Biology Today - February 2018

• Man is always most important biotic factor. He changes the environment by his activities regularly, HJ, by excessive cutting
  of trees, fire, domestication of plants and animals, by causing different types of pollution, etc.

ADAPTATIONS

• Adaptation is any attribute of the organism (morphological, physiological or behavioural) that enables it to survive and
  reproduce in its habitat.

Plant Adaptations

Shade plants

• Plants growing in shade or low light intensity are sciophytes


• Stems are narrower with longer internodes


• Epidermis is thin walled and cuticle is thin


• Stomata occur in level with surface and generally on both the
  surfaces

Sun plants

• Plants growing in bright light are heliophytes


• Stems are thicker with shorter internodes


• Epidermis is thick walled and cuticle is thick


• Stomata are generally sunken and are present on
  lower surface

Plant adaptations to light

Plant adaptations to water

Xerophytes

• Extensive root system, roots spread
  along soil surface to absorb every
  drop of rain.


• Leaves possess prickles and spines. In
  grasses, leaves are rolled up to reduce
  exposed surface for transpiration.


• Sunken stomata restricted to lower
  surface of leaf.


• Cuticle is thick.

Halophytes

• Plants adapted to grow in
  mangroves, saline habitat.


• Cuticle is thick.


• Sunken stomata.


• Negatively geotropic, verti-
  cal roots called pneumato-
  phores are present. They
  possess lenticels for gaseous
  exchange.

Hydrophytes

• Roots are either absent, poorly developed
  or used for balancing, root caps are
  replaced by root pockets.


• Xylem is poorly developed or absent.


• Aerenchyma, LH, special air storage
  parenchyma is present.


• Submerged leaves are thin, small or finely
  dissected while floating leaves are large, have
  stomata and waxy coating on upper surface.

Table: Adaptations of animals

Type of adaptation Activity Example

(i) Migration

(a) Daily migration

(b) Seasonal migration

(c) Periodic migration

Two-way movement of an animal group to other places for food,

climate and breeding.

Migration between feeding and resting places.

Migration to avoid stressful and inhospitable seasons.

When population increases beyond feeding capacity, large

population migrate to various directions in search of food.

Blackbird

Arctic tern

Locust

(ii) Camouflage Ability to blend with the surroundings to remain unnoticed for

protection or aggression.

Grasshopper and Praying Mantis

(iii) Mimicry Resemblance of one species with another in order to obtain

advantage, especially against predation. The species which is imitated

is called model while the animal which imitates is known as mimic.

(a) Batesian mimicry Resemblance to a dangerous or unpalatable model so that the

predator usually does not prey upon it.

Viceroy butterfly mimics unpalata-

ble toxic Monarch butterfly

(b) Mullerian mimicry Resemblance of two animal species, especially insects, both

unpalatable or ferocious, to their mutual benefit.

Monarch butterfly and Queen

butterfly

(iv) Echolocation Producing high frequency sound which produce echoes after

striking various objects, it helps to locate path and predators.

Bats and whales

(v) Hibernation Undergo winter sleep, body temperature drops, breathing and

heartbeat become slow.

Northern ground squirrels

(vi) Aestivation Avoid heat by spending dry-hot period in a torpid (dormant) state

into burrows.

Ground squirrels of South Western

deserts