When Ectoparasites First Arrive and Adapt to the Fur or Feathery

question 26

Essay

When ectoparasites first arrive and adapt to the fur or feathery habitat of a host,they often lose more complex ancestral features.So it is possible to gain a trait in evolution and subsequently lose it.However,it is considered vastly improbable that this same trait will again re-evolve.Therefore,in trying to trace evolutionary lineages,can we always expect the most primitive forms to be the simplest and the most advanced to be the most complex? Why or why not?

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Definitions:

Pulmonary Arteries

The pulmonary arteries are the vessels that carry deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.

Pulmonary Veins

Veins that transfer oxygenated blood from the lungs to the left atrium of the heart.

EDV

End-Diastolic Volume, the amount of blood in the ventricles of the heart immediately before it contracts.

ESV

End-Systolic Volume, the volume of blood in the ventricle at the end of contraction, just before ventricular relaxation.