Read more: Handwritten note of  Adaptation and Migration

Unit: 9 Biota and environment

Adaptation: Adaptation are any behavioral or physical characteristic of an animal that help it to survive in its environment. Animal adaptation is broadly categorized into following types: 

1. Aquatic adaptation: They are the animals who live in water or situations with a higher percentage of water.

      a. Aquatic adaptation in fish:

•  They have streamlined body that offers the least resistance during locomotion through water.
• Fins help in locomotion. Pectoral fins act as balancers and the caudal fin helps in changing the direction.
• They breathe through gills which are well adapted for gaseous exchange under water. 
• The entire body is covered with waterproof scales with mucous coating on the surface.

       b. Other aquatic animals: 

• They also have a streamlined body with reduced neck.
• The limbs have become webbed (frogs, ducks) or modified to form paddles or flippers (Whales, dolphins).
• Aquatic mammals lack hairs and skin glands (sweat and oil glands).
• They all are air breathers and have muscular flaps in their nostrils to keep them closed when the animals are diving. 

        2. Terrestrial adaptation: the land-dwelling animals are called terrestrial animals. Animals living on land show the following types of adaptations:

       a. Cursorial adaptation: It include those animals which are adapted for fast running. 

• They inhabit open spaces on land and are adapted for running on hard ground.
• The body is streamlined and offers the least resistance during swift movement.
• The neck is long and eyes are raised high up on the head with keen vision.
• Eg. Ostrich, emu etc. 

      b. Fossorial adaptation:  Animals living beneath the ground ie. underground are called fossorial animals and their adaptations are called fossorial adaptations:

• They are adapted for the burrowing mood of life. 
• Body is either cylindrical or spindle-shaped to offer least resistance during burrowing. 
• The head tapers anteriorly to form a about. 
• The forelimbs are short and have powerful claws for digging. 
• They undego hibernation in winter due to sarcity of food.
• The tail is short or vestigial. 

      c. Arboreal or scansorial adaptations: The terrestrial animals which have adaptive character for climbing or inclined or vertical surfaces such as trees, walls, rocks etc are called arboreal adaptations:

• They are adapted for climbing on trees or other objects. 
• The pectoral girdle is strong with a well-developed clavicle and scapula.
• Forelimbs become elongated for swinging on trees.
• Adhesive pads are present on the tips of digits or the soles of feet help to hold on the wall or branches of trees.
• They move on their whole foot. 

      d. Aerial or volant adaptation: The adaptative characters which enable organisms to glide or fly in the air are called volant adaptations.

• They have a boat shapted body which offers little resistance during flight.
• The forelimbs in birds are modified into wings which have large surface area provided by feathers.
• In bats, forelimbs are modified into patagium which is supported by all the digits except the first and extends along the sides of the body up to the tail. 
• In insects, wings are the membranous fold of their exoskeleton. 
• Sense organs are well developed. (Specially eyes)
• In birds, the jaws are modified into beaks.

     e. Desert adaptations: The adaptative characters which enable organisms to live in the desert are called desert adaptations.