1.3 Evolutionary perspectives in animal physiology

Evolution shapes animal physiology through natural selection and adaptation. Organisms with favorable traits survive and reproduce, passing on genes that enhance their ability to thrive in specific environments. This process leads to diverse adaptations in morphology, physiology, and behavior.

Comparative physiology examines how different species tackle similar challenges. By studying phylogenetic relationships and physiological trade-offs, scientists uncover the mechanisms behind adaptations. This approach reveals how evolutionary history influences modern physiological systems across species.

Evolutionary Processes

Natural Selection and Adaptation

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• Natural selection is the process by which organisms with favorable traits are more likely to survive and reproduce, passing on their genes to future generations
• Adaptation refers to the development of traits that enhance an organism's ability to survive and reproduce in a specific environment
• Adaptations can be morphological (physical structures), physiological (internal processes), or behavioral
• Examples of adaptations include camouflage (leaf-tailed gecko), echolocation (bats), and antifreeze proteins (Arctic fish)

Convergent and Divergent Evolution

• Convergent evolution occurs when unrelated species develop similar traits in response to similar environmental pressures (analogous structures)
  • Examples include wings in birds and bats, and fins in sharks and dolphins
• Divergent evolution occurs when closely related species develop different traits in response to different environmental pressures
  • Leads to the formation of new species over time (speciation)
  • Examples include Darwin's finches (beak shape) and cichlid fish in African lakes (mouth shape)
• Environmental pressures drive both convergent and divergent evolution by selecting for traits that enhance survival and reproduction in specific conditions
  • Pressures can include climate, predation, competition for resources, and disease

Comparative Physiology

Phylogenetic Relationships and Comparative Studies

• Phylogenetic relationships describe the evolutionary history and relatedness of different species
  • Closely related species share a more recent common ancestor than distantly related species
• Comparative physiology studies how different species have evolved to solve similar physiological challenges
  • Helps identify the underlying mechanisms and adaptations that have evolved in response to specific environmental pressures
• Comparing the physiology of related species can reveal how evolutionary history has shaped their physiological systems
  • Example: studying the respiratory systems of terrestrial and aquatic mammals to understand the evolution of lungs

Physiological Trade-offs and Evolutionary Constraints

• Physiological trade-offs occur when an adaptation that enhances one aspect of an organism's physiology comes at the cost of another aspect
  • Example: hummingbirds have high metabolic rates for hovering flight but require frequent feeding to maintain energy balance
• Evolutionary constraints are limitations on the evolution of a trait due to the organism's evolutionary history or developmental processes
  • Constraints can arise from the need to maintain the functionality of existing physiological systems while adapting to new challenges
  • Example: the vertebrate eye has a "blind spot" due to the arrangement of the optic nerve, a constraint imposed by its evolutionary history