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13+ · Biology

CE.S-B3 Biology: Plants, Ecology and Health

ISEB COMMON ENTRANCE ISEB Common Entrance Biology (13+) · Calculator allowed · about 75 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

Plants make their own food by photosynthesis.

(a)Complete the word equation for photosynthesis.

carbon dioxide + ______ -> glucose + ______ (light energy, chlorophyll)(2)

(b)Name the green pigment that absorbs light energy for photosynthesis, and name the cell structure (organelle) in which it is found.(2)

(c)Name the layer of leaf cells that contains the most chloroplasts, and explain why this layer is positioned near the upper (top) surface of the leaf.(2)

(Total for Question 1 is 6 marks)

The diagram shows a cross-section through a leaf. Structures P, Q, R and S are labelled.

Figure (to be drawn): Cross-section of a leaf (side view), top to bottom: P = a single layer of closely packed, transparent cells at the very top surface; Q = tall, column-shaped cells packed with green chloroplasts, just below P; R = loosely packed, rounded cells with large air gaps between them, below Q; S = a small pore with two bean-shaped cells either side, on the lower surface, opening into the air gaps of R.

(a)Identify structures P, Q, R and S.(4)

(b)Explain how the large air spaces in structure R help the leaf carry out gas exchange efficiently.(2)

(Total for Question 2 is 6 marks)

In a hedgerow habitat, oak trees are eaten by caterpillars. Caterpillars are eaten by blue tits. Blue tits are eaten by sparrowhawks.

(a)Write this information as a food chain, using arrows to show the direction of energy flow.(2)

(b)Identify the producer and the secondary consumer in this food chain.(2)

(c)One year, a disease kills most of the caterpillars. Predict what is likely to happen to the number of sparrowhawks, and explain your answer.(2)

(Total for Question 3 is 6 marks)

The table shows some features of three animals found in the UK.

Figure (to be drawn): Table with columns Animal | Skin covering | Body temperature | How young are produced. Frog: moist, permeable skin; body temperature varies with surroundings; soft eggs laid in water. Robin: feathers; constant body temperature; hard-shelled eggs. Hedgehog: fur; constant body temperature; live young.

(a)Using the table, identify the vertebrate group that each animal belongs to.(3)

(b)Give one feature from the table that the robin and the hedgehog share, but the frog does not.(1)

(Total for Question 4 is 4 marks)

Priya investigates how light intensity affects the rate of photosynthesis in pondweed. She places a piece of pondweed in a beaker of water and moves a lamp to different distances from the beaker. She counts the number of oxygen bubbles released in one minute at each distance.

(a)Identify the independent variable and the dependent variable in this investigation.(2)

(b)State three variables Priya should control to make this a fair test, and explain why each should be controlled.(3)

(c)Suggest one improvement Priya could make to increase the reliability of her results.(1)

(Total for Question 5 is 6 marks)

Priya's results are shown in the table below.

Distance of lamp from pondweed (cm): 60, 50, 40, 30, 20, 10
Bubbles counted per minute: 3, 5, 9, 14, 14, 14

(a)Describe the pattern shown by the results as the lamp is moved closer to the pondweed (from 60 cm to 10 cm).(1)

(b)Explain why the rate of bubbling stops increasing after 30 cm, even though the light intensity keeps increasing as the lamp moves closer.(2)

(c)Calculate the percentage increase in the rate of bubbling between 60 cm and 30 cm.(2)

(Total for Question 6 is 5 marks)

Leaves are described as being 'well adapted for photosynthesis'. Describe and explain four ways in which the structure of a leaf is adapted to carry out photosynthesis efficiently.

(Total for Question 7 is 4 marks)

The diagram shows a food web from a pond ecosystem.

Figure (to be drawn): Food web with arrows pointing from each organism to what eats it: pondweed -> tadpole; pondweed -> water snail; tadpole -> newt; water snail -> newt; newt -> heron; tadpole -> heron.

(a)Identify the only producer in this food web.(1)

(b)Name a secondary consumer in this food web.(1)

(c)A disease wipes out the water snail population. Explain the likely effect this could have on (i) the tadpole population and (ii) the newt population.(3)

(Total for Question 8 is 5 marks)

Energy is lost between each trophic level (stage) of a food chain.

(a)State two ways in which energy is lost from one trophic level to the next.(2)

(b)A field contains grass with a total energy content of 8,000 kJ. The grasshoppers that eat this grass contain a total of 640 kJ of energy. Calculate the percentage of energy transferred from the grass to the grasshoppers.(2)

(c)One oak tree can support thousands of caterpillars, which are eaten by only a few birds. Explain why a pyramid of numbers for this food chain would not be a true pyramid shape, even though a pyramid of biomass for the same food chain would be.(1)

(Total for Question 9 is 5 marks)

Kwame uses a 1m x 1m quadrat to estimate the number of daisy plants in a school field of area 800 m^2. He places the quadrat randomly and counts the daisies inside it five times. His results are: 12, 15, 9, 14, 10.

(a)Explain why Kwame places the quadrat randomly, rather than choosing where to put it himself.(1)

(b)Calculate the mean number of daisies per quadrat (per m²).(2)

(c)Use your answer to part (b) to estimate the total number of daisies in the whole 800 m² field.(2)

(d)Suggest one way Kwame could improve the accuracy of his estimate.(1)

(Total for Question 10 is 6 marks)

Dead leaves and animal droppings do not build up indefinitely on a woodland floor.

(a)Name the group of organisms mainly responsible for breaking down dead plant and animal material.(1)

(b)Explain why decomposers are important for the growth of new plants in the woodland.(2)

(Total for Question 11 is 3 marks)

Sort each of the following human features into one of these groups: 'caused only by genes', 'caused only by the environment', or 'caused by both genes and the environment'.

1) Blood group
2) A tattoo
3) Height
4) A scar from an injury

(Total for Question 12 is 4 marks)

Mrs Okafor's class of 30 Year 8 students measured their height and recorded their blood group.

(a)State whether height is an example of continuous or discontinuous variation, and describe the shape of a graph used to display the height data for the whole class.(2)

(b)Blood group is an example of discontinuous variation. Explain what this means, and state the type of graph that should be used to display the blood group data.(2)

(c)The blood groups of the 30 students were: A = 12, B = 6, AB = 3, O = 9. Calculate the percentage of the class with blood group O.(2)

(Total for Question 13 is 6 marks)

Four leaves, W, X, Y and Z, have the following features.

W: smooth edge, single leaf (not divided into leaflets)
X: toothed (jagged) edge, single leaf
Y: smooth edge, divided into several leaflets
Z: toothed edge, divided into several leaflets

Construct a dichotomous key, using only yes/no questions about the features above, that could be used to identify leaves W, X, Y and Z.

(Total for Question 14 is 3 marks)

Diseases can be caused by different types of pathogen.

Figure (to be drawn): Table with columns Pathogen type | Example disease | Main method of spread, and rows to complete for Bacterium, Virus and Fungus.

(a)Complete the table by giving an example disease caused by each pathogen type, and stating its main method of spread.(3)

(b)Suggest one way the spread of an airborne pathogen could be reduced in a school.(1)

(Total for Question 15 is 4 marks)

The human body has several ways of defending itself against pathogens.

(a)State how each of the following forms a barrier against pathogens entering the body: (i) the skin, (ii) mucus and cilia in the airways, (iii) stomach acid.(3)

(b)If a pathogen does get into the body, explain how white blood cells help to protect against it.(2)

(c)Explain how having a vaccination can protect a person from a serious disease in the future.(2)

(Total for Question 16 is 7 marks)

A balanced diet contains several nutrients, each with an important role in the body.

(a)Complete the table below.

Carbohydrate - main function: ______
Protein - main function: ______
Fat - main function: ______
Vitamin C - main function: ______ ; deficiency disease: ______(5)

(b)Name one nutrient (other than vitamin C) that is important for strong, healthy bones and teeth.(1)

(Total for Question 17 is 6 marks)

Arjun is a 13-year-old boy who needs approximately 2,200 kcal of energy per day to maintain a stable body mass. On one particular day, his meals and snacks provide: breakfast 450 kcal, lunch 620 kcal, dinner 780 kcal, and snacks 260 kcal.

(a)Calculate his total energy intake for the day.(2)

(b)Calculate the difference between his energy intake and his energy requirement for that day, and state whether he is in energy balance, surplus or deficit.(2)

(c)Explain why a boy who plays competitive rugby would need a greater daily energy intake than a boy of the same age who does very little physical activity.(2)

(Total for Question 18 is 6 marks)

Cigarette smoke contains tar, nicotine and carbon monoxide. Explain the effects of long-term smoking on the gas exchange system, including how these effects reduce the efficiency of gas exchange in the lungs.

(Total for Question 19 is 6 marks)

Large areas of tropical rainforest are being cut down (deforestation) to create space for farming and to obtain timber. Discuss the effects that deforestation can have on the ecosystem, and describe two methods that could be used to conserve rainforest habitats.

(Total for Question 20 is 6 marks)

The graph shows changes in the population of snowshoe hares (prey) and lynx (predators) in a forest over 20 years.

Figure (to be drawn): Line graph, Year (0-20) on the x-axis against Population in thousands on the y-axis. Hare population (solid line): oscillates between about 20 and 140 thousand, with peaks around Years 3 and 12 and rising again toward Year 20. Lynx population (dashed line): follows the same cyclical pattern but stays much lower, between about 2 and 15 thousand, with each lynx peak occurring one to two years after the corresponding hare peak.

(a)Describe the relationship between the hare population and the lynx population shown on the graph.(2)

(b)Explain why an increase in the hare population is followed by an increase in the lynx population.(2)

(c)Explain why the hare population then decreases after the lynx population has increased.(2)

(Total for Question 21 is 6 marks)

Mark scheme · CE.S-B3 Biology: Plants, Ecology and Health

Question 1

(a) B1 water (first blank)
(a) B1 oxygen (second blank)
(a) Answer: carbon dioxide + water -> glucose + oxygen
(b) B1 chlorophyll
(b) B1 chloroplast
(b) Answer: Chlorophyll, found in the chloroplast.
(c) B1 palisade (mesophyll) layer
(c) B1 positioned near the upper surface so it receives the most light, for efficient photosynthesis oe
(c) Answer: The palisade mesophyll layer; it is near the top surface so it absorbs the most light.

Question 2

(a) B1 P = upper epidermis
(a) B1 Q = palisade mesophyll
(a) B1 R = spongy mesophyll
(a) B1 S = stoma (guard cells)
(a) Answer: P upper epidermis; Q palisade mesophyll; R spongy mesophyll; S stoma.
(b) B1 large air spaces increase the surface area (of mesophyll cells) in contact with air oe
(b) B1 this allows carbon dioxide and oxygen to diffuse into and out of cells more quickly/easily oe
(b) Answer: The air spaces give a large surface area, so gases can diffuse into and out of the cells more quickly.

Question 3

(a) B1 organisms in the correct order: oak tree, caterpillar, blue tit, sparrowhawk
(a) B1 arrows drawn from each organism to the one that eats it, showing the direction of energy flow oe
(a) Answer: oak tree -> caterpillar -> blue tit -> sparrowhawk
(b) B1 producer = oak tree
(b) B1 secondary consumer = blue tit
(b) Answer: Producer: oak tree. Secondary consumer: blue tit.
(c) B1 the number of sparrowhawks is likely to decrease oe
(c) B1 linked explanation: fewer caterpillars means fewer blue tits (less food for them), so less food is available for the sparrowhawks oe
(c) Answer: Sparrowhawk numbers are likely to fall, because there is less food further along the food chain.

Question 4

(a) B1 frog = amphibian
(a) B1 robin = bird
(a) B1 hedgehog = mammal
(a) Answer: Frog: amphibian. Robin: bird. Hedgehog: mammal.
(b) B1 constant body temperature (endothermic/warm-blooded) oe
(b) Answer: They keep a constant body temperature.

Question 5

(a) B1 independent variable = distance of the lamp from the pondweed (i.e. light intensity)
(a) B1 dependent variable = number of bubbles produced per minute (rate of photosynthesis)
(a) Answer: Independent: distance of the lamp (light intensity). Dependent: bubbles per minute.
(b) B1 temperature of the water (kept constant, e.g. using a water bath), because temperature also affects the rate of photosynthesis/enzyme activity
(b) B1 concentration of carbon dioxide in the water (e.g. the same amount of sodium hydrogencarbonate added), because carbon dioxide can also limit the rate of photosynthesis
(b) B1 the same species and size of pondweed used (or the same counting time at each distance), because different plants/times could otherwise affect the result
(b) Answer: Any three of: water temperature; carbon dioxide concentration; species/size of pondweed; counting time - each with a linked reason.
(c) B1 repeat each measurement (at each distance) and calculate a mean oe
(c) Answer: Repeat the readings at each distance and take a mean.

Question 6

(a) B1 the rate of bubbling increases as the distance decreases (light intensity increases) from 60 cm to 30 cm, then levels off (stays constant at 14 bubbles per minute) from 30 cm to 10 cm oe
(a) Answer: The rate increases as the lamp gets closer, then levels off (plateaus) from 30 cm onward.
(b) B1 light is no longer the limiting factor oe
(b) B1 another factor, such as carbon dioxide concentration or temperature, is now limiting the rate of photosynthesis oe
(b) Answer: Light is no longer limiting the rate; another factor (carbon dioxide concentration or temperature) is now limiting it.
(c) M1 correct method: (14 - 3) / 3 x 100 oe
(c) A1 awrt 366-367% cao
(c) Answer: Approximately 367% increase

Question 7

B1 broad and flat shape, giving a large surface area to absorb as much light as possible
B1 thin, giving gases and light only a short distance to travel/diffuse through
B1 many chloroplasts/palisade cells packed near the upper surface, to absorb the maximum amount of light
B1 a network of veins (xylem and phloem), to transport water and mineral ions in and carry glucose away efficiently
Answer: Any four of: large surface area (broad, flat shape); thin, giving a short diffusion distance; many chloroplasts near the top surface; a network of veins for transport.

Question 8

(a) B1 pondweed
(a) Answer: Pondweed.
(b) B1 newt (accept heron, which also eats tadpoles directly)
(b) Answer: Newt (or heron).
(c) B1 the tadpole population is likely to increase oe
(c) B1 because there is less competition for pondweed (food) now the water snails are gone oe
(c) B1 the newt population may be less affected than expected, because newts have an alternative food source (tadpoles) so are not fully dependent on water snails oe
(c) Answer: Tadpoles are likely to increase, as there is less competition for pondweed; newts are less affected, since they have an alternative food source (tadpoles).

Question 9

(a) B1 energy lost as heat, from respiration and movement
(a) B1 energy lost in waste/faeces/urine, or in parts of the organism not eaten (any one)
(a) Answer: Any two of: heat from respiration/movement; waste (faeces/urine); parts not eaten.
(b) M1 640 / 8000 x 100 oe
(b) A1 8% cao
(b) Answer: 8%
(c) B1 the oak tree is counted as a single organism (a small number), even though its mass is far greater than the combined mass of the caterpillars, so numbers give an unusual shape while biomass still gives a true pyramid oe
(c) Answer: The tree counts as only one organism despite having a huge mass, so the numbers pyramid is an odd shape, but the biomass pyramid (based on mass, not numbers) stays a true pyramid.

Question 10

(a) B1 to avoid bias (e.g. choosing areas with more or fewer daisies), so the sample is representative of the whole field oe
(a) Answer: Random placement avoids bias and gives a representative sample.
(b) M1 (12 + 15 + 9 + 14 + 10) / 5 oe
(b) A1 12 (per m²) cao
(b) Answer: 12 per m²
(c) M1 12 x 800 oe (ft from (b))
(c) A1 9600 (ft)
(c) Answer: 9600 daisies
(d) B1 use more quadrats (a larger sample size), or use a systematic sampling method (e.g. a transect) alongside random sampling oe
(d) Answer: Take more quadrat samples to increase the sample size.

Question 11

(a) B1 decomposers (bacteria and fungi)
(a) Answer: Decomposers (bacteria and fungi).
(b) B1 decomposers break down dead material, releasing nutrients (e.g. nitrates/minerals) into the soil oe
(b) B1 these nutrients are absorbed by plant roots and used for growth oe
(b) Answer: They release nutrients from dead material into the soil, which plant roots then absorb and use for growth.

Question 12

B1 blood group = genes only
B1 tattoo = environment only
B1 height = both genes and environment
B1 scar = environment only
Answer: Blood group: genes only. Tattoo: environment only. Height: both. Scar: environment only.

Question 13

(a) B1 continuous variation
(a) B1 a graph/histogram with a smooth, bell-shaped curve (normal distribution), since height can take any value across a range oe
(a) Answer: Continuous variation, shown as a histogram with a bell-shaped curve.
(b) B1 discontinuous variation means the feature falls into a small number of distinct categories, with no intermediate values oe
(b) B1 a bar chart (with gaps between the bars)
(b) Answer: It falls into distinct categories with no values in between; it should be shown using a bar chart.
(c) M1 9 / 30 x 100 oe
(c) A1 30% cao
(c) Answer: 30%

Question 14

B1 first question correctly splits the four leaves into two groups of two, e.g. 'Is the leaf divided into leaflets?' Yes -> {Y, Z}, No -> {W, X}
B1 a second question correctly separates {Y, Z} using leaf edge, e.g. 'Is the edge smooth?' Yes = Y, No = Z
B1 a second question correctly separates {W, X} using leaf edge, e.g. 'Is the edge smooth?' Yes = W, No = X
Answer: 1) Is the leaf divided into leaflets? Yes -> go to 2, No -> go to 3. 2) Is the edge smooth? Yes = Y, No = Z. 3) Is the edge smooth? Yes = W, No = X.

Question 15

(a) B1 bacterium: e.g. Salmonella/food poisoning, spread mainly through contaminated food or water
(a) B1 virus: e.g. influenza (flu), spread mainly through airborne droplets (coughs/sneezes)
(a) B1 fungus: e.g. athlete's foot, spread mainly through direct contact with infected skin or damp shared surfaces
(a) Answer: Bacterium: Salmonella (food poisoning), spread via contaminated food/water. Virus: influenza, spread via airborne droplets. Fungus: athlete's foot, spread via direct contact/damp surfaces. (Accept other valid named examples.)
(b) B1 good ventilation of rooms, or covering the mouth/nose when coughing or sneezing, or regular hand washing, or staying at home when ill (any one)
(b) Answer: For example, good ventilation, covering coughs and sneezes, washing hands regularly, or staying home when ill.

Question 16

(a) B1 skin: acts as a physical barrier, preventing pathogens from entering the body
(a) B1 mucus and cilia: mucus traps pathogens/particles and the cilia sweep (waft) it up and away from the lungs
(a) B1 stomach acid: kills most pathogens/microorganisms swallowed in food or drink
(a) Answer: Skin: physical barrier. Mucus and cilia: trap and sweep pathogens out of the airways. Stomach acid: kills swallowed pathogens.
(b) B1 some white blood cells (phagocytes) engulf and digest pathogens oe
(b) B1 some white blood cells (lymphocytes) produce antibodies that help destroy pathogens oe
(b) Answer: Phagocytes engulf and digest pathogens; lymphocytes produce antibodies that help destroy them.
(c) B1 the vaccine contains a small/weakened/inactive amount of the pathogen (or a harmless part of it), which triggers the immune system to produce antibodies oe
(c) B1 memory cells remain in the blood, allowing a faster/stronger antibody response if the same pathogen infects the body again oe
(c) Answer: The vaccine triggers antibody production without causing the disease; memory cells then give faster protection if the pathogen is met again.

Question 17

(a) B1 carbohydrate: provides energy
(a) B1 protein: growth and repair of cells/tissues
(a) B1 fat: energy store, and/or insulation
(a) B1 vitamin C: helps make/maintain healthy skin and connective tissue oe
(a) B1 vitamin C deficiency disease: scurvy
(a) Answer: Carbohydrate: energy. Protein: growth and repair. Fat: energy store/insulation. Vitamin C: healthy skin/connective tissue - deficiency causes scurvy.
(b) B1 calcium (accept vitamin D)
(b) Answer: Calcium (or vitamin D).

Question 18

(a) M1 450 + 620 + 780 + 260 oe
(a) A1 2110 (kcal) cao
(a) Answer: 2110 kcal
(b) M1 2200 - 2110 (ft from (a)) oe
(b) A1 90 kcal deficit (ft)
(b) Answer: 90 kcal deficit
(c) B1 more physical activity/exercise means more respiration occurs in the muscles oe
(c) B1 more energy is needed for muscle contraction/movement, so more energy (food) must be taken in oe
(c) Answer: More exercise means more respiration in muscles, so more energy is needed to fuel movement, meaning more energy must be taken in.

Question 19

Level 1 (1-2): Basic, isolated statement(s) about smoking and health, with little or no reference to the gas exchange system. Limited use of scientific terminology.
Level 2 (3-4): Some relevant effects of smoking on the gas exchange system are described, with a partial or generalised explanation of how these reduce gas exchange efficiency. Some scientific terminology used.
Level 3 (5-6): A clear, logically linked explanation of the effects of smoking on the gas exchange system, fully explaining how these effects reduce the efficiency of gas exchange. Correct scientific terminology used throughout.
Indicative content:
- tar coats the airways and damages/paralyses the cilia, so mucus (containing trapped dirt and pathogens) is not removed effectively, leading to a 'smoker's cough' and a greater risk of chest infections
- tar and repeated infection can damage the walls of the alveoli, causing them to break down (emphysema)
- this reduces the surface area available for gas exchange
- a smaller surface area means oxygen diffuses into the blood more slowly, so less oxygen is absorbed per breath
- carbon monoxide binds to haemoglobin (forming carboxyhaemoglobin) in place of oxygen, reducing the amount of oxygen the blood can carry to the body's cells
- nicotine is addictive and increases heart rate, making the heart work harder
- reduced gas exchange efficiency means the body may not get enough oxygen for respiration, causing breathlessness and reduced fitness

Question 20

Level 1 (1-2): Basic statement(s) that cutting down trees is 'bad for the environment', with little detail; no named conservation method, or a method with no relevant detail.
Level 2 (3-4): Some relevant effects of deforestation on the ecosystem are given, and at least one conservation method is described, but links between ideas may be incomplete.
Level 3 (5-6): A clear, well-linked discussion of the effects of deforestation on the ecosystem, together with two conservation methods described in appropriate detail. Correct scientific terminology used throughout.
Indicative content:
- habitat is destroyed, so animals and plants that lived there lose their home and food sources, reducing biodiversity (some species may become endangered or extinct)
- fewer trees means less photosynthesis, so less carbon dioxide is removed from the atmosphere, which can contribute to climate change/the greenhouse effect
- removing tree roots can increase soil erosion, as there are fewer roots to bind the soil together, leading to nutrients being washed away and reduced soil fertility
- conservation method: creating protected areas/national parks where logging and farming are restricted or banned
- conservation method: replanting trees (reforestation) to replace those that have been cut down
- conservation method: captive breeding programmes for endangered species, with reintroduction to the wild
- conservation method: education and sustainable farming methods (e.g. selective logging) to reduce the rate of deforestation

Question 21

(a) B1 the lynx population follows the same cyclical pattern as the hare population oe
(a) B1 the peaks in the lynx population occur slightly after (a year or two behind) the peaks in the hare population oe
(a) Answer: Lynx numbers rise and fall in the same cycle as hare numbers, but peak one to two years later.
(b) B1 more hares means more food is available for the lynx oe
(b) B1 more lynx survive and/or reproduce successfully, so the lynx population grows oe
(b) Answer: More hares provide more food for the lynx, so more lynx survive and reproduce, increasing their population.
(c) B1 more lynx means more predation on hares oe
(c) B1 hares are eaten faster than they can reproduce, so the hare population falls oe
(c) Answer: More lynx means increased predation, so hares are killed faster than they can reproduce and their population falls.

Biology: Plants, Ecology and Health - Worksheets, Questions and Revision