The adaptation of living things to their environment is such that their features are only suitable for survival in their respective environments. Although organisms can tolerate a deviation of the environmental conditions form the optimum, severe and persistent alterations may lead to the deterioration of the organisms’ condition or even death.
The terrestrial and aquatic environments present considerably different conditions for the existence of life. Although the aquatic and terrestrial microscopic organisms may not exhibit significant structural differences, plants and animals living in these environments have distinct and different characteristics that enable them to survive in their respective environments (Dejours, 1987).
Plants feature a cuticle, which protects them from the external environmental conditions. Aquatic plants have a thin cuticle since they live in water and do not need to undertake water preservation. This is a feature of fresh water aquatic plants. In addition, the stomata, which are the respiratory openings for the plants, are in abundance on the upper side of the plant to facilitate rapid water loss to maintain osmotic balance.
Water is a dense medium, and thus plants living in water have a weak shaft for supporting the foliage and the upperparts of the plant. Furthermore, the plants’ stem is relatively weaker and they tend to float in water. Aquatic plants are submerged either partially or wholly in water.
Thus, water covers most of their surfaces and can be readily absorbed. Their roots are small, highly flexible, and adapted for absorbing oxygen rather than water. Aquatic plants may also feature wide leaves to enable them to float and enhance transpiration (Cavendish, 2001).
On the other hand, terrestrial plants have a thick cuticle on their leaves for protection from excessive transpiration that could desiccate the plant’s cells. In addition, the plants’ stomata are few and are located on the bottom of the leaves away from direct sunlight and convection current.
Air, the atmospheric medium in which terrestrial plants thrive, is much less dense compared to water. Thus, terrestrial plants need stronger stems and shafts for the support of the foliage and other upper parts of the plant. Terrestrial plants have rigid and highly developed roots that facilitate water absorption and anchorage. Terrestrial plants may have thin leaves or leaves of various shapes adapted to the environmental temperatures rather than a mechanism of support (Solomon, 2005).
One of the major unique features of the aquatic animals is that their appendages have undergone differentiation into fins or webbed feet for movement in water. Their skin or outer covering is smooth and may consist of a mucus membrane to reduce friction during movement.
Aquatic animals feature a thick subcutaneous fat deposit. This fat helps the animals to maintain a regular and constant body temperature in the relatively cold water. Most aquatic animals have transparent eyelid to protect against friction with water. Although some of aquatic animals have lungs for ventilation, most of the animals have gills for respiration or a combination of lungs and gills (Cavendish, 2001).
On the other hand, terrestrial animals have limbs with separated digits for grasping or climbing. Furthermore, some flying animals have their limbs differentiated into wings for flight purposes. Most animals have their outer covering covered with fur or hair. This keeps the animal warm in the air and may serve to protect the skin.
Most terrestrial animals have a thin subcutaneous fat layer, but have more muscles to aid their locomotion and elevation from the ground. Except for some reptiles such as snakes, most animals have thick and opaque eyelids to protect their eyes from solid objects and dryness. For terrestrial animals, lungs are the primary respiratory organs, and they are highly developed (Solomon, 2005).
References
Cavendish, M., B. b. (2001). Aquatic life of the world. New York: Benchmark books.
Dejours, P. (1987). Comparative physiology: life in water and on land. Padova: Liviana.
Solomon, E. P., Berg, L. R., & Martin, D. W. (2005). Biology (7th ed.). Belmont, CA: Brooks/Cole Thomson Learning.