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Chapter 19: ORGANISMS AND ENVIRONMENT - II
19.1 POPULATION AND ECOLOGICAL ADAPTATIONS :
POPULATION:
A group of individuals belonging to the same species within an ecosystem is called a population.
The populations of the different species that live and interact together in the ecosystem are referred to as community.
The interactions between organisms in a community are called biological interactions.
No organism can exist in absolute isolation. Every organism must interact with other organisms and the environment. Interactions are fundamental to the survival of that organism and the functioning of the ecosystem.
ADAPTATIONS:
Adaptation is the adjustment made by an organism to the changing environment. It brings about structural and functional changes necessary for the survival. These changes can be for adapting to different conditions. Organisms living on land undergo certain modifications, which are useful for their survival.
Terrestrial adaptations.
Cursorial Adaptation is for running.
Cockroach exhibits this adaptation for running. It helps the animal to escape easily from its enemy. Cockroaches show presence of three pairs of long thoracic legs. The legs show presence of claws and adhesive pads which help in running.
The Fossorial Adaptation is adaptation for digging.
In rats, the fore-limbs are strong and stout. They are provided with claws which are useful in digging. They have a pointed, elongated snout which is also used in digging.
Arboreal adaptation is adaptation for climbing and balancing on trees.
The hind limbs of tree-dwelling animals like Monkey are provided with longer toes useful in swinging on branches.
The body is provided with long prehensile tail for balancing.
Desert adaptations are for survival in the desert.
In camel minimum water is lost through urine.
Water is stored in the muscles, water cells of stomach and connective tissues of the hump.
They show longer loop of Henle in their nephrons for more reabsorption of water.
Aquatic adaptation is an adaptation for aquatic mode of life.
In fish, ( Labeo) body is streamlined covered with scales for protection.
They are provided with gills for respiration and fins for locomotion.
Aerial / Volant adaptation is an adaptation for flying.
In birds, (e.g. Pigeon) the forelimbs are modified into wings.
They possess spindle-shaped body with hollow, pneumatic or spongy bones.
Only left ovary and oviduct are present to reduce weight.
Body is covered by feathers to facilitate flying.
