Class 11 Biology | Animal adaptation Notes

Class 11 Biology | Animal adaptation Notes
UNIT 09 • BIOTA AND ENVIRONMENT
CLASS 11 BIOLOGY • ZOOLOGY

Animal Adaptation

Chapter 9.1

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Adaptation

Adaptation is the process of adjustment in the external environment.

The source also defines adaptation as the ability of organisms to make themselves adjustable to the environment.

The handwritten notes state that the term “adaptation” was first used by H. S. Osborne in 1902. This is reproduced as source content.

The supplied notes discuss four major types of animal adaptation:

1 Aquatic Adaptation to life in water 2 Terrestrial Adaptation to life on land 3 Volant / Aerial Flying or gliding adaptation 4 Amphibious Adaptation to both land and water

1. Aquatic Adaptation

The ability of organisms to live in, or remain adjusted to, an environment having a high proportion of water is called aquatic adaptation.

The source divides aquatic adaptation into two types:

Aquatic Adaptation → Primary Aquatic Adaptation Secondary Aquatic Adaptation

Primary and Secondary Aquatic Adaptation

Feature Primary Aquatic Adaptation Secondary Aquatic Adaptation
Origin of aquatic life Belongs to an originally aquatic mode of life from ancient times. Belongs to terrestrial life originally and later became adapted to the aquatic medium during the evolutionary course.
Locomotory organ Fins act as locomotory organs. Paddles act as locomotory organs.
Respiration Respiration through gills. Respiration by pulmonary mode.
Examples in the source Fishes Turtle, whale, etc.
The table above follows the comparison written on page 1 of the supplied scan.

2. Terrestrial Adaptation

The ability of organisms to remain adjusted to life on land is called terrestrial adaptation.

The source explains three sub-types of terrestrial adaptation:

CursorialFast-running adaptation FossorialBurrowing adaptation ArborealScansorial / climbing adaptation

a. Cursorial (Fast-Running) Adaptation

Cursorial adaptation refers to adaptation for fast running on land.

The source lists reptiles, mammals and flightless birds such as emu and ostrich among cursorial animals.

Reptiles Mammals Emu Ostrich
The handwritten notes state that the cheetah is the fastest land animal and give its speed as “up to 80 km/h.” This value is preserved from the source.

b. Fossorial (Burrowing) Adaptation

The adaptation of animals for partial or complete underground life is called fossorial adaptation.

Examples given in the notes include:

Earthworms Snakes Rodents Arthropods

The source also states that most digging animals undergo winter sleep or hibernation.

c. Arboreal (Scansorial or Climbing) Adaptation

Arboreal adaptation refers to adaptation for climbing and, as written in the source, gliding in animals.

Examples listed in the scan are:

Chameleon Monkey Spider Lizard Gecko

3. Volant (Aerial) Adaptation

The flying or gliding ability of animals is known as volant adaptation. It is also called aerial adaptation.

The source gives the following examples:

Bat

An example of volant adaptation.

Exocoetus

A fish listed in the source as using fins for gliding.

Rhacophorus

A tree frog listed as an example of gliding / volant adaptation.

The notes state that the body of volant animals is “boat-like or streamlined.”

Patagium

Patagium is the lateral extension of the forelimb and body skin that acts as a wing in secondary volant adaptation.

The example given in the source is the patagium of a bat.

Forelimb + body skin → Lateral extension → Wing-like surface → Patagium

4. Amphibious Adaptation

The ability of animals having adaptive characters that allow them to survive both on land and in water is called amphibious adaptation.

The source divides amphibious adaptation into two categories on the basis of their life:

a. Adaptations for Aquatic Life

The notes state that such animals have a short neck, light bones, a shorter brain box, and wrist and ankle bones that make the body lighter for easy swimming.

Examples: frog and toad (Bufo).

b. Adaptations for Terrestrial Life

The source states that toads are more terrestrial than frogs and respire through lungs.

Terrestrial amphibians may also show burrowing, arboreal and volant adaptations.

Burrowing Frogs
Arboreal Hyla
Volant Rhacophorus
The uploaded PDF contains four scanned pages, but pages 2 and 3 repeat the same terrestrial and volant-adaptation material. The typed notes present that repeated content once rather than duplicating it.

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