ead Article here https://academic.oup.com/bioscience/article/55/5/416/226046 1.

Question

ead Article here https://academic.oup.com/bioscience/article/55/5/416/226046 1. What environmental conditions do desert animals face? What adaptations would be predicted in desert animals? 2. Where does the idea that desert birds lack physiological specialization come from? 3. Preadaptation is mentioned as an explanation of the lack of physiological specialization in desert birds; however, it is not fully described. What do you think is meant by preadaptation? 4. What is the main finding regarding energy adaptation in desert birds? 5. Figure 1 includes two scatterplots of BMR and FMR with body mass. Best-fit equation lines are included which correct for phylogeny. a. What is the reason for a correction for phylogeny? (Hint: check the article text). b. Why is a correction for phylogeny not needed for Figure 2? 6. What is TEWL? Why do desert birds face the greatest problems of dehydration compared with other vertebrates? 7. Reduced TEWL is suggested for birds. How would each of the following contribute to reduced TEWL? a. Hyperthermia b. Decreased respiratory water loss c. Decreased cutaneous water loss 8. What is the main finding regarding TEWL adaptation in desert birds? 9. What aspects of desert bird life history were examined? What is the main finding regarding life history adaptation in desert birds? 10. What did you find most interesting about the article?

Explanation / Answer

Any characteristic change in the physical build up or behavior of an organism that increases the chances of its survival in extreme environment is termed as adaptation. Animals living in desert have to cope with high temperature conditions and extreme dryness. Many organisms surviving in these areas are nocturnal i.e. they remain active during the night or are crepuscular which means that they remain active during dawn and dusk. This strategy prevents the animals from getting exposed to harsh environmental conditions. Physical adaptations allow the body to dissipate more heat. Example- Long limbs and large ears provide them with more surface area to radiate heat from the body. Animals like the camel store fat in one particular area such as hump providing more surface area to dissipate heat. Light or pale body color is another adaptation which helps them to blend with the surroundings to camouflage them from predators and helps in less absorption of heat. Reptiles possess tough, thick skin that doesn't allow water to be lost from the body. Desert mammals have few sweat glands. Small mammals and rodents dig burrows in the desert soil and this helps them to escape extreme surface temperature.

Evaporation of water from the surface cools that body. Water balance is important for the survival of birds in hot conditions. The phenomenon of total evaporative water loss (TEWL) has been noted in desert birds. It is the sum of cutaneous water loss (CWL) and respiratory water loss. Reduction of TEWL has been noted in desert species. It is a physiological trait and a way of natural selection. The reduction in CWL is attributable to changes in the lipid structure of the stratum corneum of the skin. Besides reduced rate of metabolism, the birds also have a small clutch size and slow nestling development. The low rate of metabolism leads to reduced oxygen consumption at the tissue level under basal conditions. Example- desert larks have shown low rate of energy metabolism and this low metabolic rate translates into a lower overall energy requirement. These attributes are correlated with traits that affect reproductive success. Dilation of the blood vessels in scaly leg also helps in avoiding/removing excess body heat.

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