Adaptation to Environment In Animals

Animals too have to face the problem of water scarcity or abundance. They also have to meet the various vagaries of nature. So, for their survival under these conditions, animals have developed a number of adaptations to meet the challenges.

Migration

This involves long distance or short distance movement of animals from one region to another.

For example:

Arctic terns are sea birds, which nests close to North Pole in summer. They fly south to Antarctica in autumn and returns to north pole again inspiring. Locust migrates in large populations in search of food.

Camouflage

Some animals have the capacity to blend with surroundings, which is known as camouflage. Some insects and reptiles have markings on their bodies, which look like shadows and branches. Leaf the gross hopper resembles the complete leaf or part of leaf. Praying mantis looks either a dead leaf.

Mimicry

It is the resemblance of organisms to other organisms or with non-living objects in form, colour and behaviour to escape predator's notice. An organism that bears resemblance is called mimic and the organism to which it resembles is called model.

It was first described by Henry Bates in 1862 and is adopted by nature to protect individuals from enemies.

It is of three types

a) Protective

b) Aggressive

c) Conscious

Protective mimicry

Organisms mimic themselves in form and also in colour, which protect them form their enemies. It is of 2 types - concealing or warning type.

Concealing mimicry is the most common. In this the mimic makes itself hidden or camouflaged by changing the colouration so as to fit the background. Cryptic colours appear like environmental conditions. In some cases, the organisms mimic the shape and colour of the other organism or object.

Example:

1) Common stick caterpillars of geometric moths - Solenica detralunaria resemble small twigs in colour and shape.

2) The leaf insect Phylum frondosum has green and expanded body with irregular small yellowish spots, which simulate the fungus grown upon a leaf.

3) The dead leaf butterfly Kalima parolecte resembles a dry leaf.

Protective Concealing Mimicry

4) The preying mantis: Mantis religiosia mimic the green foliage to conceal themselves from predators and preys.

Warning mimicry

Warning mimicry also known as Batesian mimicry.

The organisms, which are harmless, palatable and non-poisonous resemble with the forms which are distasteful or poisonous.

Warning type Protective Mimicry

Monarch butterfly (Danaus plexippus)

Example: Non poisonous Elaps snake mimics poisonous coral snakes.

Aggressive mimicry

Aggressive mimicry also known as Mullerian mimicry.

It is demonstrated by some carnivorous animals such as spiders and fishes. It is characterised by the development of cryptic colours by the mimic similar to its model.

Example:

a) The yellow colour body of some spiders resemble so much with the flowers upon which they sit and they become invisible to the visiting insects upon which they prey.

b) Certain African lizards are protectively coloured except for a brilliant coloured spot at the corner of the mouth, which attracts insects.

Conscious mimicry

Animals show conscious imitation at the time of danger they behave as dead.

Example: American opossum - Didelphis virgiana consciously becomes unconscious and stimulates as dead due to which it saves its life from the enemy.

Warning colouration

Concealing form and colour enables a species to avoid its predator. The brightly coloured and highly poisonous dart flogs are recognised and avoided by the predators.

Adaptations to water scarcity

Animals reduce water loss from their body. For example, the kangaroo rat conserves water by creating solid urine and can love without drinking water. Camels are very economical in temperature and can maintain blood stream moisture even in extreme heat.

Adaptations to cold

Animals like Barnacles and molluscs living in very cold northern shores, tolerate cold spells by a process called cold hardening. They have ice nucleating proteins which induce ice formatting in the extra cellular spaces.

Some animals accumulate glycerol or antifreeze proteins, which lower freezing point of their body fluids.

Aquatic Adaptations

All aquatic animals have developed certain morphological structures to live in water.

Stream Lined Body

The body is boat shaped or stream lined.

Aquatic Adaptations in Fish

Head, body and tail are compressed to make it suitable for locomotion in water, so that it offers little or no resistance for swimming in water.

Presence of Fins

The pelvic fins, pectoral fins, dorsal fin, anal and caudal fins act as paddles and control the direction of movement in water and provide balance.

Gills

The gills are well developed and suited for gaseous exchange in water.

Gills in Fish

Lateral Line Sense Organs

The lateral line receptors enable the fish to detect any changes caused by mechanical disturbances in the surrounding water.

Structure of a Fish

Swim Bladder

The presence of air bladders in many bony fishes act as an accessory respiratory organ as well as an organ for buoyancy. Using these bladders the fishes are able to maintain themselves at desired depths.

• The body is covered with scales.

• The presence of a third membrane called the nictitating membrane in the eye.

Desert Adaptations

Two important characteristics of the desert i.e., the scarcity of rainfall and high temperature determine the existence, distribution and adaptations of the animals of the desert.

The characteristic animals of the desert are small herbivorous rodents, reptiles and insects. Birds and mammals which have a constant body temperature are comparatively rare or absent altogether. Animals which can match their internal temperature to the external environment can live much more easily in the desert.

Desert animals have adaptations along 3 lines.

• To live without or with very little water

• To conserve water

• To protect themselves against high temperatures.

The important adaptations are as follows:

• Relatively impervious integuments

• Excretion in the form of uric acid and guanine.

• The animals burrow deeply into the ground or are nocturnal in habit to escape the direct rays of the sun.

• To avoid contact with the hot ground the animals scurry quickly from the protection of one bush to another. Some lizards can hold their bodies away from the ground on their thin long legs.

• The eyes, ears and nostrils are protected against entry of sand by having either long eye lashes or flaps.

• They have protective colouration or spiny covering on their body to protect against predators.

• They have long limbs and padded feet to run easily on sand for long distances in search of water and food.

• Have well developed sense organs of sight, hearing and smell.

• The camel - also called the ship of the desert - stores water in every cell of its body. It also has a hump of stored fat. It can go for many days without water. When it gets water, it can drink upto 50 litres of water.