Transcript Animals and Organisms in Desert Environments: By David Hawes

Animals and Organisms in Desert Environments:
By David Hawes and Ajusi Tabu
The Various Life Forms Inhabiting this Environment:
Iguana
Bandicoot
Thorny
devil lizard
Camel
Gazelle
Hedgehog
The Conditions of the Environment:
Desert rainfall has very little rainfall in a year because
there is very little moisture in the air to hold onto the heat
from the hot days, however, desert nights tend to be very
cold.
•
• Food and water is hard to find, as desert animals live in
ways that require very little energy at all and waste little
water.
• E.g.. Snakes, scorpions and lizards must hunt other
desert animals and organisms for food use, as they use
either by biting or by their venoms from abdomen to kill
their prey.
Animal Adaptations to Desert
Environment Conditions:
• Desert animals must know how to deal with lack of water and how to deal
with extremes in temperature.
• Desert animals get their water from food such as succulent plants, seeds or
prey.
• Desert animals prevent water leaving their bodies in a number of different
ways.
• E.g.. Kangaroo live in burrows which are used for the animal to stay cool
whilst in hot conditions, which produces more humid (damp) air inside the
burrow.
• Other animals have structural adaptations designed to save water.
• E.g.. Scorpions and wolf spiders have a thick outer covering, which reduces
moisture loss. The kidneys of desert animals concentrate urine, so that they
excrete less water.
Plant and Animal Adaptations to the Desert Environment:
• There are 3 basic methods plants and animals use to live in the desert:
• Expire-when the going gets tough in the desert, animals and plants may die, however, plants and animals may
leave behind seeds/eggs to reproduce species. This is what our annual wildflowers do, just like this Bahia and its
seeds.
•
Evade-animals may leave by going north or south, go up or down a mountain, change activity from day to night
from above ground to below. Here is a kangaroo rat asleep in its burrow during the hot day.
•Saves Energy:
By decreasing temperature difference between body and outside, the rate of heat loss is lowered, thus
reducing energy expenditure to replace the lost heat energy.
By slowing metabolism, all tissues use less energy.
•Saves Water:
By decreasing coetaneous water loss (lower body temperature means lower rate of evaporation out
external surface).
By decreasing excretory water loss (lower metabolism generates less urine and feces thus less water lost).
By decreasing respiratory water loss (fewer breaths per minute and less water lost per breath). Lower
metabolism requires slower breathing rate and lower TB means exhaled air is cooler, thus contains less
water.
• Endure-take it but animals have better desert adaptations unlike these types
of plants.
Plant Adaptations to Temperature
Change:
• Plants can be damaged at temperature extremes when enzyme structures
are altered or membranes change their properties. As many important
enzymes that are involved in photosynthesis and respiration are
embedded in plant membranes, extremes of temperature can be a major
concern.
• In cold conditions, extracellular ice formations causes dehydration.
Some plants can tolerate freezing temperatures as low as -50*C, by altering
their solute concentrations and through the lack of ice nucleating sites in cells
to prevent intracellular freezing.
• In hot desert conditions, plants have to develop a compromise between
access to gases for photosynthesis and access to gases for respiration by
keeping their stomatus open and cooling by evaporation. This risks
dehydration of that particular plant.
Strategies to endure the harsh Desert Conditions are many, but can be
Organised as follows:
Ways to endure lack of water:
• Store water-water can be stored by animals in fatty deposits in their tails and other tissues (e.g.. In the Gila monster’s
tail). Water can be stored in the roots, stems, and/or leaves of plants (succulents).
• Conserve water-minimise loss of water out of skin (coetaneous loss) from urine and faeces (excretory loss) and from
breathing (respiratory loss) through various means.
• Tolerate dehydration-many of the desert plants (e.g.. Prickly pear cactus) and animals (e.g.. Desert toads) can tolerate
great losses of water out of their bodies without dying.
Ways to endure high temperatures:
Reduce heat input-this can be done by staying out of the sun, by shading (e.g.. Spines/fur) by posture and
orientation (e.g.. Orienting leaves vertically to minimise surface area directly hit by the sun) by insulation
and by shiny surfaces that reflect the sun.
•
• Dissipate
heat-if heat reduction wasn’t enough, then it’s time to get rid of body heat by evaporation (costs
water through), long appendages (legs, ears, etc) or small bodies (e.g.. Whole body leaves, etc) that radiates
heat.
• Tolerate hyperthermia-some plants and animals can survive body temperatures that would be dangerous to
humans (e.g.. This antelope squirrel tolerates body temperatures over 104 degrees F).
Identify the broad range of Temperatures over
which life is formed compared with the narrow
limits for Individual Species:
• Life in some form can be found at extremes ranging from - 40*C to
+120*C. However, the great majority of living organisms are found in
the – 2*C to +40*C range and for each individual species the range
is even narrower.
•Below 0*C, cells risk ice crystals forming in them and above 45*C,
proteins cells may denature.