π
ADAPTATIONS
β’ Aquatic Adaptation / Water Inhabitant:
β Primary Aquatic Adaptation / Gill Breathers:
β Definition: Aquatic animals with gills as primary respiratory organs
β Adaptive Features:
Table 1: Primary Aquatic Adaptations
Feature | Adaptation | Function |
|---|---|---|
Body shape | Streamlined + laterally compressed | Easy movement in water |
Head | Subconical | Reduces water resistance |
Neck | Absent | Smooth body contour |
Locomotion | Lateral undulation of flexible body | Primary swimming mechanism |
Fins | Present | Secondary locomotion + balance |
Swim bladder / Air bladder | Hydrostatic organ | Buoyancy control + also helps in breathing |
Gills | Primary respiratory organs | Respiration in water |
Lateral line sense organs | Present | Detect mechanical disturbances in surrounding water |
Scales | Protective exoskeleton | Body protection |
Nictitating membrane / 3rd eyelid | Protective transparent eyelid | Eye protection + clear vision underwater |
β Examples:
β Secondary Aquatic Adaptation / Lung Breathers:
β Definition: Originally terrestrial lung-breathing animals secondarily adapted to aquatic life
β Adaptive Features:
β Body Contour:
Table 1: Body Contour in Secondary Aquatic Animals
Part | Adaptation |
|---|---|
Head | Sub-conical |
Neck | Shortened |
Tail | Enlarged |
External ears | Reduced in amphibious mammals; lost in fully aquatic forms |
Lungs | Large; store large amount of oxygen |
β Locomotive Mechanism:
Table 1: Locomotion in Secondary Aquatic Animals
Type | Limb / Tail Feature | Propulsion |
|---|---|---|
Oar propulsion | Equally sized limbs e.g. turtle | Water displaced like oar |
Tail propulsion | Hind limbs tend to disappear e.g. cetacea, sirenians | Strong tail generates propulsive power |
β Note: Propulsive power stronger in oar propulsion than tail propulsion
β Limbs:
- β’Webbed feet
- β’Limbs modified into flippers / paddles
- β’Hyperdactyly + hyperphalangy β β digits + phalanges β enlarged limb β more water displacement
β Integument:
Table 1: Aquatic Integument
Feature | Adaptation |
|---|---|
Skin | Naked; hair + skin glands reduced |
Blubber | Subcutaneous fat layer; compensates hair loss |
β Examples:
β’ Aerial / Volant Adaptation / Flying:
β Adaptive Features:
Table 1: Aerial Adaptations
Feature | Adaptation | Function |
|---|---|---|
Body shape | Boat-shaped / spindle-shaped | Reduces air resistance |
Neck | Long + modified | Flexible head movement |
Beak | Modified jaw bones | Feeding + preening |
Preening | Beak spreads oil from uropygial glands | Feather maintenance |
Tail | Short | Balance + flight control |
Body covering | Feathers | Flight + insulation |
Forelimbs | Modified into wings | Flight |
Hindlimbs | Strong + automatic perching | Landing + perching |
Hindlimb position | Slightly anterior | Body balance |
Respiratory system | Inelastic lungs + air sacs | Efficient respiration |
Nervous system | Highly developed cerebellum | Coordination + balance during flight |
Reproductive system | Single functional left ovary | Weight reduction |
β Flight Muscles:
Table 1: Flight Muscles
Muscle | Action |
|---|---|
Pectoralis major | Depresses / lowers wings |
Pectoralis minor | Elevates / raises wings |
β Flight Types:
Table 1: Types of Flight
Type | Description | Examples |
|---|---|---|
Gliding / Passive flight | No locomotive power applied from body | Exocoetus / flying fish; Rhacophorus / flying frog; Draco / flying lizard |
True / Active flight | Locomotive power applied from body | Birds, bat |
β’ Desert Adaptation:
β Adaptive Features:
Table 1: Desert Adaptations
Feature | Adaptation | Function |
|---|---|---|
Skin | Tough + thick | Avoids perspiration |
Sweat glands | Reduced | Water conservation |
Urine | Highly concentrated | Water conservation |
Water cells in rumen | Present in camel | Water storage |
Senses | Well-developed sight, hearing, smell | Survival in desert |
Eyes, ears, nostrils | Protected from sand | Sand protection |
Eyelids | Highly enlarged | Eye protection |
Desert lizard skin | Hygroscopic | Absorbs atmospheric water |
β Examples:
β’ Fossorial / Burrowing Adaptation:
β Adaptive Features:
Table 1: Fossorial Adaptations
Feature | Adaptation | Examples / Function |
|---|---|---|
Body shape | Cylindrical | Snakes, Ichthyophis |
Body shape | Fusiform / spindle-shaped | Mole |
Head | Tapers into snout | Burrowing |
Forelimbs | Short + powerful claws | Digging |
β Examples:
β’ Arboreal / Scansorial Adaptation / Climbing:
β Adaptive Features:
β Body Contour:
Table 1: Body Contour in Arboreal Animals
Feature | Adaptation |
|---|---|
Body shape | Long, narrow, elongated |
Vertebrae | Dorsolumbar elongation |
Vertebral count | Increased from 19 to 25β27 |
β Limb Girdles:
- β’Strongly built
- β’Curved ribs
- β’Well-developed clavicle + scapula
- β’Broad flat ilium β visceral support
β Limbs:
Table 1: Limbs in Arboreal Animals
Type | Feature |
|---|---|
General | Usually plantigrade |
Branch runners | Forelimbs + hindlimbs equal |
Suspending forms | Elongated humerus in forelimbs |
β Feet:
- β’Prehensile / grasping feet
- β’Opposable digits
- β’Syndactyly common
- β’Non-prehensile forms also present
β Tail:
- β’Prehensile
- β’Long tail for balancing
β Examples:
β Marsupials:
- β’Kangaroo
- β’Koala
β’ Cursorial / Running Adaptation:
β Adaptive Features:
Table 1: Cursorial Adaptations
Feature | Adaptation | Function |
|---|---|---|
Body | Spindle-shaped / streamlined | Fast running |
Neck | Shortened | Compact body |
Forelimbs | Less developed | Reduced resistance / weight |
Hindlimbs | Stout, muscular, longer | Main running force |
Fibula | Reduced | Lightness + speed |
Ulna | Reduced | Lightness + speed |
β Foot Posture: β
β Examples:
β’ High-Yield Recall:
Table 1: Adaptation One-Liners
Fact | Answer |
|---|---|
Primary aquatic animals | Gill breathers |
Secondary aquatic animals | Lung breathers |
Aquatic body shape | Streamlined / laterally compressed |
Primary aquatic respiration | Gills |
Hydrostatic organ | Swim bladder / air bladder |
Water disturbance detector | Lateral line sense organ |
3rd eyelid | Nictitating membrane |
Subcutaneous fat in aquatic mammals | Blubber |
Aquatic limb modification | Flippers / paddles |
β digits | Hyperdactyly |
β phalanges | Hyperphalangy |
Aerial body shape | Boat / spindle-shaped |
Bird body covering | Feathers |
Wing lowering muscle | Pectoralis major |
Wing raising muscle | Pectoralis minor |
Bird preening gland | Uropygial gland |
Flight coordination | Highly developed cerebellum |
Weight reduction in female bird | Single functional left ovary |
Passive flight | Gliding flight |
True flight animals | Birds + bat |
Desert urine | Highly concentrated |
Camel water cells | Rumen |
Desert lizard skin | Hygroscopic |
Burrowing adaptation | Fossorial |
Burrowing forelimbs | Short + powerful claws |
Climbing adaptation | Arboreal / scansorial |
Grasping tail | Prehensile tail |
Running adaptation | Cursorial |
Cursorial main limbs | Long muscular hindlimbs |
Cursorial reduced bones | Fibula + ulna |