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ECOLOGY &
POLLUTION

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Ecology & Pollution

I N T H I S C A P S UL E
ECOLOGY ....................................................................................................................................................... 4

TYPES OF POPULATION INTERACTIONS: .............................................................................................. 4

MUTUALISM .................................................................................................................................................................... 4

COMPETITION ................................................................................................................................................................. 4

PREDATION ..................................................................................................................................................................... 4

PARASITISM ..................................................................................................................................................................... 5

COMMENSALISM ............................................................................................................................................................5

AMENSALISM .................................................................................................................................................................. 5

ECOSYSTEM .................................................................................................................................................. 5

ABIOTIC COMPONENTS (NONLIVING) ........................................................................................................................6

BIOTIC COMPONENTS (LIVING) .................................................................................................................................... 6

FUNCTIONS OF ECOSYSTEM .......................................................................................................................................... 6

TYPES OF ECOSYSTEMS ............................................................................................................................. 7

NATURAL ECOSYSTEMS ................................................................................................................................................. 7

MANMADE ECOSYSTEMS ..............................................................................................................................................7

FOOD CHAIN ................................................................................................................................................ 7

AUTOTROPHS .................................................................................................................................................................7

HERBIVORES .................................................................................................................................................................... 8

CARNIVORES ................................................................................................................................................................... 8

OMNIVORES.................................................................................................................................................................... 8

DECOMPOSERS ............................................................................................................................................................... 8

TYPES IN THE FOOD CHAIN...................................................................................................................... 8

GRAZING FOOD CHAINS ...............................................................................................................................................8

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DETRITUS FOOD CHAINS: ............................................................................................................................................. 8

FOOD WEB ...................................................................................................................................................................... 9

ECOLOGICAL PYRAMID ............................................................................................................................. 9

PYRAMID OF NUMBER ...................................................................................................................................................9

PYRAMID OF BIOMASS ..................................................................................................................................................9

PYRAMID OF ENERGY.................................................................................................................................................. 10

BIODIVERSITY ............................................................................................................................................. 10

GENETIC DIVERSITY ..................................................................................................................................................... 10

SPECIES DIVERSITY ....................................................................................................................................................... 10

ECOLOGICAL DIVERSITY .............................................................................................................................................. 10

ENVIRONMENTAL ISSUES....................................................................................................................... 11

POLLUTION ................................................................................................................................................. 11

TYPES OF POLLUTION .............................................................................................................................. 12

AIR POLLUTION ........................................................................................................................................................... 12

WATER POLLUTION..................................................................................................................................................... 12

NOISE POLLUTION ...................................................................................................................................................... 13

RADIOACTIVE POLLUTION.......................................................................................................................................... 13

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Ecology
• Ecology gives us holistic perspective about biological understanding of
how organisms, while remaining an individual, interact with other organisms
and physical habitat as a group and hence behave like organized wholes,
i.e., population, community, ecosystem or even as the whole biosphere.
• Ecology is basically concerned with four levels of biological organization
– organisms, populations, communities and biomes and there are certain key
elements or factors that leads to variation in the physical and chemical conditions
of different habitats.
• Those key factors can be of two types:
Abiotic Factors: Temperature, water, Light, Soil
Biotic Factors: Pathogens, parasites, predators and competitors

Ecological Niche

Each organism has an invariably defined range of conditions that it can tolerate,
diversity in the resources it utilizes and a distinct functional role in the ecologi-
cal system, all these together comprise its niche.

Types of Population Interactions:

Mutualism:
Symbiosis which is mutually beneficial to both organisms involved.
Example:
• Oxpecker (a kind of bird) and the rhinoceros or zebra.
• Oxpeckers land on rhinos or zebras and eat ticks and other parasites that
live on their skin. The oxpeckers get food and the beasts get pest control.

Competition:
• Competition is an interaction between organisms or species in which both
the organisms or species are harmed.
• Limited supply of at least one resource (such as food, water, and territory)
used by both can be a factor.
Example:
• Cheetahs and Lions
• Both species feed on similar prey, they are negatively impacted by the presence
of the other because they will have less food.

Predation:
• It is a form of ecological relationship between two organisms of unlike species
in which one of them acts as predator that captures and feeds on the other
organism that serves as the prey.
• In ecology, predation is a mechanism of population control.
Example:

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• Lion (predator) and zebra (Prey)
• Bear (predator) and fish (Prey), and
• Fox (predator) and rabbit (Prey).

Parasitism:
• It is a relationship between species, where one organism, the parasite,
lives on or in another organism, the host, causing it some harm, and is
adapted structurally to this way of life.
Example
• Tapeworms
• Fleas, and
• Barnacles.

Commensalism:
• This is the interaction in which one species benefits and the other is neither
harmed nor benefited.
Example:
• The cattle egret and grazing cattle in close association, a sight you are most likely
to catch if you live in farmed rural areas, is a classic example of commensalism.

Amensalism:
• One species is harmed whereas the other is unaffected.
Example:
• The bread mold Penicillium commonly grows on any bread that has passed its shelf life.
• This mold can produce penicillin, which destroys many of the forms of bacteria that would
also like to grow on this bread.
• It is this understanding of bacteria killing properties of penicillin that led to the use of
it as an antibiotic medicine.
• The Penicillium does not benefit from the death of other bacteria.

Ecosystem
• An ecosystem can be visualized as a functional unit of nature, where living organisms
interact among themselves and also with the surrounding physical environment.
• Ecosystem varies greatly in size from a small pond to a large forest or sea.
The components of ecosystem are as shown in the diagram below:

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Abiotic components (Nonliving):

The abiotic component can be grouped into following three categories: -
• Physical factors: Sun light, temperature, rainfall, humidity and pressure.
They sustain and limit the growth of organisms in an ecosystem.
• Inorganic substances: Carbon dioxide, nitrogen, oxygen, phosphorus, Sulphur,
water, rock, soil and other minerals.
• Organic compounds: Carbohydrates, proteins, lipids and humic substances.
They are the building blocks of living systems and therefore, make a link
between the biotic and abiotic components.

Biotic components (Living):

• Producers: The green plants manufacture food for the entire ecosystem through
the process of photosynthesis.
Green plants are called autotrophs, as they absorb water and nutrients from the soil,
carbon dioxide from the air, and capture solar energy for this process.
• Consumers: They are called heterotrophs and they consume food synthesized by
the autotrophs. Based on food preferences they can be grouped into three
broad categories.
Herbivores (e.g. cow, deer and rabbit etc.) feed directly on plants,
Carnivores are animals which eat other animals (e.g. lion, cat, dog etc.) and
Omnivores organisms feeding upon both plants and animals e.g. human, pigs and sparrow.
• Decomposers: Also called saprotrophs. These are mostly bacteria and fungi that feed
on dead decomposed and the dead organic matter of plants and animals by secreting
enzymes outside their body on the decaying matter.
They play a very important role in recycling of nutrients.
They are also called detrivores or detritus feeders.

Functions of ecosystem
Ecosystems are complex dynamic system. They perform certain functions. These are: -
• Energy flow through food chain
• Nutrient cycling (biogeochemical cycles)
• Ecological succession or ecosystem development

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• Homeostasis (or cybernetic) or feedback control mechanisms

1. Ponds 2. Lakes 3. Meadows

4. Marshlands 5. Grasslands 6. Deserts and forests are examples of natural ecosystem.

Many of you have seen an aquarium; a garden or a lawn etc. in your neighbourhood.
These are manmade ecosystem.

Types of Ecosystems
Ecosystems are classified as follows:

Natural Ecosystems
• Totally dependent on solar radiation
• Example: forests, grasslands, oceans, lakes, rivers and deserts.
• They provide food, fuel, fodder and medicines.
• Ecosystems dependent on solar radiation and energy subsidies (alternative sources)
such as wind, rain and tides.
• Example: tropical rain forests, tidal estuaries and coral reefs.

Manmade ecosystems
• Dependent on solar energy e.g. Agricultural fields and aquaculture ponds.
• Dependent on fossil fuel e.g. urban and industrial ecosystems.

Ecosystem Function–Energy Flow Through Ecosystem

• Food chains and energy flow are the functional properties of ecosystems
which make them dynamic.
• The biotic and abiotic components of an ecosystem are linked through them.

Food Chain
Transfer of food energy from green plants (producers) through a series of organisms
with repeated eating and being eaten is called a food chain. e.g.

Grasses → Grasshopper → Frog → Snake → Hawk/Eagle

• Each step in the food chain is called trophic level. In the above example grasses are
1st, and eagle represents the 5th trophic level.
• During this process of transfer of energy some energy is lost into the system as
heat energy and is not available to the next trophic level.
• Therefore, the number of steps are limited in a chain to 4 or 5.

Following trophic levels can be identified in a food chain.

Autotrophs:

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• They are the producers of food for all other organisms of the ecosystem.
• They are largely green plants and convert inorganic material in the presence of
solar energy by the process of photosynthesis into the chemical energy (food).
• The total rate at which the radiant energy is stored by the process of photosynthesis
in the green plants is called Gross Primary Production (GPP).
• This is also known as total photosynthesis or total assimilation.
• From the gross primary productivity, a part is utilized by the plants for its own metabolism.
• The remaining amount is stored by the plant as Net Primary Production (NPP) which
is available to consumers.

Herbivores:
• The animals which eat the plants directly are called primary consumers or herbivores
• e.g. insects, birds, rodents and ruminants.

Carnivores:
• They are secondary consumers if they feed on herbivores and tertiary consumers
if they use carnivores as their food.
• e.g. frog, dog, cat and tiger.

Omnivores:
• Animals that eat both plant and animals
• e.g. pig, bear and man

Decomposers:
• They take care of the dead remains of organisms at each trophic level and help
in recycling of the nutrients
• e.g. bacteria and fungi.

Types in the Food Chain

There are two types of food chains:

Grazing food chains

• This starts from the green plants that make food for herbivores and herbivores
in turn for the carnivores.

Detritus food chains:

• This starts from the dead organic matter to the detrivore organisms which in turn
make food for protozoan to carnivores etc.
In an ecosystem the two chains are interconnected and make y-shaped food chain.
These two types of food chains are: -

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Producers → Herbivores → Carnivores
Producers → Detritus Feeders → Carnivores

Food Web

• Trophic levels in an ecosystem are not linear rather they are interconnected and
make a food web.
• Thus, food web is a network interconnected food chains existing in an ecosystem.
• One animal may be a member of several different food chains.
• Food webs are more realistic models of energy flow through an ecosystem.

The flow of energy in an ecosystem is always linear or one way.

Ecological Pyramid

• Ecological pyramids are the graphic representations of trophic levels in an ecosystem.

• They are pyramidal in shape and they are of three types:
• The producers make the base of the pyramid and the subsequent tiers of the pyramid
represent herbivore, carnivore and top carnivore levels.

There are three types of Ecological Pyramid

Pyramid of Number:
• This represents the number of organisms at each trophic level.
• For example, in a grassland the number of grasses is more than
the number of herbivores that feed on them and
the number of herbivores is more than the number of carnivores.
• In some instances, the pyramid of number may be inverted,
i.e. herbivores are more than primary producers as you may
observe that many caterpillars and insects feed on a single tree.

Pyramid of Biomass:
• This represents the total standing crop biomass at each trophic level.
• Standing crop biomass is the amount of the living matter at any given time.
• It is expressed gm/unit area or kilo cal/unit area.
• In most of the terrestrial ecosystems the pyramid of biomass is upright.
• However, in case of aquatic ecosystems the pyramid of biomass may be inverted

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• e.g. in a pond phytoplankton are the main producers, they have very short life cycles
and a rapid turnover rate (i.e. they are rapidly replaced by new plants).
• Therefore, their total biomass at any given time is less than the biomass of herbivores
supported by them.

Pyramid of Energy:
• This pyramid represents the total amount of energy at each trophic level.
• Energy is expressed in terms of rate such as kcal/unit area /unit time or
cal/unit area/unit time.
• Energy pyramids are never inverted.

Biodiversity

• Biodiversity is the term popularized by the socio-biologist Edward Wilson

to describe the combined diversity at all levels of biological organization.
• The most important of them are: -

Genetic Diversity:
• A single species might show high diversity at the genetic level
over its distributional range.
• The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing
in different Himalayan ranges might be in terms of the potency and concentration
of the active chemical (reserpine) that the plant produces.
• India has more than 50,000 genetically different strains of rice, and
1,000 varieties of mango.

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.

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Environmental Issues

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 as pollutants.
• To control environmental pollution, the Government of India has passed the
Environment (Protection) Act, 1986 to protect and improve
the quality of our environment (air, water and soil).

Few important terminologies:

Biological Oxygen Demand (BOD):

• Biochemical Oxygen Demand is the amount of dissolved oxygen needed
(i.e. demanded) by aerobic biological organisms to break down organic material present
in a given water sample at certain temperature over a specific time-period.
• The BOD value is most commonly expressed in milligrams of oxygen consumed per litre
of sample during 5 days of incubation at 20 °C and is often used as a surrogate of the
degree of organic pollution of water.

Biomagnification:
• It refers to increase in concentration of the toxicant at successive trophic levels.
• This happens because a toxic substance accumulated by an organism cannot be
metabolized or excreted and is thus passed on to the next higher trophic level.
• This phenomenon is well known for mercury and DDT.

Eutrophication:
• It is the natural aging of a lake by nutrient enrichment of its water.
• In a young lake the water is cold and clear, supporting little life.
• With time, streams draining into the lake introduce nutrients such as nitrogen
and phosphorus, which encourage the growth of aquatic organisms.
• As the lake’s fertility increases, plant and animal life burgeons, and organic remains
begin to be deposited on the lake bottom.
• Over the centuries, as silt and organic debris pile up, the lake grows shallower and warmer,
with warm-water organisms supplanting those that thrive in a cold environment.
• Marsh plants take root in the shallows and begin to fill in the original lake basin.
• Eventually, the lake gives way to large masses of floating plants (bog),
finally converting into land.

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Types of Pollution

Air Pollution
• When harmful or excessive quantities of substances including gases,
particulate Matters (PM), and biological molecules are introduced into
Earth's atmosphere then we say that the air in our surrounding is polluted
and hence air pollution has happened.
• Various air pollutants are: CO2 (Carbon Dioxides), SOX (Sulfur Oxides),
NOx (Nitrogen Oxides), CO (Carbon Monoxides), Volatile Organic Compounds (VOCs),
Particulate Matters (e.g. PM 2.5),
• Toxic Metals such as Lead and Mercury, Chlorofluorocarbons (CFCs), NH3 (Ammonia),
Radioactive Pollutants etc.
• Diseases: Asthma, lung cancer, Chronic obstructive Pulmonary Disease (COPD), Leukemia,
Pneumonia etc.

Effects of Air Pollution

Greenhouse Effect:
• It is the process by which radiation from a planet's atmosphere warms the planet's surface to a
temperature above what it would be without its atmosphere. The greenhouse effect is a naturally
occurring phenomenon that is responsible for heating of Earth’s surface and atmosphere.
• In this the sun's warmth is trapped in the lower atmosphere of the planet, due to the greater
transparency of the atmosphere to visible radiation from the sun than to infrared radiation emitted
from the planet's surface.
• Greenhouse gases in the order of decreasing contribution towards global warming: Carbon Dioxide
(60 %), Methane (20%), Chlorofluorocarbon (CFCs) (14%), N2O (6%).

Photochemical Smog:
• It is a type of smog produced when ultraviolet light from the sun reacts with Nitrogen Oxides in the
atmosphere. It is visible as a brown haze, and is most prominent during the morning and afternoon,
especially in densely populated, warm cities. Cities that experience this smog daily include
Los Angeles, Sydney, Mexico City, Beijing, and many more.

Acid Rain:
• It is a rain or any other form of precipitation that is unusually acidic, meaning that it has elevated
levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals and infra-
structure. Acid rain is caused by emissions of Sulphur Dioxide and Nitrogen Oxide, which react with
the water molecules in the atmosphere to produce acids.

Water Pollution
• Water pollution occurs when harmful substances, often chemicals or microorganisms,
contaminate a stream, river, lake, ocean, aquifer, or other body of water,
degrading water quality and rendering it toxic to humans or the environment.

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Causes:
• Water is uniquely vulnerable to pollution. Known as a “universal solvent,” water can
dissolve more substances than any other liquid on earth.
• That is why water is so easily polluted. Toxic substances from farms, towns, and
factories readily dissolve into and mix with it, causing water pollution.

Waterborne Diseases:
• Dysentery: Bacteria or Amoeba
• Arsenicosis: Groundwater contamination via chemicals containing Arsenic
• Polio: polio Virus
• Trachoma: Bacteria
• Typhoid fever: Bacteria
• Schistosomiasis: Exposure to a certain type of freshwater snail in contaminated water
• Cholera: Bacteria
• Diarrhea: Bacteria
• Malaria: Plasmodium Parasite
• Lead poisoning: Groundwater contamination by Lead
• E.Coli: E.coli Bacteria
• Hepatitis A and E: Virus from Fecal matter etc.

Noise Pollution
• Noise pollution is generally defined as regular exposure to elevated sound levels that may lead to
adverse effects in humans or other living organisms. According to the World Health Organization,
sound levels less than 70 dB are not damaging to living organisms, regardless of how long or con-
sistent the exposure is.
• Effect of noise pollution on human health: Hearing loss, Cardiovascular diseases, psychological im-
pacts etc.

Radioactive Pollution
• It is the deposition of, or presence of radioactive substances on surfaces or within solids,
liquids or gases (including the human body), where their presence is unintended or undesirable.
• Various radioactive pollutants: α, β, ϒ radiations, radioactive decay, Nuclear power
plant radioactive residues etc.
• Diseases caused due to radioactive pollutions: Cancer, tumors, genetic mutations etc

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