Year 7 Science · Unit 1 · Lesson 16

Adaptations

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Learning Goals

Warm Up

Read the graph

Study the bar chart below, then answer the questions.

Daily water loss rate in Australian desert animals Daily Water Loss Rate in Australian Desert Animals Water loss (mL/day) — log scale 0.001 0.05 800 2500 2,500 mL Camel 800 mL Sand goanna 50 mL Desert mouse 1 mL Desert frog*

*Desert frog shown while aestivating (sealed in mucus cocoon, dormant during dry season). Data: estimated from Spotila & Berman (1976) and Warburg (1971), Australian herpetology literature.

(a) Which animal loses the least water per day, and approximately how much does it lose?

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(b) The desert frog seals itself in a mucus cocoon and enters aestivation during dry periods, remaining dormant underground. Classify this as structural, behavioural or physiological, and justify your choice.

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(c) Explain how a camel's physiological adaptations help it conserve water in the desert. Use at least one specific example.

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Your Turn

Order the steps

Number the events from 1 to 6 to show the correct order in which natural selection produces an adaptation over many generations. Event 1 = what happens first.

OrderEvent
The proportion of individuals in the population that carry the beneficial trait increases with each generation.
Organisms with the beneficial trait survive long enough to reproduce more successfully than those without it.
The beneficial trait is passed from parents to offspring through inheritance.
Random variation in a particular trait exists across individuals in the population.
Over many generations, the trait becomes so common that it is characteristic of the species — it is now an adaptation.
The environment creates survival pressure — for example, predators, food scarcity or extreme temperatures.

Show What You Know

1. A camel and a desert mouse both live in hot, dry environments, yet the graph shows they lose very different amounts of water each day. Using your knowledge of adaptations, suggest two reasons why a smaller animal might lose proportionally less water than a larger one.

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2. A friend says: "Giraffes got long necks because they stretched up into tall trees over their lifetime, and their babies inherited that longer neck." Using what you know about how adaptations actually develop, explain what is wrong with this idea.

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Wrap Up

In one sentence, what was the main idea of this lesson?

HSCScience · Year 7 Science · Unit 1 · Lesson 16 · Apply Worksheet