Year 8 Photosynthesis and Plants Worksheet - Intermediate

Year 8 Photosynthesis and Plants worksheet for Year 8 (Key Stage 3 / Year 7-9 (Ages 11-14)). Intermediate level science practice, aligned to the UK National Curriculum. Print-ready with answer key included.

Science•Key Stage 3 / Year 7-9 (Ages 11-14)•Plantsintermediate

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Photosynthesis and Plant Survival

Year 8 Science • Ages 12–13 • Intermediate

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Instructions: Complete each activity using the information and data provided. Use scientific vocabulary, show calculations where needed, and check that your explanations link plant structures and conditions to their functions.

Photosynthesis: The Word Equation

Complete each statement using the word bank. Then use the completed equation to explain what happens to the products. Remember that light energy is needed, but it is not a raw material in the word equation.

Word bank: carbon dioxide, glucose, light energy, oxygen, water

1. Photosynthesis uses ___ and ___ to make ___.

2. The other product released during photosynthesis is ___.

3. Write the complete word equation for photosynthesis, including the condition needed. [3 marks]

4. Give one way a plant can use the glucose it makes. [1 mark]

A Leaf Built for Photosynthesis

Use your knowledge of leaf tissues and their functions. Give precise answers and explain how each feature helps photosynthesis or gas exchange.

1. Which tissue near the upper surface contains many chloroplasts and carries out most photosynthesis? [1 mark]

2. Explain how a broad, flat leaf helps a plant photosynthesise. [2 marks]

3. What is the function of stomata, and which cells control whether they open or close? [2 marks]

4. Explain how the air spaces in the spongy mesophyll help gas exchange. [2 marks]

What Changes the Rate?

Read the results table carefully. Identify patterns using the figures, then apply the idea of limiting factors: increasing one condition may have little effect if another condition is limiting.

Light intensity (arbitrary units)	Carbon dioxide concentration (%)	Rate of photosynthesis (bubbles per minute)
20	0.04	8
40	0.04	15
60	0.04	21
60	0.08	30

1. At 0.04% carbon dioxide, how does the rate change when light intensity increases from 20 to 60 units? [1 mark]

2. At light intensity 60 units, how many more bubbles per minute are produced at 0.08% carbon dioxide than at 0.04%? [1 mark]

3. Name the two factors varied in the investigation. [1 mark]

4. State one other factor that can affect the rate of photosynthesis. [1 mark]

Minerals for Healthy Plants

Use the word bank to complete the statements about mineral ions absorbed from the soil. Each option is used once. Then explain the effect of a shortage.

Word bank: magnesium, nitrate, potassium

1. ___ ions are needed to make amino acids and proteins for growth. [1 mark]

2. ___ ions are needed to make chlorophyll. [1 mark]

3. ___ ions help plants grow well and support healthy flowering and fruiting. [1 mark]

4. Explain why a plant with too little magnesium may photosynthesise more slowly. [2 marks]

From Producers to Consumers

Use the food chain and food web below to answer the questions. Arrows point from the food to the organism that eats it, showing the direction in which energy is transferred.

Food chain: grass → grasshopper → frog → hawk

Food web links: grass → rabbit; grass → grasshopper; grasshopper → frog; grasshopper → small bird; rabbit → fox; frog → hawk; small bird → hawk

1. Which organism is the producer in the food chain? [1 mark]

2. In the food chain, which organism eats the grasshopper? [1 mark]

3. Name one consumer in the food web that eats grass directly. [1 mark]

4. Using the food web, give one possible effect on the hawk population if the number of grasshoppers falls. [2 marks]

Answer Key

Activity 1: 1. carbon dioxide; water; glucose ; 2. oxygen ; 3. carbon dioxide + water → glucose + oxygen (in the presence of light energy) ; 4. Any one: used in respiration; converted to starch for storage; used to make cellulose or other substances.

Activity 2: 1. Palisade mesophyll ; 2. A broad, flat surface absorbs more light / provides a large surface area for light absorption ; 3. Stomata allow carbon dioxide to enter and oxygen to leave; guard cells control their opening and closing ; 4. Air spaces provide a large internal surface and allow carbon dioxide and oxygen to diffuse through the leaf.

Activity 3: 1. It increases from 8 to 21 bubbles per minute, a rise of 13 ; 2. 9 bubbles per minute ; 3. Light intensity and carbon dioxide concentration ; 4. Temperature.

Activity 4: 1. Nitrate ; 2. Magnesium ; 3. Potassium ; 4. Magnesium is needed to make chlorophyll; a shortage reduces chlorophyll, so less light is absorbed and photosynthesis may slow.

Activity 5: 1. Grass ; 2. Frog ; 3. Rabbit or grasshopper ; 4. The hawk population may fall because fewer grasshoppers could mean fewer frogs and/or small birds for hawks to eat.