1. Arid Environments E3176 Erçin Öncel E3331 Vassilis Bitsikas E3175 Aslıhan Çoban School of Sciences Department of Biology Do Minho University Animal Physiology 14.01.2010

7. Deserts in the World

16. Physiological and behavioural adaptations

26. tough, dry, heavily keratinized skin shelled, amniotic egg Adaptations that unshackled reptiles from the aquatic environment. No more dependence on aquatic or very moist terrestrial environments.

27. Arthropod cuticle Lipid-like deposits provide waterproof properties and minimise water losses by reducing the cuticular transpiration

28. Specialized spiracle structure that minimises water loss

29. Behavioural thermoregulation

30. A ctivity of the antelope ground squirrel Ammospermophilus leucurus during a typical day in the Nevada desert Ammospermophilus is an evader but a degree of endurance is indicated too.

31. Adaptive heterothermy The ability of an endothermic animal to allow its body temperature to fluctuate in response to some form of environmental stress. Saving significant amounts of energy and water. Maximum fluctuation during 1 day: 6,2 ° C

32. Osmoregulation Period of dehydration: day 4 - 12

33. Negative f eedback control of the secretion of antidiuretic hormone, ADH

34. T wo types of nephron, distinguished by the length of their loops of Henle Most mammalian kidneys contain a mixture of the two types but some species have only one or the other

36. Uric acid is highly insoluble and easily precipitates from solution, allowing its removal in almost solid form. Excertion The key feature that seems to determine choice of nitrogenous waste is availability of water in the environment.

42. Conclusions The key to the survival in hot, dry environments consists in avoiding climatic extremes as far as possible, by a combination of seeking refuge from the most adverse conditions, morphological adaptations, behaviour and specialized physiology. Whereas thermal reactions are primarily behavioural, adaptational responses to aridity are mostly physiological. Exploitation of desert habitats involves a vast complex of adaptive compromises between set of factors.