Life on Earth - Chapter 15 Class 11 NCERT Geography

1. Multiple choice questions. 

(i) Which one of the following is included in biosphere?

(a) only plants

(b) all living and  non-living organisms

(c) only animals  

(d) all living organisms

(ii) Tropical grasslands are also known as :

(a)    the prairies

(b) the savannas

(c) the steppes

(d) none of the above

(iii) Oxygen combines with iron found in the rocks to form :

(a)    iron carbonate

(b) iron nitrites

(c) iron oxides

(d) iron sulphate

(iv) During photosynthesis, carbon dioxide combines with water in the presence of sunlight to form : (a) proteins

(b) amino acids

(c) carbohydrates

(d) vitamins

2. Answer the following questions in about 30 words.

(i) What do you understand by the term ‘ecology’?

Ans. The term ecology is derived from the Greek word ‘oikos’ meaning ‘house’, combined with the word ‘logy’ meaning the ‘science of’ or ‘the study of’. Ecology is the study of the earth as a ‘household’, of plants, human beings, animals and micro-organisms.

(ii) What is an ecological system? Identify the major types of ecosystems in the world.

Ans. 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.

The two major types of ecosystem are - terrestrial and aquatic

(iii) What is a food-chain? Give one example of a grazing food-chain identifying the various levels.

Ans. This sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as the food-chain. For e.g. – Plants (producers) get eaten by rabbits, deer, cow etc...(herbivores animals), similarly herbivores animals get eaten by fox, lion, tiger, eagle etc...(carnivores animals).

(iv) What do you understand by the term ‘food web’? Give examples.

Ans. A food web is a natural interconnection of food chains. In other words, a network of food chains mixed together to form food web.

(v) What is a biome?

Ans. A biome is a plant and animal community that covers a large geographical area. This geographical area is usually determined by climate.

3. Answer the following questions in about 150 words.

(i) What are bio-geochemical cycles? Explain how nitrogen is fixed in the atmosphere.

Ans. Bio-geochemical cycles are chemical exchange between living organisms that is where the term “bio” come from, and the “geographic” element of the earth such as - rocks, soil, air, and water. In simple terms, it is a cycle that shows the movement of chemical elements between the biotic (living organism) and the abiotic (non-living organism) components of the environment.

Nitrogen is a major constituent of the atmosphere comprising about 79% of the atmospheric gases. Nitrogen is considered as an unreactive gas. Nitrogen gas is formed when two nitrogen atoms bond together. Nitrogen molecules have a triple covalent bond and it requires a huge amount of energy to break triple bonds. Hence, this massive energy can be obtained by lightning and cosmic radiation.

(ii) What is an ecological balance? Discuss the important measures needed to prevent ecological imbalances.

Ans. Ecological balance is a state where there is equality between organisms and their environment in terms of coexistence.

Ecological imbalance occurs due to the introduction of new species, natural hazards or human causes.

Measures to prevent ecological imbalance:-

1. Manage Natural Resources Carefully

2. Controlling Population - reducing human consumption of natural resources

3. Protecting the Water

4. Recycling

5. Planting more trees

6. Improving farming techniques to avoid land degradation

7. Shifting from Fossil Fuels to Sustainable Energy

The Origin and Evolution of Earth - Chapter 2 Class 11 NCERT Geography Solutions

1. Multiple choice questions.

(i) Which one of the following figures represents the age of the earth?

(a) 4.6 million years     

(b) 13.7 billion years

(c) 4.6 billion years    

(d) 13.7 trillion years

(ii) Which one of the following has the longest duration?

(a) Eons

(b) Period

(c) Era

(d) Epoch

(iii) Which one of the following is not related to the formation or modification of the present atmosphere?

(a) Solar winds

(b) Differentiation

(c) Degassing

(d) Photosynthesis

(iv) Which one of the following represents the inner planets?

(a) Planets between the sun and the earth

(b) Planets between the sun and the belt of asteroids

(c) Planets in gaseous state

(d) Planets without satellite(s)

(v) Life on the earth appeared around how many years before the present?

(a) 13.7 billion

(b) 3.8 million

(c) 4.6 billion

(d) 3.8 billion

2. Answer the following questions in about 30 words.

(i) Why are the terrestrial planets rocky?

The planets that falls under the title "terrestrial" planets are Mercury, Venus, Earth and Mars . They are similar to Earth in composition. And these planets are also nearer to the sun. Due to extreme heat from the Sun evaporated lightweight elements like hydrogen and helium from these terrestrial planets leaving behind rocky and metallic elements.

(ii) What is the basic difference in the arguments related to the origin of the earth given by :

(a) Kant and Laplace

German philosopher Immanuel Kant was well known for his argument on Nebular Hypothesis. Then in 1796 Mathematician Laplace revised it. According to Laplace, the planets were formed out of a cloud of material associated with a youthful sun and that cloud was known as Nebula.

(b) Chamberlain and Moulton

In 1904, Chamberlain and Moulton proposed the planetesimal hypothesis. They considered that:

1. Sun always existed way before the planets were formed.
2. Then a wandering star came closer to the sun.
3. Due to gravitational pull of the star, a cigar-shaped extension of material was separated from the solar surface.
4. As the passing star moved away, the material separated from the solar surface continued to revolve around the sun and it slowly condensed into planets.

(iii) What is meant by the process of differentiation?

It is a process in which the materials that formed the layers of the earth which are - crust, upper mantle and lower mantle, outer core and inner core. These layers got separated based on their material densities.

(iv) What was the nature of the earth surface initially?

The planet earth initially was a barren, rocky and hot object with a thin atmosphere of hydrogen and helium.

(v) What were the gases which initially formed the earth’s atmosphere?

Hydrogen and Helium.

3. Answer the following questions in about 150 words.

(i) Write an explanatory note on the ‘Big Bang Theory’.

The other name of Big Bang Theory is the expanding universe hypothesis. It is referred as the modern theory when it comes to the origin of earth. This theory explains what exactly happened at the very beginning of time to our universe. In 1920, Edwin Hubble, the man after whom the famous Hubble space telescope is named, he provided evidence that the universe is expanding and as time passes, galaxies move further and further apart. While Edwin Hubble was correct with his observation that galaxies were moving apart, but other scientists believed that there is no evidence that supports the galaxies themselves are expanding.

(ii) List the stages in the evolution of the earth and explain each stage in brief.
I am yet to write this answer!

Geography as a discipline - Chapter 1 Class 11 NCERT Geography Solutions

Answer the questions in about 30 words.

(i) What important cultural features do you observe while going to school? Are they similar or dissimilar? Should they be included in the study of geography or not? If yes, why?
Ans. Cultural features are also known as man-made features. Therefore some cultural features that can be seen while going to school are:- roads, bridges, railways, markets etc. They are absolutely dissimilar features and they should be included in the study of geography as they are found on the earth’s surface and geography as a subject is concerned with the study of physiographic, social and cultural features, and the interactions between them.

(ii) You have seen a tennis ball, a cricket ball, an orange and a pumpkin. Which one among these resembles the shape of the earth? Why have you chosen this to describe the shape of the earth?

Ans. The shape of the earth could be best resembled with a pumpkin because earth is not a perfect circle, it is spherical in shape and the radius of the earth from the center deceases as we go towards North and South Pole.

(iii) Do you celebrate Vanmahotsava? Why do we plant more trees? How do the trees help in maintaining the ecological balance?
Ans. Planting trees is as essential part of instantiating the ecosystem because trees and plants absorb carbon dioxide and convert it to oxygen therefore it helps in fixing and consuming carbon from the atmosphere. When the carbon content in the atmosphere is high, it affects the the global climate tremendously. Trees also help in balancing environmental pollution.

(iv) You have seen elephants, deer, earthworms, trees and grasses. Where do they grow or live? What is the name given to this sphere? Describe some of the important features of this sphere?
Ans. These all animals and organism live together forming a Biosphere. The biosphere is made up of the three components and they are - air, land and water. And if you see life exists in all these spheres.

(v) How much time do you take to reach your school from your house? If your school was located across the road from your house, how much time will it take you to reach school? What is the effect of the distance between your residence and the school? Can you convert time in terms of space and vice versa?
Ans. It is possible to convert time in terms of space and space in terms of time. For example, it can be said that place A is 5 km away from place B or in other words it can also be said that place A is 10 minutes away from place B, if the mode of transportation is with a bike.

3. Answer the following questions in about 150 words.

(i) You observe every day in your surroundings that there is variation in natural as well as cultural phenomena. All the trees are not of the same variety. All the birds and animals you see, are different. All these different elements are found on the earth. Can you now argue that geography is the study of “areal differentiation”?
Ans.


(ii) You have already studied geography, history, civics and economics as parts of social studies. Attempt an integration of these disciplines highlighting their interface.
Ans.