Which of the following are plausible hypotheses that could explain why mammals never evolved unidirectional airflow through their lungs, while birds did? Select one or more: a. Mammals may have never experienced a need for unidirectional flow in their evolutionary past. b. The necessary alleles of developmental genes to develop associated structures of unidirectional flow never arose in mammals. c. Mammal-like lungs and bird-like lungs occupy different fitness optima in terms of having optimized capacity for gas exchange, and individuals of intermediate phenotype necessary to change to a bird-like lung would have to cross a valley in the fitness landscape. d. Unidirectional airflow would only benefit individuals but not the species overall. e. The necessary changes might need to happen at such an early developmental stage that altering the expression patterns of the genes involved might cause some additional severe developmental anomalies.

The laminar airflow or the unidirectional airflow refers to the air velocity in a straight unrestrained path. The airflow in the birds is largely fresh and more plentiful in oxygen content.

The correct answer is:

Option E. The significant changes might require to happen at such an early developmental stage that modifying the expression models of the genes associated might cause some further severe developmental anomalies.

This can be explained as:

Therefore, birds have unidirectional airflow.

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e. The necessary changes might need to happen at such an early developmental stage that altering the expression patterns of the genes involved might cause some additional severe developmental anomalies.

Explanation:

Birds fly mainly at higher altitude when the air is very thin and thus the oxygen concentration is very low. Thus, to compensate for it birds have unidirectional air flow thereby leading to a higher oxygen concentration. However mammals despite of this model being more efficient don't have it because this might interrupt with the functioning of other organs. The appropriate answer is option E

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