Year 9 Respiration and Ecosystems Worksheet - Intermediate

Year 9 Respiration and Ecosystems worksheet for Year 9 (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)•Respiration and Ecosystemsintermediate

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Energy, Ecosystems and Food Chains

Year 9 Science • Ages 13–14 • Intermediate

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Instructions: Complete the five activities in order, showing working where a question involves data or a calculation. Use precise scientific vocabulary, including reactants, products, interdependence and bioaccumulation. Check that each answer is supported by the information given or by your knowledge of respiration and ecosystems.

Aerobic Respiration: Equation and Conditions

Complete the word equation using the word bank. Then answer the questions using your knowledge of aerobic respiration. Remember that energy is transferred by the process; it is not a substance used up like a reactant.

Word bank: oxygen, carbon dioxide, glucose, water

1. Complete the word equation:

___ + ___ → ___ + ___

2. Name the organelle in most human cells where aerobic respiration mainly takes place.

3. State one reason muscle cells need energy released by respiration during exercise.

4. Explain why a person breathes more rapidly during vigorous exercise.

Anaerobic Respiration: Humans and Microorganisms

Use the word bank to complete the two equations, then compare the products. In your explanations, distinguish respiration without oxygen from aerobic respiration and identify a useful application of microbial anaerobic respiration.

Word bank: lactic acid, ethanol, carbon dioxide, glucose

1. In human muscle cells, glucose → ___

2. In yeast, glucose → ___ + ___

3. Name the type of respiration that releases more energy per glucose molecule: aerobic or anaerobic.

4. Give one use of anaerobic respiration by yeast in food production.

Respiration and Photosynthesis Compared

Compare the two processes using the word bank and your knowledge of plant cells. For the final question, explain how the processes are connected in a plant rather than simply stating that they are opposites.

Word bank: carbon dioxide, oxygen, glucose, water

1. Photosynthesis uses ___ and ___ to make glucose and oxygen.

2. Which process transfers energy from glucose for cell activities: photosynthesis or respiration?

3. State one way the products of photosynthesis are used in respiration.

4. Explain why a plant respires both during the day and at night, while photosynthesis requires light.

Ecosystems and Interdependence

Study the food chain and the data table. Arrows in a food chain show the direction in which energy is transferred—from the organism eaten to the organism that eats it. Use the table values to support your response to the final question.

Food chain: grass → grasshopper → frog → heron

Organism	Number observed	Food source
Grass	120	Sunlight
Grasshopper	48	Grass
Frog	12	Grasshopper
Heron	3	Frog

1. Which organism in the chain is the primary consumer?

2. What does the arrow from frog to heron show?

3. Predict one possible effect on the frog population if the grasshopper population falls sharply.

4. Give one reason the organisms in this ecosystem are interdependent.

Toxic Materials in Food Chains

Use the data table to identify the pattern in pesticide concentration. The concentrations are measured in the same units, so compare the figures directly. Explain the pattern using the idea that a predator may consume many contaminated prey over time.

Organism in food chain	Pesticide concentration (units)
Water	0.02
Plankton	0.3
Small fish	2.4
Large fish	18
Heron	96

1. Which organism has the highest pesticide concentration?

2. How many times greater is the heron’s concentration than the large fish’s?

3. Describe the overall pattern in pesticide concentration along this food chain.

4. Explain why a top predator can accumulate a higher concentration of a persistent toxic substance than organisms lower in the food chain.

Answer Key

Activity 1: 1. Glucose + oxygen → carbon dioxide + water ; 2. Mitochondrion (mitochondria) ; 3. Any valid example, such as muscle contraction or movement ; 4. To take in more oxygen and remove the extra carbon dioxide produced as the muscles respire more rapidly

Activity 2: 1. Lactic acid ; 2. Ethanol + carbon dioxide ; 3. Aerobic ; 4. Any valid example, such as bread-making or brewing

Activity 3: 1. Carbon dioxide and water ; 2. Respiration ; 3. Glucose and/or oxygen are used in respiration ; 4. Respiration releases energy needed for cell activities and does not require light; photosynthesis requires light to make glucose

Activity 4: 1. Grasshopper ; 2. Energy and matter are transferred from the frog to the heron when the heron eats it ; 3. The frog population may decrease because there are fewer grasshoppers to eat ; 4. Any valid example, such as the frog depends on grasshoppers for food, or the heron depends on frogs for food ; table data: Grass 120 and sunlight, grasshopper 48 and grass, frog 12 and grasshopper, heron 3 and frog

Activity 5: 1. Heron ; 2. 96 ÷ 18 = 5⅓ times (approximately 5.3 times) ; 3. Concentration increases at each successive level from water to heron ; 4. Persistent toxins are not readily broken down or excreted; predators eat many contaminated organisms, so the toxin accumulates and becomes more concentrated at higher trophic levels