Transcript Arid habitats

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
What are the challenges of living in
an arid habitat?
Lack of
plants
Lack of water
Challenges?
Lack
of food
Temperature
Movement
Cold
Hot
What is adaptation?
“the process whereby a species evolves characteristics
that enable it to survive in a particular habitat”
 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
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
Green tree frog
Takes refuge in any available
water sources, including pipes,
water tanks and toilet bowls!
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
Grandidier’s
baobab
Stores water in trunk
which can expand
after rainfall
Bristlecone pine
Parts of the living
tissue die back during
drought. Can still
produce cones and
seeds when
conditions improve
Activity 1
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 - Answers
Adaptation
Behavioural?
Being nocturnal

Physical?
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


Summary
• 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.
Activity 2
The aim of this activity is to compare how effective different
adaptations are at helping a species to conserve water.
You will be given sponges soaked in water to
represent your arid “animals”.
You need to design an experiment to measure how much
water your sponges lose under various conditions set up to
represent different adaptations.
You need to weigh the sponges before and after the
experiment so that you can record how much weight
(water) each has lost.