Biology_Today_-_October_2016

s Partial regulators are organisms that have ability to regulate body functions to a limited
extent. Beyond that limit, they become conformers.
s Homeostasis, especially thermoregulation is energetically expensive process.
s Heat loss or heat gain is directly related to surface area.
s Small animals (e.g., shrew, humming bird) have large surface area as compared to their
volume.
s In colder environment, they tend to lose heat very fast. They will have to spend more
energy in maintaining their body temperature as compared to large sized animals.
s It is because of this reason small sized animals do not occur in polar regions.

ADAPTATIONS

s Adaptation is the ability of an organism to survive and reproduce in its habitat. They develop due to natural selection of suitable
variations, which appear through mutation and recombination.

Plant Adaptations

Shade Plants

s Plants growing in shade or low light intensity are sciophytes

s The stems are narrower with longer internodes

s Epidermis is thin walled. Cuticle is thin

s Stomata occur in level with surface and generally on both the

surfaces

Sun Plants

s Plants growing in bright light are heliophytes

s The stems are thicker with shorter internodes

s Epidermis is thick walled. Cuticle is thick

s Stomata are generally sunken and are present on

lower surface

Plant Adaptations to Light

Plant adaptations to water

Xerophytes

s Extensive root system. Roots spread along soil surface to
absorb every drop of rain.

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

s Sunken stomata restricted to lower surface of leaf.

s Cuticle is thick.
Hydrophytes

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

s Xylem is poorly developed or absent.

s Aerenchyma, i.e., special air storage parenchyma is present.

s Submerged leaves are thin, small or finely dissected, floating

leaves are large, have stomata and waxy coating on upper

surface.

Halophytes

s Plants adapted to grow in mangroves, saline habitat.

s Cuticle is thick.

s Sunken stomata.

s Negatively geotropic, vertical roots called pneumatophores

are present. They possess lenticels for gaseous exchange.

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,

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.

Arctic tern

Locust

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

or aggression.

Grasshopper, Praying Mantis

(iii) Mimicry

(a) Batesian mimicry

(b) Mullerian 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.

Resemblance to a dangerous or unpalatable model so that the predator

usually does not prey upon it.

Resemblance of two animal species, especially insects, both unpalatable

or ferocious, to their mutual benefit.

Viceroy butterfly mimics

unpalatable Monarch butterfly.

Monarch butterfly and Queen

butterfly.