Vertebrate Adaptations to Local and Desert Ecosystems

Term 1, Week 4, Lesson 2

Do Now

Look at the image below of the Australian outback at midday in summer.

Australian outback at midday in summer — harsh sunlight, red soil.

In your book, list THREE challenges that a small mammal would face trying to survive here during a summer’s day.

You have 3 minutes.

Daily Review

Answer the following 5 multiple choice questions in your book:

1. A plant that releases seeds from its follicles only after being exposed to intense heat is described as:
   • 1. Deciduous
   • 2. Serotinous
   • 3. Epiphytic
   • 4. Xerophytic
2. A lignotuber is classified as which type of adaptation?
   • 1. Behavioural
   • 2. Physiological
   • 3. Structural
   • 4. Ecological
3. Grass trees (Xanthorrhoea) can resprout rapidly after bushfire because they have:
   • 1. Serotinous cones
   • 2. Thick, fire-resistant bark
   • 3. Very deep tap roots
   • 4. Lignotubers at the base of their stems
4. In which type of WA plant would you most commonly find epicormic buds?
   • 1. Mangroves
   • 2. Desert succulents
   • 3. Eucalypts
   • 4. Rainforest ferns
5. Which of the following correctly classifies the fire-adaptive trait?
   • 1. Thick bark — physiological
   • 2. Serotinous follicles — behavioural
   • 3. Lignotuber — structural
   • 4. Epicormic buds — behavioural

Learning Intentions

Today we are learning about how vertebrates in south-west WA and Australian desert ecosystems display structural, behavioural and physiological adaptations that help them survive in hot, dry conditions.

Success Criteria

You will be successful if you have:

• Identified at least three vertebrate adaptations found in local or desert-dwelling animals
• Correctly classified each adaptation as structural, behavioural or physiological
• Explained how each adaptation improves the animal’s ability to survive in hot, dry conditions

Keywords

Nocturnal

Active at night and resting during the day. A behavioural adaptation to avoid the intense heat of the day, which reduces the risk of overheating and dehydration.

Pinnae

The external, visible portions of the ears. In desert animals such as the bilby, enlarged pinnae provide a greatly increased surface area for radiating excess body heat.

Torpor

A state of reduced metabolic activity and body temperature in which an animal conserves energy and water during periods of extreme heat, cold or food scarcity. Different from hibernation, which lasts months; torpor can last hours or days.

Diurnal temperature variation

The difference in temperature between the hottest part of the day and the coolest part of the night. In the Australian desert, this can exceed 30°C — a variation that animals exploit through behavioural adaptations.

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Learning Activities

Activity 1 — I DO: How Vertebrates Survive in Hot, Dry Environments

The Challenges

Vertebrates living in hot, arid ecosystems face three main challenges:

Challenge	Consequence
High temperatures	Risk of overheating and protein denaturation
Water scarcity	Risk of dehydration; water must be conserved
Food scarcity	Energy must be used efficiently

Key Vertebrate Adaptations

1. Nocturnal Behaviour — Bilby (Macrotis lagotis)

Greater bilby emerging from burrow at night in Australian desert.

The greater bilby is found across the Kimberley and arid regions of WA. It is entirely nocturnal:

• Spends the day in a deep spiral burrow (up to 2 m deep) where temperatures remain much cooler than the surface.
• Emerges at night to forage when temperatures can be 20–30°C lower than midday.
• Reduces water loss through respiration by avoiding the hottest, driest part of the day.

Type of adaptation: Behavioural (nocturnal activity) + Structural (adapted for burrowing — strong forelimbs, wedge-shaped snout)

2. Large Pinnae (Ears) — Bilby

Close-up of bilby large ears showing blood vessels for thermoregulation.

The bilby’s distinctive large ears serve a thermoregulation function:

• The thin skin of the ears contains a dense network of blood vessels close to the surface.
• Warm blood from the body core flows through these vessels, and heat radiates out into the cooler night air.
• This lowers the animal’s core body temperature without needing to use water (unlike sweating or panting).

Type of adaptation: Structural

3. Concentrated Urine Production

Kidney nephron and water reabsorption in desert mammals.

Many arid-zone vertebrates have kidneys that are adapted to reabsorb water very efficiently:

• The loop of Henle in the kidney nephron is longer in desert-adapted mammals, creating a steeper osmotic gradient.
• This allows more water to be reabsorbed from urine before it is excreted, producing very concentrated urine.
• The animal loses less water through excretion, conserving body fluids.

WA examples: bilby, red kangaroo (Osphranter rufus), spinifex hopping mouse (Notomys alexis).

Type of adaptation: Physiological

4. Pale / Sandy Colouration — Thorny Devil (Moloch horridus)

Thorny devil on red sandy desert soil showing camouflage colouration, Western Australia.

The thorny devil is found across the arid and semi-arid regions of WA. Its pale, sand-coloured scales:

• Provide camouflage against the red-orange sandy desert substrate, reducing predation risk.
• Lighter colours also reflect more solar radiation, reducing heat gain from sunlight.
• Its spiky body surface also collects dew overnight, channelling moisture to its mouth via capillary action — a remarkable physiological adaptation.

Type of adaptation: Structural (colouration and body spines)

5. Burrowing — Marsupial Mole (Notoryctes typhlops)

Marsupial mole in sandy desert soil showing adaptations for burrowing.

The marsupial mole spends almost its entire life underground:

• Powerful, spade-like forelimbs and a hardened nose cone for pushing through sand.
• No functional eyes (vestigial) — no need for vision underground.
• Underground temperatures are significantly cooler and more stable than the surface.

Type of adaptation: Structural (body form) + Behavioural (underground lifestyle)

Summary Table

Adaptation	Type	Animal	How It Helps
Nocturnal behaviour	Behavioural	Bilby	Avoids peak heat; reduces water loss
Large pinnae	Structural	Bilby	Radiates excess body heat
Concentrated urine	Physiological	Bilby, kangaroo, hopping mouse	Conserves water
Sandy/pale colouration	Structural	Thorny devil	Camouflage + reflects solar radiation
Burrowing	Structural + Behavioural	Marsupial mole, bilby	Escapes heat; stable temperature underground

Check for Understanding

True or False: Write T or F for each statement.

Statement	T / F
Nocturnal behaviour is a physiological adaptation.
The bilby’s large ears help it radiate body heat.
A longer loop of Henle in the kidney helps conserve water.
The thorny devil’s colouration is a behavioural adaptation.
Burrowing is an example of a structural adaptation.

Answers: F, T, T, F, F (burrowing is behavioural; the body structure enabling it is structural)

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Activity 2 — WE DO: Comparing Two WA Desert Vertebrates

As a class, we will compare the adaptations of the bilby and the thorny devil.

Bilby and thorny devil comparison — desert adaptations, Western Australia.

Guided Comparison Table

For each animal, identify one structural, one behavioural and one physiological adaptation:

Adaptation	Bilby	Thorny Devil
Structural
Behavioural
Physiological
Ecosystem challenge addressed

Discussion Questions

• Both animals live in the same desert ecosystem but are very different in body size. How does body size affect the challenge of thermoregulation?
• The thorny devil collects dew through its skin and body spines. Is this a structural, behavioural or physiological adaptation? Justify your answer.
• Could the bilby survive in the south-west WA jarrah forest? What adaptations would or would not be useful there?

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Activity 3 — YOU DO: Vertebrate Adaptations to Local and Desert Ecosystems

Complete the worksheet: 142-vertebrate-adaptations-local-desert-you-do.docx

You will match vertebrate adaptations to their function, classify them, and write a short explanation for a chosen WA desert species.

Work independently. You have 10 minutes.

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Notes

Use this space to write any important points from today’s lesson.

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Reflection

1. Being active at night to avoid heat is classified as:
   • 1. Structural
   • 2. Physiological
   • 3. Behavioural
   • 4. Ecological
2. The bilby’s large ears help it survive in the desert by:
   • 1. Improving its hearing to detect predators
   • 2. Radiating excess body heat
   • 3. Collecting morning dew
   • 4. Shading its eyes from the sun
3. Producing very concentrated urine in desert mammals is which type of adaptation?
   • 1. Structural
   • 2. Behavioural
   • 3. Physiological
   • 4. Physical
4. Which WA animal uses both deep burrowing and nocturnal behaviour to avoid heat?
   • 1. Red kangaroo
   • 2. Thorny devil
   • 3. Wedge-tailed eagle
   • 4. Bilby
5. Short answer: Explain why burrowing is an effective adaptation for a desert mammal on a day when the surface soil temperature reaches 65°C. Mention what is happening to the temperature underground.

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Home-study

Choose a WA vertebrate animal not mentioned in today’s lesson that lives in a hot, dry environment. Identify and describe one of its adaptations and classify it as structural, behavioural or physiological. Write 3–4 sentences.