Adaptations to Arid Habitats

What is an arid habitat?

Arid habitats:

are extremely dry

receive little or no rainfall

usually have high temperatures

may suffer periodic droughts

Where are arid habitats found?

Estimates suggest that arid and semi arid habitats account for more than one third of the earth’s land surface

Credit: U. S. Geological Survey

Lack of food

What are the challenges of living in an arid habitat?

Lack of plants

Movement

Lack of water

HotCold

Temperature

Challenges?

“the process whereby a species evolves characteristics that enable it to survive in a particular habitat”

What is adaptation?

Adaptations allow species to live successfully in their habitat

Species living in different habitats need different adaptations

Adaptations can be behavioural or physical

Barrow Island: Case Study

- Approximately 70 km off the coast of Western Australia

- Receives an average of 320 mm rainfall per year

- Most of the island is covered by spinifex grassland

- Nearly 2,600 different species have been recorded here

A flooded channel on the west coast of the island, a rare and important source of freshwater on Barrow

Mammals on Barrow Island

Common wallaroo (Macropus robustus)

Found across most of Australia, with one subspecies on Barrow Island

Seeks shelter in caves and rocky outcrops

Can go for a few months without drinking

Licks saliva onto forearms to help it lose heat through evaporation

Stops breeding during prolonged droughts, but breeds quickly in good conditions

Other mammal examples

Wild Bactrian camel

Many adaptations to conserve water, cope in intense heat and survive sandstorms!

Bat-eared fox

Large ears to help dissipate heat

Fawn hopping mouse

Can obtain water from seeds

Produces concentrated urine + dry faeces

Shelters in a burrow during day

Kangaroo rats

‘Nasal counterflow system’ reduces water lost through breathing

Amphibians on Barrow Island

Main’s frog (Litoria maini)

Only amphibian species found on Barrow Island

Spends the dry season underground in a state of torpor

Produces a membrane over the skin to prevent drying out

Only emerges after rainfall

Eggs laid in temporary pools, tadpoles develop quickly

Other amphibian examples

Green tree frog

Takes refuge in any available water sources, including pipes, water tanks and toilet bowls!

Spotted marsh frog

Shelters under logs and stones in the heat of the day

Water holding frog

Can reabsorb water stored in its bladder or pockets under the skin

Reptiles on Barrow Island

Perentie (Varanus giganteus)

General adaptations common to reptiles

Shelters underground or in rock shelters; basks in sun in early morning and late afternoon

On very hot days, may shelter in shade or climb termite mounds or shrubs to get off hot ground

Other reptile examples

Thorny devil

Tiny grooves over body direct moisture to the mouth

Can change colour depending on temperature

Desert tortoise

Dormant during hottest part of summer (aestivation)

Lives in burrows

Eastern sandfish

Streamlined body allows it to ‘swim’ through sand

Saudi fringe-fingered lizard

Fringes of elongated scales on the toes help in moving across sand

Sidewinder

‘Sidewinding’ movement across loose sand

Plants on Barrow Island

Spinifex grass (Triodia species)

Extensive root system to collect water both from the surface and underground. Roots can be up to 3 metres long.

Leaves have a waxy, impermeable surface (cuticle) to reduce water loss.

Leaves curl inwards into long pointed tubes to slow the rate of transpiration.

Other plant examples

Lava cactus

Stores water in thick stems, leaves

reduced to spines to reduce transpiration

Bristlecone pine

Parts of the living tissue die back during

drought. Can still produce cones and

seeds when conditions improve

Grandidier’s baobab

Stores water in trunk which can expand

after rainfall

You will be given a worksheet with a list of adaptations

species use to survive in arid habitats.

Your task is to decide whether each adaptation is a

behavioural or a physical adaptation.

Activity 1

Activity 1 - AnswersAdaptation Behavioural? Physical?

Being nocturnal

Impermeable skin

Producing concentrated urine

Aestivation

Panting

Ability to withstand high body temperatures

Seeking shade

Ability to store water inside the body

Light colouration

Living in a burrow

Large surface area

Leaves reduced to spine

Breed only after rainfall

Nasal counterflow

• Arid habitats are dry areas with little rainfall and are usually hot, although they can be cold at night.

• Arid habitats cover over a third of the Earth’s land surface.

• Animals and plants have evolved a range of adaptations to help them survive in arid habitats.

• These adaptations can be behavioural, such as sheltering in a burrow during the heat of the day, or physical, such as having a large surface area to lose heat more quickly.

Summary

Activity 2The aim of this activity is to compare how effective differentadaptations are at helping a species to conserve water.

You will be given sponges soaked in water torepresent your arid “animals”.

You need to design an experiment to measure how muchwater your sponges lose under various conditions set up torepresent different adaptations.

You need to weigh the sponges before and after theexperiment so that you can record how much weight(water) each has lost.