Question

Compare and contrast selective pressures, constraints, and features of swimming and burrowing vertebrates.

Answer 1

It is believed that certain vertebrates adopted fossorial lifestyles as above the ground they failed to find adequate food sources and protection/defence mechanism to fight predators. Fossorial (burrowing) adaptations aid in regulation of temperature as well as an underground safe place from predators or as a hideout for food storage. Fusiform vertebrates generally have a spindle-shaped body (tapering at both ends), poorly developed eye sight (due to subsurface darkness), small external ears to reduce the friction that might occur during burrowing, short tail, short and stout limbs and broad and stout forelimbs. Due to the constraints such as weak eye sight and almost missing external ear, they have developed other physical and sensory traits such as conspecific signalling and presence of hypertrophied malleus which allows detection of low frequency signals.

The constraints for adapting to an aquatic life included mechanisms for feeding, osmoregulation, locomotion and sharp sensory abilities in the aqueous environment. Aquatic vertebrates developed a streamlined body to minimise water resistance, gills developed as the primary respiratory organ, fins, flippers and paddles developed as a means of locomotion. Certain aquatic animals living in extremely cold conditions modified their skin keeping a thick layer of fat beneath. In certain aquatic animals webbed structures developed to increase the surface area for swimming. Aquatic birds showed adaptations such as higher oil production to keep the feathers dry and making them resistant to wetting. Wading birds such as flamingos and cranes have developed long thin legs that allow them to easily walk through shallow waters.