ECOLOGY
DR. TILAK RAJ MAITY
Assistant Professor
Department of Biotechnology
Haldia Institute of Technology
Ecology and Environment
Environment refers to all the conditions that influence and affect the
development and sustainability of life of all organisms present on the earth. It
is an immediate surrounding of living organisms in which it lives and operates.
Ecology is the study of inter-relationship of organisms with physical as well
as biotic environments. Organisms and environment are interrelated and
interdependent. Any change in the environment affects the living organisms
and vice-versa.
Ecosystem is the structural and functional unit of ecology. It is a community
of living organisms along with the abiotic components interacting together
through energy flows and nutrient cycles.
Biotic vs Abiotic
Biotic and abiotic are the two essential factors responsible for shaping the
ecosystem. The biotic factors refer to all the living beings present in an
ecosystem, and the abiotic factors refer to all the non-living components
Characteristics of Living Things
Levels of Ecology
Organism → Species (population) → Biotic
community → Ecosystem → Biome → Biosphere
Organism: is the smallest and basic unit of ecology. It includes all the
living organisms, unicellular or multicellular having a fixed lifespan.
Species or Population: members of the same species living in a
specific geographical area. A species is a group of organisms that have a
common gene pool and can interbreed to produce fertile offspring.
Community: the interacting group of various different species living in
an area, it includes plants, animals and microbes.
Ecosystem: it is the functional unit of the ecology. It includes the biotic
community and the interacting physical environment associated with it.
Biotic components and abiotic components constitute an ecosystem.
Biome: consists of communities present in a large geographical area.
Biosphere: it is the total sum of all ecosystems. It is also known as the
zone of life on Earth. It includes all the living organisms, their relationships
and interaction with the elements of atmosphere, hydrosphere and
lithosphere.
Component of Ecosystem
An ecosystem is defined as a community of life forms in
concurrence with non-living components, interacting with each other
Types of Ecosystem
Energy flow in ecosystems
When, GPP < MA, NPP becomes negative; i.e. Biomass undergoes
degradation
When, GPP > MA, NPP becomes positive; i.e. Accumulation of biomass
When, GPP = MA, There is no change in energy content (NPP=0)
Trophic level
The producers and consumers in the ecosystem can be arranged
into different feeding groups and are known as trophic level
The producers (plants) represent the first trophic level
Herbivores (primary consumers) present the second trophic level
Primary carnivores (secondary consumers) represent the third trophic level
Top carnivores (tertiary consumers) represent the last level
Functions of Ecosystem
It regulates the essential ecological processes, supports life
systems and renders stability.
It is also responsible for the cycling of nutrients between biotic
and abiotic components.
It maintains a balance among the various trophic levels in the
ecosystem.
It cycles the minerals through the biosphere.
The abiotic components help in the synthesis of organic
components that involves the exchange of energy.
Food Chain
A food chain is a linear flow of energy and nutrients from one
organism to another
Different types of food chains
Grazing food chain (GFC) – This is the normal food chain that we
observe in which plants are the producers and the energy flows from
the producers to the herbivores (primary consumers), then to
carnivores (secondary consumers) and so on.
Parasitic food chain (PFC) – In this type of food chain, large
organisms either the producer or the consumer is exploited and
therefore the food passes to the smaller organism.
Saprophytic or Detritus food chain (DFC) – In this type of food
chain, the dead organic matter occupies the lowermost level of the
food chain, followed by the decomposers and so on.
Food Web
A food web can be termed as the combination of many
different food chains and the relationship that exists between
each organism
Food chain vs Food web
Ecological Pyramid
Ecological pyramid is a graphical
representation of the relationship
10 Percent Energy between different organisms in
Rule an ecosystem
Primary consumers do not get Each of the bars that make up
100% of the sun’s energy from the pyramid represents a different trophic
the producers or the plants on level
which they feed. This is because
only some amount of the sun’s
energy is utilized by the plant to
synthesize their food.
In fact, they only get 10% of the
energy. This is termed as the 10%
Rule, which states that only 10
per cent of the energy available
gets passed onto the next level of
consumers.
Pyramid of numbers
A pyramid of numbers is a graphical representation that
shows the number of organisms at each trophic level
Pyramid of biomass
A biomass pyramid is the representation of total
living biomass or organic matter present at different trophic
levels in an ecosystem
Pyramid of energy
Biogeochemical Cycles
“Biogeochemical cycles mainly refer to the
movement of nutrients and other elements between
biotic and abiotic factors”
Biogeochemical cycles are basically divided into two types:
Gaseous cycles – Includes Carbon, Oxygen, Nitrogen, and the
Water cycle.
Sedimentary cycles – Includes Sulphur, Phosphorus, Rock
cycle, etc.
Oxygen Cycle
Importance of Oxygen Cycle
Breathing
Combustion
Supporting aquatic life
Decomposition of organic waste
Carbon Cycle
Carbon cycle is the process where carbon compounds are
interchanged among the biosphere, geosphere, pedosphere,
hydrosphere, and atmosphere of the earth
Nitrogen Cycle
“Nitrogen Cycle is a biogeochemical process which transforms the inert nitrogen
present in the atmosphere to a more usable form for living organisms”
Nitrogen fixation:
Rhizobium
Azotobacter
Clostridium
Ammonification:
Bacillus subtilis
Nitrification:
Nitrosomonas
Nitrococcus
Nitrobactor
Denitrification:
Bacillus cereus
Thiobacillus
Sulphur Cycle
The sulfur cycle is the collection of processes by which
sulfur moves between rocks, waterways and living systems
Phosphorus Cycle
“Phosphorus cycle is a biogeochemical process that involves the movement of
phosphorus through the lithosphere, hydrosphere and biosphere”
Email ID : tilakrajpathshala@gmail.com
