Year 8 Science · Unit 1 · Lesson 12
Challenge Worksheet
Learning Goals
Evaluate the claim
Someone claims...
"A living system is basically like a one-way street, you just need to keep putting in food, water and oxygen, and the body will automatically sort itself out. There is no need to worry about waste removal because the body is designed to use everything it takes in, so there is nothing left to remove. The digestive, respiratory and circulatory systems are all you need, the excretory system is optional."
(a) What part of this claim is partially correct? Identify at least one accurate idea in the statement.
(b) Identify at least two scientific errors in the claim. For each one, explain what the correct idea should be.
(c) Using the input-output model from this lesson, write a corrected version of the claim in two or three sentences.
1. Think of a living system as a cycle: inputs → cell processes → outputs. Using this idea, explain why removing waste is just as important as taking in food and oxygen. Give one specific example of a waste that must be removed from the body, and explain what would happen if it built up.
2. A student has studied lessons 9–12. Write a short paragraph (3–4 sentences) connecting the roles of the circulatory system, respiratory system, digestive system and excretory system as part of one complete living system. Use the words input, output, transport and waste in your answer.
Wrap Up
In one sentence, what was the main idea of this lesson?