"The record of life that existed on this planet in different periods is found in rocks in the form of fossils". Explain

The microscopic structures closely related to the present form of blue algae have been found in geological formations that are much older than these were some 3,000 million years ago 

Discuss the various stages of formation of the earth's atmosphere.

There are three stages in the evolution of the present atmosphere. 

• The first stage is marked by the loss of primordial atmosphere. 
• In the second stage, the hot interior of the earth contributed to the evolution of the atmosphere.
• During the cooling of the earth, gases and water vapour were released from the interior solid earth. 
• This started the evolution of the present atmosphere. 
• The early atmosphere largely contained water vapour, nitrogen, carbon dioxide, methane, ammonia and very little of free oxygen. 
• The process through which the gases were outpoured from the interior is called degassing.
• Continuous volcanic eruptions contributed water vapour and gases to the atmosphere. 
• As the earth cooled, the water vapour released started getting condensed. 
• The carbon dioxide in the atmosphere got dissolved in rainwater and the temperature further decreased causing more condensation and more rains. 
• The rainwater falling onto the surface got collected in the depressions to give rise to oceans.
• The earth’s oceans were formed within 500 million years from the formation of the earth.  
• Finally, the composition of the atmosphere was modified by the living world through the process of photosynthesis. 
• around 2,500-3,000 million years before the present, the process of photosynthesis got evolved. 
• Life was confined to the oceans for a long time. Oceans began to have the contribution of oxygen through the process of photosynthesis. 
• Eventually, oceans were saturated with oxygen, and 2,000 million years ago, oxygen began to flood the atmosphere. 

What factors lead to the formation of lithosphere?

1. Differential rate of cooling of earth led to separation of layers. Lighter material came up and heavier sank down.

2. During the formation of moon,due to the giant impact, the earth was further heated up. It is through the process of differentiation that the earth forming material got separated into different layers.

 

What do you understand by the term "big-splat"?

It is now generally believed that the formation of moon, as a satellite of the earth, is an outcome of ‘giant impact’ or what is described as “the big splat”. A body of the size of one to three times that of mars collided into the earth sometime shortly after the earth was formed. It blasted a large part of the earth into space. This portion of blasted material then continued to orbit the earth and eventually formed into the present moon about 4.44 billion years ago. 

What reasons could be attributed to for the difference between the terrestrial and the jovian planets?

1. (i)  The terrestrial planets were formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles. Jovian planets were formed at quite a distant location.
   
   
2. (ii)  The solar wind was most intense nearer the sun; so, it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets.
   
   
3. (iii)  The terrestrial planets are smaller and their lower gravity could not hold the escaping gases. 
   

Monsoon forests are the most varied. What is understood by this statement. What factors are responsible for such variations?

Monsoon forests are most varied because of they range from forests to thickets and from savanna to scrubland.
This is primarily because unequal spatial distribution of rainfall.

Differentiate between tropical monsoon and tropical marine climates

Tropical Monsoon Climate

• On-shore wet monsoons in the summer and off-shore dry monsoons in the winter
• Indian subcontinent, Myanmar, Thailand, Laos, Cambodia, parts of Vietnam and South China, Northern Australia

Tropical Marine Climate:

• influence of on-shore trade winds all the year round
• more evenly distributed rainfall
• Central America, West Indies, NE Australia, the Philippines, parts of E. Africa, Madagascar,  the Guinea Coast, eastern Brazil

Despite being endowed with many natural resources, equatorial countries have not displayed commensurate economic progress. What do you think are the factors responsible for this?

1. Equatorial Climate and health:

• Harsh conditions: extreme heat and rain
• Favorable for growth of parasites and hence diseases like malaria and yellow fever

2. Prevalence of bacteria and insect pests:

• climate suitable for growth of pests and insects: diseases and damages to crops

3. Jungle hinders development and maintenance:

• High undergrowth impedes the growth of crops ==> once cleared they regrow faster ==> choke crops
• due to density of forests problem in building and maintaining communication infrastructure like railways, roads etc

4. Rapid deterioration of tropical soil: due to heavy downpour

• But exceptions are Java: rich soil because of volcanic ashes
• Malaysia, Singapore and eastern Brazil: systematic planning for land development

5. Difficulties in lumbering

• hardwood makes it difficult to transport: cant float on water and there is no ice to slide upon

6. Livestock farming:

• handicapped due to absence of meadow grass
• tall and coarse grasses: non nutritious 
• animal diseases: ngana (caused by tsetse flies)

What are different crops produced in tropical regions of the world?

1. Rubber ==> Malaysia, Indonesia
2. Cocoa ==> West Africa, Areas bordering Gulf of Guinea, Nigeria, Ghana
3. Oil Palm ==> West Africa, Areas bordering Gulf of Guinea, Nigeria, Ghana
4. Coconuts
5. Sugarcane
6. Coffee
7. Tea
8. Tobacco
9. Spices
10. Chinchona
11. Bananas
12. Pineapple
13. Sago

Though Rubber was first discovered in Amazon basin yet this area is not the leading producer of rubber in the world. Which countries are the leading producers and what are the factors leading to this shift?

Ans:
Malaysia and Indonesia
1. Europeans introduced rubber to these countries
2. The problems of tree diseases and the lack of commercial organization of the tribals in Amazon lowlands.

Mention the characteristics of Equatorial Vegetation

Ans:

1. A great variety of vegetation
2. A distinct layer arrangement
3. Multiple species
4. Forest clearings (for agriculture)

Why are the tropical countries a net timber importers?

Ans:
1. Many species are found in a smaller area. For example Malaysian jungles have around 200 species in a acre of forest land. Hence, commercial exploitation of trees becomes difficult.

2. Since the species of trees found in the tropical rain forests (found in tropical countries) are hardwoods and do not float easily on water , haulage becomes unviable.