Adaptations

ADAPTATIONS

Living organisms are found in many types of ecosystem The environment in these ecosystem very considerably.Generally, organisms show features that enable them to live successfully and reproduce in a particular environment. These features may be structural,functional or behavioural.such features are known as adaptations.Adaptations to a particular environment are evolved over a long period of time.

Aquatic and Terrestrial Adaptations
The two most contrasting environment are The aquatic and Terrestrial environment. Organ ism living in each of these environment show adaptations that are suited to their particular environment.

Nature of medium
Water is denser medium than air .it is difficult to move rapidly through it .As a result, active aquatic animals like fish have streamlined bodies. Water, however, helps to support the body mass of large aquatic animals. This is not the case with large aquatic animals. This is not the case with large land plants and animals as air is a much lighter medium than water. Hence, large terrestrial plants and animals have better developed supporting (vascular xylem and skeleton) than aquatic ones.these adaptations are mainly structural.

Osmoregulation and water loss
Most marine organisms have body fluids that are nearly the same concentration as the sea water, in which they live. So the body fluids of freshwater organisms are at a much higher concentration than the surrounding water. So more water enters the body cell than leaves them. Successful freshwater organisms have osmoregulatory structures that get rid of the excess water that enters the body cells. The contractile vacuole in Amoeba is such a structure. The adaptation here is mainly functional.
Bony fishes are the most successful aquatic organisms. The body fluid of the marine bony fish is less concentrated than its surrounding water, while the body fluid of the freshwater bony fish is more concentrated. Shows how each has adapted successfully to its environment. The adaptation are mainly functional.
Unlike most aquatic organisms, Terrestrial organisms are faced with a great problem of water loss from their bodies. Plants overcome this by having waterproof cuticles covering their external surfaces.they also have well developed roots for the Terrestrial animals have developed
Exoskeletons (invertebrates) which envelop the whole body, and covering such as scales, features and hair (vertebrates) and trachear systems (insect) so that water loss is greatly reduced; and
Gaseous exchange surfaces enclosed within the body such as lungs (vertebrates) and trachear systems (insect) so that water loss is greatly reduced; and
Excretory structures like the Malpighian tubules and kidneys which are efficient at reabsorbing water and saits.
Thus, to conserve water, Terrestrial organisms had to adapt both structurally and functionally
NOTE In aquatic organisms where there is no need to conserve water, gaseous exchange occurs through the whole body surface or through special structures Callen gills.

Movement
Aquatic organisms that move actively use appendages like fins which are modified for swimming. Many plankton which drift In the water have devices go for keeping them afloat such as oil droplets and ciliated bands. Animals are the actively moving Terrestrial organisms. They have
Jointed limbs (arthropods),and
Pentadactyl limbs(verthropods)
That are specially adapted for running, jumping , crawling, climbing and digging.in birds, the pentadactyl upper limbs have been structurally adapted into wings for flying.

Plant Adaptations to water Availability
Rainfall is the main factor that is responsible for the major bioms of the world. This is be cause plants (the organisms that characterise biomes) are greatly affected by the availableility of water in their environment. They shows various adaptations that are related to the amount of water in their environment.

Hydrophytes
Hydrophytes are plants, such as water hyacinth and water lily, that live in freshwater. All or part of their body is in water. In these plants, the cuticle of the immersed body parts is thin and allows water to enter freely over the whole body surfast . As a result , special water absorbing and water conducting structures are not important. In addition , since there are surrounded by water, they do not need much mechanical support like land plants. Hence , in hydrophytes,
The roots (water absorbing), and
Vascular xylem or wood (water conducting and mechanical ) is poorly developed.
Shows the differences in the internal
Stricture of the stems of water and land plants. Water contains less oxgen than air. Most aquatic plants , therefore, not only provide a supply of oxgen to the underwater parts of the plant but also make the plant buoyant and so help it to float.
NOTE The floating parts of hydrophytes that are exposed to air are covered with a thick cuticle to prevent water loss.

Mesophytes
Mesophytes are land plants , such as the Hibiscus and cassava , that are found in an environment with an adequate water supply. A waxy cuticle covers the body surface to minimise water loss. Stomata are present on leaves for gaseous exchange to occur.

Xerophytes
Xerophytes are plants that can survive in an environment, such as the desert, where water supply is scarce. They show the following adaptations:
The roots are well developed. They grow down to great depths if necessary, and branch extensively in order to absorb water from as large an area as possible.
Some xerophytes have swolled stems or leaves containing water storage cells. These are known as succulents and can withstand long periods of drought. Example include cacti, Euphorbia and Aloe.
Xerophytes have various ways of reducing water loss from leaves by transpiration. For example, in many cacti, the leaves are reduced to spines . the stems become fleshy and green and take over the function of photosynthesis . in Acacia , the leaf blade is absent and the leaf stalk becomes flattened to carry out photo synthesis. The leaves of some xerophytes are covered with thick waxy cuticles or hairls, while in some , the number of stomata are greatly reduced or sunken into pits.
The protoplasm in the cells of xerophytes can tolerate a high degree of water loss without being damaged. This is an extremely important adaptation that enable xerophytes to withstand prolonged droughts.

Reference

Leroi, Armand Marie (2015). The Lagoon: How Aristotle Invented Science. Bloomsbury. pp. 91–92, 273, 288. ISBN 978-1408836224.^ Desmond 1989, pp. 31–32, fn 18^ Voltaire (1759). Candide. Cramer et al.^ Sober 1993, chpt. 2^ Darwin 1872, p. 397: "Rudimentary, Atrophied, and Aborted Organs"^ Bowler, Peter J. (1989) [1983]. Evolution The History of an Idea (Revised ed.). University of California Press. p. 86. ISBN 978-0-520-06386-0.^ See, for example, the discussion in Bowler 2003, pp. 86–95: "Whatever the true nature of Lamarck's theory, it was his mechanism of adaptation that caught the attention of later naturalists." (p. 90)^ Provine 1986^ Ford 1975^ a b Orr, H. Allen (February 2005). "The genetic theory of adaptation: a brief history". Nature Reviews Genetics. 6 (2): 119–127. doi:10.1038/nrg1523. PMID 15716908. S2CID 17772950.^ Huxley 1942, p. 449^ Mayr 1982, p. 483: "Adaptation... could no longer be considered a static condition, a product of a creative past, and became instead a continuing dynamic process."^ Price 1980^ Daintith, John; Martin, Elizabeth A., eds. (2010) [First published 1984 as Concise Science Dictionary]. "adaptation". A Dictionary of Science. Oxford Paperback Reference (6th ed.). Oxford University Press. p. 13. ISBN 978-0-19-956146-9. LCCN 2010287468. OCLC 444383696. Any change in the structure or functioning of successive generations of a population that makes it better suited to its environment.