This set of questions is designed to test Key Stage 3 students’ knowledge of photosynthesis and how plants make food to support other organisms in an ecosystem. The questions are divided into three levels of difficulty: Easy, Medium, and Hard. Each section contains 20 questions, followed by answers at the end for self-assessment.

Sample Example for Readers

Sample Question
What is the process called by which plants make their own food?

Answer: The process is called photosynthesis.

Photosynthesis and Ecosystem Support – Easy Level

Q1: What gas do plants take in from the air to use in photosynthesis?
Q2: What gas do plants release during photosynthesis?
Q3: In which part of the plant does photosynthesis mainly occur?
Q4: True or false: Plants need sunlight to carry out photosynthesis.
Q5: What is the green pigment in plants that absorbs light for photosynthesis?
Q6: What are the two main products of photosynthesis?
Q7: What substance do plants take in from the soil for photosynthesis?
Q8: Name the process by which plants make their own food.
Q9: True or false: Photosynthesis takes place only at night.
Q10: What simple sugar is produced during photosynthesis?
Q11: What is the main function of roots in a plant?
Q12: Which type of organism relies on plants for food energy?
Q13: True or false: Oxygen is a waste product of photosynthesis.
Q14: What do plants need in addition to carbon dioxide and water to perform photosynthesis?
Q15: What is the role of chlorophyll in photosynthesis?
Q16: True or false: Plants are producers in an ecosystem.
Q17: What is the energy source for photosynthesis?
Q18: What part of the plant absorbs water from the soil?
Q19: Name a gas that animals exhale which plants use in photosynthesis.
Q20: What colour are the leaves that contain the most chlorophyll?

Photosynthesis and Ecosystem Support – Medium Level

Q21: Explain why photosynthesis is important for animals.
Q22: How do plants use the glucose produced during photosynthesis?
Q23: What is the role of stomata in leaves during photosynthesis?
Q24: Describe how plants contribute to the oxygen cycle.
Q25: What happens to the rate of photosynthesis when light intensity increases?
Q26: Why do plants appear green?
Q27: How do plants support herbivores in an ecosystem?
Q28: What factors can affect the rate of photosynthesis?
Q29: Explain the importance of photosynthesis to the food chain.
Q30: How does carbon dioxide enter the plant for photosynthesis?
Q31: What is the equation for photosynthesis?
Q32: How do plants store the glucose they produce?
Q33: Describe how light energy is converted into chemical energy in photosynthesis.
Q34: Explain the relationship between photosynthesis and respiration in plants.
Q35: How do carnivores indirectly depend on photosynthesis?
Q36: How do plants help maintain a balanced ecosystem?
Q37: What role do decomposers play in the cycling of nutrients that plants use?
Q38: Why is water essential for photosynthesis?
Q39: Explain how photosynthesis contributes to reducing carbon dioxide levels in the atmosphere.
Q40: How do changing seasons affect the rate of photosynthesis?

Photosynthesis and Ecosystem Support – Hard Level

Q41: Discuss how light wavelength affects the rate of photosynthesis.
Q42: Explain the role of the Calvin cycle in photosynthesis.
Q43: How do plants adapt to environments with low light levels to maximise photosynthesis?
Q44: Describe the impact of deforestation on the carbon cycle and photosynthesis.
Q45: Explain how C4 plants differ from C3 plants in their photosynthesis process.
Q46: Discuss the role of photosynthesis in mitigating climate change.
Q47: How does temperature affect the enzymes involved in photosynthesis?
Q48: Describe how photosynthesis is connected to the energy flow in an ecosystem.
Q49: How do limiting factors such as light, water, and carbon dioxide interact to affect photosynthesis?
Q50: Explain the significance of the light-dependent reactions in photosynthesis.
Q51: How does the process of photosynthesis help regulate global temperatures?
Q52: Explain why some plants have adapted to perform photosynthesis at night (CAM plants).
Q53: How does photosynthesis affect the pH balance of bodies of water?
Q54: Discuss the evolutionary importance of photosynthesis in the development of life on Earth.
Q55: How does photosynthesis contribute to the carbon sequestration process?
Q56: Describe the role of accessory pigments in capturing light energy for photosynthesis.
Q57: How do artificial lights affect the rate of photosynthesis in plants grown indoors?
Q58: Explain how an increase in atmospheric carbon dioxide levels affects photosynthesis rates globally.
Q59: Discuss how climate change might impact the availability of water and its effects on photosynthesis.
Q60: How does the stomatal density of leaves influence the rate of photosynthesis?

Answers

Easy Level Answers

Q1: Carbon dioxide
Q2: Oxygen
Q3: Leaves
Q4: True
Q5: Chlorophyll
Q6: Glucose and oxygen
Q7: Water
Q8: Photosynthesis
Q9: False
Q10: Glucose
Q11: To absorb water and nutrients
Q12: Herbivores (or animals)
Q13: True
Q14: Sunlight
Q15: Chlorophyll absorbs light energy for photosynthesis.
Q16: True
Q17: Sunlight
Q18: Roots
Q19: Carbon dioxide
Q20: Green

Medium Level Answers

Q21: Photosynthesis produces oxygen, which animals need to breathe, and it creates food (glucose) that forms the base of the food chain.
Q22: Plants use glucose for energy, growth, and storing it as starch.
Q23: Stomata are tiny openings in leaves that allow gases like carbon dioxide to enter and oxygen to exit.
Q24: Plants release oxygen as a by-product of photosynthesis, contributing to the oxygen available for respiration.
Q25: As light intensity increases, the rate of photosynthesis generally increases until it reaches a maximum point.
Q26: Plants appear green because chlorophyll reflects green light while absorbing other wavelengths for photosynthesis.
Q27: Herbivores eat plants to obtain energy, which they need for survival.
Q28: Factors like light intensity, carbon dioxide levels, and temperature can affect the rate of photosynthesis.
Q29: Photosynthesis provides the energy (in the form of glucose) that starts the food chain.
Q30: Carbon dioxide enters the plant through small openings called stomata.
Q31: Carbon dioxide + Water + Light → Glucose + Oxygen (6CO₂ + 6H₂O + Light → C₆H₁₂O₆ + 6O₂)
Q32: Plants store glucose as starch, which can be used later for energy.
Q33: Light energy is converted into chemical energy (glucose) during photosynthesis.
Q34: Photosynthesis produces oxygen, which plants use in respiration, while respiration produces carbon dioxide for photosynthesis.
Q35: Carnivores eat herbivores, which rely on plants that perform photosynthesis for energy.
Q36: Plants provide oxygen and food to support other organisms, helping to maintain a balanced ecosystem.
Q37: Decomposers break down dead organic matter, recycling nutrients that plants use for growth.
Q38: Water provides the hydrogen needed to form glucose during photosynthesis.
Q39: Plants absorb carbon dioxide from the air during photosynthesis, helping to reduce greenhouse gases.
Q40: Photosynthesis rates decrease in winter due to lower light levels and cooler temperatures.

Hard Level Answers

Q41: Light at different wavelengths affects photosynthesis, with red and blue light being most effective, and green light being least effective.
Q42: The Calvin cycle is the stage of photosynthesis where carbon dioxide is used to form glucose in the stroma of the chloroplasts.
Q43: Plants in low-light environments may have larger leaves or more chlorophyll to maximise light absorption.
Q44: Deforestation reduces the number of plants that absorb carbon dioxide, increasing atmospheric carbon and reducing photosynthesis.
Q45

: C4 plants have a modified pathway for capturing carbon dioxide, allowing them to photosynthesise more efficiently in hot, dry environments compared to C3 plants.
Q46: Photosynthesis removes carbon dioxide from the atmosphere, which helps mitigate the effects of climate change.
Q47: Higher temperatures can increase the rate of photosynthesis up to an optimal point, but extreme heat can denature enzymes, reducing the rate.
Q48: Photosynthesis is the first step in capturing solar energy and converting it into chemical energy, which is passed through the food chain.
Q49: Photosynthesis is limited by the availability of light, water, and carbon dioxide, and a deficiency in any of these factors slows the process.
Q50: The light-dependent reactions produce ATP and NADPH, which provide the energy and electrons needed for the Calvin cycle.
Q51: Photosynthesis absorbs carbon dioxide and produces oxygen, helping to regulate the Earth’s temperature and reduce global warming.
Q52: CAM plants open their stomata at night to minimise water loss, allowing them to photosynthesise in hot, dry environments.
Q53: Photosynthesis in aquatic plants can raise the pH of the water by removing carbon dioxide, which forms carbonic acid in water.
Q54: Photosynthesis was crucial for the development of life on Earth as it produced oxygen, allowing for the evolution of aerobic organisms.
Q55: Plants sequester carbon through photosynthesis, storing it in their biomass and helping to reduce atmospheric carbon levels.
Q56: Accessory pigments like carotenoids capture additional light wavelengths that chlorophyll cannot absorb, increasing photosynthesis efficiency.
Q57: Artificial lights, particularly those that emit red and blue wavelengths, can be used to enhance photosynthesis in indoor plants.
Q58: Higher atmospheric carbon dioxide levels can increase photosynthesis rates, but other factors like water and nutrient availability may limit this effect.
Q59: Climate change can lead to droughts, reducing water availability and slowing photosynthesis rates in affected ecosystems.
Q60: Stomatal density affects how much carbon dioxide enters the leaves, influencing the overall rate of photosynthesis.

This set of questions provides a comprehensive understanding of photosynthesis and its role in supporting ecosystems, tailored for Key Stage 3 students.