Part- III

Question 1

Biodiversity

Answer 1

1. Biodiversity itself is a combination of two words, Bio (life) and diversity (variety).
2. It is the number and variety of organisms found within a specified topographical region.
3. It brings up to the varieties of flora, fauna, and micro-organisms, the genes they contain and the ecosystems they form.
4. It relates to the variability among living organisms on the earth, including the variability within and between the species and that within and between the ecosystems.
5. Biodiversity is an arrangement in continuous evolution, from the viewpoint of an individual organism as well as from a viewpoint of species.
6. It is not found uniformly on the earth.

Question 2

Biodiversity Types

Answer 2

Biodiversity can be discussed at three levels:

1. Genetic diversity
2. Species diversity
3. Ecosystem diversity

Question 3

Genetic Diversity

Answer 3

1. Genetic biodiversity refers to the variation of genes within species.
2. Genes are the basic building blocks of several life forms.
3. Species are the groups of individual organisms having definite resemblances in their physical characteristics.
4. Human beings inherently belong to the Homo sapiens group.
5. They also differ in their features such as physical appearance, height, etc. This is due to genetic diversity.
6. This genetic diversity is vital for healthy breeding of population of species

Question 4

Species Diversity

Answer 4

1. Species Diversity refers to the variety of species.
2. It relates to the number of species in a demarcated area.
3. The diversity of species can be measured through its abundance, richness, and types.
4. The regions rich in species diversity are called hotspots of diversity.

Question 5

Ecosystem Diversity

Answer 5

1. The wide differences between types of ecosystem and the diversity of habitats and ecological processes happening inside each ecosystem type set up the ecosystem diversity.
2. The boundaries of communities and ecosystems are not very strictly demarcated.
3. Hence the demarcation of ecosystem boundaries is intricate and difficult.

Question 6

Importance of Biodiversity

Answer 6

• The concept of biodiversity is an integral part of many human cultures.
• Biodiversity plays the following roles:

1. Ecological
2. Economic
3. Scientific

• It has contributed in several ways to the development of human culture and, in turn, human communities.
• It has played a major role in shaping the diversity of nature at the genetic, species and ecological levels.

Question 7

Ecological Role of Biodiversity

Answer 7

• Each organism contributes something of use to other organisms besides extracting its needs.
• The major functions done by species which are important for ecosystem function and human survival are:

1. Capture and store energy
2. Produce and decompose organic materials
3. Help to cycle water and nutrients throughout the ecosystem
4. Fix atmospheric gases and help to regulate the climate

• The more diverse an ecosystem, better are the chances for the species to survive through adversities and attacks, and subsequently, is more productive.
• Hence, the loss of species would decline the ability of the system to maintain itself.
• The more the diversity of species in an ecosystem, the more stable the ecosystem is likely to be.

Question 8

Economic Role of Biodiversity

Answer 8

• Biodiversity is an important resource in their day-to-day life for all humans.
• It is comprehended as a reservoir of resources to be drawn upon for the manufacture of food, cosmetic products, and pharmaceuticals.
• Some of the significant economic commodities that man derives from biodiversity are:

1. Food crops
2. Livestock
3. Forests
4. Fish
5. Medicinal resources

• The vital part of biodiversity is ‘crop diversity’, which is also known as agro-biodiversity.
• This idea of biological resources is accountable for the deterioration of biodiversity.

Question 9

Scientific Role of Biodiversity

Answer 9

1. All species can contribute some evidence to show how life evolved and will continue to evolve.
2. Biodiversity helps in sensing how life functions and the role of each species in sustaining ecosystems.
3. The level of biodiversity is a good indicator of the state of the relationships of human beings with other living species.

Question 10

Loss of biodiversity

Answer 10

1. About three-fourth of the human population resides in the Tropical regions which occupy only about one-fourth of the total area of the world.
2. The tropical rain forests contain 50 percent of the species on the earth.
3. The excessive population has resulted in the rampant exploitation of resources and deforestation.
4. The destruction of the Tropical regions has resulted in the loss of natural habitats which is catastrophic for the whole biosphere.
5. Natural calamities like forest fires, droughts, floods, volcanic eruptions, earthquakes, etc. cause damage to both flora and fauna of the earth.
6. Pesticides and other pollutants like toxic heavy metals and hydrocarbons destroy the feeble and sensitive species.
7. Loss of biodiversity in an area may cause

• Decline in plant production
• Lowered resistance to environmental perturbations
• Increased variability in definite ecosystem developments such as water use, plant productivity, and disease cycles and pests.

Question 11

IUCN

Answer 11

• The IUCN issues data about endangered species universally as the Red List of threatened species.
• The organization has categorized the threatened species of plants and animals into three categories for the purpose of their conservation.

1. Endangered Species
2. Vulnerable Species
3. Rare Species

Question 12

Endangered Species

Answer 12

It comprises those species which are in danger of extinction.

Question 13

Vulnerable Species

Answer 13

1. This comprises the species which are probable to be in danger of extinction in near the future if the factors threatening to their extinction continue.
2. Survival of these species is not guaranteed as their population has decreased greatly.

Question 14

Rare Species

Answer 14

• The population of these species is very small in the world and they are restricted to limited areas or thinly scattered over a wider area.

Question 15

Causes of biodiversity losses

Answer 15

• The accelerated rates of species extinctions that the world is facing now are largely due to human activities.
• There are four major causes

1. Habitat loss and fragmentation
2. Over-exploitation
3. Alien species invasions
4. Co-extinctions

Question 16

Habitat loss and fragmentation

Answer 16

1. Habitat loss and fragmentation is the most important cause driving animals and plants to extinction.
2. The most intense examples of habitat loss come from tropical rain forests.
3. The Amazon rain forests protecting probably millions of species is being cut and cleared for agricultural purposes or for conversion to grasslands for raising beef cattle.
4. In addition to the total loss, the degradation of several habitats by pollution also threatens the existence of many species.
5. When large habitats are broken up into small fragments due to anthropogenic activities, mammals and birds necessitating large territories and certain animals with migratory habits are severely affected, leading to population regressions.

Question 17

Over-exploitation

Answer 17

1. Humans have always depended on nature for food and shelter, etc.
2. The population explosion is the major reason for the over-exploitation of available resources.
3. Many species extinctions in the last 500 years such as Steller’s sea cow, passenger pigeon were due to overexploitation by humans.
4. Currently, several marine fish populations around the world are over harvested, threatening the sustained existence of certain commercially important species.

Question 18

Alien species invasions

Answer 18

1. When alien species are introduced by chance or deliberately, some of them turn aggressive and cause the extinction of local species.
2. The Nile perch introduced into Lake Victoria in East Africa led ultimately to the extinction of a naturally unique group of more than 200 species of cichlids fish in the lake.
3. The illegal introduction of the African catfish, Clarias gariepinus for aquaculture purposes is posing a danger to the local catfishes.

Question 19

Co-extinctions

Answer 19

1. When a species becomes extinct, the flora and fauna related with it in an essential way also become extinct.
2. When a host fish species becomes extinct, its unique assemblage of parasites also meets the same destiny.

Question 20

Conservation of Biodiversity

Answer 20

1. Biodiversity is important for human existence.
2. All forms of life are so closely interlinked that disturbance in one gives rise to imbalance in the others.
3. As the problem of loss of biodiversity tends to continue, the need of the hour is to educate people to adopt environment-friendly practices and reorient their activities in a way that the development is harmonious with other life forms.
4. The critical problem is not only the conservation of species nor the habitat but the extension of the process of conservation.
5. There is an increasing awareness of the fact that such conservation with sustainable use is possible only with the participation and cooperation of local groups and individuals.

Question 21

Development of institutional structures

Answer 21

• To create awareness and ensure participation and cooperation, development of institutional structures at local levels is essential.

Question 22

Convention on Biodiversity

Answer 22

1. The Government of India signed the Convention on Biodiversity at the Earth Summit.
2. The Earth Summit was held in Rio de Janeiro, Brazil in June 1992.
3. Along with India, 155 other nations have also signed this.

Question 23

World Conservation Strategy

Answer 23

1. The world conservation strategy has suggested the following steps for biodiversity conservation:

• Efforts should be made to preserve the species that are endangered.
• Prevention of extinction needs proper management and planning.
• Varieties of forage plants, livestock, food crops, timber trees, animals and their wild lineages should be preserved.

1. Every country should recognize habitats of wild flora and fauna, and ensure their protection.
2. Habitats where species breed, feed, rest and nurture their young should be maintained and protected.
3. International trade in animals and wild plants should be regulated.

Question 24

Wild Life (Protection) Act, 1972

Answer 24

1. To protect, preserve and propagate the diversity of species within natural boundaries, the Government of India passed the Wild Life (Protection) Act, 1972.
2. Under this act only, the sanctuaries and national parks were established and biosphere reserves declared.

Question 25

Megadiversity

Answer 25

1. There are some countries which are situated in the tropical region; they possess a large number of species diversity in the World. They are called mega diversity centres. 2. There are 12 such countries, namely Mexico, Columbia, Ecuador, Peru, Brazil, Democratic Republic of Congo, Madagascar, China, India, Malaysia, Indonesia and Australia in which these centres are located.

Question 26

Hot spots

Answer 26

1. Hotspots are defined according to the vegetation. 2. Plants are vital as they determine the primary productivity of an ecosystem. 3. Most of the hotspots depend on species-rich ecosystems for food, firewood, cropland, and revenue from timber.

Question 27

Koeppen’s Climate Classification

Answer 27

* Koeppen’s Classification of climate is the most commonly used classification of climate. * This climate classification scheme was developed by Wladimir Peter Koeppen in 1884. * He recognized a close relationship between the distribution of vegetation and climate. * The categories are based on the data of annual and monthly averages of temperature and precipitation. * He selected specific values of temperature and precipitation and related them to the distribution of vegetation and used these values for classifying the climates. * The Koeppen climate classification system recognizes five major climatic types and each type is designated by a capital letter- A, B, C, D, E, and H. * The seasons of dryness are indicated by the small letters: f, m, w, and s. 1. f -no dry season 2. m – Monsoon climate 3. w- Winter dry season 4. s – Summer dry season * The small letters a, b, c, and d refer to the degree of severity of temperature.

Question 28

List of climatic groups and their characteristics according to Koeppen

Answer 28

**Group & Characteristics** **Group A-** TropicalAverage temperature of the coldest month is 18° C or higher **Group B-** Dry ClimatesPotential evaporation exceeds precipitation **Group C-** Warm TemperateThe average temperature of the coldest month of the (Mid-latitude) climates years is higher than minus 3°C but below 18°C **Group D-** Cold Snow forestThe average temperature of the coldest month is minus 3° C or below **Group E-** Cold ClimatesCold Climates Average temperature for all months is below 10° C **Group H-** HighlandsCold due to elevation

Question 29

Climatic Types According to Koeppen

Answer 29

Question 30

Koppen's Group A Climates

Answer 30

1. Koeppen’s Group-A climates are found in the unbroken belt around the Earth at low latitudes, typically within 15° North and South. 2. Group A climates are regulated largely by the seasonal variations of the trade winds, the Inter-Tropical Convergence Zone (ITCZ), and the Asian monsoon.

Question 31

Group A: Tropical Humid Climates

Answer 31

1. Tropical humid climates exist between Tropic of Cancer and Tropic of Capricorn. 2. Inter-Tropical Convergence Zone makes the climate hot and humid. 3. The annual range of temperature in this region is very low whereas the annual rainfall is high. 4. The tropical group is divided into three types. They are: * Af – Tropical wet climate * Am – Tropical monsoon climate * Aw – Tropical wet and dry climate

Question 32

Tropical Wet Climate (Af)

Answer 32

1. Tropical wet climate is seen near the equator. 2. The chief areas that lie in this climate are: * Amazon Basin in South America * Western Equatorial Africa * The islands of East Indies 1. A substantial amount of rainfall occurs in every month of the year. 2. These regions receive thundershowers in the afternoon. 3. The temperature is uniformly high. 4. The annual range of temperature is negligible. 5. The maximum temperature during daytime is about 30°C whereas the minimum temperature is about 20°C. 6. The region is bestowed with Tropical evergreen forests and large biodiversity.

Question 33

Tropical Monsoon Climate (Am)

Answer 33

1. Tropical monsoon climate (Am) is found over: * The Indian sub-continent * North Eastern part of South America * Northern Australia. 1. These regions receive heavy rainfall in summer. 2. Winter in this area seems to be dry.

Question 34

Tropical Wet and Dry Climate (Aw)

Answer 34

1. Tropical wet and dry climate is found in north and south of Tropical Wet Climate (Af) type climate regions. 2. It borders with Cf or Cw on the eastern part and dry climate on the western part of the continent. 3. Extensive Aw climate is found in * Sudan * South of Central Africa * North and South of the Amazon forest in Brazil * Connecting parts of Bolivia and Paraguay in South America 1. The annual rainfall in Tropical Wet and Dry Climate is significantly less than that in Af and Am climate types. 2. The wet season is shorter in this region. 3. The dry season is longer with the drought being more severe. 4. The diurnal ranges of temperature are extreme in the dry season. 5. Temperature is high throughout the year. 6. Deciduous forest and tree-shredded grasslands main flora found in this region.

Question 35

Koeppen's Group-B Climates

Answer 35

1. The Group-B Climates of Koppen’s Climate Classification are Dry Climates 2. These arid and semiarid climates cover about a quarter of the land surface of the Earth. 3. This region lies between 50° North and 50° South. 4. But these regions are predominantly seen in the 15–30° latitude belts in northern and southern hemispheres. 5. These regions have intense solar radiation and clear skies. 6. These regions experience * Low precipitation * Great variability in precipitation from year to year * Low relative humidity * High evaporation rates 1. Dry climates are divided into: * Steppe or semi-arid climate (BS) 1. Subtropical steppe (BSh)- Latitudes from 15° – 35° 2. Mid-latitude steppe (BSk) * Desert climate (BW) 1. Subtropical desert (BWh) – Latitudes between 35°- 60° 2. Mid-latitude desert (BWk)

Question 36

Subtropical Steppe (BSh) and Subtropical Desert (BWh) Climates

Answer 36

1. Subtropical steppe (BSh) and subtropical desert (BWh) have common temperature and precipitation characteristics. 2. The maximum temperature in this region in summer is very high. 3. The annual and diurnal ranges of temperature are also high. 4. The highest temperature of 58°C was recorded at Libya in 1922 at Al Aziziyah. 5. This region is positioned in the transition zone between dry climates and humid. 6. Subtropical steppe region receives slightly more rainfall than the subtropical desert which is sufficient enough for the growth of meager grasslands. 7. The rainfall in both the climates is highly variable. 8. Rain occurs in short intense thundershowers in deserts and is futile in building soil moisture. 9. The inconsistency in the rainfall distresses the life in the steppe much more than in the desert, more frequently causing famine. 10. Fog is common in coastal deserts neighboring cold currents.

Question 37

Koeppen's Group C Climates--Warm Temperate (Mid-Latitude) Climates

Answer 37

* Warm temperate (mid-latitude) climates stretch from 30° – 50° of latitude mainly on the western and eastern margins of continents. * These climates usually have warm summers with mild winters. * They are classified into four types: 1. Humid subtropical – Cwa 2. Mediterranean Climate – Cs 3. Humid subtropical climate – Cfa 4. Marine west coast climate – Cfb

Question 38

Humid Subtropical Climate (Cwa)

Answer 38

1. The Humid subtropical climate is found in the poleward of Tropic of Cancer and Capricorn. 2. This climate is predominantly found in the North Indian plains and interior plains of South China. 3. The Humid Subtropical Climate is similar to Tropical Wet and Dry Climate (Aw) climate excluding that the temperature in winter is warm.

Question 39

Mediterranean Climate (Cs)

Answer 39

1. Mediterranean climate is found around Mediterranean sea, along the west coast of continents in subtropical latitudes between 30° – 40° latitudes 2. The climate is predominantly found in the * Central Chile * Central California * Along the coast in South Eastern * South Western Australia 1. These areas come under the influence of westerly wind in winter and sub-tropical high in summer. 2. Therefore, the climate is characterized by hot, dry summer and mild, rainy winter. 3. The monthly average temperature in winter below 10°C and in summer is around 25° C. 4. The annual precipitation ranges from 35 – 90 cm.

Question 40

Humid Subtropical Climate (Cfa)

Answer 40

* The Humid subtropical climate is found in the Eastern parts of the continent lying in the subtropical latitudes. * In this area, the air masses are usually uneven and cause rainfall throughout the year. * This Climate is found in: 1. The Eastern United States of America 2. Southern and eastern China 3. Southern Japan 4. North-eastern Argentina 5. Coastal South Africa 6. Eastern coast of Australia * The annual average of precipitation stretches from 75-150 cm. * Frontal precipitation in winter and thunderstorms in summer are usual. * The average monthly temperature in winter it differs from 5°-12° C and in summer is about 27°C.

Question 41

Marine West Coast Climate (Cfb)

Answer 41

* Marine west coast climate is situated poleward from the Mediterranean climate on the west coast of the continents. * **The main areas are:** 1. North-western Europe 2. West coast of North America 3. North of California 4. Southern Chile 5. South-eastern Australia 6. New Zealand * The temperature is moderate and in winter, it is warmer than for its latitude due to marine influence. * The mean temperature in winter 4°-10°C and in summer months ranges from 15°-20°C.

Question 42

Koeppen's Group D Climates

Answer 42

* In a major portion of the middle and high latitudes lie a group of climates classified within the Koeppen scheme as C and D. 1. The average temperature is above 10 °C in their warmest months. 2. The average temperature in the coldest month is below −3 °C. 3. This climatic condition is generally found in the interiors of continents and on their upper east coasts, typically north of 40°N. 4. Group D climates are very rare in the Southern Hemisphere, due to the smaller land masses in the middle latitudes and the almost complete absence of land at 40–60° south. 5. It exists only in some highland locations.

Question 43

Cold Snow Forest Climates (D)

Answer 43

* Cold snow forest climate is found in the large continental area in the northern hemisphere between 40°-70° North latitudes. * The regions lying in this climate are: 1. Europe 2. Asia 3. North America * Cold snow forest climates are divided into two types: 1. Df- cold climate with humid winter. 2. Dw- cold climate with dry winter. * The severity of winter is more pronounced in higher latitudes.

Question 44

Cold Climate with Humid Winters (Df)

Answer 44

1. Cold climate with humid winters is found in the poleward of mid-latitude steppe and marine west coast climate. 2. The winters are snowy and cold. 3. The frost free season is short. 4. The annual ranges of temperature are high. 5. The weather changes are unexpected and short. 6. Poleward, the winters are extreme.

Question 45

Cold Climate with Dry Winters (Dw)

Answer 45

1. Cold climate with dry winter mainly found over North-Eastern Asia. 2. Precipitation occurs in summer. 3. The annual precipitation is low from 12-15 cm. 4. The progress of pronounced winter anticyclone and its weakening in summer sets in monsoon-like reversal of the wind in this area. 5. Poleward summer temperatures are poorer and winter temperatures are very low with several locations experiencing below freezing point temperatures.

Question 46

Group E climates

Answer 46

* Group E climates are regulated by the polar and arctic air masses of high latitudes which lie above 60° North and South latitudes.

Question 47

Polar Climates (E)

Answer 47

1. Polar climates are found in the poleward beyond 70° latitude. 2. Polar climates consist of two types: * Tundra (ET) * Ice Cap (EF)

Question 48

Tundra Climate (ET)

Answer 48

1. The tundra climate (ET) is so called after the types of vegetation, such as lichens, low-growing mosses, and flowering plants. 2. The regions experiencing this climate are: * Mount Rainier * Macquarie Island * Crozet Islands * Campbell Island * Kerguelen Islands * Prince Edward Islands 1. This is the region of permafrost. 2. The subsoil in this region is permanently frozen. 3. The water logging and short growing season support only low growing plants. 4. The tundra regions have a very long period of daylight during summer.

Question 49

Ice Cap Climate (EF)

Answer 49

1. The ice cap climate (EF) found in the interior Greenland and Antarctica. 2. The regions experiencing this climate are: * Vostok Station, Antarctica * Mount Ararat, in Turkey * Mount Everest * Scott Base, Antarctica * Summit Camp, Greenland * Plateau Station, Antarctica 1. The temperature is below freezing point even in summer. 2. This region receives very little precipitation. 3. The ice and snow get amassed and the increasing pressure causes the deformation of the ice sheets and they break. 4. These broken pieces move as icebergs and float in the Antarctic and Arctic waters.

Question 50

Climate

Answer 50

1. Climate is the average weather in a place over many years. 2. The weather can change in just a few hours whereas climate takes millions of years to change. 3. Planet earth has witnessed many variations in climate since the beginning.

Question 51

Evidence of Climate Change

Answer 51

1. Sea level rise 2. Global temperature rise 3. Warming oceans 4. Shrinking ice sheets 5. Declining Arctic sea ice 6. Glacial retreat 7. Extreme natural events 8. Ocean acidification 9. Decreased snow cover

Question 52

Causes of Climate Change

Answer 52

* There are several causes of climate change. The most significant anthropogenic effect on the climate is the increasing trend in the concentration of greenhouse gases in the atmosphere. The causes can be grouped into two: 1. Astronomical causes 2. Terrestrial causes 3. Volcanism 4. Concentration of greenhouse

Question 53

Astronomical causes

Answer 53

1. The astronomical causes are the variations in solar output related to sunspot activities. 2. Sunspots are dark and cooler patches on the sun which rise and fall in a recurring manner. 3. When the number of sunspots increases, cooler and wetter weather and greater storminess occur. 4. These modify the amount of insolation received from the sun, which in turn, might have a bearing on the climate.

Question 54

Volcanism

Answer 54

1. Volcanism is regarded as another cause for climate change. 2. Volcanic eruptions throw up loads of aerosols into the atmosphere. 3. These aerosols persist in the atmosphere for a substantial period of time decreasing the radiation of sun reaching the surface of Earth.

Question 55

Concentration of greenhouse gases

Answer 55

1. The primary Greenhouse gases of concern are Chlorofluorocarbons (CFCs), Methane (CH4), Nitrous oxide (N2O), Carbon dioxide (CO2), and Ozone (O3). 2. Some other gases such as nitric oxide (NO) and carbon monoxide (CO) easily react with Greenhouse gases and affect their concentration in the atmosphere. 3. The largest concentration of Greenhouse gas in the atmosphere is carbon dioxide.

Question 56

Greenhouse effect

Answer 56

1. The greenhouse effect is a normal process that warms the surface of the Earth. 2. Solar radiation reaches the atmosphere of Earth and some of this is reflected back into space. 3. The rest of the energy of the sun is absorbed by the terrestrial and the oceans, heating the Earth. 4. Heat radiates from Earth towards space. 5. Some of this heat is trapped by greenhouse gases in the atmosphere, keeping the Earth warm enough to sustain life. 6. Human activities such as burning fossil fuels, agriculture, and land clearing are increasing the amount of greenhouse gases released into the atmosphere. 7. This is trapping extra heat, and causing the temperature of the earth to rise and ultimately result in Global Warming.

Question 57

Global Warming

Answer 57

1. Global warming is the gradual heating of the surface of the Earth, ocean, and atmosphere. 2. Global warming begins with the greenhouse effect, which is caused by the interaction between incoming radiation from the sun and the atmosphere of Earth. 3. The atmosphere is acting as a greenhouse due to the presence of greenhouse gases.

Question 58

Water

Answer 58

1. Water is a cyclic resource as it is used and re-used. 2. About 71% of the planetary water is found in the oceans. 3. The remaining is held as freshwater in glaciers and ice caps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life. 4. About 59% of the water on the land surface evaporates and returns back to the atmosphere. 5. The remaining run-off on the surface penetrates into the ground or a part of it becomes glaciers.

Question 59

Distribution of water on the surface of the earth

Answer 59

Question 60

Hydrological cycle / Water Cycle

Answer 60

1. The hydrological cycle is the circulation of water within the hydrosphere of Earth in different forms such as liquid, solid and gaseous states. 2. It also denotes the uninterrupted exchange of water between the land surface, oceans and subsurface and the organisms. 3. The hydrologic cycle begins with the evaporation of water from the surface of the ocean.

Question 61

Hydrological Cycle Processes

Answer 61

Components and Processes of the Water Cycle **Water storage in oceans:** 1. Evaporation 2. Transpiration 3. Sublimation **Water in the atmosphere:** 1. Condensation 2. Precipitation **Water storage in ice and snow:** 1. Snowmelt runoff to streams **Surface runoff:** 1. Streamflow freshwater storage infiltration **Groundwater storage:** 1. Groundwater discharge springs

Question 62

Evaporation

Answer 62

1. The conversion of water from liquid to gas stage as it moves from the ground or bodies of water into the atmosphere. 2. The source of energy for evaporation is mainly solar radiation.

Question 63

Transpiration

Answer 63

Water vapour is also discharged from plant leaves by a process called transpiration.

Question 64

Sublimation

Answer 64

The process in which solid water such as snow or ice directly changes into water vapour.

Question 65

Condensation

Answer 65

The transformation of water vapour to liquid water droplets in the air, forming fog and clouds.

Question 66

Precipitation

Answer 66

1. The condensed water vapour falling to the surface of the Earth is known as Precipitation. 2. It occurs in the form of rain, snow, and hail.

Question 67

Runoff

Answer 67

Runoff is a visible flow of water in rivers, creeks, and lakes as the water stored in the basin drains out.

Question 68

Snowmelt

Answer 68

The runoff created by melting snow.

Question 69

Percolation

Answer 69

Water flows vertically through the soil and rocks under the effect of gravity.

Question 70

Ocean Waves

Answer 70

1. Waves are formed by energy passing through water, resulting it to move in a circular motion. 2. Water particles travel only in a small circle as a wave passes. 3. The Wind provides energy to the waves. 4. The Wind causes waves to travel in the ocean and the energy is released on coastlines. 5. The movement of the surface water rarely affects the stagnant deep bottom water of the oceans. 6. As a wave approaches the coastline, it slows down. This is due to the friction happening between the moving water and the sea floor. 7. When the depth of water is less than half the wavelength of the wave, the wave breaks. 8. The largest waves are found in the open oceans. 9. Waves continue to grow larger as they move and absorb energy from the wind. 10. The size and shape of the waves reveal its origin. 11. Steep waves are young ones and are perhaps created by local wind. 12. Slow and steady waves originate from faraway places, probably from another hemisphere.

Question 71

Characteristics of Waves

Answer 71

1. **Wave crest and trough** * The highest of a wave is called crest. * The lowest point of a wave is called trough. 1. **Wave height** * It is the perpendicular distance from the bottom of a trough to the top of a crest of a wave. 1. **Wave amplitude** * It is one-half of the wave height. 1. **Wave period** * It is merely the time interval between two successive wave crests or troughs as they pass a fixed point. 1. **Wavelength** * It is the horizontal distance between two successive crests. 1. **Wave speed** * It is the rate at which the wave moves through the water. * It is measured in knots.

Question 72

Clouds

Answer 72

1. Cloud is a mass of minuscule water drops or minute crystals of ice formed by the condensation of water vapour in free air at significant altitudes. 2. According to their altitude, stretch, density, and transparency or opaqueness clouds are classified under four types: * Cirrus * Cumulus * Stratus * Nimbus

Question 73

What are Cirrus clouds?

Answer 73

1. Cirrus clouds are formed at high altitudes of 8,000 – 12,000m. 2. They are detached thin clouds. 3. They have a feathery appearance. 4. They are always white in colour.

Question 74

What are Cumulus clouds?

Answer 74

1. Cumulus clouds are generally formed at a height of 4,000 – 7,000 m. 2. They look like cotton wool. 3. They exist in patches and can be seen dispersed here and there. 4. They have a flat base.

Question 75

What are Stratus Clouds?

Answer 75

1. Stratus clouds are layered clouds covering big portions of the sky. 2. These clouds are usually formed due to the mixing of air masses with various temperatures or due to loss of heat.

Question 76

What are Nimbus Clouds?

Answer 76

1. Nimbus clouds form at middle levels or very near to the surface of the earth. 2. They are usually found in black or dark gray colour. 3. These are very dense and opaque to the rays of the sun. 4. Occasionally, the clouds are so low that they seem to touch the ground. 5. These clouds are shapeless masses of thick vapour. 6. A combination of these four types can give rise to the following types of clouds: * **High clouds** 1. Cirrus 2. Cirrostratus 3. Cirrocumulus * **Middle clouds** 1. Altostratus 2. Altocumulus * **Low clouds** 1. Stratocumulus 2. Nimbostratus * **Clouds with extensive vertical development** 1. Cumulus 2. Cumulonimbus

Question 77

Evaporation

Answer 77

1. Evaporation is a process by which water is converted from liquid to gaseous state. 2. Temperature is the main cause for evaporation. 3. The temperature at which the water starts evaporating is known as latent heat of vaporisation. 4. Rise in temperature escalates water absorption and retention capacity of the given parcel of air. 5. Movement of air substitutes the saturated layer with the unsaturated layer. 6. Hence, the greater the movement of air, the greater is the evaporation.

Question 78

Condensation

Answer 78

1. The conversion of water vapour into the water. 2. Condensation is caused by the loss of heat. 3. When moist air is cooled, it may reach a level when its capacity to hold water vapour terminates. 4. The surplus water vapour condenses into the liquid stage. 5. In free air, condensation results from cooling around very small particles named as hygroscopic condensation nuclei. 6. Condensation depends upon the amount of cooling and the relative humidity of the air. 7. It is influenced by the volume of air, temperature, pressure and humidity.

Question 79

Condensation takes place

Answer 79

1. When the temperature of the air is decreased to dew point with its volume remaining constant. 2. When both the temperature and the volume are decreased. 3. When moisture is added to the air through evaporation. However, the most favourable circumstance for condensation is the reduction in air temperature.

Question 80

Valleys

Answer 80

1. Valleys start as small and narrow rills. These rills will progressively develop into long and wide gullies. 2. The gullies will again deepen, widen and lengthen to give rise to valleys. 3. The valley types depend upon the type and structure of rocks in which they form. 4. Depending upon sizes and shapes, several types of valleys like V-shaped valley, gorge, canyon, etc. can be recognized. 5. A gorge is a deep valley with very steep to straight sides. 6. It is almost equal in width at its top as well as its bottom. 7. A canyon is characterized by steep step-like side slopes and might be as deep as a gorge. 8. It is a variant of the gorge. 9. A canyon is wider at its top than at its bottom. 10. It is commonly formed in horizontal bedded sedimentary rocks and gorges form in hard rocks.

Question 81

Potholes

Answer 81

1. Potholes are cylindrical holes drilled into the bed of a river that varies in depth and diameter from a few centimetres to several metres. 2. They are found in the upper course of a river where it has enough potential energy to erode vertically and its flow is turbulent.

Question 82

Plunge Pools

Answer 82

1. A sequence of such depressions ultimately joins and the stream valley gets deepened. 2. At the foot of waterfalls also, large potholes, quite deep and wide, form because of the absolute influence of water and rotation of boulders. 3. These large and deep holes at the base of waterfalls are called plunge pools. 4. These pools also help in the deepening of valleys.

Question 83

Incised or Entrenched Meanders

Answer 83

1. Entrenched meanders are symmetrical and form when the river down cuts quickly. 2. The speed of the river downcutting gives less opportunity for lateral Thus giving them symmetrical slopes. 3. These are very deep and wide meanders can also be found cut in hard rocks. 4. It is common to find meandering courses over floodplains and delta plains where stream gradients are very gentle.

Question 84

River Terraces

Answer 84

1. River terraces are surfaces marking old valley floor or floodplain levels. 2. They may be bedrock surfaces without any alluvial cover or alluvial terraces consisting of stream deposits. * **Paired terraces:** The river terraces may occur at the similar elevation on either side of the rivers. * **Unpaired terraces:** When a terrace is present only on one side of the stream and with none on the other side or one at quite a different elevation on the other side. 1. The terraces may result due to * Change in hydrological regime due to climatic changes. * Sea level changes in case of rivers closer to the sea. * Receding water after a peak flow. * Tectonic uplift of land.

Question 85

Various Glacial Depositional Landforms

Answer 85

1. Glaciers have played an important role in the moulding of landscapes in the mid and high latitudes of alpine environments. The major depositional landforms made by glaciers are: * Esker * Outwash plains * Drumlins

Question 86

Eskers

Answer 86

1. The esker is one of the most striking landforms of fluvioglacial deposition. 2. They are usually formed of washed sand and gravel. 3. Eskers vary in shape and size. 4. When glaciers melt, the water flows on the surface of the ice or leaks down along the margins. 5. These waters amass underneath the glacier and flow like streams in a channel beneath the ice. Such streams flow over the ground with ice forming its banks. 6. Very coarse materials like stones and blocks along with some minor segments of rock debris transported into this stream settle down in the valley of ice underneath the glacier and after the ice melts can be found as a winding ridge called Esker.

Question 87

Outwash Plains

Answer 87

1. It is also known as called a sandur. 2. It is a plain formed of glacial sediments deposited by meltwater outwash at the limit of a glacier.

Question 88

Drumlins

Answer 88

1. These are smooth oval shaped ridge-like topographies composed primarily of glacial till with masses of gravel and sand. 2. It forms due to the dumping of rock debris underneath heavily loaded ice through fissures in the glacier. 3. The long axes of drumlins are parallel to the direction of ice movement. 4. Drumlins give an indication of the direction of glacier movement. 5. The Stoss end is the steeper of the two ends and used to face into the ice flow.

Question 89

Glacial Erosional Landforms

Answer 89

1. Glaciers have played a prominent role in the shaping of landscapes in the mid and high latitudes of alpine environments. The major erosional landforms made by glaciers are * Cirque * Horns and Serrated Ridges * Glacial Valleys/Troughs

Question 90

Cirque

Answer 90

1. Cirque is an amphitheatre-like valley formed by glacial erosion. 2. They are long, deep, and wide troughs or basins with very steep concave to vertically dropping high walls on its head as well as sides. 3. They are the commonly found of landforms in glaciated mountain especially at the heads of glacial valleys. 4. The amassed ice cuts these cirques whereas moving down the mountain tops. 5. A lake of water can be seen frequently inside the cirques after the glacier vanishes. 6. Such lakes are called Cirque or tarn lakes.

Question 91

Horns and Serrated Ridges

Answer 91

1. Horns form through headward erosion of the cirque walls. 2. Horns form when three or more radiating glaciers cut the headward until their cirques meet high, sharp pointed and steep-sided peaks. 3. The splits between Cirque side walls or head walls get narrow because of progressive erosion and turn into saw-toothed ridges occasionally mentioned to as arêtes with very sharp crest and a zig-zag outline. 4. Horns formed through headward erosion of radiating cirques are: * The highest peak in the Alps * Matterhorn * The highest peak in the Himalayas Everest

Question 92

Glacial Valleys/ Troughs

Answer 92

1. They are U-shaped and trough-like with broad floors and comparatively smooth and steep edges. 2. The valleys may comprise scattered debris or debris moulded as moraines with swampy 3. The very deep glacial troughs occupied with sea water and making up shorelines in high latitudes are known as fjords.

Question 93

Types of Rainfall

Answer 93

* Rainfall has been classified into three main types – 1. Convectional rainfall 2. Orographic or relief rainfall 3. Cyclonic or frontal rainfall

Question 94

Convectional Rain

Answer 94

1. The air on getting heated becomes light and rises up in convection currents. 2. As the air rises, it expands and drops the temperature and subsequently, condensation takes place and cumulus clouds are formed. 3. Heavy rainfall with lightning and thunder takes place which does not last long. 4. Such rain is usual in the summer or in the hotter part of the day. 5. This type of rainfall generally takes place in the equatorial regions and internal parts of the continents, predominantly in the northern hemisphere.

Question 95

Orographic Rain

Answer 95

1. When the saturated air mass comes across a mountain, it is forced to rise. 2. The rising air expands, eventually, the temperature falls, and the moisture gets condensed. 3. The principal characteristic of this type of rain is that the windward slopes get more rainfall. 4. After giving rain on the windward side, when these winds reach the other slope, they drop away, and their temperature increases. Then their ability to take in moisture increases and hence, these leeward slopes remain dry and rainless. 5. The region situated on the leeward side is known as the rain-shadow area.

Question 96

Cyclonic Rain

Answer 96

1. Cyclonic activity causes cyclonic rain and it occurs along the fronts of the cyclone. 2. When two masses of air of unlike density, temperature, and humidity meet then it is formed. 3. The layer that separates them is known as front. 4. Warm front and the cold front are the two parts of the front. 5. At the warm front, the warm lighter wind increases slightly over the heavier cold air. 6. As the warm air rises, it cools, and the moisture present in it condenses to form clouds 7. This rain falls gradually for a few hours to a few days.

Question 97

External crystal form

Answer 97

The external crystal form determined by the internal arrangement of the molecules — cubes, octahedrons, hexagonal prisms, etc.

Question 98

Cleavage

Answer 98

1. It denotes the splitting of a crystal along a smooth plane. 2. Not every mineral exhibits cleavage. 3. A plane of structural weakness along which a mineral is likely to split. 4. The quality of a mineral’s cleavage indicates both the ease with which the mineral cleaves and the character of the exposed surface.

Question 99

Fracture

Answer 99

1. Fracture takes place when a mineral sample is split in a direction which does not serve as a plane of perfect or distinct cleavage. 2. A mineral fractures when it is fragmented or crushed. 3. Fracture does not result in the occurrence of clearly demarcated planar surfaces. 4. Minerals may fracture in any possible direction. 5. If the internal molecular arrangement is so complex that there are no planes of molecules; the crystal will break in an irregular manner, not along planes of cleavage.

Question 100

Lustre

Answer 100

1. Minerals may be categorized according to whether they are opaque or transparent. 2. Each mineral has a unique lustre like silky, metallic, glossy, etc.

Question 101

Colour

Answer 101

1. Some minerals have a characteristic colour determined by their molecular structure. 2. Eg: malachite, azurite, chalcopyrite, etc. 3. Some minerals are coloured by impurities and because of impurities quartz may be white, green, red, yellow, etc.

Question 102

Streak

Answer 102

1. Streak is the shade of a mineral when it has been crushed to a fine powder. 2. It may be of the same colour as the mineral or may differ. 3. For eg: * Malachite is green and gives green streak. * Fluorite is purple or green but gives a white streak.

Question 103

Transparency

Answer 103

**Transparent**: Light rays pass through so that objects can be seen plainly. **Translucent**: Light rays pass through but will get diffused so that objects cannot be seen. **Opaque**: Light will not pass at all through the opaque objects.

Question 104

Structure

Answer 104

Structure refers to the particular arrangement of the individual crystals.

Question 105

Hardness

Answer 105

* Hardness is defined as the level of difficulty with which a smooth surface of a mineral specimen may be scratched. * It is dependent upon the strength of the bonds which compose its crystal structure. * Ten minerals are selected to measure the degree of hardness from 1-10. They are: 1. Talc 2. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Feldspar 7. Quartz 8. Topaz 9. Corundum 10. Diamond

Question 106

Specific gravity

Answer 106

1. Specific gravity is a unit-less quantity. 2. It is defined as the ratio between the weight of a given object and the weight of an equal volume of water.