fe unit 1 components of environment

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Fundamentals of Environment Unit 1

Unit 1 Environment and its Components

Structure

1.1 Introduction

Objectives

1.2 Biotic and Abiotic components of the Earth

Role of Abiotic Components

Biotic Components

Characters of a biotic community

Self Assessment Questions

1.4 Earth Sun relations

Earths radiation budget

Green house effect

1.5 Earths climate

Atmospheric circulation

Latitude and Elevation

Regional climate


1.6 Climate - Biosphere Interaction

Tropical rain forests

Temperate Deciduous Forests

Temperate Evergreen Forests

Temperate Grasslands

DesertsSelf Assessment Questions

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1.7 Summary

1.8 Glossary

1.9 Terminal Questions

1.10 Answers

1.1 Introduction

Carcass Dumps are large areas in Northern India where people can bring

the bodies of deceased cattle. As cows are sacred to Indians, they are not

consumed, not even when they die naturally. In the dumping yards, millions

of vultures play a crucial role in disposing of thousands of tonnes of

carcasses. Vultures help in maintaining a clean environment and insafeguarding human population, livestock and wildlife from infections and

other diseases by the rapid and efficient removal of carcasses. A steady

decline in vulture population since late 1990s has left a vast number of

carcasses unscavengedliterally piling up corpses in the land. It has taken

scientists years to figure out what happened to Indias vulture population.

The few remaining vultures were seen to be in poor shape, appearing to be

knocking on deaths door themselves. Few specimens of dead vultures could

be obtained for examination, but finally researchers had their culprit.

Diclofenac, a non-steroidal anti-inflammatory drug (NSAID) is used to treat

pain or inflammation caused by arthritis. Recent studies indicate that it isresponsible for the devastating decrease in the South Asian vulture

population. A three-year study done by the Peregrine Fund and

Ornithological Society of Pakistan has revealed that 85 percent of 259

vultures surveyed had died due to a condition caused by renal failure

termed as visceral gout. Although Diclofenac was widely used to treat

humans, it was launched in the Indian subcontinent veterinary market only

in the early 1990s. Diclofenac is cheap and is used for treating pain, fever

and inflammation in livestock. As the vultures ate of the dead cows at the

carcass dumps, they developed visceral gout.

As scavengers, vultures provide important ecological service as they help in

rapidly reducing animal carcasses and plants to simpler constituents,

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maintaining the food chain and ecosystem. During the period of 1993-2006,

the estimated total cost of the health expenses attributable to vulturedeclines is a staggering US$ 34 billion. This episode highlights the important

fact that human beings are intimately tied to the components of the

environment. Like vulture all the components of the environment,

irrespective of living or non-living nature, are crucial for our life support

system.

Objectives

After studying this unit you will be able to

define the biotic and abiotic components

recognize the role of physical abiotic components in life support

system

explain the relation between sun and earth in terms of radiation and

energy budget and greenhouse effect

describe the role of solar radiation and atmospheric circulation in

regional weather climate

distinguish features responsible for micro-climatic variation in earth

and climate in relation to biomes of the earth

1.2 Biotic and Abiotic components of earth

Like vultures, bacteria, trees and many more, for our comfortable livelihood

many components in the environment do their service. We use many

products such as furniture, utensils vehicles for transportation and so on. All

these materials come from the environment and are they all interrelated. All

the substances present in our earth are the products of interaction between

Biotic Components (living things constitute the environment) and Abiotic

components (the non-living substances of the environment such as air,

water, soil etc.). In our earth, biosphere can be recognised as a thin zone ofland, air, and water that is home to all living things on earth where the

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interaction takes place. Biosphere is further classified into small functional

units called Ecosystems. In ecosystems, there are biotic communities ofspecies interacting with one another and with their abiotic environmental

components exchanging energy and matter (Figure 1.1). The ecosystem

may also consist of a number of sub-units that are all directly or indirectly

related to each other. An open ecosystem freely exchanges matter and

energy from outside. But, a closed ecosystem is isolated from outside with

respect to exchange of matter. Ecosystems largely differ in their size,

composition, structure, etc. However, certain basic structural and functional

features, which are common, help in characterisation of ecosystems. The

structure of an ecosystem includes composition and organisation of

biological societies and abiotic components. Various kinds of ecosystems

exist in the biosphere like the forests, grasslands, oceans, lakes, rivers,

mountains, deserts and estuaries. These ecosystems generally differ in their

structural composition and functions.

Role of Abiotic Components in the environment

Now let us see some important abiotic components without which our daily

activities, life, services and business is impossible. Atmosphere that

consists of gases and aerosols provides us with oxygen for our life and

Carbon dioxide for the growth of plants. Lower most part of the atmospherethat is primarily responsible for rainfall, temperature changes and climate.

All our telecommunication network and technologies is possible only due to

the active gaseous ions in the atmosphere.

Hydrosphere or the water that covers 71% of the Earth's surface is also

significant in climate determination, food supply (fish and other marine

organism) and transportation.

Lithosphere that refers to the rocks of the Earths surface and upper mantle

provides us with minerals, metals and metallic ore.

The interaction of the atmosphere, lithosphere and hydrosphere makes ourplanet habitable. These spheres are elaborated in subsequent units.

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Apart from the above mentioned factors, many other abiotic components are

essential to make life conducive on the earth. The natural factors such astemperature, sunlight and soil are imperious to sustain life on this planet. It

took over billions of years for formation of these abiotic factors in the present

condition. Any minimal change in their levels would make this earth

uninhabitable for living things. Let us see briefly about these factors:

Temperature:All biotic life is adapted to live within a relatively narrow range

of temperatures and will not thrive if temperatures are colder or warmer.

Temperature decides what crop to be grown, what sort industries can thrive

in a region etc.

Sunlight: Solar energy from sun is the only source of energy to the

biosphere. This energy is efficiently captured by plants and converted into

products by a process called photosynthesis. All our food directly or

indirectly depends on it. The coal or petroleum energy which we extensively

use today is the product this process that are captured by ancient plant

forms.

Soil: Topsoil consists of sulphur, phosphorous, nitrogen and other essential

minerals for plant growth and agricultural production.

Biotic components

Different living organisms constitute the biotic component of an ecosystem

and they are classified into the following categories:

Producers

Consumers

Decomposers

Producers: Producers orGreen plants that produce food by photosynthesis

process are a miracle and even today the underlying mechanism is

understood to be complex. None of our modern day technology can capturecarbon-dioxide from atmosphere and convert it into energy products. To

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compare with, human designed silicon-based photocells are only 50%

efficient and require huge amounts of energy to manufacture.Producers are also known asphoto-autotrophs (auto = self, photo = light,

troph = food).

Consumers: These organisms feed on other organisms to get their food

and they are of the following types:

Herbivores These organisms feed on plants. For example, rabbit, deer.

Carnivores These organisms feed on herbivores as secondary carnivores

(for example, frog, small fish) or tertiary carnivores (for example , snake, big

fish), which feed on other consumers.

Omnivores These organisms feed on both plants and animals. For

example, humans, rats and many birds.

Detritivores These organisms feed on dead organisms. For example, earth

worm, ants, crab.

All of them have their own role in an ecosystem.

Decomposers: We dispose our wastes to the environment and forget it.

Who takes the role of converting these wastes into useful nutrients and

minerals? There are some micro-organisms like bacteria and fungi thatwhile deriving their nutrition break down large complex organic matter into

simple inorganic compounds. These micro-organisms play a crucial role in

transforming the essential nutrients from unavailable organic form to free

inorganic form that can be used by plants. These micro-organisms are

widely used in biotech industries for manufacture of several products and

also in waste degradation.

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Figure 1.1 Components of an ecosystem

(Source: http/www.rbnc.org/schoolunits/terraeco)


1. Which of following in atmosphere has a role to play in telecommunication

technology?

(a) Water vapour,

(b) Carbon dioxide

(c) Ions

(d) None of these

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2. Identify which of the following takes part in scavenging and cleansing role

in environment?(a) Solar radiations

(b) Vultures

(c) Soil texture

(d) Carbon.

3. The components of earth can be broadly classified as........ and..............

4. Plants are autotrophs (True/False)

5......... % of earth is covered by water.

1.4 Earth Sun relations

The Earth would simply be a frozen rock stranded in space without the Sun.

The Sun keeps the Earth warm and ensures life on the Earth. The Suns

energy produces clouds, cleans our water, helps in growth of plants, keeps

wildlife and humans warm and drives ocean currents and thunderstorms. In

spite of the Suns importance, scientists have only started to study all

aspects of it in recent decades. Before 1979, astronomers and Earth

scientists did not have exact information on the total amount of solar energy

that reaches the earths outermost atmosphere. As clouds and aerosols

absorb different amounts of sunlight, the researchers could not precisely

measure solar radiation before it reached the Earths atmosphere.

In 1978, the Nimbus-7 satellite was launched. This helped us to measure

sunlight for the first time without any interference from the atmosphere. The

levels of solar radiation before they reached the earths atmosphere were

measured using the Earth Radiation Budget (ERB) instrument on the

satellite. The successive satellite missions have helped scientists to collect

detailed information about the sun and solar energy that influences our

worlds climate system.

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Earth's Radiation Budget

The Earth's Radiation Budget is a concept that helps to clearly understand

the amount of heat energy that enters the earth through suns rays and the

energy that is radiated back into the atmosphere as invisible light. The earth

becomes warm when both the earth and its atmosphere continue to hold

more solar energy than they radiate back to space. The earth can become

cool when both the earth and the earth-system radiate more energy to

space that they receive from the sun. Scientists visualise the Radiation

Budget as a see-saw or a balance. If the earth retains more solar energy,

the earth becomes warmer and emits more infrared energy. This balances

the Earths Radiation Budget. If the earth emits more infrared energy than it

absorbs, then the earth becomes cooler. As the earth cools, it emits lesser

energy. This change also balances the Radiation Budget. Absorbed sunlight

increases the earths temperature and emitted radiation or heat decreases

the temperature. When there is a balance between absorbed sunlight and

emitted heat, the earths temperature does not vary and the radiation budget

is also balanced.

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Figure1. 2. Earths radiation budget (Source: NASA homepage)

The earths surface, gases, water vapour and aerosols in the atmosphereabsorb the incoming solar radiation. The earths surface, atmosphere, and

clouds reflect this incoming solar radiation. The earth-atmosphere system

emits the absorbed energy as longwave radiation. The component diagram

(Figure1.1) has additional details.

The greenhouse effect

The earth is not a simple solid ball. A thin layer of air surrounds the earth

which is held by gravity and consists almost entirely of nitrogen (78% by

volume) and oxygen (21%). These major components are transparent to

both the infrared (long wave) radiation and the incoming solar (short wave)radiation emitted upward from the surface of the earth. There are many

minor components, mainly water vapour and carbon dioxide, which are

largely transparent to the incoming solar radiation, but strongly absorb the

infrared radiation emitted from the ground. Water vapour is the most

significant component and it is not well mixed and may differ locally from

less than 0.01% by volume to more than three per cent. Carbon dioxide

(CO2) is the next most abundant component which has a long lifetime in the

atmosphere and is well mixed globally. Some major trace gases include:

Nitrous oxide

Methane

Ozone

Anthropogenic halocarbon compounds including ozone-depleting

chlorofluorocarbons and hydrofluorocarbons.

These trace gases absorb radiation which is reemitted in all directions,

some back towards the surface resulting in a net warming of the surface.

Through greenhouse effect, the greenhouse gases trap heat in the near

surface layers of the atmosphere and make the earths surface significantly

warmer than if there was no greenhouse effect. Figure 1.3 illustrates the

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mechanism of the natural greenhouse effect and its influence on the earths

surface and atmospheric temperatures.

Greenhouse gases have many sources, but they can be commonly grouped

under the following four forms:

Carbon dioxide (CO2)

Methane (CH4)

Nitrogen oxides (NO2)

Fluorinated gases

These gases comprise about 1% of the earths atmosphere.

Figure 1.3 Greenhouse effect(Source:http://chemlevel2.wikispaces.com/Period+7)

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The different sources of greenhouse gas emission varies over a wide field

ranging from power stations, other industrial processes, burning of fossilfuels, domestic activities etc. The burning of fossil fuels like coal in the

power plants for generating electricity is a major reason for the emission of

gases that cause the greenhouse effect. The burning of fossil fuels results in

high emissions of CO2 gas. Methane captures more than 20 times the heat

captured by CO2 in the atmosphere. Sources such as bovine flatulence, rice

paddies, bacteria in bogs and fossil fuel manufacture produce methane. The

major sources of nitrous oxide (N2O)are:

Nylon and nitric acid production

Cars with catalytic converters

Use of fertilizers in agriculture

Burning of organic matter

The role of each sector in emission of GHGs have been illustrated in the

following diagram 1.4

Figure 1.4 Sources of GHGs emissions

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Source:http://en.wikipedia.org/wiki/Image:Greenhouse_Gas_by_Sector.png

Global Warming

In the last century, there has been a significant increase in the average

temperature of earth. This increase in temperature is due to the

accumulation of greenhouse gases in the atmosphere which is termed as

Global Warming.


3. The long wave infrared radiation is received by earth from space Say

true or false

4. Pick out the non greenhouse gas

a) Methane b) Ozone c) Nitrogen d) CFC

5. _____________percentage of solar energy from sun is absorbed by land

and oceans

1.5 Earths climate

The climate system is a complex, interactive system, which comprises land

surface, snow and ice, atmosphere, oceans and other water resources andliving creatures. Climate is generally explained in terms of the mean and

variability of temperature, precipitation and wind over a time period, ranging

from months to millions of years.

Regional climate refers to the climate where you live and it is the average

weather conditions in a place for a period of more than 30 years. The

regional climate depends on several factors and they include:

The amount of sunlight the region receives

The height above sea level

The shape of the land

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The regions closeness to oceans

Global climate refers to the climate of the whole planet with all the regionaldifferences averaged. The amount of solar energy received and the amount

of energy trapped in the system are the two major factors that affect the

overall global climate. These amounts of energy vary for different planets.

Changes in the weather can happen in a few hours, but changes in the

climate take place over a longer timeframe.

BOX: 1.1 Temperature driven changes to earth

According to a report by the Division of Earth & Life Studies, NationalAcademy of Sciences, USA, each degree Celsius (or 1.8 degrees F)

of warming leads to:

5-10% changes in precipitation in a number of regions 3-10% increases in heavy rainfall 5-15% yield reductions of a number of crops 5-10% changes in stream-flow in many river basins worldwide About 15% and 25% decreases in the extent of annually

averaged and September Arctic sea ice, respectively

The important factors that determine the patterns of climate on earth

include:

1. The strength of the incident solar radiation, which influences the

overall temperature of the earth.

2. The orientation of the earths axis and its spherical shape

3. The greenhouse effect of water vapour and other radioactively

active trace gases

4. The different physical, chemical and biological processes that

occur within the atmosphere-geosphere-biosphere climate

system, especially, the global energy balance, the global watercycle, the global carbon cycle and other biogeochemical cycles.

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5. The rotation of the earth which greatly changes the large-scale

thermally-driven circulation patterns of the ocean andatmosphere.

6. The distribution of continents and oceans

Due to the spherical shape of the earth, the equatorial regions, receive

much more solar radiation per unit area than the poles. If each latitude band

were individually considered to be in balance with the incoming and

outgoing radiation, the equatorial belt would reach temperatures in excess

of 100C (373K) around solar noon while the poles would be close to

absolute zero (0K or 273C). The atmospheric and oceanic circulations

normally transport heat from the equator to the poles.

Atmospheric Circulation

Both the Earths revolution around the sun and its daily rotation on its own

axis determine its climate (figure 1.5). Progression of seasons throughout

the Earth away from the equator occurs due to the annual cycle and the

inclination of the Earths axis at about 23.5 from its plane of revolution

around the Sun. At all times, one or the other pole is inclined closer to the

sun except during the spring and autumn equinoxes. The capacity of air to

hold moisture decreases when it cools and increases when it warms.

Evaporation occurs due to high temperatures near the equator and createswarm and moist air. When this air rises and flows toward the poles, it cools

and loses most of its moisture. As a result, most of the precipitation on earth

occurs near the equator. This low pressure equatorial area of rising air is

termed doldrums and draws air from both north and south of the equator.

When the rising air masses reach about 30 north and south latitude, they

become cooler, sink and once again get reheated. There is an increase in

the evaporative capacity as the air reheats, and it forms a zone of

decreased precipitation. The air, as it is still warmer than in the Polar

Regions, continues to flow toward the poles. It once again rises at about 60

north and south latitude, and forms an additional zone of high precipitation.The polar front is another low-pressure area at this latitude. A part of this

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rising air flows back to the equator. The remainder continue to flow north

and south, descend near the poles and form another zone of lowprecipitation before returning to the equator.

Figure 1.5

Relationships between the Earth and the Sun greatly influence the nature

and distribution of life on Earth in the following ways:

(a) A beam of solar energy that is incident on the Earth in the mid-latitudes

extends over a wider area of the earths surface than a similar beam that

strikes the earth close to the equator.

(b) The effect of Earths rotation around the Sun on the climate is profound.

The slight tilting of the earths axis in relation to its plane of orbit around the

Sun causes the temperatures to change in an annual cycle in the northern

and southern hemispheres.

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Figure 1.6General patterns of atmospheric circulation

The general patterns of Earths atmospheric circulation include:

(a) The pattern of air movement toward and away from the surface of the

earth.

(b) The major wind currents across the face of the earth.

(Source:

http://cimss.ssec.wisc.edu/sage/oceanography/lesson3/concepts.html)

Why are tropical regions warmer?

Earth has a great diversity of biomes as its climate changes greatly fromplace to place. On a given day, Miami, Florida, Delhi, and Maine, often do

not have a similar weather Some parts of Earth receive more solar energy

than others due to its spherical shape. This variation results in major climatic

differences over the earths surface and indirectly contributes to the diversity

of biomes. Since the suns rays appear almost perpendicular to regions near

the equator, the temperate regions are not as warm as the tropic regions.

The angle of incidence of the suns rays near the poles spreads them out

over a much larger area, and provides less energy per unit area. ((This is

shown in figure1.6).

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Precipitation

The condensation of atmospheric water vapour that falls under gravityresults in precipitation. Drizzle, rain, snow, sleet, hail and gravel are the

major forms of precipitation. When a local portion of the atmosphere is

saturated with water vapour, the water condenses, and precipitation occurs.

Precipitation is normally low near 30 north and south latitude, where air is

descending and becoming warm. It is relatively high near 60 north and

south latitude, where air is rising and becoming cool (Figure 1.7). All the

great deserts of the world are located near 30 north or south latitude partly

because of these factors. Other major deserts are seen in the interiors of

large continents. These regions have limited precipitation due to their

distance from the sea, the crucial source of most moisture.

BOX 1.2In 2008, Indian farmers experienced the weakest monsoon in 40 yearsand so began to pray for rain. The very weak monsoon had resulted intheir crops being stricken by drought. The rains that finally came wereforceful and continuous. South India received a rainfall that was six timesthe normal level. The incessant rains caused the worst floods that SouthIndia had experienced in more than a century.

The weather officials explained that a low-pressure system over the Bayof Bengal was the cause for the heavy rains in Karnataka and AndhraPradesh. About 250 people died due to the floods that worsened whenofficials released water from dams fearing that they might burst. About2.5 million people were displaced due to the raging floods that destroyedtheir villages, washed away roads, bridges, crops and livestock. Hence,about 1,500 relief camps were established for these displaced people.This flooding did not surprise the experts who tracked the effects ofclimate change. The Inter- Government Panel on Climate Change (IPCC)predicted in its fourth assessment report of 2007, that more severedroughts, floods, and storms, would become commonplace in the future.They also predicted that these extreme weather conditions would comeclose succession and often in the same areas.

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Figure 1.7. Temperature and Precipitation determines the ecosystem types

(Source:http://www.globalchange.umich.edu/globalchange1/current/lectures

/kling/ecosystem/ecosystem.html)

Mountain ranges interrupt moisture-laden winds from the sea resulting in the

formation of deserts. When mountain ranges block the moisture laden

winds, the air rises and the moisture-holding capacity of the air decreases.

This results in greater precipitation on the windward side of the mountains

the side from which the wind is blowing. As the air moves down the other

side of the mountains, the leeward side, it becomes warm. Its moisture-

holding capacity rises and it tends to block precipitation. For example, the

eastern parts of the Sierra Nevada Mountains in California are much drier

than the western parts, and the vegetation also varies. This process is

referred to as the rain shadow effect. (figure 1.8).

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Figure 1.8. Rain shadow effect

(Source:

http://www.theweatherprediction.com/weatherpapers/068/index.html)

Regional Climates

Four relatively small regions, each situated in a different continent, share a

climate that resembles the climate of Mediterranean region. So-called

Mediterranean climates are found in portions of Baja, California, and

Oregon; in central Chile; in south-western Australia; and in the Cape regionof South Africa. The prevailing westerlies blow during the summer season

from a cool ocean onto warm land in all of these regions. As a result, the

airs moisture-holding capacity increases, the air absorbing moisture and

creating hot rainless summers. Such climates are unusual in the world. In

the five regions that have a Mediterranean climate, several unique types of

animals and plants, which are often local in distribution, have evolved. Due

to the prevailing westerlies, the great deserts of the world (apart from those

in the interiors of continents) and the regions having Mediterranean climate,

are found on the western sides of the continents.

In Southern Asia, another type of regional climate is seen. The monsoon

climatic conditions that are a characteristic of India and southern Asia occur

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during the summer months. The trade winds blow from the east northeast

off the cool land onto the warm sea during the winter. From June to October,as the land gets heated, the air flows in the reverse direction. The winds turn

around to blow onto the Indian subcontinent and adjacent areas from the

southwest region bringing rain. The duration and strength of the monsoon

winds indicate the difference between starvation and food adequacy for

hundreds of millions of people in this region every year.

Elevation

The height above a fixed reference point, normally a reference geoid (a

mathematical model of the earths sea level as an equipotential gravitational

surface) is the elevation of a geographic location.

Temperature also changes with elevation, with higher altitudes becoming

increasingly colder. At any given latitude, air temperature decreases by

about 6C for every 1000-meter rise in elevation. The ecological outcomes

of temperature changing with elevation are similar to that of temperature

changing with latitude. Therefore, in North America, a 1000-meter increase

in elevation leads to a temperature drop equal to that of an 880-kilometer

increase in latitude. This is one factor that has contributed to the occurrence

of timberline (the elevation above which trees do not grow) at

progressively lower elevations as one goes farther from the equator.

Within an ecosystem, climate also changes on a very fine scale. Within thelitter on a forest floor, there is a lot of difference in shading, local

temperatures, and rates of evaporation from the soil which is called

microclimate. These localised climatic conditions can greatly vary when

compared to the overhead atmosphere. Straw is evenly spread by

gardeners over newly seeded lawns to obtain a moisture-retaining

microclimate.

Activity 1: What is the elevation of your city from the mean sea level? Also

list out the elevation of other neighbouring areas to your city. Discuss how it

influences the variation in climate during different seasons.

Hint: Refer the sub-section, Elevation.

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Climate - Biosphere Interaction

Different environmental factors play a role in determining the occurrence of

specific biomes at particular locations. Moisture and temperature are two

key parameters that determine ecosystem productivity. Other factors such

as soil structure and its mineral composition, or seasonal versus constant

climate, are also important. Different places with similar annual precipitation

and temperature sometimes support several biomes, and hence other

factors must also be important. But, moisture and temperature play a major

role in determining the type of biomes that occur in most places. Ifmountains were not present and if the irregular outlines of continents and

different sea temperatures did not cause any climatic effect, each biome

would form a uniform belt around the globe, determined mainly by latitude.

Actually, the other factors also have a great impact on the distribution of

biomes. Distance from the ocean has a crucial effect on rainfall, and

elevation impacts temperature. The summits of the Rocky Mountains are

covered with a vegetation type that is similar to the tundra which is usually

seen at much higher latitude.

Biomes

Biomes are the regions of our planet that are differentiated by their climate,

fauna and flora. There are several ways of categorising biomes. However,

the most common elements are:

Habitat

Climate

Biodiversity

Animal and plant adaptation

Human activity.

There are five major biomes in the world and they are:

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Aquatic

Desert

Forest

Grasslands

Tundra

These biomes are also further divided into many categories and sub-

categories. In this unit let us study in brief about the following biomes:

Tropical Rain Forests




Deserts

Tropical Rain Forests

Rain forests receive 140 to 450 centimetres of rain a year and are the

richest ecosystems on earth. At least half of the earths species of terrestrial

plants and animals (more than 2 million species!) are found in the rain

forests. 1200 species of butterflies are present in one square mile of tropical

forest in Rondonia, Brazil. This is double the total number of butterflies

found in both Canada and U.S.A. Although the regions of tropical rain

forests have diversity in each type of animal, plant, or microorganism, only

few human beings live here. There are extensive tropical rain forests in

South America, Africa, and Southeast Asia. But humans are destroying the

worlds rain forests. Thousands of species, many of them never seen by

humans, are becoming extinct. During our lifetime, we can expect a quarter

of the worlds species to disappear with the rain forests.


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In Eurasia, the north-eastern United States and eastern Canada, the factors

that support the growth of deciduous (hardwood) forests are mild climates(characterised by cool winters and warm summers) and abundant rains.

Deciduous trees shed their leaves during the winter. We can find animals

such as bears, beavers, deer and raccoons in the temperate regions. The

temperate deciduous forests are the remnants of more extensive forests

that were spread across Eurasia and North America several million years

ago. As a result, the remaining regions in eastern Asia and eastern North

America share plants and animals that were widespread in the past.

Alligators, for example, are found today only in China and in the south-

eastern United States. Since the climatic conditions have remained constant

in the past, the deciduous forest in eastern Asia is rich in species. Many

perennial herbs can be found in temperate deciduous forests.


Temperate evergreen forests are seen in regions having cold winters and a

strong, seasonal dry period. The pine forests of western United States and

oak woodlands of California are examples of temperate evergreen forests.

Temperate evergreen forests are found in regions having nutrient-poor soils.

Temperate-mixed evergreen forests are located in a broad transitional zone

existing between temperate deciduous forests to the south and Taiga to the

north. Overlogging has endangered many of these forests, especially in the

western United States.


Rich grasslands grow halfway between the equator and the poles in

temperate regions. In the past, these grasslands were found in most of the

interior of North America, South America and Eurasia. When such

grasslands are converted for agricultural use, they are often very useful.

Prairies, another name for temperate grasslands, initially covered most of

the rich agricultural lands in Southern Canada and United States. The roots

of perennial grasses penetrate deep into the soil and grassland soils are

generally deep and fertile. Many grazing mammals can be found intemperate grasslands. Huge herds of bison and pronghorns lived in the

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prairies of North America in the past. But now, the herds have almost

disappeared as most of the prairies have been transformed into the richestagricultural area on earth.

Deserts

The worlds greatest deserts can be found in the interior of continents. The

Sahara is located in the interior of Africa, the Gobi desert in the interior of

Asia and the Great Sandy Desert can be found in the interior of Australia. ).

We term dry places having less than 25 centimetres of rainfall in a year as

deserts. This amount of rainfall is so less that there is sparse vegetation and

survival depends on water conservation. Plants and animals restrict their

activities to those times of the year when water is available. . As the daytime

temperature in the desert is very high, most desert vertebrates have made

deep, cool and sometimes moist burrows as their homes. . The desert

vertebrates that are active over a greater part of the year come out of their

burrows only at night, when temperatures are cooler. Some desert animals

like the camels, can drink large quantities of water whenever it is available

and thus survive the long, dry periods. Many animals just roam about the

desert searching for any seasonal food that may be available in abundance.


6. Temperate Evergreen Forests contain at least half of the earths

species of terrestrial plants and animals more than 2 millionspecies Say True or false

7. Evergreen forest plants shed the leaves during summer - Say True

or false

8. Precipitation is high in equatorial regions Say True or false

1.6 Summary

Let us recapitulate some important points discussed in this unit

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Environment is the sum total of land, air and water and the

interrelationships existing among them and with human beings, otherliving organisms and materials.

The earth presents a mosaic of different combinations of abiotic

factors (physical components such as air, water, minerals, nutrients

etc.) providing a myriad of habitats for biotic components (living

organisms from bacteria to plants to animals).

Various factors that determine the climate of a region are the amount

and seasonal patterns of the abiotic components of radiant energy

(sunlight), water which includes precipitation and humidity,

temperature, wind, and ocean currents. These have a significantimpact on the biotic elements of ecosystems including the type of

species present and population growth.

Different environmental factors play a role in determining the

occurrence of specific biomes at particular locations Moisture and

temperature are two key parameters that determine ecosystem

productivity. Different types of biomes are Tropical Rain Forests,

Temperate Deciduous Forests, Temperate Evergreen Forests,

Temperate Grasslands and Deserts

1.7 Glossary

Biodiversity: degree of variation oflife forms within a given ecosystem

(Bio- living, diversity- variety)

Biome:Biomes are climatically and geographically defined as similar

climatic conditions on the Earth, such as communities of plants, animals,

and soil organisms, and are often referred to as ecosystems

Eccentricity:Eccentricity is a measure of the elliptical nature of the earths

orbit. The shape of Earth's orbit around the Sun becomes slightly more and

then less oval every 100,000 years

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Moisture: Moisture refers to the presence of a liquid, especially water, often

in trace amountspH: pH is a measure of the acidityorbasicity of a medium

1.8 Terminal Questions

1. Discuss the significance of greenhouse effect.

2. Why are the majority of great deserts located near 30 north and

south latitude?

3. What are chemo-autotrophs?

4. Elaborate rain shadow phenomenon?

5. Explain why temperature, precipitation and climate vary across

different places in earth?

6. How Indian subcontinent climate is unique compared to the rest of

the world?

1.9 Answers

SAQ

1. (c) Air, water, land, materials and living organisms

2. (b) Bacteria

3. False

4. c) Nitrogen

5. 51%

6. False

7. False

8. True

Terminal questions

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http://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Base_(chemistry)


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1. Refer section 1.4. 2 The greenhouse effect

2. Refer section 1.5. 3 Precipitation

3. Refer section 1.3.2 Biotic components

4. Refer section 1.5. 3 Precipitation

5. Refer section 1.5. 1 Atmospheric Circulation

6. Refer section 1.5. 4 Regional Climates

Reference

Physical Geography: A Landscape Appreciation, 8th Edition, Tom L.

McKnight & Darrel Hess, 2005 Prentice Hall, Inc. A Pearson

Company

Biology, 6/e, George B. Johnson, Peter H. Raven, Contributors: Dr.

Susan Singer, Dr. Jonathan Losos, 2002, 2002 McGraw-Hill Higher

Education

Environmental Science, by G Tyler Miller, Thompson Brooks Cole

Environmental science systems and solutions, 4th Edition Michael

L. Mckinney, R.M. Schoch, L. Yonavjak, 2006, Jones and Bartlett

Publishers.

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fe unit 1 components of environment

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