NCERT Class 11 Geography Life On The Earth

By now you might have realised that all units of this book have acquainted you with the three major realms of the  environment, that is, the lithosphere, the tmosphere and the hydrosphere. You know that living organisms of the earth, constituting the biosphere, interact with other environmental realms. The biosphere includes all the living components of the earth. It consists of all plants and animals, including all the micro-organisms that  live on the planet earth and their   nteractions with the surrounding environment. ost of the organisms exist on the lithosphere  and/or the hydrosphere as well as in the atmosphere. There are also many organisms that move freely from one realm to the other. The biosphere and its components are very significant elements of the environment. These elements interact with other components of the natural landscape such as land, water and soil. They are also influenced by the atmospheric elements such as the temperature, rainfall, moisture and sunlight. The interactions of biosphere with land, air and water are important to the growth, development and evolution of the organism.

ECOLOGY
You have been reading about ecological and environmental problems in newspapers and magazines. Have you ever thought what ecology is? The environment as you know, is made up of abiotic and biotic components. It
would be interesting to understand how the diversity of life-forms is maintained to bring a kind of balance. This balance is maintained in a particular proportion so that a healthy interaction between the biotic and the abiotic
components goes on. The interactions of a particular group of organisms with abiotic factors within a particular habitat resulting in clearly defined energy flows and material cycles on land, water and air, are called ecological systems.

A habitat in the ecological sense is the totality of the physical and chemical factors that constitute the general environment. A system consisting of biotic and abiotic components is known as ecosystem. All these components in ecosystem are inter related and interact with   ach other. Different types of ecosystems exist with varying ranges of environmental conditions where various plants and animal species have got adapted through evolution.
This phenomenon is known as ecological adaptation.

Types of Ecosystems
Ecosystems are of two major types: terrestrial and aquatic. Terrestrial ecosystem can be further be classified into ‘biomes’. A biome is a plant and animal community that covers a large geographical area. The boundaries of
different biomes on land are determined mainly by climate. Therefore, a biome can be defined as the total assemblage of plant and animal species interacting within specific conditions. These include rainfall, temperature, humidity and soil conditions. Some of the major biomes of the world are: forest, grassland, desert and tundra biomes. Aquatic ecosystems can be classed as marine and freshwater ecosystems. Marine ecosystem includes the oceans, coastal estuaries and coral reefs. Freshwater ecosystem includes lakes, ponds, streams, marshes and bogs. Structure and Functions of Ecosystems The structure of an ecosystem involves a description of the available plant and animal species. From a structural point of view, all ecosystems consist of abiotic and biotic factors. Abiotic factors include rainfall, temperature, sunlight, atmospheric humidity, soil conditions, inorganic substances (carbon dioxide, water, nitrogen, calcium, phosphorus, potassium, etc.). Biotic factors include the producers, (primary, secondary, tertiary) the  onsumers and the decomposers. The producers include all the green plants, which manufacture their own food through photosynthesis. The primary consumers include herbivorous animals like deer, goats, mice and all plant-eating animals. The carnivores include all the flesh-eating animals like snakes, tigers and lions. Certain carnivores that feed also on carnivores are known as top carnivores like hawks and mongooses. Decomposers are those that feed on dead organisms (for example, scavengers like vultures and crows), and further breaking down of the dead matter by other decomposing agents like bacteria and various microorganisms.

Excercise

1. Multiple choice questions.
(i) Which one of the following is included in biosphere?
(a) only plants (c) only animals
(b) all living and non-living organisms (d) all living organisms
(ii) Tropical grasslands are also known as :
(a) the prairies (c) the steppes
(b) the savannas (d) none of the above
(iii) Oxygen combines with iron found in the rocks to form :
(a) iron carbonate (c) iron oxides
(b) iron nitrites (d) iron sulphate
(iv) During photosynthesis, carbon dioxide combines with water in the presence of sunlight to form :
(a) proteins (c) carbohydrates
(b) amino acids (d) vitamins
2. Answer the following questions in about 30 words.
(i) What do you understand by the term ‘ecology’?
(ii) What is an ecological system? Identify the major types of ecosystems in the world.
(iii) What is a food-chain? Give one example of a grazing food-chain identifying the various levels.
(iv) What do you understand by the term ‘food web’? Give examples.

3. Answer the following questions in about 150 words.
(i) What are bio-geochemical cycles? Explain how nitrogen is fixed in the atmosphere.
(ii) What is an ecological balance? Discuss the important measures needed to prevent ecological imbalances.

Please refer to attached file for NCERT Class 11 Geography Life On The Earth