Year 8 Science · Unit 1 · Lesson 1
Challenge Worksheet
Learning Goals
Read the graph
The bar chart below shows the approximate size of four biological structures. Study the chart and answer the questions below.
Data: approximate values based on standard cell biology references (Alberts et al., Molecular Biology of the Cell, 6th ed.)
(a) Which structure is the smallest, and approximately how many times smaller is it than a red blood cell?
(b) How many times larger is the egg cell than the bacterium? Show your working.
(c) The red blood cell has no nucleus and is biconcave in shape. Using this and the size data in the graph, explain why the red blood cell is well suited to its function of carrying oxygen.
Evaluate the claim
Someone claims...
"A cell is just a tiny version of an organism. It can do everything an organism does, it digests food, breathes, moves and reproduces, so there is no real difference between the two. If you made a cell big enough, it would essentially be the same as a whole organism."
(a) What part of this claim is supported by the science you have learned? Identify at least one point the claim gets right.
(b) What is misleading or missing from this claim? Explain what the claim fails to account for when it says a cell is "the same as" an organism.
(c) A specialised cell such as a human red blood cell cannot survive on its own outside the body for long. What does this tell you about the relationship between cells and the higher levels of organisation (tissues, organs, organ systems)?
1. Muscle tissue is made of many similar muscle cells. Explain how this is different from an organ, using the heart as your organ example.
2. A unicellular organism like an amoeba must carry out all life processes in a single cell. Explain why this limits what it can do compared to a multicellular organism like a kangaroo.
Wrap Up
In one sentence, what was the main idea of this lesson?