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.
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
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
The behavior under natural conditions
The development in the course of evolution
The biological productivity and energy flow in
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
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
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
3)Based On the level of organization:
Depending upon the level of organism
synecology can be divided into may types :
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
• 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
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
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
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
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
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
‘Photoautotrophs’ = (Photo=light, auto=self;
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,
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.
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.
• 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.
Transfer of Energy in an Ecosystem
Herbivores – eat
feed only on
• This pattern of energy flow among different
organisms is the TROPHIC STRUCTURE of an
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
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
Energy enters the ecosystem form solar radiation
and converted into chemical energy by producers,
from them energy passes to lower tropic level to
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
3) Universal energy flow model
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
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
*Since these chemicals are non biodegradable, they
get accumulated at every trophic level and their
*The increase in concentration of harmful chemicals
in the bodies of organisms at higher trophic levels is
called biological magnification.
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
The producers of an ecosystem take up several
basic inorganic nutrients from their nonliving
These nutrients get transformed into biomass of
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 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
All Animals and Other Consumers Use Oxygen.
• We use oxygen to break down simple sugar and
• This can be done through respiration or
• Animals mainly use 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.
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
Other organisms use the free oxygen for
How are photosynthesis and cellular
• Photosynthesis uses carbon dioxide and
• Cellular respiration uses oxygen and produces
• This happens on land and in the water.
• Algae and aquatic plants produce food underwater
• They use CO2 dissolved in the water.
• Other aquatic organisms use the dissolved oxygen
these plants release into the water.
• 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
• 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
Animals Eat Plants
• When organisms eat plants, they take in the
carbon and some of it becomes part of their
• C is also released back as CO2 after respiration
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 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
• 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
What We Need to Do
• Burn less, especially fossil fuels
• Promote plant life, especially trees
Roles of Nitrogen
• Plants and bacteria use nitrogen in the
form of NH4
+ or NO3
• It serves as an electron acceptor in
• Nitrogen is often the most limiting nutrient
in soil and water.
Atmospheric nitrogen (about 78% of our air) is converted
to ammonia or nitrates.
with Hydrogen to make
with Oxygen to make
It is one of nature’s
• Nitrogen is an essential
component of DNA, RNA,
• the majority of the air we
breathe is nitrogen yet most
living organisms are unable to
use nitrogen as it exists in the
“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.
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
Free-living bacteria live
in soil and combine
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
Roots with nodules
where bacteria live
Nitrogen changes into
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) is used by
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
Ammonia Nitrites Nitrates
Denitrification: The conversion of nitrates (NO3) in the soil
to atmospheric nitrogen (N2) thereby replenishing the
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
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!
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.