NCERT Short

Notes
ENVIRONMENT AND ECOLOGY

Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Organisms and Populations
ENVIRONMENT & ECOLOGY

Niche
• Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises
and a distinct functional role in the ecological system, all these together comprise its niche.

Major Abiotic Factors

• Temperature: A few organisms can tolerate and thrive in a wide range of temperatures (they are called
eurythermal), but, a vast majority of them are restricted to a narrow range of temperatures (such organisms are
called stenothermal). The levels of thermal tolerance of different species determine to a large extent their
geographical distribution.

• Water: Water is another the most important factor influencing the life of organisms. In fact, life on earth originated
in water and is unsustainable without water. For aquatic organisms the quality (chemical composition, pH) of water
becomes important. Some organisms are tolerant of a wide range of salinities (euryhaline) but others are restricted
to a narrow range (stenohaline).

• Light: Since plants produce food through photosynthesis, a process which is only possible when sunlight is available
as a source of energy.

• Soil: Various characteristics of the soil such as soil composition, grain size and aggregation determine the
percolation and water holding capacity of the soils. These characteristics along with parameters such as pH, mineral
composition and topography determine to a large extent the vegetation in any area.

Responses to Abiotic Factors

The organism should try to maintain the constancy of its internal environment (a process called homeostasis) despite
varying external environmental conditions that tend to upset its homeostasis.

• Regulate: Some organisms are able to maintain homeostasis by physiological means which ensures constant body
temperature, constant osmotic concentration, etc. All birds and mammals, and a very few lower vertebrate and
invertebrate species are indeed capable of such regulation (thermoregulation and osmoregulation).

ENVIRONMENT & ECOLOGY | Organisms and Populations Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• Conform: An overwhelming majority (99 percent) of animals and nearly all plants cannot maintain a constant
internal environment. Their body temperature changes with the ambient temperature. In aquatic animals, the
osmotic concentration of the body fluids changes with that of the ambient air, water osmotic concentration. These
animals and plants are simply conformers.

• Migrate: The organism can move away temporarily from the stressful habitat to a more hospitable area and return
when the stressful period is over. Every winter the famous Keoladeo National Park (Bharatpur) in Rajasthan hosts
thousands of migratory birds coming from Siberia and other extremely cold northern regions.

• Suspend: In bacteria, fungi and lower plants, various kinds of thick- walled spores are formed which help them to
survive unfavourable conditions – these germinate on availability of suitable environment.

Adaptations: It is an attribute of the organism (morphological, physiological, behavioural) that enables the organism to
survive and reproduce in its habitat. Example- Many desert plants have a thick cuticle on their leaf surfaces and have
their stomata arranged in deep pits (sunken) to minimise water loss through transpiration.

Populations
Population Attributes

• A population has certain attributes whereas an individual organism does not. An individual may have births and
deaths, but a population has birth rates and death rates.

• For the human population, the age pyramids generally show the age distribution of males and females in a diagram.
The shape of the pyramids reflects the growth status of the population - (a) whether it is growing, (b) stable or (c)
declining.

Source : NCERT

Population Growth:

The size of a population for any species is not a static parameter. It keeps changing with time, depending on various
factors including food availability, predation pressure and adverse weather. the density of a population in a given habitat
during a given period, fluctuates due to changes in four basic processes, two of which (natality and immigration)
contribute to an increase in population density and two (mortality and emigration) to a decrease.

ENVIRONMENT & ECOLOGY | Organisms and Populations Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• Natality refers to the number of births during a given period in the population that are added to the initial density.

• Mortality is the number of deaths in the population during a given period.

• Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during
the time period under consideration.

• Emigration is the number of individuals of the population who left the habitat and went elsewhere during the time
period under consideration.

Population Interactions:
Species A Species B Name of Interaction

+ + Mutualism

- - Competition

+ - Predation

+ - Parasitism

+ 0 Commensalism

- 0 Amensalism
Source : NCERT

Predation: It is an interaction, where an animal called predator kills and consumes the other weaker animal called prey.
There are various roles of predators like-

• Keep the prey population under control and play a very important role to provide population stability.

• Help in maintaining species diversity in a community by reducing the intensity of competition among prey species.

• If a predator is too efficient and exploits its prey, then the prey might become extinct. Following it, the predator will
also become extinct because of the lack of food.

• Prey species have evolved various defence mechanisms to lessen the impact of predation.

Competition: Competition occurs when closely related species compete for the same resources that are limited in a
given habitation.

• It can be best defined as a process in which the fitness of one species is significantly lower in the presence of another
species.

• It is a type of interaction, where both the species suffer.

• In interspecific competition, the feeding efficiency of one species might be reduced due to the interfering and
inhibitory presence of the other species, although the resources are plenty.

ENVIRONMENT & ECOLOGY | Organisms and Populations Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• Gause‘s competitive exclusion principle states that the two closely related species competing for the same
resources cannot coexist indefinitely and the competitively inferior one will be eliminated eventually.

Parasitism: It is the mode of interaction between the two species in which one species (parasite) depends on the other
species (host) for food and shelter and damages the host. In this process, one organism is benefited (parasite), while the
other is harmed (host).

• Parasite is host-specific in a way that both host and parasite tend to co-evolve.

• The life cycles of parasites are often complex, involving one or two intermediate hosts or vectors to facilitate
parasitisation of its primary host.

• Parasites that feed on the external surface of the host organism are called ectoparasites.

• Endoparasites are those that live inside the host body at different sites (liver, kidney, lungs, red blood cells, etc.).

• Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of
its host and lets the host incubate them.

Commensalism: It is the interaction between two species, where one species is benefitted and the other is neither
harmed nor benefitted.

• An Orchid growing as an epiphyte on a mango tree gets shelter and nutrition from the mango tree, while the mango
tree is neither benefited nor harmed.

• Sea anemone has stinging tentacles and the clown fish lives among them. The fish gets protection from predators,
which stay away from the stinging tentacles. The anemone does not appear to derive any benefit by hosting the
clown fish.

Mutualism: It is an interaction that confers benefits to both the interacting species.

• Lichens represent an intimate mutualistic relationship between a fungus and photosynthesizing algae or
cyanobacteria. Here, the fungus helps in the absorption of nutrients and provides protection, while algae prepare
the food.

• Mycorrhizae are a close mutual association between fungi and the roots of higher plants. Fungi help the plant for
absorption of nutrients, while the plant provides food for the fungus.

• Plants need help from animals for pollination and dispersal of seeds. In return, plants provide nectar, pollen and
fruits to the pollinators.

• The male bee is attracted to what it perceives as a female and ‘pseudo-copulates’ with the flower. During that
process, pollen is dusted from the flower. When the same bee pseudo-copulates with another flower, it transfers
pollen to it and pollinates another flower.
ENVIRONMENT & ECOLOGY | Organisms and Populations Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Probable Questions
Q. Which of the following statements best explains ‘Parasitism’?

A. One organism is benefited.

B. Both the organisms are benefited.

C. One organism is benefited, another is not affected.

D. One organism is benefited, another is affected.

Q. Explain different types of population interactions. Also try to give their importance in population stabilization.
(250 words)

ENVIRONMENT & ECOLOGY | Organisms and Populations Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Ecosystem
ENVIRONMENT & ECOLOGY

Ecosystem
An ecosystem can be visualised as a functional unit of nature, where living organisms interact among themselves and
also with the surrounding physical environment. It is convenient to divide it into two basic categories, namely the
terrestrial and the aquatic.

• Forest, grassland and desert are some examples of terrestrial ecosystems.

• Pond, lake, wetland, river and estuary are some examples of aquatic ecosystems.

• Crop fields and an aquarium may also be considered as man-made ecosystems.

Ecosystem – Structure and Function

Interaction of biotic and abiotic components result in a physical structure that is characteristic for each type of
ecosystem. The components of the ecosystem are seen to function as a unit when you consider the following aspects:

• Productivity: Amount of biomass or organic matter produced per unit area over a time period by plants during
photosynthesis. The rate of biomass production is called productivity. It can be divided into gross primary
productivity (GPP) and net primary productivity (NPP). Gross primary productivity of an ecosystem is the rate of
production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in
respiration. Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP).

• Decomposition: Decomposers break down complex organic matter into inorganic substances like carbon dioxide,
water and nutrients and the process is called decomposition. Dead remains of animals, including fecal matter,
constitute detritus, which is the raw material for decomposition. The important steps in the process of
decomposition are fragmentation, leaching, catabolism, humification and mineralisation.

• Energy flow: Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems
on Earth. Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR).
Plants capture only 2-10 percent of the PAR and this small amount of energy sustains the entire living world. The
green plants in the ecosystem are called producers. All animals depend on plants (directly or indirectly) for their
food needs. They are hence called consumers and also heterotrophs. The detritus food chain (DFC) begins with
dead organic matter. It is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria.

ENVIRONMENT & ECOLOGY | Ecosystem Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 They meet their energy and nutrient requirements by degrading dead organic matter or detritus. These are also
known as saprotrophs. These natural interconnections of food chains make it a food web. Based on the source of
their nutrition or food, organisms occupy a specific place in the food chain that is known as their trophic level.

Source : NCERT

Each trophic level has a certain mass of living material at a particular time called the standing crop. The
standing crop is measured as the mass of living organisms (biomass) or the number in a unit area. only 10
percent of the energy is transferred to each trophic level from the lower trophic level.

Ecological Pyramids
The three types of ecological pyramids that are usually studied are (a) pyramid of number; (b) pyramid of biomass and
(c) pyramid of energy.

Source : NCERT

ENVIRONMENT & ECOLOGY | Ecosystem Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Source : NCERT

Source : NCERT

Source : NCERT

ENVIRONMENT & ECOLOGY | Ecosystem Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Ecological Succession
• An important characteristic of all communities is that their composition and structure constantly change in response
to the changing environmental conditions.

• This change is orderly and sequential, parallel with the changes in the physical environment. These changes lead
finally to a community that is in near equilibrium with the environment and that is called a climax community.

• The gradual and fairly predictable change in the species composition of a given area is called ecological succession.

• The entire sequence of communities that successively change in a given area are called sere(s).

• The individual transitional communities are termed seral stages or seral communities.

• Succession is hence a process that starts in an area where no living organisms are there – these could be areas
where no living organisms ever existed, say bare rock; or in areas that somehow, lost all the living organisms that
existed there. The former is called primary succession, while the latter is termed secondary succession.

Succession of Plants
• Hydrarch succession takes place in wet areas and the successive series progress from hydric to the mesic conditions.

• Xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions.

• hydrarch and xerarch succession lead to medium water conditions (mesic) – neither too dry (xeric) nor too wet
(hydric).

• The species that invade a bare area are called pioneer species.

Nutrient Cycling
• Organisms need a constant supply of nutrients to grow, reproduce and regulate various body functions.

• The amount of nutrients, such as carbon, nitrogen, phosphorus, calcium, etc., present in the soil at any given time, is
referred to as the standing state.

• The movement of nutrient elements through the various components of an ecosystem is called nutrient cycling.

• Another name of nutrient cycling is biogeochemical cycles (bio: living organism, geo: rocks, air, water).

• Nutrient cycles are of two types: (a) gaseous and (b) sedimentary.

ENVIRONMENT & ECOLOGY | Ecosystem Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Ecosystem Services
• The products of ecosystem processes are named as ecosystem services, for example, healthy forest ecosystems
purify air and water, mitigate droughts and floods, cycle nutrients, generate fertile soils, provide wildlife habitat,
maintain biodiversity, pollinate crops, provide storage site for carbon and also provide aesthetic, cultural and
spiritual values.

• Provisioning Services includes food, water, medicines and other resources from ecosystems.

• Regulating Services includes the services which regulate the ecological balance. For example, terrestrial
environments like forests purify and regulate air quality, prevent soil erosion, and control greenhouse gases.

• Supporting services form the basis for other services. They provide habitat for different life forms, retain
biodiversity, nutrient cycling, and other services for supporting life on the earth.

• Cultural services includes tourism; provides recreational, aesthetic, cultural and spiritual services, etc.

Probable Questions
Q. What is the percentage of photosynthetically active radiation (PAR) in the incident solar radiation?

A. 100%

B. 50 %

C. 1-5%

D. 2-10%

Q. Describe the components of an ecosystem. Mention various services provided by the ecosystem. (250 words)

ENVIRONMENT & ECOLOGY | Ecosystem Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts
Biodiversity and Conservation
ENVIRONMENT AND ECOLOGY

Biodiversity: Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined
diversity at all the levels of biological organisation.

The most important of them are–

1. Genetic diversity: A single species might show high diversity at the genetic level over its distributional range.

2. Species diversity: The diversity at the species level, for example, the Western Ghats have a greater amphibian
species diversity than the Eastern Ghats.

 Ecological diversity: At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral
reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like
Norway.

Patterns of Biodiversity
Latitudinal gradients: In general, species diversity decreases as we move away from the equator towards the poles.
With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbour more species than temperate or polar
areas.

Tropics account for their greater biological diversity compare to other regions because:

 Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past,
tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary
time for species diversification,

 Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such
constant environments promote niche specialisation and lead to a greater species diversity.

 There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might
contribute indirectly to greater diversity.

Species-Area relationships: within a region species richness increased with increasing explored area, but only up to a
limit.

ENVIRONMENT AND ECOLOGY | Biodiversity and Conservation Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
The importance of Species Diversity to the Ecosystem
A stable community should not show too much variation in productivity from year to year; it must be either resistant
or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien
species. The rich biodiversity is not only essential for ecosystem health but imperative for the very survival of the
human race on this planet.

Loss of Biodiversity: Loss of biodiversity in a region may lead to decline in plant production, lowered resistance to
environmental perturbations such as drought and increased variability in certain ecosystem processes such as plant
productivity, water use, and pest and disease cycles.

Causes of biodiversity losses: The accelerated rates of species extinctions that the world is facing now are largely due
to human activities. There are four major causes (‘ The Evil Quartet’ is the sobriquet used to describe them).

1. Habitat loss and fragmentation:

 This is the most important cause driving animals and plants to extinction.

 The most dramatic examples of habitat loss come from tropical rainforests. Once covering more than 14 percent of
the earth’s land surface, these rain forests now cover no more than 6 per cent.

 The Amazon rainforest (it is so huge that it is called the ‘lungs of the planet’) harbouring probably millions of
species is being cut and cleared for cultivating soybeans or for conversion to grasslands for raising beef cattle.

 The degradation of many habitats by pollution also threatens the survival of many species.

 When large habitats are broken up into small fragments due to various human activities, mammals and birds
requiring large territories and certain animals with migratory habits are badly affected, leading to population
declines.

2. Over-exploitation:

 Humans have always depended on nature for food and shelter, but when ‘need’ turns to ‘greed’, it leads to over -
exploitation of natural resources.

 Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due to overexploitation
by humans.

 Presently many marine fish populations around the world are over harvested, endangering the continued existence
of some commercially important species.

3. Alien species invasions:

 When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn
invasive, and cause decline or extinction of indigenous species.

ENVIRONMENT AND ECOLOGY | Biodiversity and Conservation Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically
unique assemblage of more than 200 species of cichlid fish in the lake.

 You must be familiar with the environmental damage caused and threat posed to our native species by invasive
weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia).

 The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to
the indigenous catfishes in our rivers.

4. Co-extinctions:

 When a species becomes extinct, the plant and animal species associated with it in an obligatory way also
become extinct.

 When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.

 Another example is the case of a coevolved plant-pollinator mutualism where extinction of one invariably leads to
the extinction of the other.

Biodiversity Conservation
There are many reasons, some obvious and others not so obvious, but all equally important. They can be grouped into
three categories: narrowly utilitarian, broadly utilitarian, and ethical.

 The narrowly utilitarian arguments for conserving biodiversity are obvious; humans derive countless direct
economic benefits from nature. With increasing resources put into ‘bioprospecting’ (exploring molecular, genetic
and species-level diversity for products of economic importance), nations endowed with rich biodiversity can
expect to reap enormous benefits.

 The broadly utilitarian argument says that biodiversity plays a major role in many ecosystem services that nature
provides. The fast- dwindling Amazon forest is estimated to produce, through photosynthesis, 20 percent of the
total oxygen in the earth’s atmosphere. Pollination (without which plants cannot give us fruits or seeds) is
another service, ecosystems provide through pollinators layer – bees, bumblebees, birds and bats.

 The ethical argument for conserving biodiversity relates to what we owe to millions of plant, animal and microbe
species with whom we share this planet. Philosophically or spiritually, we need to realise that every species has an
intrinsic value, even if it may not be of current or any economic value to us. We have a moral duty to care for their
well-being and pass on our biological legacy in good order to future generations.

Ways of Biodiversity conservation

ENVIRONMENT AND ECOLOGY | Biodiversity and Conservation Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 In situ conservation– on site conservation or conservation of species in their natural habitat. example - ‘biodiversity
hotspots’ regions with very high levels of species richness and high degree of endemism. In India, ecologically
unique and biodiversity-rich regions are legally protected as biosphere reserves, national parks and sanctuaries.
India now has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries. In many cultures, tracts of
forest were set aside, and all the trees and wildlife within were venerated and given total protection. Such sacred
groves are found in Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, Western Ghat regions of
Karnataka and Maharashtra and the Sarguja, Chanda and Bastar areas of Madhya Pradesh.

 Ex situ Conservation– off site conservation of species. Threatened animals and plants are taken out from their
natural habitat and placed in special settings where they can be protected and given special care. Zoological parks,
botanical gardens and wildlife safari parks serve this purpose. Now gametes of threatened species can be
preserved in viable and fertile condition for long periods using cryopreservation techniques, eggs can be fertilised
in vitro, and plants can be propagated using tissue culture methods. Seeds of different genetic strains of
commercially important plants can be kept for long periods in seed banks.

Probable Questions
Q. Which of the following is not the cause of biodiversity loss?

A. Co-extinctions

B. Habitat loss

C. In situ conservation

D. All of the above

Q. Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic
components of the ecosystem? (150 marks)

ENVIRONMENT AND ECOLOGY | Biodiversity and Conservation Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Environmental Issues
ENVIRONMENT & ECOLOGY

Pollution
• It is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil. Agents that
bring about such an undesirable change are called pollutants.

Air Pollution and Its Control

Air pollutants cause injury to all living organisms. They reduce growth and yield of crops and cause premature death of
plants. Air pollutants also deleteriously affect the respiratory system of humans and of animals. Harmful effects depend
on the concentration of pollutants, duration of exposure and the organism.

• Electrostatic precipitator: It helps in separation/filtered out of pollutants before releasing the harmless gases into
the atmosphere. which can remove over 99 per cent particulate matter present in the exhaust from a thermal
power plant.

• Catalytic converters, having expensive metals namely platinum-palladium and rhodium as the catalysts, are fitted
into automobiles for reducing emission of poisonous gases.

Water Pollution and Its Control

Human beings have been abusing the water-bodies around the world by disposing of all kinds of waste. Realising the
importance of maintaining the cleanliness of the water bodies, the Government of India has passed the Water
(Prevention and Control of Pollution) Act, 1974 to safeguard our water resources.

• Solids are relatively easy to remove, what is most difficult to remove are dissolved salts such as nitrates,
phosphates, and other nutrients, and toxic metal ions and organic compounds.

• It is possible to estimate the amount of biodegradable organic matter in sewage water by measuring Biochemical
Oxygen Demand (BOD).

• Presence of large amounts of nutrients in waters also causes excessive growth of planktonic (free-floating) algae,
called an algal bloom.

• Sewage disposal into water without proper treatment may cause an outbreak of serious diseases, such as,
dysentery, typhoid, jaundice, cholera, etc.

ENVIRONMENT & ECOLOGY | Environmental Issues Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• Biomagnification refers to an increase in concentration of the toxicant at successive trophic levels. This happens
because a toxic substance accumulated by an organism cannot be metabolised or excreted, and is thus passed on to
the next higher trophic level. This phenomenon is well- known for mercury and DDT.

• Eutrophication is the natural aging of a lake by nutrient enrichment of its water.

• Pollutants from man’s activities like effluents from the industries and homes can radically accelerate the aging
process. This phenomenon has been called Cultural or Accelerated Eutrophication.

Solid Wastes
Solid wastes refer to everything that goes out in trash. Municipal solid wastes are wastes from homes, offices, stores,
schools, hospitals, etc., that are collected and disposed of by the municipality. The municipal solid wastes generally
comprise paper, food wastes, plastics, glass, metals, rubber, leather, textile, etc.

• Burning and sanitary landfills are used as ways to dump the solid wastes.

• The use of incinerators is crucial to disposal of hospital solid waste.

• Irreparable computers and other electronic goods are known as electronic wastes (e-wastes). E-wastes are buried in
landfills or incinerated.

Agro-Chemicals and Their Effects

• In the wake of the green revolution, use of inorganic fertilisers and pesticides has increased manifold for enhancing
crop production. Pesticides, herbicides, fungicides, etc., are being increasingly used. These incidentally, are also toxic
to non-target organisms, that are important components of the soil ecosystem.

Radioactive Wastes:
Initially, nuclear energy was hailed as a non-polluting way for generating electricity. Later on, it was realised that the
use of nuclear energy has two very serious inherent problems. The first is accidental leakage, as occurred in the Three
Mile Island and Chernobyl incidents and the second is safe disposal of radioactive wastes.

• Radiation that is given off by nuclear waste is extremely damaging to organisms, because it causes mutations at a
very high rate.

• At high doses, nuclear radiation is lethal but at lower doses, it creates various disorders, the most frequent of all
being cancer.

ENVIRONMENT & ECOLOGY | Environmental Issues Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Greenhouse Effect and Global Warming
• The greenhouse effect is a naturally occurring phenomenon that is responsible for heating of Earth’s surface and
atmosphere. Without greenhouse effect the average temperature at surface of Earth would have been a chilly –18°C
rather than the present average of 15°C. Carbon dioxide and methane – are commonly known as greenhouse gases
because they are responsible for the greenhouse effect.

Ozone Depletion in the Stratosophere

‘Bad’ ozone, formed in the lower atmosphere (troposphere) that harms plants and animals. There is ‘good’ ozone also;
this ozone is found in the upper part of the atmosphere called the stratosphere, and it acts as a shield absorbing
ultraviolet radiation from the sun. UV rays are highly injurious to living organisms since DNA and proteins of living
organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules. The
thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson
units (DU).

• Ozone gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular
oxygen in the stratosphere.

• There should be a balance between production and degradation of ozone in the stratosphere.

• Of late, the balance has been disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs).

• CFCs find wide use as refrigerants. CFCs discharged in the lower part of the atmosphere move upward and reach the
stratosphere.

• Recognising the deleterious effects of ozone depletion, an international treaty, known as the Montreal Protocol, was
signed at Montreal (Canada) in 1987 (effective in 1989) to control the emission of ozone depleting substances.
Subsequently many more efforts have been made and protocols have laid down definite roadmaps, separately for
developed and developing countries, for reducing the emission of CFCs and other ozone depleting chemicals.

Degradation by Improper Resource Utilisation and Maintenance

• Soil erosion and desertification: The development of the fertile top-soil takes centuries. But, it can be removed very
easily due to human activities like over-cultivation, unrestricted grazing, deforestation and poor irrigation practices,
resulting in arid patches of land.

• Waterlogging and soil salinity: Irrigation without proper drainage of water leads to waterlogging in the soil. Besides
affecting the crops, waterlogging draws salt to the surface of the soil.

ENVIRONMENT & ECOLOGY | Environmental Issues Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Deforestation
• Deforestation is the conversion of forested areas to non-forested ones. According to an estimate, almost 40 percent
forests have been lost in the tropics, compared to only 1 per cent in the temperate region.

• Slash and burn agriculture, commonly called as Jhum cultivation in the north-eastern states of India, has also
contributed to deforestation.

• Reforestation is the process of restoring a forest that once existed but was removed at some point of time in the
past.

• The Government of India has recently instituted the Amrita Devi Bishnoi Wildlife Protection Award for individuals
or communities from rural areas that have shown extraordinary courage and dedication in protecting wildlife.

• Chipko Movement of Garhwal Himalayas of 1974, where local women showed enormous bravery in protecting
trees from the axe of contractors by hugging them.

• The Government of India in the 1980s introduced the concept of Joint Forest Management (JFM) so as to work
closely with the local communities for protecting and managing forests.

Probable Questions
Q. Consider the following statements about water pollution:

1. Biochemical Oxygen Demand helps in measuring the level of pollution in a given water body.

2. Eutrophication is the natural aging of a lake by nutrient deficiency of its water.

Which of the above statements is/are correct?

A. 1 only

B. 2only

C. 1 and 2 both

D. None of the above

Q. What is the difference between ‘good ozone’ and ‘bad ozone’ present into the atmosphere? (150 words)

ENVIRONMENT & ECOLOGY | Environmental Issues Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Sources of Energy
ENVIRONMENT & ECOLOGY

Conventional Sources of Energy

The conventional sources of energy are generally non-renewable sources of energy, which have been used for a long
time.

Fossil Fuels
• The growing demand for energy was largely met by fossil fuels – coal and petroleum.

• These fuels were formed over millions of years ago and there are only limited reserves. The fossil fuels are non-
renewable sources of energy, so we need to conserve them.

• If we were to continue consuming these sources at such alarming rates, we would soon run out of energy.

Thermal Power Plant

• Large amounts of fossil fuels are burnt every day in power stations to heat up water to produce steam which further
runs the turbine to generate electricity.

• The transmission of electricity is more efficient than transporting coal or petroleum over the same distance.

• Therefore, many thermal power plants are set up near coal or oil fields. The term thermal power plant is used since
fuel is burnt to produce heat energy which is converted into electrical energy.

Hydro Power Plants:

• Another traditional source of energy was the kinetic energy of flowing water or the potential energy of water at a
height.

• Hydro power plants convert the potential energy of falling water into electricity. A quarter of our energy
requirement in India is met by hydro power plants.

Improvements in the Technology for using Conventional Sources of

Energy
Biomass: Fuels from plant and animal products are generally said to be biomass. These fuels, however, do not produce
much heat on burning and a lot of smoke is given out when they are burnt.

ENVIRONMENT & ECOLOGY | Sources of Energy Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• When wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and
charcoal is left behind as the residue. Charcoal burns without flames, is comparatively smokeless and has a higher
heat generation efficiency.

• Cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are
decomposed in the absence of oxygen to give bio-gas.

• Bio-gas is an excellent fuel as it contains up to 75% methane. It burns without smoke, leaves no residue like ash in
wood, charcoal and coal burning. Its heating capacity is high.

Wind Energy: A number of windmills are erected over a large area, which is known as wind energy farm. The energy
output of each windmill in a farm is coupled together to get electricity on a commercial scale. Wind energy is an
environment-friendly and efficient source of renewable energy.

• It requires no recurring expenses for the production of electricity. But there are many limitations in harnessing wind
energy.

• Wind energy farms can be established only at those places where wind blows for the greater part of a year. The
wind speed should also be higher than 15 km/h to maintain the required speed of the turbine.

• There should be some back-up facilities (like storage cells) to take care of the energy needs during a period when
there is no wind.

• Establishment of wind energy farms requires large areas of land. The initial cost of establishment of the farm is
quite high.

Alternative or Non-Conventional Sources of Energy

These sources of energy are also known as a renewable source of energy and are generally not responsible for the cause
of pollution.

Solar Energy
• The Sun has been radiating an enormous amount of energy at the present rate for nearly 5 billion years and will
continue radiating at that rate for about 5 billion years more.

• The limitation of using solar energy is overcome by using solar cells that convert solar energy into electricity.

Tidal Energy
• Due to the gravitational pull of mainly the moon on the spinning earth, the level of water in the sea rises and falls.

• This phenomenon is called high and low tides and the difference in sea-levels gives us tidal energy.

ENVIRONMENT & ECOLOGY | Sources of Energy Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at the opening
of the dam converts tidal energy to electricity.

Wave Energy
• The kinetic energy possessed by huge waves near the sea- shore can be trapped in a similar manner to generate
electricity.

• The waves are generated by strong winds blowing across the sea. Wave energy would be a viable proposition only
where waves are very strong.

• A wide variety of devices have been developed to trap wave energy for rotation of turbines and production of
electricity.

Ocean Thermal Energy:

• The water at the surface of the sea or ocean is heated by the Sun while the water in deeper sections is relatively
cold. This difference in temperature is exploited to obtain energy in ocean-thermal-energy conversion plants.

• These plants can operate if the temperature difference between the water at the surface and water at depths up to
2 km is 20 K (20°C) or more.

• The warm surface-water is used to boil a volatile liquid like ammonia.

• The vapours of the liquid are then used to run the turbine of the generator. The cold water from the depth of the
ocean is pumped up and condenses vapour again to liquid.

• The energy potential from the sea (tidal energy, wave energy and ocean thermal energy) is quite large, but efficient
commercial exploitation is difficult.

Geothermal Energy
• Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upward and
trapped in certain regions called ‘hot spots’.

• When underground water comes in contact with the hot spot, steam is generated.

• Sometimes hot water from that region finds outlets at the surface. Such outlets are known as hot springs.

• The steam trapped in rocks is routed through a pipe to a turbine and used to generate electricity.

• The cost of production would not be much, but there are very few commercially viable sites where such energy can
be exploited. There are a number of power plants based on geothermal energy operational in New Zealand and the
United States of America.

ENVIRONMENT & ECOLOGY | Sources of Energy Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Nuclear Energy
• In a process called nuclear fission, the nucleus of a heavy atom (such as uranium, plutonium or thorium), when
bombarded with low-energy neutrons, can be split apart into lighter nuclei.

• The fission of an atom of uranium, for example, produces 10 million times the energy produced by the combustion
of an atom of carbon from coal.

• In a nuclear reactor designed for electric power generation, such nuclear ‘fuel’ can be part of a self- sustaining
fission chain reaction that releases energy at a controlled rate.

• The released energy can be used to produce steam and further generate electricity.

• The major hazard of nuclear power generation is the storage and disposal of spent or used fuels – the uranium still
decaying into harmful subatomic particles (radiations).

• Improper nuclear-waste storage and disposal result in environmental contamination.

Probable Questions
Q. Consider the following statements wrt Ocean thermal energy:

1. Ocean thermal energy comes under the conventional sources of energy.

2. These plants can operate if the temperature difference between the water at the surface and water at depths up to
2 km is 20 K (20°C) or more.

Which of the above statements is/are incorrect?

A. 1 only

B. 2only

C. 1 and 2 both

D. None of the above

Q. Differentiate between Conventional and Non-Conventional sources of energy with examples. (150 words)

ENVIRONMENT & ECOLOGY | Sources of Energy Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Our Environment
ENVIRONMENT & ECOLOGY

Ecosystem — What are its Components?

All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact
with each other and maintain a balance in nature.

• All the interacting organisms in an area together with the non-living constituents of the environment form an
ecosystem.

• An ecosystem consists of biotic components comprising living organisms and abiotic components comprising
physical factors like temperature, rainfall, wind, soil and minerals.

Food Chains and Webs

• When a series of organisms feed on one another then the series or organisms taking part at various biotic levels
form a food chain.

• Each step or level of the food chain forms a trophic level.

• The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for
heterotrophs or the consumers.

• The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the
third and larger carnivores or the tertiary consumers form the fourth trophic level.

• Thus the interactions among various components of the environment involves flow of energy from one component
of the system to another.

Source : NCERT

ENVIRONMENT & ECOLOGY | Our Environment Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Source : NCERT

Flow of Energy
The flow of energy between various components of the environment has been extensively studied and it has been found
that –

• The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves and
convert it into food energy.

• When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some
amount goes into digestion and in doing work and the rest goes towards growth and reproduction. An average of
10% of the food eaten is turned into its own body and made available for the next level of consumers.

• Therefore, 10% can be taken as the average value for the amount of organic matter that is present at each step and
reaches the next level of consumers.

• The loss of energy at each step is so great that very little usable energy remains after four trophic levels.

• There are generally a greater number of individuals at the lower trophic levels of an ecosystem, the greatest
number is of the producers.

• The flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert back to the solar
input and the energy which passes to the herbivores does not come back to autotrophs.

• The energy available at each trophic level gets diminished progressively due to loss of energy at each level.

• Chemicals are not degradable, these get accumulated progressively at each trophic level. This phenomenon is known
as biological magnification.

• The process of accumulating toxic chemicals such as pollutants, pesticides and other toxins at a particular trophic
level is termed as bioaccumulation.

ENVIRONMENT & ECOLOGY | Our Environment Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Top Carnivores

Carnivores

Herbivores

Producers

Sunlight
Source : NCERT
Diagram Showing Flow of Energy in an Ecosystem

How do our Activities Affect the Environment?

Ozone Layer and How it is Getting Depleted:
Ozone is a deadly poison. However, at the higher levels of the atmosphere, ozone performs an essential function. It
shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to
organisms, for example, it is known to cause skin cancer in human beings.

• The amount of ozone in the atmosphere began to drop sharply in the 1980s. This decrease has been linked to
synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.

• In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC
production at 1986 levels.

Probable Questions
Q. Consider the following statements wrt to flow of energy in a food chain:

1. The flow of energy is unidirectional.

2. As we move up in a food chain, energy keeps on increasing as per the 10% rule.

Which of the above statements is/are correct?

A. 1 only

B. 2only

C. 1 and 2 both

D. None of the above

Q. Differentiate between the process of bioaccumulation and biomagnification in a food chain system. (150 words)

ENVIRONMENT & ECOLOGY | Our Environment Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Management of Natural Resources
ENVIRONMENT & ECOLOGY

Five R’s to Save the Environment

• Refuse: This means to say No to things people offer you that you don’t need. Refuse to buy products that can harm
you and the environment, say No to single-use plastic carry bags.

• Reduce: This means that you use less. You save electricity by switching off unnecessary lights and fans. You save
water by repairing leaky taps. Do not waste food.

• Reuse: This is actually even better than recycling because the process of recycling uses some energy. In the ‘reuse’
strategy, you simply use things again and again.

• Repurpose: This means when a product can no longer be used for the original purpose, think carefully and use it for
some other useful purpose.

• Recycle: This means that you collect plastic, paper, glass and metal items and recycle these materials to make
required things instead of synthesising or extracting fresh plastic, paper, glass or metal. In order to recycle, we first
need to segregate our wastes so that the material that can be recycled is not dumped along with other wastes.

Why do We Need to Manage Our Resources?

• The natural resources are not unlimited and with the human population increasing at a tremendous rate due to
improvement in health-care, the demand for all resources is increasing at an exponential rate.

• The management of natural resources requires a long-term perspective so that these will last for the generations to
come.

• Another factor to be considered while we exploit these natural resources is the damage we cause to the
environment while these resources are either extracted or used.

Forests and Wildlife

• One of the main aims of conservation of forest and wildlife is to try and preserve the biodiversity we have inherited.

• Experiments and field studies suggest that loss of diversity may lead to loss of ecological stability.

ENVIRONMENT & ECOLOGY | Management of Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• These nature-loving people have for centuries, been conserving the flora and fauna to the extent of sacrificing their
lives to protect the environment. They are living with the basic philosophy that all living things have a right to
survive and share all resources.

• The Government of India has recently instituted an ‘Amrita Devi Bishnoi National Award for Wildlife Conservation’
in the memory of Amrita Devi Bishnoi, who in 1731 sacrificed her life along with 363 others for the protection of
‘khejri’ trees in Khejarli village near Jodhpur in Rajasthan.

• Management of protected areas by keeping the local people out or by using force cannot possibly be successful in
the long run.

• Forest resources ought to be used in a manner that is both environmentally and developmentally sound – in other
words, while the environment is preserved, the benefits of the controlled exploitation go to the local people, a
process in which decentralised economic growth and ecological conservation go hand in hand.

• The Chipko Andolan (‘Hug the Trees Movement’) was the result of a grassroot level effort to end the alienation of
people from their forests.

Water for All

Water is a basic necessity for all terrestrial forms of life. Watershed management emphasises scientific soil and water
conservation in order to increase the biomass production. Watershed management not only increases the production
and income of the watershed community, but also mitigates droughts and floods and increases the life of the
downstream dam and reservoirs.

• Water harvesting is an age-old concept in India.

• Khadins, tanks and nadis in Rajasthan, bandharas and tals in Maharashtra, bundhis in Madhya Pradesh and Uttar
Pradesh, ahars and pynes in Bihar, kulhs in Himachal Pradesh, ponds in the Kandi belt of Jammu region, and eris
(tanks) in Tamil Nadu, surangams in Kerala, and kattas in Karnataka are some of the ancient water harvesting,
including water conveyance, structures still in use today.

Coal and Petroleum

Since the industrial revolution, we have been using increasing amounts of energy to meet our basic needs and for the
manufacture of a large number of goods upon which our lives depend. These energy needs have been largely met by
the reserves of coal and petroleum.

• Overexploitation of these resources may lead to unsustainability in their use and also cause environment impact.

ENVIRONMENT & ECOLOGY | Management of Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• We need to make judicious use of these resources and bring out some alternatives which are environmentally
friendly in the longer run.

• Coal and petroleum once exploited takes thousands of years to replenish.

• We should give rise to the use of renewable sources of energy to make our environment clean and save our
conventional resources to the extent possible.

Probable Questions
Q. Consider the following statements:

1. Watershed management emphasises scientific soil and water conservation in order to increase the biomass
production.

2. Ahars and pynes water harvesting techniques were present in Rajasthan state.

Which of the above statements is/are correct?

A. 1 only

B. 2only

C. 1 and 2 both

D. None of the above

Q) Write down about the traditional systems of water harvesting/management prevalent in our country. Also bring
out their significance in water management in the present context. (250 words)

ENVIRONMENT & ECOLOGY | Management of Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Natural Resources
ENVIRONMENT & ECOLOGY

What are these Resources on the Earth?

• These are the land, the water and the air.

• The outer crust of the Earth is called the lithosphere.

• Water covers 75% of the Earth’s surface. It is also found underground. These comprise the hydrosphere.

• The air that covers the whole of the Earth like a blanket, is called the atmosphere.

• Living things are found where these three exist. This life-supporting zone of the Earth where the atmosphere, the
hydrosphere and the lithosphere interact and make life possible, is known as the biosphere.

• Living things constitute the biotic component of the biosphere. The air, the water and the soil form the non-living or
abiotic component of the biosphere.

The Role of the Atmosphere in Climate Control

• The atmosphere keeps the average temperature of the Earth fairly steady during the day and even during the
course of the whole year.

• The atmosphere prevents the sudden increase in temperature during the daylight hours.

• And during the night, it slows down the escape of heat into outer space.

The Movement of Air: Winds

• What causes the movement of air, and what decides whether this movement will be in the form of a gentle breeze, a
strong wind or a terrible storm? What brings us the welcome rains?

• All these phenomena are the result of changes that take place in our atmosphere due to the heating of air and the
formation of water vapour.

• Water vapour is formed due to the heating of water bodies and the activities of living organisms.

• The atmosphere can be heated from below by the radiation that is reflected back or re-radiated by the land or
water bodies.

• On being heated, convection currents are set up in the air. when air is heated by radiation from the heated land or
water, it rises.
ENVIRONMENT & ECOLOGY | Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• But since land gets heated faster than water, the air over land would also be heated faster than the air over water
bodies.

• The movement of air from one region to the other creates winds.

• But various other factors also influence these winds – the rotation of the Earth and the presence of mountain
ranges in the paths of the wind are a couple of these factors.

• During the day, the direction of the wind would be from the sea to the land. At night, both land and sea start to
cool. Since water cools down slower than the land, the air above water would be warmer than the air above land.

Rain
• When water bodies are heated during the day, a large amount of water evaporates and goes into the air.

• The hot air rises up carrying the water vapour with it. As the air rises, it expands and cools.

• This cooling causes the water vapour in the air to condense in the form of tiny droplets.

• This condensation of water is facilitated if some particles could act as the ‘nucleus’ for these drops to form around.
Normally dust and other suspended particles in the air perform this function.

• Once the water droplets are formed, they grow bigger by the ‘condensation’ of these water droplets. When the
drops have grown big and heavy, they fall down in the form of rain.

• Sometimes, when the temperature of air is low enough, precipitation may occur in the form of snow, sleet or hail.

• Rainfall patterns are decided by the prevailing wind patterns.

Air Pollution
• How is the quality of air affected and how does this change in quality affect us and other life forms?

• The fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur. When these fuels are burnt,
nitrogen and sulphur too are burnt and this produces different oxides of nitrogen and sulphur.

• Not only is the inhalation of these gases dangerous, they also dissolve in rain to give rise to acid rain.

• The combustion of fossil fuels also increases the amount of suspended particles in air.

• These suspended particles could be unburnt carbon particles or substances called hydrocarbons.

• Presence of high levels of all these pollutants causes visibility to be lowered, especially in cold weather when water
also condenses out of air. This is known as smog and is a visible indication of air pollution.

ENVIRONMENT & ECOLOGY | Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• This causes the incidence of allergies, cancer and heart diseases.

• An increase in the content of these harmful substances in air is called air pollution.

Water Pollution
• The addition of undesirable substances to water-bodies. These substances could be the fertilisers and pesticides
used in farming or they could be poisonous substances, like mercury salts which are used by paper-industries. These
could also be disease-causing organisms, like the bacteria which cause cholera.

• The removal of desirable substances from water-bodies. Dissolved oxygen is used by the animals and plants that
live in water. Any change that reduces the amount of this dissolved oxygen would adversely affect these aquatic
organisms. Other nutrients could also be depleted from the water bodies.

• A change in temperature. Aquatic organisms are used to a certain range of temperature in the water-body where
they live, and a sudden marked change in this temperature would be dangerous for them or affect their breeding.
The eggs and larvae of various animals are particularly susceptible to temperature changes.

Mineral Riches in the Soil

Soil is an important resource that decides the diversity of life in an area. The outermost layer of our Earth is called the
crust and the minerals found in this layer supply a variety of nutrients to life-forms.

• The Sun: The Sun heats results in the formation of cracks and ultimately the huge rocks break up into smaller pieces.

• Water: Flowing water wears away even hard rock over long periods of time. Fast flowing water often carries big and
small particles of rock downstream. The water then takes these particles along with it and deposits it further down
its path. Soil is thus found in places far away from its parent-rock.

• Wind: The wind also carries sand from one place to the other like water does.

• Living organisms: They also influence the formation of soil. The lichen also grows on the surface of rocks. While
growing, they release certain substances that cause the rock surface to powder down and form a thin layer of soil.
Other small plants like moss, are able to grow on this surface now and they cause the rock to break up further.

The type of soil is decided by the average size of particles found in it and the quality of the soil is decided by the
amount of humus and the microscopic organisms found in it. The nutrient content of a soil, the amount of humus
present in it and the depth of the soil are some of the factors that decide which plants will thrive on that soil. Thus, the
topmost layer of the soil that contains humus and living organisms in addition to the soil particles is called the topsoil.
The quality of the topsoil is an important factor that decides biodiversity in that area.

ENVIRONMENT & ECOLOGY | Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Biogeochemical Cycle
The Water-Cycle

Source : NCERT

The Nitrogen-Cycle

Source : NCERT

ENVIRONMENT & ECOLOGY | Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
The Carbon-Cycle

Source : NCERT

The Oxygen-Cycle

Source : NCERT

ENVIRONMENT & ECOLOGY | Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Probable Questions
Q. Which of the following factors helps in formation of soil?

A. Sun

B. Water and wind

C. Living organisms

D. All of the above

Q. Elaborate on the significance of the Nitrogen cycle present in the atmosphere, also support your answer with an
appropriate diagram. (150 words)

ENVIRONMENT & ECOLOGY | Natural Resources Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Pollution of Air and Water
ENVIRONMENT & ECOLOGY

Air Pollution
Air consists of a mixture of gases. By volume, about 78% of this mixture is nitrogen and about 21% is oxygen. Carbon
dioxide, argon, methane, ozone and water vapour are also present in very small quantities. When air is contaminated
by unwanted substances which have a harmful effect on both the living and the non-living, it is referred to as air
pollution.

• The substances which contaminate the air are called air pollutants.

• The sources of air pollutants are factories, power plants, automobile exhausts and burning of firewood and dung
cakes.

• Vehicles produce high levels of pollutants like carbon monoxide, carbon dioxide, nitrogen oxides and smoke.

• Smoke may contain oxides of nitrogen which combine with other air pollutants and fog to form smog. The smog
causes breathing difficulties such as asthma, cough and wheezing in children.

• Petroleum refineries are a major source of gaseous pollutants like sulphur dioxide and nitrogen dioxide. Sulphur
dioxide is produced by combustion of fuels like coal in power plants.

• Other kinds of pollutants are chlorofluorocarbons (CFCs) which are used in refrigerators, air conditioners and
aerosol sprays. CFCs damage the ozone layer of the atmosphere.

• These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids
drop down with rain, making the rain acidic. This is called acid rain.

• The average temperature of the earth’s atmosphere is gradually increasing. This is called global warming.

Ways to Tackle Air Pollution

• Switch to fuels like CNG and unleaded petrol.

• Use of alternate sources of energy which are environmentally friendly.

• Planting more and more trees.

• Implementation of policies related to air pollution control.

• Awareness generation among the youth about air pollution and its impact.

• Regulation over the industrial emissions.

ENVIRONMENT & ECOLOGY | Pollution of Air and Water Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Water Pollution
Harmful substances such as sewage, toxic chemicals, silt, etc., get mixed with water, the water becomes polluted. The
substances that pollute water are called water pollutants.

• The World Wide Fund for Nature (WWF) found that Ganga is one of the ten most endangered rivers in the world.

• Large quantities of garbage, untreated sewage, dead bodies, and many other harmful things are the leading causes
of river water bodies.

• An ambitious plan to save the river, called the Ganga Action Plan was launched in 1985. It aimed to reduce the
pollution levels in the river.

• Many industries discharge harmful chemicals into rivers and streams, causing the pollution of water.

• The chemicals released include arsenic, lead and fluorides which lead to toxicity in plants and animals.

• Water contaminated with sewage may contain bacteria, viruses, fungi and parasites which cause diseases like
cholera, typhoid and jaundice.

Some of the Ways to Tackle Water Pollution

• Laws for industrial units should be strictly implemented so that polluted water is not disposed of directly into rivers
and lakes.

• Water treatment plants should be installed in all industrial areas.

• At our individual levels we should consciously save water and not waste it.

• Reduce, reuse and recycle should be our mantra.

• We can think of creative ideas like reusing water used for washing and for other household tasks. water used for
washing vegetables may be used to water plants in the garden.

Potable Water
Water which is suitable for drinking is called potable water. Chlorination is a commonly used chemical method for
purifying water. It is done by adding chlorine tablets or bleaching powder to the water. We must be cautious.

ENVIRONMENT & ECOLOGY | Pollution of Air and Water Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Probable Questions
Q. Consider the following statements regarding air pollution:

1. Smoke may contain oxides of nitrogen which combine with other air pollutants and fog to form smog.

2. The gases present in the atmosphere react with the water vapours to form sulphuric acid and nitric acid and result
in acid rain.

Which of the above statements is/are correct?

A. 1 only

B. 2 only

C. Both 1 and 2

D. None of the above

Q. What is water pollution? List down its causes in brief. Also write some of the ways to tackle this problem?
(150 words)

ENVIRONMENT & ECOLOGY | Pollution of Air and Water Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Water : A Precious Resource
ENVIRONMENT & ECOLOGY

22 March is celebrated as the world water day. No wonder we celebrate water day every year to attract the attention of
everybody towards the importance of conserving water. The amount of water recommended by the United Nations for
drinking, washing, cooking and maintaining proper hygiene is a minimum of 50 litres per person per day.

• You are aware that about 71% of the earth’s surface is covered with water.

• Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in
the atmosphere.

• Water on the earth has been maintained for millions of years by various processes which make the water cycle.

Forms of Water
• Water circulates through the water cycle it can be found in all the three forms, i.e., solid, liquid and gas—at any
given time somewhere on the earth.

• The solid form, snow and ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers.

• Liquid water is present in oceans, lakes, rivers, and even underground.

• The gaseous form is the water vapour present in the air around us.

• The continuous cycling of water among its three forms keeps the total amount of water on the earth constant even
when the whole world is using it.

Groundwater as an Important Source of Water

If we dig deeper and deeper, we would reach a level where all the space between particles of soil and gaps between
rocks are filled with water. The upper limit of this layer is called the water table.

• The water table varies from place to place, and it may even change at a given place. The water table may be at a
depth of less than a metre or may be several metres below the ground.

• The water found below the water table is called groundwater.

• The rainwater and water from other sources such as rivers and ponds seeps through the soil and fills the empty
spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration.

ENVIRONMENT & ECOLOGY | Water : A Precious Resource Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
• The groundwater thus gets recharged by this process. At places the groundwater is stored between layers of hard
rock below the water table. This is known as an aquifer.

• Water in the aquifers can be usually pumped out with the help of tube wells or handpumps.

Source : NCERT

Depletion of Water Table

Water drawn from under the ground gets replenished by seepage of rainwater. The water table does not get affected as
long as we draw as much water as is replenished by natural processes. However, the water table may go down if the
water is not sufficiently replenished. This may happen due to many reasons.

• Increase in population, industrial and agricultural activities are some common factors affecting the water table.

• Scanty rainfall is another factor that may deplete the water table.

• Yet another factor affecting the water table could be deforestation and decrease in the effective area for seepage
of water.

• Increasing population creates demand for construction of houses, shops, offices, roads and pavements. This
decreases the open areas like parks, and playgrounds. This, in turn, decreases the seepage of rainwater into the
ground.

• Water is used by all the industries. The number of industries is increasing continuously. Water used by most of the
industries is drawn from the ground and is leading to water table depletion.

• Farmers have to use groundwater for irrigation due to erratic rainfall.

ENVIRONMENT & ECOLOGY | Water : A Precious Resource Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Source : NCERT
Rain Map of India

ENVIRONMENT & ECOLOGY | Water : A Precious Resource Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Water Management
Managing water is the need of the hour because “If you have water, you can think of the future”. We have seen that
most of the water that we get as rainfall just flows away. This is a waste of precious natural resources.

• The rainwater can be used to recharge the groundwater. This is referred to as water harvesting or rainwater
harvesting.

• We have at many places in India an age old practice of water storage and water recharge like the bawris. Bawri was
the traditional way of collecting water. There is a need to revive that culture again to preserve water for local use.

• Agricultural water efficiency can be brought out by using sprinkler and drip irrigation techniques.

• Adopt water-wise habits like turn off taps while brushing and mop the floor instead of washing.

Probable Questions
Q. Which one of the following is not responsible for water shortage?

A. Rapid growth of industries.

B. Increasing population.

C. Heavy rainfall.

D. Mismanagement of water resources.

Q. What is the need of conserving water as a resource? Write some of the ways to tackle the problem of water
wastage. (250 words)

ENVIRONMENT & ECOLOGY | Water : A Precious Resource Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT Forests: Our Lifeline
Shorts
ENVIRONMENT AND ECOLOGY

The forests serve as green lungs and water purifying systems in nature. There are several other trees, shrubs, herbs
and grasses in the forest. Branchy part of a tree above the stem is known as the crown of the tree. Branches of the
tall trees look like a roof over the other plants in the forest and are called a canopy.

Source: NCERT

 All animals, whether herbivores or carnivores, depend ultimately on plants for food.

 Organisms which feed on plants often get eaten by other organisms, and so on. For example, grass is eaten by
insects, which in turn, is taken by the frog. The frog is consumed by snakes.

 This is said to form a food chain: Grass→ insects→ frog→ snake→ eagle.

 Many food chains can be found in the forest. All food chains are linked. If any one food chain is disturbed, it
affects other food chains.

 Every part of the forest is dependent on the other parts. If we remove one component, say trees, all other
components would be affected.

 There are several organisms and microorganisms that live in the soil and they feed on the dead plant and animal
tissues and convert them into a dark coloured substance called humus.

ENVIRONMENT AND ECOLOGY | Forests: Our Lifeline Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 The micro-organisms which convert the dead plants and animals to humus are known as decomposers.

 Plants release oxygen through the process of photosynthesis. The plants help to provide oxygen for animal
respiration. They also maintain the balance of oxygen and carbon dioxide in the atmosphere. That is why forests
are called lungs.

Source: NCERT

 The forest provides food, shelter, water and medicines.

 They protect soil and provide habitat to a large number of animals. Forests help in bringing good rainfall in
neighbouring areas.

 Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the
forest is a ‘dynamic living entity’ — full of life and vitality.

 Noise pollution, too, is less because the forest absorbs the noise of the nearby surroundings.

Loss of forest lead to

ENVIRONMENT AND ECOLOGY | Forests: Our Lifeline Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 If forests disappear, the amount of carbon dioxide in air will increase, resulting in the increase of earth’s
temperature.

 In the absence of trees and plants, the animals will not get food and shelter.

 In the absence of trees, the soil will not hold water, which will cause floods.

 Deforestation will endanger our life and environment.

 It may lead to loss of biodiversity permanently.

Source: NCERT

Probable Questions
Q. Which of the following statements is not correct?

A. Forests protect the soil from erosion. Source: NCERT

B. Plants and animals in a forest are not dependent on one another.

C. Forests influence the climate and water cycle.

D. Soil helps forests to grow and regenerate.

Q. Enumerate the major and minor functions of forest. How does the forest act as a lifeline to us? (250 words)

ENVIRONMENT AND ECOLOGY | Forests: Our Lifeline Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Wastewater Story
ENVIRONMENT AND ECOLOGY

 In our daily life, we have seen water which is rich in lather, mixed with oil, black– brown in color that goes down
the drains from sinks, showers, toilets, laundries is dirty and is called wastewater.

 Clean water that is fit for use is unfortunately not available to all. It has been reported that more than one billion
of our fellow human beings have no access to safe drinking water.

 This accounts for a large number of water-related diseases and even deaths. Increasing scarcity of fresh- water due
to population growth, pollution, industrial development, mismanagement and other factors.

 Cleaning of water is a process of removing pollutants before it enters a water body or is reused. This process of
wastewater treatment is commonly known as “Sewage Treatment”. It takes place in several stages.

 Sewage is a liquid waste. Most of it is water, which has dissolved and suspended impurities. These impurities are
called contaminants.

Wastewater Treatment Plant (WWTP)

 Treatment of wastewater involves physical, chemical, and biological processes, which remove physical, chemical
and biological matter that contaminates the wastewater.

 Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are
removed.

Source: NCERT

ENVIRONMENT AND ECOLOGY | Wastewater Story Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Water then goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow
sand, grit and pebbles to settle down.

Source: NCERT

 The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at
the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and
grease. Water so cleared is called clarified water.
 The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas
produced in the process can be used as fuel or can be used to produce electricity.
 The activated sludge is about 97% water. The water is removed by sand drying beds or machines. Dried sludge is
used as manure, returning organic matter and nutrients to the soil.
 The treated water has a very low level of organic material and suspended matter. It is discharged into a sea, a
river or into the ground.
 Sometimes it may be necessary to disinfect water with chemicals like chlorine and ozone before releasing it into
the distribution system.

Sanitation and Disease

 Poor sanitation and contaminated drinking water is the cause of a large number of diseases.

 A very large fraction of our people defecate in the open, on dry riverbeds, on railway tracks, near fields and
many a time directly in water.

 Untreated human excreta is a health hazard. It may cause water pollution and soil pollution. Both the surface
water and groundwater get polluted.

 Groundwater is a source of water for wells, tubewells, springs and many rivers. Thus, it becomes the most common
route for water borne diseases. They include cholera, typhoid, polio, meningitis, hepatitis and dysentery.

ENVIRONMENT AND ECOLOGY | Wastewater Story Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Alternative Arrangement for Sewage Disposal
 To improve sanitation, low cost onsite sewage disposal systems are being encouraged. Examples are septic tanks,
chemical toilets, composting pits.

 Septic tanks are suitable for places where there is no sewerage system, for hospitals, isolated buildings or a
cluster of 4 to 5 houses.

 Some organisations offer hygienic on-site human waste disposal technology. These toilets do not require
scavenging. Excreta from the toilet seats flow through covered drains into a biogas plant. The biogas produced is
used as a source of energy.

Sanitation at Public Places

 In our country fairs and other religious processions are organised periodically. A large number of people participate
in them.

 In the same way railway stations, bus depots, airports, hospitals are very busy places. Thousands of people visit
them daily. Large amount of waste is generated here.

 It must be disposed of properly otherwise epidemics could break out. The government has laid down certain
standards of sanitation but, unfortunately, they are not strictly enforced.

 However, all of us can contribute in maintaining sanitation at public places. We should not scatter litter anywhere.
If there is no dustbin in sight, we should carry the litter home and throw it in the dustbin.

Probable Questions
Q. Consider the following statements about ozone:

1. It is used to disinfect water.

2. It absorbs ultraviolet rays.

Which of the above statements is/are correct?

A. Only 1

B. Only 2

C. Both 1 and 2

D. None of the above

Q. Explain the steps involved in the treatment of wastewater. Also write down the benefits of doing so. (150 words)

ENVIRONMENT AND ECOLOGY | Wastewater Story Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Environment
ENVIRONMENT AND ECOLOGY

The place, people, things and nature that surround any living organism is called environment. It is a combination of
natural and human made phenomena. While the natural environment refers to both biotic and abiotic conditions
existing on the earth, the human environment reveals the activities, creations and interactions among human beings.

Source: NCERT

Natural Environment
 Land, water, air, plants and animals comprise the natural environment. Lithosphere, hydrosphere, atmosphere
and biosphere are all part of it.

ENVIRONMENT AND ECOLOGY | Environment Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Lithosphere is the solid crust or the hard top layer of the earth. It is made up of rocks and minerals and covered
by a thin layer of soil. It is an irregular surface with various landforms such as mountains, plateaus, plains, valleys,
etc.

 The domain of water is referred to as hydrosphere. It comprises various sources of water and different types of
water bodies like rivers, lakes, seas, oceans, etc. It is essential for all living organisms.

 The atmosphere is the thin layer of air that surrounds the earth. The gravitational force of the earth holds the
atmosphere around it. The changes in the atmosphere produce changes in the weather and climate.

 Plant and animal kingdom together make biosphere or the living world. It is a narrow zone of the earth where land,
water and air interact with each other to support life.

Source: NCERT

Ecosystem
 All plants, animals and human beings depend on their immediate surroundings. Often they are also interdependent
on each other.

 This relation between the living organisms, as well as the relation between the organisms and their surroundings
form an ecosystem.

 There could be an ecosystem of large rain forest, grassland, desert, mountains, lake, river, ocean and even a small
pond.

ENVIRONMENT AND ECOLOGY | Environment Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Human Environment
 Human beings interact with the environment and modify it according to their need.

 Early humans adapted themselves to the natural surroundings. They led a simple life and fulfilled their
requirements from the nature around them.

 With time needs grew and became more varied. Humans learn new ways to use and change the environment.
They learn to grow crops, domesticate animals and lead a settled life. The wheel was invented, surplus food was
produced, barter systems emerged, trade started and commerce developed.

 The Industrial revolution enabled large scale production. Transportation became faster. Information revolution
made communication easier and speedy across the world.

 A perfect balance is necessary between the natural and human environment. Humans must learn to live and use
their environment in a harmonious way.

Probable Questions
Q. Which of the following is not a natural ecosystem?

A. Desert

B. Aquarium

C. Forest

D. Mountains

Q. Distinguish between ecosystem and biosphere with appropriate examples. (150 words)

ENVIRONMENT AND ECOLOGY | Environment Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 The Tropical and Subtropical
NCERT
Shorts Region
ENVIRONMENT AND ECOLOGY

Life in the Amazon Basin

 The tropical region lies very close to the equator; between 10°N and 10°S. So, it is referred to as the equatorial
region.

 The river Amazon flows through this region. Notice how it flows from the mountains to the west and reaches the
Atlantic Ocean to the east.

 The place where a river flows into another body of water is called the river’s mouth.

 Numerous tributaries join the Amazon River to form the Amazon basin. The river basin drains portions of Brazil,
parts of Peru, Bolivia, Ecuador, Columbia and a small part of Venezuela. The Amazon Basin is the largest river
basin in the world.

Source: NCERT

ENVIRONMENT AND ECOLOGY | The Tropical and Subtropical Region Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Climate
 As you now know, the Amazon Basin stretches directly on the equator and is characterized by hot and wet climate
throughout the year.

 Both day and night are almost equally hot and humid. It rains almost everyday, that too without much warning.

 The day temperatures are high with very high humidity. At night the temperature goes down but the humidity
remains high.

Rainforests
 As it rains heavily in this region, thick forests grow. The forests are in fact so thick that the dense “roof” created by
leaves and branches does not allow the sunlight to reach the ground.

 The ground remains dark and damp. Only shade tolerant vegetation may grow here. Orchids, bromeliads grow as
plant parasites.

 The rainforest is rich in fauna. Birds such as toucans, hummingbirds, birds of paradise with their brilliantly
coloured plumage, oversized bills for eating make them different from birds we commonly see in India.

 Animals like monkeys, sloth and ant-eating tapirs are found here. Various species of reptiles and snakes also
thrive in these jungles.

 Crocodiles, snakes, pythons abound. Anaconda and boa constrictor are some of the species. Besides, the basin is
home to thousands of species of insects.

 Several species of fishes including the flesh- eating Piranha fish is also found in the river. This basin is thus
extraordinarily rich in the variety of life found there.

People of the Rainforests

 People grow most of their food in small areas after clearing some trees in the forest. They mainly grow tapioca,
pineapple and sweet potato. They practice “slash and burn agriculture”.

 The staple food is manioc, also known as cassava that grows under the ground like the potato. They also eat queen
ants and egg sacs.

 Cash crops like coffee, maize and cocoa are also grown. The rainforests provide a lot of wood for the houses. There
are other large apartment-like houses called “Maloca'' with a steeply slanting roof.

 Life of the people of the Amazon basin is slowly changing. In the olden days the heart of the forest could be
reached only by navigating the river. In 1970 the Trans Amazon highway made all parts of the rainforest accessible.

ENVIRONMENT AND ECOLOGY | The Tropical and Subtropical Region Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 The developmental activities are leading to the gradual destruction of the biologically diverse rainforests. It is
estimated that a large area of the rainforest has been disappearing annually in the Amazon basin.

Life in the Ganga-Brahmaputra Basin

 The tributaries of rivers Ganga and Brahmaputra together form the Ganga-Brahmaputra basin in the Indian
subcontinent. The basin lies in the subtropical region that is situated between 10°N to 30°N latitudes.

 The tributaries of the River Ganga like the Ghaghra, the Son, the Chambal, the Gandak, the Kosi and the tributaries
of Brahmaputra drain it.

 The plains of the Ganga and the Brahmaputra, the mountains and the foothills of the Himalayas and the
Sundarbans delta are the main features of this basin.

 Ox-bow lakes dot the plain area. The area is dominated by monsoon climate.

 The mountain areas with steep slopes have inhospitable terrain. Therefore less number of people live in the
mountain area of the Ganga- Brahmaputra basin

Source: NCERT

ENVIRONMENT AND ECOLOGY | The Tropical and Subtropical Region Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 The plain area provides the most suitable land for human habitation. The soil is fertile. Agriculture is the main
occupation of the people where flat land is available to grow crops.

 The density of the population of the plains is very high. The main crop is paddy. Since cultivation of paddy
requires sufficient water, it is grown in the areas where the amount of rainfall is high.

 Wheat, maize, sorghum, gram and millets are the other crops that are grown. Cash crops like sugarcane and jute
are also grown.

 In West Bengal and Assam tea is grown in plantations.

 Silk is produced through the cultivation of silk worms in parts of Bihar and Assam.

 In the mountains and hills, where the slopes are gentle, crops are grown on terraces. The vegetation cover of the
area varies according to the type of landforms.

 In the Ganga and Brahmaputra plain tropical deciduous trees grow, along with teak, sal and peepal.

 Thick bamboo groves are common in the Brahmaputra plain. The delta area is covered with the mangrove forests.

 In parts of Uttarakhand, Sikkim and Arunachal Pradesh, coniferous trees like pine, deodar and fir can be seen
because the climate is cool and the slopes are steep.

 There is a variety of wildlife in the basin. Elephants, tigers, deer and monkeys are common. The one-horned
rhinoceros is found in the Brahmaputra plain.

 In the delta area, Bengal tiger, crocodiles and alligators are found. Aquatic life abounds in the fresh river waters,
the lakes and the Bay of Bengal Sea.

 The most popular varieties of the fish are the rohu, catla and hilsa. Fish and rice is the staple diet of the people living
in the area.

Probable Questions
Q. Deodars and firs comes under the category of which of the following types of trees:

A. Coniferous trees

B. Deciduous trees

C. Shrubs

D. None of the above

Q. Write down some of the features of tropical and subtropical regions giving examples from the Amazon and Ganga-
brahamputra region. (250 words)

ENVIRONMENT AND ECOLOGY | The Tropical and Subtropical Region Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Life in the Temperate grasslands
ENVIRONMENT AND ECOLOGY

Grassland can be defined as a region where grasses form the dominant type of plant life. Grasslands make up almost
a quarter of the total land surface. The types of plants that grow here greatly depend on what the climate and soil are
like. As climate plays an important role in the formation of grasslands, it is generally used as a basis to divide the
world’s grasslands into two broad categories:

 those that occur in the temperate region.

 those that occur in the tropical regions.

The Prairies
 The temperate grasslands of North America are known as the Prairies. It is a region of flat, gently sloping or hilly
land.

 For the most part, prairies are treeless but, near the low lying plains, flanking river valleys, woodlands can be
found.

 Tall grass, upto two metres high, dominates the landscape. It is actually a “sea of grass.”

Source: NCERT

ENVIRONMENT AND ECOLOGY | Life in the Temperate grasslands Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 The prairies are bound by the Rocky Mountains in the West and the Great Lakes in the East.

 The prairies cover parts of the United States of America and parts of Canada.

 In the USA, the area is drained by the tributaries of Mississippi and the Canadian prairies are drained by the
tributaries of Saskatchewan Rivers.

 The grasslands of Prairies were the home of native Americans often called “Red Indians”.

 The Prairies were home of other tribes also like the Apache, the Crow, the Cree and the Pawnee.

Climate
 Being located in the heart of a continent, the climate is of continental type with extreme temperatures.

 The summers are warm with temperatures of around 20°C, while in winter -20°C has been recorded in Winnipeg,
Canada. In winters a thick blanket of snow covers this region.

 The annual rainfall is moderate and is ideal for the growth of grass. Due to the absence of the north-south
barrier, a local wind “Chinook” blows here.

Flora and Fauna

 Prairies are practically tree-less. Where water is available, trees such as willows, alders and poplars grow.

 Places that receive rainfall of over 50 cm, are suitable for farming as the soil is fertile. Though the major crop of
this area is maize, other crops including potatoes, soybean, cotton and alfa-alfa are also grown.

 Areas where rainfall is very little or unreliable, grasses are short and sparse.

 These areas are suitable for cattle rearing. Large cattle farms and ranches are looked after by sturdy men called
cowboys.

 Bison or the American buffalo is the most important animal of this region. It nearly got extinct due to its
indiscriminate hunting and is now a protected species. The other animals found in this region are rabbits, coyotes,
gophers and Prairie dogs.

People
 Scientific methods of cultivation and use of tractors, harvesters and combines has made North America a surplus
food producer.

 The Prairies are also known as the “Granaries of the world,” due to the huge surplus of wheat production.

ENVIRONMENT AND ECOLOGY | Life in the Temperate grasslands Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Dairy farming is another major industry. The dairy belt extends from the Great Lakes to the Atlantic Coast in the
east.

 Dairy farming and extensive agriculture both promote setting up of food processing industries.

 Large mineral deposits particularly coal and iron and a good network of roads, railways and canals in this region
have made it the most industrialised region in the world.

The Velds
 The temperate grasslands of South Africa are called the velds. Velds are rolling plateaus with varying heights
ranging from 600 m to 1100 m.

 It is bound by the Drakensberg Mountains on the east. To its west lies the Kalahari desert.

 In the northeastern part, “high velds” are located that attain a height of more than 1600 m, in some places. The
tributaries of rivers Orange and Limpopo drain the region.

Source: NCERT

ENVIRONMENT AND ECOLOGY | Life in the Temperate grasslands Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Climate
 The velds have a mild climate due to the influence of the Indian Ocean. Winters are cold and dry. Temperatures
vary between 5°C and 10°C and July is the coldest month. Summers are short and warm.

 The velds receive rainfall mainly in the summer months from November to February. This is mainly because of
the warm ocean currents that wash the shores of the velds.

 If the rainfall is scanty in the winter months from June till August, drought may occur.

Flora and Fauna

 The vegetation cover is sparse. Grasses dominate the landscape. Red grass grows in bush velds.

 In the high velds acacia and maroola are seen to be growing. The animals of the velds are primarily lions,
leopards, cheetahs and kudu.

People
 Velds are known for cattle rearing and mining. The soils are not very fertile.

 However where the land is fertile crops are grown. The main crops are maize, wheat, barley, oats and potato. Cash
crops like tobacco, sugarcane and cotton are also grown.

 Sheep rearing is the most important occupation of the people. Sheep is bred mainly for wool and has given rise
to the wool industry in the velds. Merino sheep is a popular species and their wool is very warm.

 Dairy farming is the next important occupation. Cattle are reared in the warmer and wetter regions and the dairy
products like butter, cheese are produced for both domestic supply and also for export.

 Iron and steel industry has developed where coal and iron are present. Gold and diamond mining are major
occupations of people of this region. Johannesburg is known for being the gold capital of the world.

 Kimberley is famous for its diamond mines.

Probable Questions
Q. Drakensberg Mountains are to the west of which grasslands-

A. Prairies

B. Velds

C. Pampas

D. None of the above

ENVIRONMENT AND ECOLOGY | Life in the Temperate grasslands Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Probable Questions
Q. Kimberley is famous for-

A. diamonds

B. silver

C. platinum

D. All of the above

Q. Why most of the dairy production industries of the world are located in grassland regions. Give examples to
support your answer from regions of America and Africa. (250 words)

ENVIRONMENT AND ECOLOGY | Life in the Temperate grasslands Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
NCERT
Shorts Life in the Deserts
ENVIRONMENT AND ECOLOGY

Places in the world where people have learned to cope with extreme harsh temperatures; in some places as hot as fire
and some as cold as ice. These are the desert areas of the world. These are characterised by low rainfall, scanty
vegetation and extreme temperatures. Depending on the temperatures there can be hot deserts or cold deserts.

The Hot Desert– Sahara

 The Sahara desert covering a large part of North Africa. It is the world’s largest desert. It has an area of around 8.54
million sq. km.

 The Sahara desert touches eleven countries. These are Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco,
Niger, Sudan, Tunisia and Western Sahara.

 Besides the vast stretches of sands that the Sahara desert is covered with, there are also gravel plains and elevated
plateaus with bare rocky surfaces.

Source: NCERT

ENVIRONMENT AND ECOLOGY | Life in the Deserts Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
Climate
 The climate of the Sahara desert is scorching hot and parch dry. It has a short rainy season. The sky is cloudless and
clear.

 The temperatures during the day may soar as high as 50°C, heating up the sand and the bare rocks, which in turn
radiates heat making everything around hot.

 The nights may be freezing cold with temperatures nearing zero degrees.

Flora and Fauna

 Vegetation in the Sahara desert includes cactus, date palms and acacia. In some places there are oasis – green
islands with date palms surrounding them.

 Camels, hyenas, jackals, foxes, scorpions, many varieties of snakes and lizards are the prominent animal species
living there.

People
 Groups of nomadic tribes like Bedouins and Tuaregs rearing livestock such as goats, sheep, camels and horses.
These animals provide them with milk, hides from which they make leather for belts, slippers, water bottles; hair is
used for mats, carpets, clothes and blankets.

 They wear heavy robes as protection against dust storms and hot winds.

 The oasis in the Sahara and the Nile Valley in Egypt supports settled populations. Since water is available, the
people grow date palms.

 Crops such as rice, wheat, barley and beans are also grown. Egyptian cotton, famous worldwide, is grown in
Egypt.

 The discovery of oil – a product in great demand throughout the world, in Algeria, Libya and Egypt is constantly
transforming the Sahara desert.

The Cold Desert - Ladakh

 Ladakh is a cold desert lying in the Great Himalayas, on the eastern side of Jammu and Kashmir.

 The Karakoram Range in the north and the Zanskar mountains in the south enclose it.

 Several rivers flow through Ladakh, Indus being the most important among them. The rivers form deep valleys and
gorges. Several glaciers are found in Ladakh, for example the Gangri glacier.

ENVIRONMENT AND ECOLOGY | Life in the Deserts Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 The altitude in Ladakh varies from about 3000m in Kargil to more than 8,000m in the Karakoram. Due to its high
altitude, the climate is extremely cold and dry.

 The air at this altitude is so thin that the heat of the sun can be felt intensely. The day temperatures in summer are
just above zero degree and the night temperatures well below –30°C.

 It is freezing cold in the winters when the temperatures may remain below –40°C for most of the time.

 As it lies in the rain shadow of the Himalayas, there is little rainfall, as low as 10 cm every year. The area
experiences freezing winds and burning hot sunlight.

Source: NCERT

Flora and Fauna

 Due to high aridity, the vegetation is sparse. There are scanty patches of grasses and shrubs for animals to graze.

ENVIRONMENT AND ECOLOGY | Life in the Deserts Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
 Groves of willows and poplars are seen in the valleys. During the summers, fruit trees such as apples, apricots
and walnuts bloom.

 Several species of birds are sighted in Ladakh. Robins, redstarts, Tibetan snowcock, raven and hoopoe are common.
Some of these are migratory birds.

 The animals of Ladakh are wild goats, wild sheep, yak and special kinds of dogs. The animals are reared to provide
for the milk, meat and hides. Yak’s milk is used to make cheese and butter. The hair of the sheep and goat is used
to make woolens.

People
 The people here are either Muslims or Buddhists. In fact several Buddhists monasteries dot the Ladakhi landscape
with their traditional ‘gompas’. Some famous monasteries are Hemis, Thiksey, Shey and Lamayuru.

 In the summer season the people are busy cultivating barley, potatoes, peas, beans and turnip.

 The climate in winter months is so harsh that people keep themselves engaged in festivities and ceremonies. The
women are very hard working. They work not only in the house and fields, but also manage small business and
shops.

 Leh, the capital of Ladakh is well connected both by road and air. The National Highway 1A connects Leh to Kashmir
Valley through the Zoji la Pass.

 Tourism is a major activity with several tourists streaming in from within India and abroad. Visits to the gompas,
treks to see the meadows and glaciers, witnessing ceremonies and festivities are important activities.

Probable Questions
Q. Sahara desert is located in which of the following countries of the world?

A. Libya

B. Mali

C. Sudan

D. All of the above

Q. Write about the characteristics of The cold desert- Ladakh from climatic and human perspective. (150 words)

ENVIRONMENT AND ECOLOGY | Life in the Deserts Copyright © 2014-2021 Testbook Edu Solutions Pvt. Ltd.: All rights reserved