evs

1. Our lives and economies depend on Sun’s energy and on the natural resources and services
(natural capital) provided by the Earth.
1. How are our ecological footprints affecting the Earth?
As our ecological footprints grow, we are depleting/degrading more of the Earth’s natural capital.
2. What is an environmentally sustainable society?
It means living off the Earth’s natural income without depleting or degrading the natural capital
that supplies it.
3. Why do we have environmental problems (what are the basic causes of environmental
problems)?
Due to excessive population growth and its associated pollution and poverty issues.
Wasteful/unsustainable use of Earth’s resources.
Excluding environmental costs from market prices, etc.
4. What are the remedial measures to combat environmental problems (Mention three principles
of sustainability)?
Population control, Forest conservation, Imposition of environmental tax, etc.
We can live more sustainably by relying more on solar energy, preserving biodiversity, and not
disrupting the earth’s natural chemical-recycling processes.
5. Define natural capital, natural resources , and natural services: Natural capital is the natural
resources and natural services that keep us and other forms of life alive and support our economies.
Natural resources are materials and energy in nature that are essential or useful to humans. These
resources are often classified as renewable (such as air, water, soil, plants, and wind) or
nonrenewable (such as copper, oil, and coal). Natural services are processes in nature such as
purification of air and water, which support life and human economies.
MODULE – 1: Environment and Ecosystem

2. IPAT equation (I = P x A x T)
Impact of human activity on the environment (I)
= Population (P) x Affluence (A) x Technology (T).
Environmental impact is a simple product of 3 independent or sometimes inter-
dependent factors P, A and T.
 Earth’s environment is a self-regenerating system and can sustain a certain
level of impact, and the maximum sustainable impact is called
the carrying capacity.
 As long as "I" < carrying capacity, then the associated P, A and T that make
up "I" are sustainable.
 If "I" > carrying capacity, then the system is said to be in overshoot.
 Overshoot may degrade the ability of the environment to sustain itself.
 How Impact is measured statistically? Impact may be measured
using ecological footprint analysis in units of global hectares (gha).
 Ecological footprint per capita = Earth's biologically productive surface that
is needed to regenerate the resources consumed per capita.

3. Population (P): Since the rise of industrial societies, human population “P” has been
increasing exponentially.
Hence, “P” factor will keep increasing “I” on the environment in the near future.
Increasing human population impact on Environment:
• Increased land use - Results in habitat loss for other species.
• Increased resource use - Results in changes in land cover
• Increased pollution - Can cause sickness and damages ecosystems.
Affluence (A): represents the average consumption of each person in the population.
With increasing consumption of each person, the total environmental impact (I) also increases.
GDP per capita is a statistical tool for measuring “A”. While GDP per capita measures
production, it is often assumed that consumption increases when production increases. Global
GDP per capita has been rising steadily over the last few centuries and is driving up “I”.
For ex. construction of a car has the following environmental impacts:
• 2.3 Million Litres of water for parts and tires
• 2500 Litres of water pollution at a mine for the lead battery.
• 8300 Litres of discharge into water supply for processing 10 kg of copper in the car.

4. Technology (T): It involves the technology utilized for creating, transporting and
disposing of the goods, services and amenities used. Improvements in efficiency can
reduce resource intensity. An appropriate unit for “T” might be greenhouse gas
emissions per unit of GDP.
Environmental impacts of technology
• Increase in efficiency can reduce overall environmental impact.
• However, since “P” has increased exponentially, and “A” has also increased
drastically, the overall environmental impact “I” has still increased.
Criticism of IPAT equation:
• Too simplistic for complex environmental problems.
• Inter-dependencies between variables.
• Cultural differences cause wide variation in impact.
• Technology cannot properly be expressed in a unit.
Ex. Native Fishing Practices (Low Technology) have a vastly smaller Impact than Industrialized
Fishing by mechanised trawlers which cause widespread damage to aquatic/sea ecosystem.
Conclusions: As a result of the interdependencies between P, A, and T, policies aimed
at decreasing environmental impact “I” through reductions in P, A, and T may not only
be very difficult to implement (Ex. population control by India and China) and also
controversial, and hence ineffective in providing a sustainable ecosystem.

5. What are Detritivores? Justify the statement “There is very little debris of nutrients in nature”.
Detritivores feed on dead organisms/debris leftover by scavengers: Examples of detritivores
are beetles, termites, ants.
The statement “ There is very little debris of nutrients in nature” implies that the detritivores
consume the debris (and the nutrients remaining in the debris) so efficiently leaving no
residue in the environment. The detritivores release the energy and nutrients back to the soil
and air by their own life processes.

6. What is ecological succession? Elaborate the different steps involved in the ecological
succession.
Ecosystem is dynamic, i.e. it continuously changes over a period of time until it gets a stable
ecosystem. Ecological succession is the orderly process of changes in a community structure
and function with time, and assisted through modifications in the physical environment.
What is Seres or Seral stages?: Ecological succession occurring in stages is called Seral stages
or Seres. In a seral stage, a collection of species dominate that stage in the succession.
What is Climax?: Some times, replacement of one community by other happen over a period
of time, but ultimately culminating in a stabilized ecosystem known as CLIMAX.
Elaborate different steps involved in ecological succession.
• Nudation: development of bare area
• Invasion: establishment of one or more species. Dispersal of seeds -> germination
(Pioneer species: simple plants with shallow or no roots).
• Competition and co-action: for space, water and nutrients.
• Reaction: the reaction on the environment. Reaction leads to several communities.
• Stabilization: attainment of equilibrium with environment (CLIMAX).
Elaborate different starting areas involved in the ecological succession.
i. Hydrarch or Hydrosere – watery area like swamp
ii. Mesarch – area with adequate moisture
iii. Xerach or Xerosere – dry area with little moisture
Lithosere – bare rock; Psammosere – sand dunes; Halosere – saline soil near estuary.

7. Two types: Primary succession and Secondary ecological succession
Primary succession: It occurs in an area of newly exposed rock, sand, lava or any area that has
not been occupied previously by a living (biotic) community.
Secondary succession: It takes place where a pre-existed community has been removed by
human intervention, e.g. a ploughed field or a clear-cut forest.
Secondary succession can reach CLIMAX stage more faster than primary succession.

8. Three types of ecological pyramids:
1. Pyramid of Energy; 2. Pyramid of Biomass; 3. Pyramid of Numbers
1. Pyramid of Energy
• Indicates the total amount of energy present in each trophic level.
• Shows the loss of energy from one trophic level to the next.
• Energy transfer from one trophic level to the next is decreased due to the
conversion of potential energy into kinetic energy (movement) and heat energy
(exhaustion).
• Only 10 % of the overall potential energy is transferred to the next tropic level.
Energy flow in an Ecosystem

9. Pond ecosystem-
Inverted pyramid
of Biomass
2. Pyramid of Biomass:
• Indicates the total dry mass (biomass) of the organisms in each trophic level.
• Thus, enormous mass of grass is required to support a smaller mass of deer, which
in turn, would support a smaller mass of lions.
Standing crop is the total weight of the organisms, whereas
standing biomass is the total dry mass (excluding abiotic components).

10. 3. Pyramid of Numbers:
• Shows the number of organisms in each trophic level
• In a pyramid of numbers, each consecutive level contains fewer organisms than
the level below it.
Parasitic food
chain-Inverted-
pyramid of
numbers

11. Energy flow in tropic structure follows 1st law of thermodynamics: Energy can neither be
created nor be destroyed but it can be transformed from one form to another. Similarly, in
a trophic structure, solar energy utilized by green plants (producers) in photosynthesis is
converted into biochemical energy of plants and later into that of consumers.
Energy flow in tropic structure follows 2nd law of thermodynamics: Energy transformation
involves dissipation of energy from a concentrated to a dispersed form. Dissipation of
energy occurs at every trophic level. Only 10% is transferred from one trophic level to the
other.
How does the energy flow in trophic structure follow laws of thermodynamics? / Correlate the
energy flow in an ecosystem based on the laws of thermodynamics.

12. Energy Flow Models
Energy flows through various trophic levels in an ecosystem:
A) Universal Energy Flow Model
B) Single Channel Energy Flow Model, and
C) Double Channel Or Y-shaped Energy Flow Model

13. 1. Water cycle
The hydrological/water cycle collects, purifies and distributes the earth’s fixed supply of water.
•The water cycle is powered by energy from the sun and involves 3 major processes
Evaporation: Incoming solar energy causes evaporation of water from the Earth’s oceans,
lakes, rivers and soil.
Precipitation: Gravity draws the water back to the earth’s surface as precipitation (rain, snow)
Transpiration: 90 % of the water that is precipitated evaporates back into the atmosphere from
the surfaces of plants and soil through a process called transpiration.
Water returning to the earth’s surface as precipitation takes various paths:
Precipitation falling on terrestrial ecosystems:
surface runoff - This water flows into streams, which carry water back to lakes and
oceans –from which it can evaporate to repeat the cycle.
Surface water- seeps into the upper layers of soils – used by plants, and some
undergoes transpiration from the soils back into the atmosphere.
Some precipitation is converted to ice that is stored in glaciers.
Some precipitation sinks through soil and permeable rock formations to underground
layers of rock, sand and gravel called aquifers and stored as groundwater.

15. 2. Carbon Cycle
Carbon is the basic building block of the carbohydrates, fats, proteins, DNA and other organic
compounds necessary for life.
The carbon cycle is based on CO2 gas (0.039 % of volume of the earth’s atmosphere), and it is
dissolved in water.
CO2 is a key component of the atmosphere’s thermostat.
• If the carbon cycle removes too much CO2 from the atmosphere, the atmosphere will cool.
• If the carbon cycle generates too much CO2, the atmosphere will get warmer.
 Consumers and decomposers release CO2 into the atmosphere and water by aerobic
respiration, which is reused by the producers.
 Terrestrial and Aquatic Producers utilize CO2 from the atmosphere and water, respectively.
Linkage between aerobic respiration in consumers/decomposers and photosynthesis in
producers circulates carbon in the biosphere.
Highlight the different ways in which humans directly or indirectly alter the carbon cycle.
Humans alter the Carbon Cycle by releasing large amount of CO2 to the atmosphere by
(a) Burning carbon-containing fossil fuels and
(b) Clearing carbon-absorbing vegetation from forests, especially tropical forests.

17. 3. Nitrogen cycle
N2 gas makes up 78 % volume of the atmosphere.
N is a crucial component of proteins, many vitamins and nucleic acids such as DNA.
N2 cannot be absorbed and used directly as a nutrient by multicellular plants/animals.
Two natural processes convert N2 into nutrients which can be used by plants and animals.
1. Electrical discharge/lightning taking place in the atmosphere: The enormous energy
of lightning breaks N2 into N atoms which combine with O2 in the air to NOx. These dissolve
in rain, forming NO3
-, that are carried to the earth. Atmospheric nitrogen fixation probably
contributes some 5– 8% of the total nitrogen fixed.
2. Nitrogen fixing bacteria in water, soil and in the roots of some plants convert atmospheric
nitrogen to NH4
+ which is a nutrient for plant growth.
Nitrogen cycle consists of several major steps (Nitrogen fixation)
Specialized bacteria in soil as well as blue green algae (cyanobacteria) in aquatic environment
combine gaseous N2 with hydrogen to make ammonia (NH3).
The bacteria use some of the NH3 as nutrient and excrete the rest into the soil / water.
The excreted NH3 is converted to ammonium ions (NH4
+) which is used by plants as a nutrient.
Plants and animals return nitrogen –rich organic compounds to the environments through
wastes and cast-off particles of tissues such as leaves, skin or hair and through their bodies
when they die, and are decomposed or eaten by detritus feeders.
Ammonification: Conversion of nitrogen-rich detritus matter back into NH3 and water soluble
ammonium salt ions (NH4
+) is called ammonification.

18. Explain with a help
of a diagram and
the effect of
human activities
on nitrogen cycle.
Human activities
have more than
doubled the
annual release of
N2 from the land
into the rest of the
environment
through the
greatly increased
use of inorganic
fertilizers (straight
type: ammonium
nitrate (NH4NO3)
and binary type:
diammonium
phosphate (DAP,
(NH4)2HPO4)) to
grow crops.
De-nitrification: specialized bacteria in waterlogged soil and in the
bottom sediments of lakes, oceans convert NH3 and NH4
+ back into
nitrate ions (NO3
-), and then into N2 gas.
These gases released to the atmosphere to begin the nitrogen cycle
again.