During exercise, muscles work harder and require more oxygen while producing more CO₂. This stimulates the respiratory center in the brain to increase both the rate and depth of breathing to meet the increased demand for gas exchange.

Question 5

Topic: 16.1

Bluebells are plants that can reproduce sexually and asexually.

(a)

(i) Define the term asexual reproduction.

(ii) State one example of a structure that is involved in asexual reproduction in a plant.

(b) Fig. 5.1 is a drawing of a bluebell plant.

On Fig. 5.1, label the structure that carries out sexual reproduction with a label line and the letter S.

(c) Bluebells grow in ancient woodlands.

Fig. 5.2 is a graph showing the percentage of land that was covered with woodland in one country from the years 1100 to 2000.

(i) State the years when the percentage of land covered with woodland was 10% in Fig. 5.2.

(ii) State the percentage of land covered with woodland in 1600 in Fig. 5.2.

(d)

(i) In many countries the percentage of land covered with woodland has decreased because of deforestation.

Suggest two reasons why deforestation occurs.

(ii) Explain the undesirable effects of deforestation.

▶️ Answer/Explanation

Solution

(a)(i) Asexual reproduction is a process resulting in the production of genetically identical offspring from one parent.

Explanation: Unlike sexual reproduction which involves two parents and genetic recombination, asexual reproduction produces offspring that are clones of the single parent plant. This method is efficient but results in less genetic variation.

(a)(ii) Bulbs / corms / cuttings / tubers / runners / meristems.

Explanation: Many plants have specialized structures for asexual reproduction. For example, bulbs (like onions) contain stored food and can grow into new plants, while runners (like strawberries) are horizontal stems that grow new plants at nodes.

(b) The flower should be labeled with S.

Explanation: In flowering plants like bluebells, the flower is the structure responsible for sexual reproduction. It contains male (stamen) and female (pistil) reproductive organs that enable pollination and fertilization.

(c)(i) 1300 and 2000.

Explanation: From the graph, we can observe that the woodland coverage was 10% in two distinct years – first around 1300 when coverage was declining, and again in 2000 when coverage had partially recovered.

(c)(ii) 8%.

Explanation: The graph shows that in the year 1600, the woodland coverage reached its lowest point at approximately 8% of the land area before beginning to recover slightly in subsequent centuries.

(d)(i) Two reasons could be:

Space for housing/urban development or roads
Space for agriculture

Explanation: Deforestation often occurs to meet human needs. Growing populations require more land for housing and infrastructure, while increasing food demands drive the conversion of forests to farmland. Other reasons might include logging for timber or clearing land for mining operations.

(d)(ii) Undesirable effects include:

Habitat loss leading to reduced biodiversity as species lose their homes
Disruption of food chains which can cause ecosystem collapse
Increased soil erosion as tree roots no longer hold soil in place
Contribution to climate change through reduced carbon absorption and release of stored carbon
Increased flooding as trees no longer intercept rainfall

Explanation: Forests play crucial roles in maintaining ecological balance. Their removal has cascading effects – species extinction, changes in local climates, loss of potential medicines from plants, and impacts on indigenous communities. The soil becomes less fertile without leaf litter, and water cycles are disrupted without tree transpiration.

Question 6

Topic: 18.1

(a) A student investigated variation in flower colour in pea plants.

The student counted the number of pea plants that had purple flowers and the number of pea plants that had white flowers.

Fig. 6.1 shows the results.

Use the information in Fig. 6.1 and your own knowledge to complete the sentences about variation.

Variation is the …… between individuals of the same species.

Flower colour in pea plants is an example of discontinuous variation. The other type of variation is known as …… variation.

Discontinuous variation results in a limited number of phenotypes with no ……

Discontinuous variation is usually caused by …… only.

The difference between the number of pea plants that had purple flowers and the number of pea plants that had white flowers is ……

The ratio of purple to white flowers in Fig. 6.1 is ……

(b) Some features of organisms show discontinuous variation.

The term discontinuous variation is in the box on the left.

The boxes on the right show some features of organisms.

Draw two lines from ‘discontinuous variation’ to two features that show discontinuous variation.

(i) State the term used to describe genetic change.

(ii) State one factor that can increase the rate at which genetic change occurs.

(d) Scientists have experimented with genetically modifying pea plants to make them resistant to pea weevils.

Pea weevils are an insect pest.

(i) Suggest why pea plants might be genetically modified to make them resistant to pests.

(ii) State two other examples of genetic modification in crop plants.

▶️ Answer/Explanation

Solution

(a)

Variation is the difference(s) between individuals of the same species.

Flower colour in pea plants is an example of discontinuous variation. The other type of variation is known as continuous variation.

Discontinuous variation results in a limited number of phenotypes with no intermediates.

Discontinuous variation is usually caused by genes only.

The difference between the number of pea plants that had purple flowers and the number of pea plants that had white flowers is 61.

The ratio of purple to white flowers in Fig. 6.1 is 3:1.

Explanation: Variation refers to the differences between individuals of the same species. Discontinuous variation shows distinct categories (like purple or white flowers) with no in-between forms, while continuous variation shows a range of values (like height). The 3:1 ratio suggests Mendelian inheritance patterns where purple is dominant over white.

(b)

Explanation: Discontinuous variation shows distinct categories with no intermediates. Blood groups (A, B, AB, O) and seed shape (round or wrinkled) are classic examples. Features like height or mass show continuous variation with a range of values.

(c)

(i) mutation

(ii) ionising radiation or (some) chemicals

Explanation: Mutations are changes in DNA that create new alleles. Factors like radiation or certain chemicals can damage DNA and increase mutation rates. These changes can lead to new traits like different flower colors.

(d)

(i) so that they are not eaten / to increase yield / so that insecticides do not have to be used

(ii) Any two from: make crops resistant to herbicides, improve nutritional qualities of crops, drought resistance, larger size, better taste

Explanation: Pest-resistant GM plants reduce crop losses and pesticide use. Other GM applications include herbicide resistance (letting farmers control weeds without harming crops) and nutritional improvements (like Golden Rice with added vitamin A). These modifications help address food security and nutritional challenges.

Question 7

Topic: 1.2

Fig. 7.1 is a photograph of a lionfish (Pterois volitans).

(a) State the genus of the lionfish.

(b) Lionfish are classified as fish. Table 7.1 shows features of organisms. Place ticks (✓) in the boxes to show the correct features of birds, fish and insects.

(c) Lionfish are an example of a foreign species that has been accidentally introduced to many marine habitats. Describe the harmful consequences of introducing a foreign species to a habitat.

(d) Removing introduced species from habitats is one method of conserving endangered species. Describe other methods of conserving endangered species.

▶️ Answer/Explanation

Solution

(a) Pterois

Explanation: The scientific name of an organism consists of two parts: the genus name (first) and the species name (second). For the lionfish, Pterois is the genus name and volitans is the species name. The genus name is always capitalized when written.

(b)

Explanation:

Compound eyes are characteristic of insects, not birds or fish.
Feathers are unique to birds and are not found in fish or insects.
Both birds and fish have internal skeletons (endoskeletons), while insects have external skeletons (exoskeletons).

(c) Any three from:

Disruption to food chains/webs through predation
Competition for food with native species
Competition for space/mating sites/habitat
Introduction of new diseases to native species
Decreasing biodiversity in the habitat
Potential extinction or endangerment of native species

Detailed Explanation: When a foreign species like the lionfish is introduced to a new habitat, it often lacks natural predators, allowing its population to grow rapidly. This can lead to overconsumption of native species, disrupting the delicate balance of the ecosystem. The lionfish, for example, is a voracious predator that can decimate populations of smaller fish and crustaceans. Additionally, the new species might compete with native species for resources like food and shelter, potentially outcompeting them. In some cases, the introduced species might bring new diseases to which native species have no immunity. All these factors can lead to a decrease in biodiversity and potentially cause the extinction of native species.

(d) Any three from:

Monitoring and protecting natural habitats
Establishing zoos, nature reserves, or wildlife parks
Implementing species monitoring and protection programs
Public education about conservation
Captive breeding programs
Creating seed banks for plants
Banning hunting/poaching of endangered species
Implementing fishing quotas for endangered marine species

Detailed Explanation: Conservation of endangered species requires a multi-faceted approach. Protecting natural habitats is crucial as it preserves the ecosystem the species depends on. Establishing protected areas like nature reserves creates safe spaces where species can thrive without human interference. Captive breeding programs help increase population numbers of critically endangered species, with the goal of eventually reintroducing them to the wild. Education raises public awareness about the importance of conservation and how individuals can help. Legal protections like hunting bans prevent further depletion of endangered populations. Each method plays an important role in the comprehensive effort to preserve biodiversity.

Question 8

Topic: 19.3

Fig. 8.1 is a diagram showing part of the carbon cycle.

(a) Identify the processes labelled W, X, Y and Z in Fig. 8.1.

(b) State the names of two biological molecules found in plants that contain carbon.

State the name of one other greenhouse gas.

▶️ Answer/Explanation

Solution

(a)

W: photosynthesis
X: death/egestion/excretion
Y: combustion
Z: respiration

Explanation: The carbon cycle involves several key processes. Photosynthesis (W) is how plants absorb carbon dioxide from the atmosphere to produce glucose. Death/egestion/excretion (X) represents how carbon returns to the environment through dead organisms and waste. Combustion (Y) occurs when fossil fuels are burned, releasing carbon dioxide back into the atmosphere. Respiration (Z) is the process by which organisms release carbon dioxide as a byproduct of energy production.

(b)

1: carbohydrates (e.g., glucose, starch, cellulose)
2: proteins
(or fats/lipids or DNA)

Explanation: Plants contain various carbon-based molecules essential for life. Carbohydrates like glucose and starch store energy, while cellulose provides structural support. Proteins are made from amino acids and perform numerous functions in plant cells. Other valid answers include fats/lipids for energy storage and membranes, and DNA which contains the genetic information.

(c)

methane (or other greenhouse gases like nitrous oxide, water vapor, ozone, CFCs)

Explanation: While carbon dioxide is the most discussed greenhouse gas, methane (CH₄) is actually more potent at trapping heat, though it persists for a shorter time in the atmosphere. Methane is released from livestock digestion, rice paddies, landfills, and fossil fuel extraction. Other significant greenhouse gases include nitrous oxide from fertilizers and water vapor that forms clouds.

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