- Characters that make an organism to adjust well and suited to its way of life.
- Variation occur in living organism due to change in environment.
- These changes are inherited.
- So organism is well suited in nature.
- Adaptation may be short term or long term.
A. SHORT TERM ADAPTATION -
These adaptation are temporary and appear in response to changing conditions.
Later on these adaptation disappear as conditions become normal.
These adaptations have survival value.
1. On exposure to sun light for a longer period, our skin becomes dark, skin may become red due to vasodilation (increase in the diameter of blood vessels).
2. In winter skin becomes white due to vasoconstriction.
3. Some animals go for hibernation (winter sleep) during winter & aestivation (summer sleep) during summer.
Example of hibernation is frog, polar bear. Example of aestivation is frog.
4. Plants show yellow leaves (etiolation) in dark.
5. Dormant seeds & buds remain inactive during the period of dormancy.
6. Viviparous germination (germination of seed in fruit) is noted in mangroove vegetation due to saline soil.
B. LONG TERM ADAPTATION -
These are permanent.
Having positive valve in evolution.
1. Class of different birds are well adapted to suit their perching habits as climbing & clinging in wood pecker, grasping in eagle, webbed feet in duck.
2. The beak's shapes of different birds are according to their feeding habits as scroping fruits in hornbill, suck necter in humming bird, tearing flesh is vulture, picking insects in wood pecker.
3. Kangaroo uses its thick tail as a fifth limb for resting & jumping.
4. Ankle bones in man are protreded backward which help us to stand erect on our legs.
5. In sub merged plants stometa are absent as gaseous exchange occur in dissolved form thorugh general body surface.
6. Xerophytic plants show long roots, green fleshy stem, leaves converted into spines to reduce transpiration.
7. Wall lizard have sucker system to walk on wall.
8. In birds pneumatic bones (hollow), one ovary, absence of urinnary bladder is to reduce weight.
9. Mouth parts of different insects are according to food habit as - Spongy - house fly. Siphoning - Honey bee Piercing & sucking - Mosquito Mendibulate (chewing) - Cockroach
10. Social insects show division of labour e.g. honey bee (queen, drones, workers) termite (queen, king, nasuitus &
11. In walrus tusk are modified canines, helpful in locomotion.
12. In orchid (ophrys) the flowers resemble to female of wasp (calpo) & is polinated by male wasp, this is mimicry.
13. Limnophila shows heterophglly i.e. plant is amphibious in nature, half part of leaf is in water, its margin is wavy, half part of leaf is outside water, its margin is not wavy i.e. smooth.
14. Some animals shows mimicry. eg. Phyllium (leaf insect).
15. In rhacophorus (flying frog) webs of fore toes & hind toes are helpfull in gliding.
16. In pteropus (bat), draco (flying lizard) skin forms wing (patagium) for flying.
17. In exocoetus (flying fish), pectoral fin is large & helpful in gliding.
18. Snakes are limb less due to creeping mode & burrowing habit.
19. Cicada sleeps for about 16 yrs. Its active period is of one year only, due to low metabolic rate.