Year 7 Science · Unit 1 · Lesson 09
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Learning Goals
Real-world context
Sickle cell anaemia is a genetic condition that affects approximately 1 in 365 African-American births and is also found in parts of Australia and the Torres Strait Islander communities. People with this condition produce abnormal haemoglobin that causes red blood cells to take on a rigid crescent (sickle) shape rather than the normal flexible biconcave disc shape. These sickle-shaped cells clump together and can block small capillaries, cutting off oxygen supply to organs and causing severe pain and organ damage.
(a) A normal red blood cell has a biconcave disc shape with no nucleus and is packed with haemoglobin. Identify which of these structural features are lost or changed in a sickle cell, and describe what a normal red blood cell looks like.
(b) The biconcave shape allows red blood cells to bend and squeeze through narrow capillaries. Using this information, explain why sickle-shaped cells block blood vessels and why this is dangerous for the body.
Because… chain
Fill in the missing effects in the chain below. Each cause leads to the next step. Shaded boxes are given — write in the empty boxes.
Overall outcome — why leaves at the top of a plant have more palisade cells than shaded lower leaves:
1. A root hair cell has a long thin extension that increases its surface area. Explain why having a larger surface area helps the plant absorb more water from the soil.
2. A neuron can have an axon up to 1 metre long. Explain how this structural feature suits its function of carrying electrical signals from the brain to distant parts of the body. What would happen if neurons were very short instead?
Wrap Up
In one sentence, what was the main idea of this lesson?