Biology • Year 11 • Module 3 • Lesson 2
Adaptations
Apply the three adaptation categories to data, reason about convergent adaptation, and interpret Australian organism examples.
1. Complete the Australian organism adaptation table
The table below shows three Australian organisms. Use the lesson content to complete the empty cells. 9 marks, 1 per correct cell
| Organism | Structural adaptation | Physiological adaptation | Behavioural adaptation |
|---|---|---|---|
| Thorny devil (Moloch horridus) | Metabolism slows in colder conditions | ||
| Red kangaroo | Crepuscular activity reduces exposure to extreme daytime heat | ||
| Acacia | Phyllodes reduce water loss compared with broad leaves |
2. Analyse a convergent adaptation claim
Use the information below to answer the questions. 8 marks
Scenario. Both the cactus family (Cactaceae) found in the Americas and the euphorbia family (Euphorbiaceae) found in Africa include species with spines, swollen water-storing stems, and reduced or absent leaves. These two plant groups are not closely related and belong to separate evolutionary lineages. Both groups evolved their similar features independently in dry, arid environments.
2.1 Identify the adaptation type (structural, physiological, behavioural) for each feature listed: spines, water-storing stems, reduced leaves. Justify one of your choices. 2 marks
2.2 Explain why these similar features in cacti and euphorbias are best explained by convergent adaptation rather than close ancestry. 2 marks
2.3 What environmental selection pressure is most likely responsible for driving both plant groups toward these similar features? 2 marks
2.4 Name one other example of convergent adaptation from the lesson and state the selection pressure that explains it. 2 marks
3. Cause-and-effect chain, how an adaptation becomes more common
Complete the cause-and-effect chain by filling in each empty box. The first box is done for you. 5 marks
Step 1: This variation in kidney function is _________________________ (i.e. can be passed to offspring).
Step 2: In a desert environment with scarce water, the selection pressure is _________________________.
Step 3: Individuals that produce more concentrated urine _________________________ and _________________________ more successfully.
Outcome: Over many generations, the ability to produce concentrated urine becomes more common in the population, making it a _________________________ adaptation.
4. Applied scenario, is it really an adaptation?
Read each scenario and decide whether it describes a true biological adaptation. Explain your reasoning. 4 marks
4.1 A wolf builds thicker muscle by running long distances every day during its lifetime. 2 marks
4.2 Over many generations, wolves in a northern population become more likely to grow thicker winter coats because individuals with thicker coats survive colder winters better and leave more offspring. 2 marks
Q1, Australian organism table (marking criteria)
- Thorny devil: Structural Spines and skin grooves channel dew toward the mouth. Behavioural Sways while walking to mimic a dead leaf.
- Red kangaroo: Structural Powerful hindlimbs for efficient long-distance movement. Physiological Embryonic diapause delays development when resources are scarce.
- Acacia: Physiological Nitrogen-fixing root nodules support growth in poor soils. Behavioural Seed dormancy delays germination until conditions improve.
Award 1 mark per correctly completed cell. Accept other valid entries supported by lesson content.
Q2.1, Adaptation type and justification
All three features (spines, water-storing stems, reduced leaves) are structural adaptations [1] because they are physical features of anatomy. For example, spines are part of the plant’s physical structure; they are not an internal biochemical process or an action pattern [1 for justification of one choice].
Q2.2, Convergent adaptation explanation
These similar features are best explained by convergent adaptation because cacti and euphorbias are not closely related, they belong to separate evolutionary lineages [1]. Both groups faced similar selection pressures in dry environments and independently evolved similar solutions, so similarity reflects environmental pressure rather than shared ancestry [1].
Q2.3, Selection pressure
The most likely selection pressure is water scarcity / drought / arid conditions [1], which favours plants that conserve water through structural features such as spines (reducing leaf surface area), swollen stems (water storage) and reduced leaves [1 for linking selection pressure to adaptive features].
Q2.4, Other example
Accept: Streamlined bodies in sharks (fish) and dolphins (mammals) [1]. Selection pressure: efficient movement through water / aquatic locomotion [1]. Accept any other valid example from the lesson.
Q3, Cause-and-effect chain (marking criteria)
- Step 1: heritable / inherited [1]
- Step 2: water scarcity / limited water availability / dehydration risk [1]
- Step 3: survive / conserve water more effectively; reproduce [1]
- Outcome: physiological [1]
Q4.1, Wolf muscle (not an adaptation)
This is not a true biological adaptation [1]. Building muscle through exercise is a phenotypic change that occurs within one organism’s lifetime, and acquired changes of this kind are not inherited by offspring. An adaptation must be an inherited characteristic shaped by natural selection over many generations [1].
Q4.2, Thick winter coat (is an adaptation)
This is a true biological adaptation [1]. The trait (thicker coat) is heritable, the trait increases survival and reproductive success in the cold environment, and it has been selected over many generations through natural selection favouring individuals with thicker coats [1].