Question

Identify some of the evolutionary events that must have occurred for animal life to move from aquatic to terrestrial habitats. Include issues such as mobility, reproduction, & oxygen demands. When possible include specific species and examples (Typed answer)

Answer 1

The evolution of land dwelling animals was an important milestone in the history of animal occurred in late Devonian epoch. The aquatic animals adapted to land ecosystem by developing several features such as lungs in the place of gills, legs and feet, complex eye vision, skin and hair to prevent loss of water, eyelids to adapt to vision on land, eardrum to separate external ear from middle ear...etc. the transition was characterised by evolution of amphibians who can live both in water and land. Later on true land dwelling emerged.

Reproduction. The aquatic animals such as fishes follow external fertilisation (egg and sperm are released into water and allowed to mix). The land animals like human on the other hand, follow internal fertilisation (egg and sperm are produced by males and females and deposited inside females body).

Mobility. The movement of animals inside water is mainly guided by fins and tails, like in fishes. But the land animals lost those fins and instead developed legs and hands. Tails was used to balancing which running or jumping. The advanced land species such as gorilla, Homo sapiens have lost the tail as well. Fishes do not have necks, whereas the land animals do. Neck mobility is important to increase the vision and spot prey and predator. Ten evolution of vertebral columns increased the neck mobility. It was followed by flexion and extension of head. Later on neck rotation evolved to allow left and right neck movement.

Oxygen demand. The fishes acquired oxygen using gills. Gills filter the oxygen dissolved in water and supplies to fish body cells. The land animals have developed full scale lungs which exchange the gases with atmosphere. The gills are completely lost in animals. Certain amphibians like frogs use skin to breathe under water and lungs to breathe while on land.