Biology: Plants, Ecology and Health
Plants, ecology and health, at 13+ Biology, covers how plants make food by photosynthesis and transport water and sugars around their bodies, how organisms in a habitat depend on each other through food chains and webs, and how diet, exercise and disease affect human health.
Method
- Learn the word equation for photosynthesis: carbon dioxide + water produces glucose + oxygen, using light energy absorbed by chlorophyll, and be able to state the raw materials, the products, and where the energy comes from.
- Learn how a leaf is adapted for photosynthesis: it is broad and thin, giving a large surface area and a short distance for gases to diffuse; it packs many chloroplasts into its upper palisade layer; and it has stomata (small pores, mostly on the underside) that let carbon dioxide in and oxygen out.
- Know the standard school practical for measuring the rate of photosynthesis: a piece of pondweed (Elodea) is placed in water under a lamp, and the bubbles of oxygen gas it releases are counted for one minute at several different distances from the lamp, measured with a ruler; counting bubbles is not very accurate, since bubbles vary in size, so a more accurate method collects the gas in a syringe and measures its volume instead.
- Learn the difference between xylem (dead, hollow cells joined into tubes that carry water and dissolved minerals upward from the roots, and also support the plant) and phloem (living cells that carry dissolved sugars up and down the plant in a process called translocation).
- Learn how to construct and read a food chain and a food web, using arrows to show the direction energy flows (from the organism being eaten to the organism eating it), and be able to identify producers, primary and secondary consumers, and predators and prey.
- Explain how a named organism's features are adaptations suited to its habitat, telling apart a structural adaptation (a physical body feature, such as thick fur) from a behavioural adaptation (something the organism does, such as migrating).
- Learn the main components of a balanced diet (carbohydrates for energy, proteins for growth and repair, fats for energy and insulation, vitamins and minerals in small amounts, fibre to aid digestion, and water) and the health effects of too much or too little of them, such as obesity or a deficiency disease.
- Learn the difference between a communicable disease, caused by a pathogen (a bacterium, virus or fungus) that can spread from person to person, and a non-communicable disease, which is not caused by a pathogen and is often linked to lifestyle factors such as diet, smoking or lack of exercise.
Worked example
A pupil measures the rate of photosynthesis in pondweed by counting the number of oxygen bubbles it releases per minute at different distances from a lamp: Distance from lamp (cm): 10, 20, 30, 40. Bubbles per minute: 32, 18, 9, 4. Explain, in terms of light intensity, why the pondweed produces fewer bubbles as the lamp is moved further away.
- Read the pattern in the table: as the distance from the lamp increases from 10 cm to 40 cm, the number of bubbles produced per minute falls from 32 to 4.
- Recall that light intensity decreases the further an object is from a light source, so moving the pondweed further from the lamp reduces the light intensity it receives.
- Light provides the energy for photosynthesis, which is absorbed by chlorophyll; a lower light intensity means less energy is available, so the rate of photosynthesis slows down.
- Oxygen gas is released as a by-product of photosynthesis, so a slower rate of photosynthesis produces fewer bubbles of oxygen per minute.
- Final answer: the number of bubbles falls as distance increases because light intensity decreases with distance, and since light supplies the energy for photosynthesis, a lower light intensity directly reduces the rate of photosynthesis and therefore the rate of oxygen production.
Practice questions
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Q1Complete the word equation for photosynthesis: carbon dioxide + water produces ___ + ___.Show answer
Answer: Glucose + oxygen
Q2Name the green pigment, found in chloroplasts, that absorbs light energy for photosynthesis.Show answer
Answer: Chlorophyll
Q3State one way the xylem is adapted for transporting water up a plant.Show answer
Answer: Any one of: it is made of dead, hollow cells joined end to end to form a continuous tube, or it has no cell contents or end walls blocking the flow of water
Q4In the food chain 'grass, rabbit, fox', name the primary consumer.Show answer
Answer: Rabbit
Q5A polar bear has thick white fur. State whether this is a structural or a behavioural adaptation, and explain why.Show answer
Answer: Structural, because it is a physical feature of the polar bear's body, not something it does
Q6Name the food group that provides the body with the most energy per gram.Show answer
Answer: Fat (fats/lipids)
Q7State one way a communicable disease differs from a non-communicable disease.Show answer
Answer: A communicable disease is caused by a pathogen and can spread from person to person, while a non-communicable disease is not caused by a pathogen and cannot be caught from someone else
Exam-style questions
Written in the style of a 13+ Common Entrance exam paper, with a full mark scheme.
A pupil measures the rate of photosynthesis in pondweed at four distances from a lamp, counting oxygen bubbles released in one minute at each distance: Distance from lamp (cm): 10, 20, 30, 40. Bubbles per minute: 40, 22, 11, 5. (a) Identify the independent variable in this investigation. (b) Suggest one variable that should be kept the same for this to be a fair test. (c) Describe the relationship shown between distance from the lamp and the number of bubbles produced. (d) Suggest one reason why counting bubbles is not a very accurate way to measure the volume of gas produced.
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A garden pond contains a food web: pondweed is eaten by both tadpoles and water snails; tadpoles are eaten by newts and by herons; newts are also eaten by herons. (a) Name the producer in this food web. (b) Name the two organisms that feed directly on the pondweed. (c) A disease kills most of the newts in the pond. State and explain what is likely to happen to the number of tadpoles shortly afterwards. (d) Suggest one reason why the tadpole population would not keep increasing without limit.
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A doctor compares two patients. Patient A has influenza (flu), which is caused by a virus and can be passed to other people by coughing and sneezing. Patient B has type 2 diabetes, which is linked to diet and body weight and cannot be passed to another person. (a) State which patient has a communicable disease, and explain how you know. (b) State which patient has a non-communicable disease, and explain how you know. (c) Suggest one lifestyle change that could help to prevent the type of disease Patient B has.
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Free printable worksheet
Want more practice on paper? Download the biology: plants, ecology and health worksheet pack - 17 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
This topic is chapter 3 of 13+ Science Workbook, the whole course as one free printable PDF.
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