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CHAPTER ONE

1.1 Introduction

A biological adaptation is any structural (morphological or anatomical),

physiological, or behavioral characteristics of an organism or group of organisms

(such as species) that make it better suited in its environment and consequently

improves its chances of survival and reproductive success. Due to individual

phenotypic plasticity (variability), individuals will be more or less successful.

Some adaptations may improve reproductive success of the population, but not a

particular individual, such as seen in altruistic behavior in social insects.

Organisms that are adapted to their environment are able to :

secure food, water, and nutrients

obtain air, warmth, and spaces

cope with physical conditions such as temperature, light, and heat

defend themselves from their natural enemies

reproduce and rear offspring

respond to changes around them

Adaptation occurs in response to changes in the environment, life style, or

relationship to other organisms. Environmental dynamicity, voluntary or

compelled shifting of habitat, and human activities may put organisms in a new

niche or in environmental stresses or pressures. In such circumstances, the

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organisms require characteristics suitable to the new situation. Organisms that are

not suitably adapted to their environment will either have to move out of the

habitat or die out. The term die out in the context of adaptation means that the

death rate over the entire population of the species exceeds the birth rate for a long

enough period for the species to disappear.

While adaptations provide for the individual purpose of the organism—

survival, reproduction, development, maintenance—these same characteristics

provide diversity and add to human fascination with, and enjoyment of, nature.

Furthermore, while adaptations often are seen as a static set of suitable

characteristics, in reality the process of developing adaptations is a dynamic

process. Whether envisioned as the product of design or natural selection, or

natural selection on the microevolutionary level and design for macroevolutionary

changes, the reality is that new adaptations are needed when organisms encounter

new environments, and such have arisen for millions of years.There is a great

difference between adaptation and acclimation or acclimatization. The process of

developing adaptations occurs over many generations; it is a population

phenomenon involving genetics and is generally a slow process. Acclimation or

acclimatization, on the other hand, generally occurs within a single lifetime or

instantly and deals with issues that are less threatening. For example, if a human

being were to move to a higher altitude, respiration and physical exertion will

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become a problem. However, after spending a period of time under the high

altitude conditions, one may acclimatize to the reduced pressure, the person's

physiology may function normally, and the change will no longer be noticed.

1.2 Types of adaptation

Adaptations can be structural, physiological, or behavioral. Structural

adaptations are special body parts of an organism that help it to survive in its

natural habitat (e.g., skin color, shape, body covering). Physiological adaptations

are systems present in an organism that allow it to perform certain biochemical

reactions (e.g., making venom, secreting slime, being able to keep a constant body

temperature). Behavioral adaptations are special ways a particular organism

behaves to survive in its natural habitat (e.g., becoming active at night, taking a

certain posture).Based on the habitats for which organisms develop adaptations,

adaptations can be categorized into 3 fundamental types, namely aquatic,

terrestrial, and volant (flying), each of which can be further divided into many

subtypes.

1.3 Aquatic adaptation

Aquatic adaptations are found in those plants and animals that live in water

habitats: fresh water, brackish water, and sea water. For example, fresh water

organisms develop features to prevent the entry of excess water or processes to

drain excess water regularly. On the contrary, marine organisms face scarcity of

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water due to hypertonic (salt concentration higher than that of body fluid) sea

water. So, they have mechanisms to retain water and excrete excess salts that enter

in water intake. Aquatic plants may be emergent rooted plants (e.g., reeds),

submersed rooted plants (e.g., Hydrilla), planktons (e.g., diatoms) or floating

plants (e.g., water hyacinth). Similarly, aquatic animals may be benthic, occurring

at the bottom of a water body, or pelagic, occurring in the water body itself. The

animals may live partially or permanently in water. Thus they may range from

non–specialized to very highly specialized water dwellers.

Primarily aquatic animals (e.g., fishes) show not a single terrestrial feature,

whereas secondarily aquatic animals (whales, dolphins) possess terrestrial

respiration through lungs, and some must visit land for laying eggs (e.g., turtle).

Partially water dwelling animals demonstrate amphibious adaptations with double

features both for land and water (e.g., frogs, salamanders), or mostly terrestrial

features and only some basic aquatic adaptations (e.g., duck).

Some characteristic aquatic adaptations are:

Body contour is spindle shaped and streamlined. For this, the head is

elongated into rostrum or similar structure, neck is short, external ears

(pinnae) are reduced, and tail is laterally or dorso–ventrally compressed.

Usually marine animals are excessively large (e.g., whale), because of the

buoyancy of the salt water.

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Organs of locomotion and balancing vary greatly among the aquatic

animals; fishes use paired and unpaired fins, whales and turtles have their

limbs modified into paddles, in some others, hands and/or feet are webbed.

Skin of most aquatic forms is rich in mucous glands to make it slippery.

Fishes are equipped with dermal scales as well. Aquatic mammals have

reduced or absent hair and skin glands (oil and sweat glands). In

compensation, they have a fatty layer below the skin known as bubbler.

Besides insulating the body, it also helps in flotation.

Primarily aquatic animals are capable of utilizing dissolved oxygen in the

water for respiration through general body surface, internal or external gills,

and so forth. However, secondarily aquatic forms respire atmospheric air

through lungs; nostrils are located at the apex of the head.

In fish, the hollow outgrowth of the alimentary canal, called air bladder,

functions as an organ of flotation and accessory respiratory organ as it is

filled with air. In whales and other mammals, extraordinarily massive lungs

and closable nostrils serve this purpose.

Fishes have lateral line systems extending the whole length of the body. It

contains neuromast organs, which act as rheoreceptors (pressure receptors).

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1.4 Aquatic habitat

Natural aquatic habitats include ponds, lakes, rivers,

streams, springs, estuaries, bays, and various types of wetlands.

Some of these habitats are shallow and others deep, some are

coldwater and others warm-water, some are freshwater and

others saltwater, and some have high oxygen levels and others

little oxygen.Aquatic habitats can be classified as:

• non-flowing waters like lakes and ponds,

• slowly-flowing waters like marshes and swamps, and

• flowing waters like rivers and streams.

Aquatic habitats may be either freshwater like lakes, ponds, rivers, spring or

saline (salt water) like oceans. A wide variety of organisms lives in these habitats.

Sudden change in water temperature is not observed because water absorbs and

loses heat gradually. Over 99.9% of the surface water is available as freshwater for

various hum an needs. The aquatic habitat offers a variety of physicochemical

factors. These include penetration of light (transparency), availability oxygen,

resistance to motion (viscosity), pressure fluctuations, nutrients, etc.

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CHAPTER TWO

2.1 Adaptive Features of Aquatic Animals (Hydrocoles)

1. They have special structures like floats, air cavities, air sacs which help them to

float in water at the desired depth.

2. For movement, animals have special appendages, for example, fishes have

streamlined body and fins. Plants do not have these special structures as they are

either fixed or drift along with the water current.

3. Animals develop special coverings like shells, cuticle, waxy coating, scales, etc.

Which prevent rotting and decay.

4. Animals have the ability to feed in water.

5. For respiration and exchange of gases animals have developed special structures

such as gills in fishes.

2.2 Adaptive Features of Aquatic Plants (Hydrophytes).

Plants which live in water are known as hydrophytes.

1. Free-floating: Some hydrophytes float freely on the water surface. They are not

attached to the bottom soil. Common examples are Eichhornta, Pistia, Lemna,

Wolffia

2. Rooted and Free-floating: In some hydrop-hytes like Nelumba, Nymphaea, the

roots are fixed in mud and leaves remain floating due to long petiole.

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3. Submerged and Rooted: Some aquatic plants like Hydrila, Vallisneria remain

submerged in water and are rotted in soil. In Vallisneria, the stem is tuberous

which bears ribbon-like leaves while Hydrila has a long stem with small leaves on

the nodes.

4. Submerged and Floating Some hydrophytes like Ceratophytllum remain

completely submerged in water and are not rooted in the mud. They have long

stems and small pointed leaves.

5. Emergent and Rooted Some hydrophytes like Ranunculus. Typha grow in

shallow water. Their roots are completely under water fixed in the soil while the

stems are partly or completely exposed to air.

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CHAPTER THREE

3.1 Adaptation in hydrophytes (Aquatic Plants)

The roots in hydrophytes become less significant due to the availability of

plenty of water. Either they have no roots or have poorly developed roots. Root

hairs and root caps are absent. Air cavities (aerenchyma) are found in the roots.

The stem is spongy, long and flexible. It floats horizontally in free-floating forms.

The stem of the water lily or lotus plant (Nelumbo) is a rhizome which contains

large boles for air.

Floating leaves are large, flat, circular or oval which float on water.

Submerged leaves are thin, long, liner or ribbon-like. Waxy coating is found on

leaves, as in lotus which does not allow it to shrink or get destroyed. They have

long flexible and mucilage-covered petioles. Narrow and long leaves of Vallisneria

provide least resistance to flowing water.

Take a lotus plant. Cut its stalk with the help of a blade. You will see large

tunnels and holes. If you press the stalk, what do you see? Observe and think why

these holes are there.Keep your hand or foot immersed in wager for about half an

hour. Your skin will wrinkle. The water lily plant (or a lotus plant) does not

wrinkle while if remains in water throughout its life. This is because of its

waterproof, oily leaf. You may compare this waterproof layer with the scales of

fish.

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3.2 Adaptation in Hydrocoles (Aquatic Animals)

If you look at the structure of fish, you will find many structural features

which reflect their adaptations to aquatic mode of life.

1. It has a streamlined body and is spindle-shaped. It has laterally compressed

head, body and tail.

2. The entire body is covered with waterproof scales. There is a mucous coating on

the scales which reduces water tension.

3. At the sides and posteriorly there are fins which help in swimming faster. The

tail functions like a rudder and helps in changing direction while swimming.

4. Gills are present on the lateral sides. These are respiratory organs capable of

oxygen uptake from water.

5. Fishes have an air bladder which is a thin-walled, gas-filled sac lying dorsal two

the alimentary canal. It helps in respiration, sound production and stabilizes any

fluctuation in pressure.

Other aquatic animals also have some modifications. In frogs and ducks,

locomotion is achieved by webs between gingers. Whales (aquatic mammals) do

not have or skin glands like sweat and oil glands. The body of whale is streamlined

in a reverse direction with a short rounded front and a rapidly tapering posterior

part with horizontal fin. Such shape helps them in locomotion in water. A thick

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layer of fat called blubber in present underneath their skin which helps in

floatation.

3.3Common Characteristics Between Aquatic Plants And Animals

3.3.1 Niche Partitioning

Aquatic animals and plants both partition themselves into different

ecological niches (or roles) to reduce resource competition and maximize utility of

their environment. Plants in a freshwater marsh pursue a range of lifestyles. Some,

such as water lilies, float their leaves and flowers at the surface, while others, such

as cattails, are rooted in sediment and extend their stalks above the water's surface.

In the oceans, some species, such as oceanic whitetip sharks and leatherback

turtles, forage in pelagic environments far out to sea, while others, such as sea

otters, favor coastal environments. Still more manage to survive in the benthic

zones of the seafloor.

3.3.2 Predators and Prey

As on land, the world's aquatic systems play host to ceaseless dramas of life and

death in the form of predatory struggles. In the oceans, many fish are schooling,

traveling in massive aggregations that reduces any one individual's chances of

sticking out to a passing predator. In the muck of a marsh rim, a northern leopard

frog camouflages itself with stillness and intricate markings. White sharks cruise

the mid-depths, their eyes trained to the surface to pick out telltale silhouettes of

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elephant seals and other favored prey. Along sloughs and wetland margins,

kingfishers and night herons pursue the same fish, but the former do it by

ambushing from tree perches, while the latter stalk the shallows and dart their prey

with lightning-fast lunges.

3.3.3 Using Aquatic Environments

Many aquatic ecosystems, particularly in semi-arid climates and those

experiencing distinct dry seasons, are ephemeral or temporary in nature. A playa

pond on Texas' high plains or a creek in East African woodland may dry up in

extended drought. Less mobile species such as fish, crayfish or aquatic snails may

be doomed if their wetland vaporizes, while others, such as crocodilians, mink,

waterfowl or hippos, can often migrate to a new home. Many migratory birds, from

geese and swans to sandpipers, use aquatic environments only during certain times

of year: for breeding, for wintering or simply as a convenient stopover on a long

journey in between.

3.3.4 Form

The streamlined shapes of so many kinds of fish and aquatic mammals are

honed for efficient travel through their watery universes. Dolphins and sharks

famously resemble one another, with sharp dorsal fins and lean forms: This is a

case of convergent evolution, when two unrelated species come to adopt similar

morphologies because of the common pressures of their environment. Aquatic or

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semi-aquatic plants do this too: Giant cane and bulrushes are not closely related

(one's a grass and one's a sedge), but they look similar with their stout, tall stalks

and constitute similar landscape features (canebrakes and tule beds).

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CHAPTER FOUR

4.1 Summary

An animal or plant which lives in water during any stage of its life or

depends upon aquatic habitats, is defined as an aquatic organism. Aquatic plant

communities provide many ecological benefits, such as food and habitat for

waterfowl, fish, and other aquatic organisms. They also help maintain water

quality by absorbing nutrients, providing oxygen, and reducing shoreline erosion.

Aquatic plants contribute to the overall health of a waterbody, enhancing shoreline

property values. Aquatic ecosystems consist of living organisms together with their

nonliving habitat. Although the ecosystem concept is a useful one, the exact

definition is somewhat arbitrary. For example, an ecosystem can range in size from

a small water droplet to the vast oceanic ecosystem, and the upper, lower, and

horizontal boundaries are often not well established. Similarly, the temporal

aspects of ecosystems are often fuzzy. For example, a vernal (spring) pond is a

temporary wetland filled with rainwater, and is transformed from an aquatic

ecosystem into a terrestrial one when it dries up during the summer. An

intermittent stream is one that sometimes is full of water and at other times dry.

Ecosystems are not always self-sustaining. For example, fish and other aquatic

animals in streams depend on leaves and insects falling from terrestrial (land)

ecosystems as energy sources. Just as no single life form (species) is sufficient

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unto itself, neither is any one ecosystem. Ecosystems and their plant and animal

life are not independent from one another in time, space, or energy.

4.2 Conclusion

Nutrient source and availability is different for aquatic

systems than land systems. Soil, not air, is the major source of

nutrients in terrestrial systems. In aquatic systems, nutrients are

dissolved in water. Nutrients generally are more available in

aquatic than terrestrial systems. Few geographic barriers inhibit

the free movement of organisms in aquatic systems. Aquatic

ecosystems are more continuous than terrestrial ecosystems.

Except for temperature, salinity, and depth barriers, aquatic

animals move freely. Aquatic ecosystems provide us with

enormous benefits at little cost. They:

• provide critical fish and wildlife habitats serving as spawning

and nursery areas for fish like bass and nesting and feeding areas

for waterfowl like geese,

• improve our water quality by filtering out sediment and toxins,

• act as natural sponges that absorb flood waters, collecting and

storing excess water, preventing floods, and

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• produce a rich variety of natural products such as fish and

shellfish, cranberries and wild rice, ducksand geese, and timber.

Wetlands provide outdoor recreational opportunities for boating,

fishing, photography, nature observation, and scenic beauty.

References

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Cook, C.D.K. (ed). 1974. Water Plants of the World. Dr W Junk Publishers, The Hague. ISBN 90-6193-024-3.

Ford, M. J. 1983. "The changing climate: Responses of the natural fauna and flora," The Journal of Ecology 71(3): 1027-1028.

Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p.

Nortman, D. The evolution of phenotypic plasticity through the Baldwin Effect. Noesis VI: Article 4, 2003. Retrieved May 20, 2007.

Pray, L. A. 2004. Epigenetics: Genome, meet your environment. The Scientist 18(13): 14. Retrieved May 20, 2007.

Science Aid 2006. Adaptation. Retrieved May 7, 2007.

Settel, J. 1999. Exploding Ants: Amazing Facts About How Animals Adapt, New York: Atheneum Books for Young Readers, ISBN 0689817398

Wells, J. 2000. Icons of Evolution: Why Much of What We Teach About Evolution Is Wrong, Washington, DC: Regnery Publishing, ISBN 0895262762