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Question
Please read this article and answer questions> https://academic.oup.com/bioscience/article/55/5/416/226046
What environmental conditions do desert animals face? What adaptations would be predicted in desert animals?
Where does the idea that desert birds lack physiological specialization come from?
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?
What is the main finding regarding energy adaptation in desert birds?
Figure 1 includes two scatterplots of BMR and FMR with body mass. Best-fit equation lines are
included which correct for phylogeny.
Explanation / Answer
In the desert environments, solar radiation is intense, air temperature is extreme, low relative humidity, unpredictable and scanty rainfall, and very low primary productivity is seen. The selection pressure is seen strongly on the physiological attributes of the animals living there. There will be an adjustment in the rate of energy expenditure towards the minimum, in the rate of water loss, and in the tolerance of high body temperatures.
The birds living in deserts have the difficulty of balancing energy and water necessity with their energy expenditure and water loss. This makes them struggle for existence.
Many authors do not accept that desert birds have physiological adaptations to deserts or they trigger preadaptation. This is not accepted partly because, the birds that do not have desert adaptation might fly to the places where the environment is conducive. The research also provides evidence that birds do not have specifically evolved physiological adaptations to the desert environments.
The evidence include the selection of birds able to survive in deserts have reduced oxygen consumption at the tissue level and the sum of cutaneous water loss and respiratory water loss is reduced. The water loss reduction is due to the alterations in the lipid structure of the stratum corneum in the skin that acts as a physical barrier to diffusion of water vapor.
Adaptation
An adaptation stresses on the past evolutionary history. For a character to be adaptive, it must have been derived from the specific selective agent. Adaptation is a process that emphasizes the utility of the current trait. Adaptation is the phenotypic trait that leads to highest fitness among the highest set of variants in a given environment.
Energy
The selective advantages attributed to the reduced basal metabolism includes lower overall energy demand, lower respiratory water loss due to reduced ventilation frequency, lower production of endogenous heat which will be dissipated in a warm environment through the process of evaporation.
The basic metabolic rate of desert birds to non-desert birds was analyzed as the function of body mass. The results showed that BMR of desert birds was 17 to 25% lower than that of non-desert birds. The field metabolic rate or FMR was found to be 49% lower in desert birds than in the non-desert birds.
The rate of living is influenced by the natural selection in the desert birds. Differences in metabolism in temperate birds were attributed to the selection of a large size of the organs with high metabolic intensity and high oxygen consumption per unit tissue like liver, kidney, heart. These organs are expected to maintain the levels of energy expenditure during the time of peak energy demand.
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