ECOLOGY
AND
ECOSYSTEM
Chapter 2
By : Yash Patel

Ecology
Ecology derived from two Greek word “oikos”
means house, habitation or place of living &
“logos” means study.
• Definition: Ecology is the study of
interrelationship between living organism and
their physical and biological environment.
• Biological environment = Biotic factors
• Physical environment = Abiotic factors

Biotic Factors

Abiotic Factors

Objectives of ecological study
 The inter-relationship between organisms in
population and diverse communities
The temporal (sequential) changes (seasonal,
annual, successional etc)
Structural adaptation and functional
adjustments
The behavior under natural conditions
The development in the course of evolution
The biological productivity and energy flow in
natural system

Scope of ecology
Helps us to tackle problems like pollution,
floods, O3 depletion, global warming
Is necessary in maintaining ecological balance
and understanding different cycles (oxygen,
nitrogen, sulfur, carbon etc.)
Helps in protecting flora and fauna
We can maintain balance in nature and can
prevent ecological disasters
Plays an important role in human welfare,
agriculture, conservation of wildlife.

Classification of ecology
1) Autecology
2) Synecology
 Autecology: It deals with the study of individual
organism or an individual species. In other words it is
study of inter relationship between individual species
or its population and environment .e.g. a tree in forest
 Synecology : it deals with the study of group of
organism or species which are associated together as a
unit. e.g. a forest. It is concerned with structure,
nature, development of that community

Further subdivisions of ecology is based on
following:
1) Based on the taxonomic affinities :
According to this ecology is divided in two part:
Plant ecology and animal ecology

2) Based on the habitats
Ecology
Aquatic
Ecology
Terrestrial
Ecology
Marine Ecology
Fresh water
Ecology
Stream Ecology
Grass Land
Ecology
Forest Ecology
Desert Ecology

3)Based On the level of organization:
Depending upon the level of organism
synecology can be divided into may types :
Desert Ecology
Autecology Synecology
Population Ecology
Community Ecology
Ecosystem Ecology

The Ecosystem
Definitions of ecosystem:
1. All organisms, their interactions with one another
and their environments make up an ecosystem.
2. It is a community of interdependent organisms
together with the environment.
3. Any unit that include all of the organisms in a given
area interacting with the physical environment, so that
a flow of energy leads to clearly defined trophic
structure, biotic diversity and material cycles within
the ecosystem.

Ecosystem - populations in a
community and the abiotic factors
with which they interact (ex.
marine, terrestrial)

Ecology
• Definition: Ecology derived from two Greek
word “oikos” means house, habitation or place
of living & “logos” means study.
• Ecology is the study of the interrelationship
between living organism and their physical and
biological environment.

Types of ecosystem
Ecosystem can be Natural or Artificial
a) Natural ecosystems:
These operate under the natural conditions without
any major interference by man. Further it can be
classified:
1) Terrestrial Ecosystem
2) Aquatic Ecosystem

b) Artificial Ecosystem
These are maintained artificially by man
where by addition of energy and planned
manipulation, natural balance is disturbed
regularly.
E.g. Cropland ecosystem

1)Terrestrial Ecosystem:Eg: Forest ,Grassland ,Desert
2) Aquatic Ecosystem:
a) Fresh water :- which may be lotic (e.g. running
water as stream, rivers) or lentic (e.g. standing
water as lake, pool)
b) Marine ecology :- Deep bodies as a ocean

Characteristics of Ecosystem
 It is a major structural and functional unit of
Ecology.
 Its structure is related to its species diversity;
the more complex ecosystem have species
diversity and vice versa.
The relative amount of energy needed to
maintain an ecosystem depend on its structure.
The more complex the structure, the lesser the
energy it needs to maintain itself.
It matures by passing from less complex to
more complex states

Structural features
1. Biotic structure
The plants, animals and microorganism present
in an ecosystem form the biotic component.
a) Producers: They are mainly the green plants,
which can synthesize their food themselves by
making use of carbon dioxide present in the air
and water through the process of
photosynthesis.
‘Photoautotrophs’ = (Photo=light, auto=self;
troph=food).

Structural features
b) Consumers: all organisms which get their organic
food by feeding upon other organism are called
consumers, which are following types:
i. Herbivores (plant eaters): e.g. Rabbit, insect,
goat, cattle.
ii. Carnivores (meat eaters): e.g. Snake, cat, fox etc.
iii. Omnivores: e.g. humans, rat, fox etc.
iv. Detritivores: (Detritus feeders or saprotrophs)
v. Predetor:(Kills other organization for food)
e.g. wolf, beer.

Structural features
c) Decomposers: They derive their nutrition by
breaking down the complex organic molecules
to simpler organic compound and ultimately
into inorganic nutrients.
e.g. bacteria, fungi etc.

primary consumers
• Also known as HERBIVORES , such as: mice,
deer, cows, and elephants
• Herbivores eat ONLY PLANTS

Secondary Consumers
• Are CARNIVORES – they eat only animals
• If the animal must be killed before it is eaten, the
secondary consumer is known as a predator.
• However, sometimes the animals does not have to
be killed to be eaten.

Secondary Consumers
O m n i v o r e s
they eat Both :
Plants and
Animals

Scavengers
Feeds on the bodies of dead organisms.

Decomposers
Break down wastes and dead organisms, and so
complete the cycle by returning nutrients to the
ecosystem. (to the soil or water and carbon dioxide to
the air and water)

Transfer of
Energy in an
Ecosystem

Transfer of Energy in an Ecosystem
CONSUMER
Herbivores – eat
plants
Carnivores –
eat animals
Scavengers –
feed only on
dead organisms
Omnivores –
eat both
plants &
animals

Energy flow
• This pattern of energy flow among different
organisms is the TROPHIC STRUCTURE of an
ecosystem.
heat
Producers Consumers
Decomposers
heat

Energy Flow in Ecosystem
 To maintain life energy is required. Energy enters in an ecosystem
from solar radiations.
 In earth’s atmosphere about 15x108 cal/m2/year of solar energy is
present .
 Out of which only 47% of the energy reaches the earth surface and
only 1-5% of energy reaching the ground is converted into
chemical energy by green plants .
 The plants make use of raw material from the environment in the
form of water, salts and carbon dioxide to prepare food with the
help of sun light.
 Thus energy form the sun enters the living world through
photosynthetic organisms and passes on from one organism to
another in form of food.

 The flow of energy is unidirectional and non
cyclic.
 Energy enters the ecosystem form solar radiation
and converted into chemical energy by producers,
from them energy passes to lower tropic level to
higher one.
 This one way flow of energy is governed by laws
of thermodynamics which state that :
a) The energy can not be created not destroyed but may be
transferred from one from to another
b) During the energy transfer there is degradation of energy
from concentrated form to a dispersed form(Heat)

No energy transformation is 100% efficient; it is
always accompanied by some dispersion or
loss of energy in the form of heat.
Heat energy is not utilized by biological system
and ultimately lost from the body

Models for energy flow in ecosystem
• The flow of energy through various trophic
levels in an ecosystem can be explained by:
1) Single channel energy flow model
2) Y shaped or double channel energy flow
model
3) Universal energy flow model

Ecological Pyramid
This shows how energy is
transferred and changed
when going up the pyramid.

Three Types of Ecological Pyramid
A. Pyramid of Energy – shows the amount
of energy in calories (Kcal / cal)
B. Pyramid of Biomass – shows the
biomass of all organisms and individuals
C. Pyramid of Numbers – shows the
number of individuals feeding at each
tropic level

Pyramid of Energy

Pyramid of Biomass

Pyramid of Numbers

Food Chain
Organisms in one level feed
upon organisms at the lower
level.

Trophic Levels
• Each link in a food chain is known as a
trophic level.
• Trophic levels represent a feeding step in
the transfer of energy and matter in an
ecosystem.

Trophic Levels
Producers- Autotrophs
Primary consumers- Herbivores
Secondary consumers-
small carnivores
Tertiary consumers-
top carnivores
E
N
E
R
G
Y

Types of Food chain

Significance of Food Chain
• Biological magnification (Biomagnification)
*Harmful chemicals like insecticides and pesticides
which are used to protect crops from insects and
pests are absorbed by plants and enter the food
chain.
*Since these chemicals are non biodegradable, they
get accumulated at every trophic level and their
concentration increases.
*The increase in concentration of harmful chemicals
in the bodies of organisms at higher trophic levels is
called biological magnification.

Biological magnification (Biomagnification)
Biomagnification of DDT Biomagnification of Mercury

Biological magnification (Biomagnification)
• The biomagnification of pollutants can be
estimated with the help of Biological
Concentration Factor (BCF).
Concentration of toxic material in organism
Concentration of toxic material in Environment
BCF =

Food Web
It is a network of interacting
food chains.

Food Web
• Food web- shows all possible feeding
relationships in a community at each
trophic level
• Represents a network of
interconnected food chains

Food web :-
Food web is a group of several interconnected food
chains. In a food web an organism gets food from more
than one group of organisms.
Examples of Terrestrial food web

Examples of Aquatic
food web

Biogeochemical Cycle
 The producers of an ecosystem take up several
basic inorganic nutrients from their nonliving
environment.
 These nutrients get transformed into biomass of
the producers.
 Then they are utilized by the consumer population
and ultimately returned to the environment with
the help of reducers and decomposers.
 The cyclic exchange of nutrients materials
between living organisms and their nonliving
environment is called biogeochemical cycle.

1) Biogeochemical cycles helps as to understand
the flow of pattern various nutrients, water, gases
etc. needed for development of life
2) Hydrological cycle deals with the interchange
water between living organisms & environment.
3) Gaseous cycle deals with the interchange of
gases like Oxygen, Nitrogen, Carbon Dioxide.
4) The sedimentary cycles deals with the
interchange of minerals like sulphur, phosphorus.

Water cycle

 Water never leaves the Earth. It is constantly being cycled
through the atmosphere, ocean, and land.
 This process, known as the water cycle, is driven by
energy from the sun.
 The water cycle is crucial to the existence of life on our
planet.

Evaporation
Evaporation: Process by which the sun heats up
liquid water and changes it to a gaseous form
(vapours).

Condensation
Condensation: Process by which water rises
into the atmosphere, cools and becomes a liquid
again.

Precipitation
Precipitation: Process by which water condenses and
falls back to the earth.

Transpiration
Transpiration: The process of evaporation from plants.
Factors affecting transpiration: Sun light intensity,
relative humidity, soil moisture availability, wind
movement, types of plants.

Runoff
Runoff: Water that collects in rivers, streams,
and oceans

Oxygen cycle
All Animals and Other Consumers Use Oxygen.
• We use oxygen to break down simple sugar and
release energy.
• This can be done through respiration or
fermentation.
• Animals mainly use respiration.

Respiration
Simple Sugar — Glucose
• The process that breaks apart simple food molecules
to release energy.
• It occurs inside cells.
The molecule most living things use for
energy — including us!
• We break down food into smaller molecules during
digestion. One of the small molecules is glucose.
• Glucose leaves your intestines, goes into your blood
and is taken to every cell in your body.

Photosynthesis
Plants take in carbon dioxide and water and
use them to make food. Their food is simple
sugar — glucose.
Plants pull the carbon off CO2 and use the
carbon in glucose. (They do not need the oxygen for this. They get
that from water, H2O.)
Plants release the oxygen (O2) back into the
atmosphere.
Other organisms use the free oxygen for
respiration.

How are photosynthesis and cellular
respiration similar?
• Photosynthesis uses carbon dioxide and
produces oxygen.
• Cellular respiration uses oxygen and produces
carbon dioxide.

Respiration
Photosynthesis

Everywhere
• This happens on land and in the water.
• Algae and aquatic plants produce food underwater
through photosynthesis.
• They use CO2 dissolved in the water.
• Other aquatic organisms use the dissolved oxygen
these plants release into the water.

Human Impact
• We keep destroying natural areas, especially
forested areas with many plants and replacing
them with buildings, parking lots, lawns, etc.
• Fewer plants mean less oxygen and more
carbon dioxide.
• This disturbs the balance of the natural cycle.

What Is Carbon?
• An element
• The basis of life of earth
• Found in rocks, oceans, atmosphere

Plants Use Carbon Dioxide
• Plants pull carbon dioxide from the atmosphere
and use it to make food –— photosynthesis.
• The carbon becomes part of the plant (stored
food).

Animals Eat Plants
• When organisms eat plants, they take in the
carbon and some of it becomes part of their
own bodies.
• C is also released back as CO2 after respiration
and combustion

Plants and Animal Die
• When plants and animals die, most of their
bodies are decomposed and carbon atoms are
returned to the atmosphere.
• Some are not decomposed fully and end up in
deposits underground (oil, coal, etc.).

Carbon Slowly Returns to Atmosphere
• Carbon in rocks and underground deposits is
released very slowly into the atmosphere.
• This process takes many years.

Carbon cycle

Carbon in Oceans
• Additional carbon is stored in the ocean.
• Animals die and carbon substances are
deposited at the bottom of the ocean.
• Oceans contain earth’s largest store of
carbon.

Human Impact
• Fossil fuels release carbon stores very slowly
• Burning anything releases more carbon into
atmosphere — especially fossil fuels
• Increased carbon dioxide in atmosphere
increases global warming
• Fewer plants mean less CO2 removed from
atmosphere

What We Need to Do
• Burn less, especially fossil fuels
• Promote plant life, especially trees

Nitrogen Cycle

Forms of Nitrogen
• Urea  CO(NH2)2
• Ammonia  NH3 (gaseous)
• Ammonium  NH4
• Nitrate  NO3
• Nitrite  NO2
• Atmospheric nitrogen N2
• Organic N (Amino acids--RCONH2)

Roles of Nitrogen
• Plants and bacteria use nitrogen in the
form of NH4
+ or NO3
-
• It serves as an electron acceptor in
anaerobic environment
• Nitrogen is often the most limiting nutrient
in soil and water.

(1) Nitrogen Fixation
(3) Nitrification (2) Ammonification
(4) Denitrification
Nitrogen
Cycle
The Nitrogen Cycle

Atmospheric nitrogen (about 78% of our air) is converted
to ammonia or nitrates.
Ammonia (NH3)
Nitrogen combines
with Hydrogen to make
Ammonia
Nitrates (NO3)
Nitrogen combines
with Oxygen to make
Nitrates
Atmospheric
Nitrogen (N2)
N
N
N
N

It is one of nature’s
great ironies…
• Nitrogen is an essential
component of DNA, RNA,
and proteins
• the majority of the air we
breathe is nitrogen yet most
living organisms are unable to
use nitrogen as it exists in the
atmosphere.

“Nitrogen Fixation” is the process that causes the strong
two-atom nitrogen molecules found in the atmosphere to
break apart so they can combine with other atoms.
Nitrogen gets “fixed” when it is combined with oxygen or hydrogen.
N
N
N
N
N
Oxygen Hydrogen
Oxygen
Hydrogen
N

Free Living Bacteria (example of nitrogen fixation)
Highly specialized bacteria live in the soil and have the ability
to combine atmospheric nitrogen with hydrogen to make
ammonia (NH3).
Free-living bacteria live
in soil and combine
atmospheric nitrogen
with hydrogen
Nitrogen changes
into ammonia
N
N
H
N H3
(NH3)
Bacteria

Symbiotic Relationship
Bacteria
Bacteria live in the roots
of legume family plants
and provide the plants
with ammonia (NH3) in
exchange for the plant’s
carbon and a protected
home.
Legume plants
Roots with nodules
where bacteria live
Nitrogen changes into
ammonia.
NH3
N
N

Ammonification: Bacteria (decomposers) break down amino
acids from dead animals and wastes into ammonium.
Bacteria decomposers break down amino acids into ammonium

Microorganisms convert the organic nitrogen to
ammonium. The ammonium is either taken up by the
plants (only in a few types of plants) or is absorbed into
the soil particles. Ammonium (NH4) in the soil is stored
up to later be changed into inorganic nitrogen, the kind of
nitrogen that most plants can use.
Ammonium (NH4) is
stored in soil.
Bacteria converts organic nitrogen to
ammonium (NH4)
Ammonium (NH4) is used by
some plants
Bacteria

Nitrification: Nitrifying bacteria in the ground combine
ammonia with oxygen to form nitrites. Then another
group of nitrifying bacteria convert nitrites to nitrates
which green plants can absorb and use.
Nitrifying bacteria in soil
combine ammonia with oxygen
Ammonia changes to nitrites
Nitrifying bacteria in soil
convert nitrites to nitrates
Plants absorb nitrates
and grow!
Ammonia Nitrites Nitrates
(NH3) (NO3)(NO2)

Denitrification: The conversion of nitrates (NO3) in the soil
to atmospheric nitrogen (N2) thereby replenishing the
atmosphere.
Nitrates (NO3)
in Soil
Nitrogen in atmosphere (N2)

Denitrifying bacteria live deep in soil and in aquatic sediments
where conditions make it difficult for them to get oxygen. The
denitrifying bacteria use nitrates as an alternative to oxygen,
leaving free nitrogen gas as a byproduct. They close the nitrogen
cycle!
Denitrifying bacteria live
deep in soil and use
nitrates as an alternative
to oxygen making a
byproduct of nitrogen gas.
Nitrogen in atmosphere
closes the nitrogen cycle!
(NO3)
(N2)

Nitrogen cycle

Sulphur Cycle
Sources
• Available in free state
• Also as sulfides, sulfates like PbS, ZnS, BaSO4
• In gas-- H2S, SO2

Acidic fog and
precipitation
Ammonium
sulfate
Ammonia
Sulfuric acid
Water
Sulfur trioxide
Oxygen
Hydrogen sulfideSulfur dioxide
Volcano
Industries
Dimethyl sulfide
Ocean
Metallic
sulfide
deposits
Decaying matter
Animals
Plants
Hydrogen sulfide
Sulfur
Sulfate salts

Dimethyl sulfide
• (CH3)2S
• Emissions from Phytoplankton
• Occurs over oceans
Sulfur dioxide
• SO2
• Emission: Industries
• example : power plants
• Volcanoes

Sulfuric acid
Sulfur Trioxide
• SO3
• Primary agent in acid rain
• Principal uses include: ore processing
• fertilizer processing
• Oil refining

Hydrogen Sulfide
• H2S
• Emitted by volcanoes and hot springs
• Remains in atmosphere for 18 hours
• Changes into sulfur dioxide

Biomes
• Determined primarily by
precipitation
–Forests (> 75 cm rain per year)
–Grasslands (30-75 cm rain per year)
–Deserts (< 30 cm rain per year)

Tropical Forest: Vertical stratification with trees in
canopy blocking light to bottom strata. Many trees
covered by epiphytes (plants that grow on other plants).

Example of Tropical, Dry Forest

http://earthobservatory.nasa.gov/Laboratory/Biome/Images/picgrassland.jpg
Grasslands

Temperate Deciduous Forest: Mid-latitudes with moderate amounts of
moisture, distinct vertical strata: trees, shrubs, herbaceous sub-
stratum. Loss of leaves in cold, many animals hibernate or migrate
then. Original forests lost from North America by logging and clearing.

http://www.ccet.ua.edu/hhmi/images/Autumn.JPG
Deciduous forest

Coniferous forest: Largest terrestial biome on earth, old growth
forests rapidly disappearing, usually receives lots of moisture as rain
or snow.

http://www3.newberry.org/k12maps/module_07/images/coniferous.jpg
Coniferous forest

Desert: Sparse rainfall (< 30 cm per year), plants and
animals adapted for water storage and conservation. Can
be either very hot, or very cold (e.g. Antarctica)

http://pangea.stanford.edu/~hsiao/desert.jpg
Desert

Temperate Grassland: Marked by seasonal drought and fires, and
grazing by large animals. Rich habitat for agriculture.

Estuary: Place where freshwater stream or river merges
with the ocean. Highly productive biome; important for
fisheries. Often heavily polluted from river input so many
fisheries are now lost.

Thank You