🌳Ecology and Environment: Study Notes Class 12 Biology

Ecology is the study of the inter-relationships among organisms and between the organism and its environment.

I. Organisms and Populations

A. Organism and its Environment:

Ecology operates at four levels: Organisms, Populations, Communities, and Biomes.

Habitat is the physical place where an organism lives.

Niche is the specific functional role (or place and function) of an organism in its environment.

B. Major Abiotic Factors: The most important abiotic factors influencing living organisms are:

Temperature: The most ecologically relevant factor. Organisms can be Eurythermal (tolerate wide range) or Stenothermal (tolerate narrow range).

Water: The second most important factor. Organisms can be Euryhaline (tolerate wide salinity) or Stenohaline (tolerate narrow salinity).

Light: Essential for photosynthesis; affects photoperiodism and diurnal/seasonal rhythms.

Soil: The nature and properties of the soil (texture, water-holding capacity, pH) determine the type of vegetation.

C. Responses to Abiotic Factors:

Regulate: Organisms maintain a constant internal environment (Homeostasis) despite external changes (e.g., all birds and mammals).

Conform: Organisms allow their internal environment to change with the external environment (e.g., most plants and cold-blooded animals).

Migrate: Organisms move temporarily from a stressful habitat to a more hospitable area (e.g., Siberian cranes).

Suspend: Organisms enter a state of suspended animation to tide over

 

unfavourable conditions:

Hibernation: Winter sleep (e.g., polar bears).

Aestivation: Summer sleep (e.g., snails, fish).

Diapause: Stage of suspended development in many zooplanktons.