Animals and Organisms in Desert Environments: By David Hawes and Ajusi Tabu

1. Animals and Organisms in Desert Environments:By David Hawes and Ajusi Tabu

2. The Various Life Forms Inhabiting this Environment: Iguana Bandicoot Thorny devil lizard Camel Gazelle Hedgehog

3. 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.

4. 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.

5. 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.

6. Endure-take it but animals have better desert adaptations unlike these types of plants.

7. 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.

8. Strategies to endure the harsh Desert Conditions are many, but can be Organised as follows: • Ways to endure lack of water: • Storewater-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). • Conservewater-minimise loss of water out of skin (coetaneous loss) from urine and faeces (excretory loss) and from breathing (respiratory loss) through various means. • Toleratedehydration-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.

9. Ways to endure high temperatures: • Reduceheatinput-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. • Dissipateheat-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. • Toleratehyperthermia-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).

10. 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.