ECOLOGY

(ECOSYSTEM ECOLOGY)

Dr. Neelam Shivnath

WHAT IS ECOLOGY?

¡ " Ecologyis the scientific study of the interactions between

organisms and their environment.

¡ It is the interdisciplinary science that seeks to describe how life survives

and grows in the relationship with their environment.
¡ Ecology comes from the Greek words
¡ Oïkos= House or dwelling place
¡ -logos= Study of
¡ Study of house/environment
¡ Ernst Haeckel, a German zoologist coined the
term Ecology in 1869.

¡ Defined ecology as ‘ the study of the natural

environment including the relation of organisms
to one another and to their surrounding’.

¡ -Danish botanist, Eugenius Warming elaborated

on the idea of Ecology (Plant ecology).
ENVIRONMENT

¡ Everything that surrounds or affects an organism during its

lifetime is collectively known as the environment.

¡ It includes both biotic and abiotic factors.

ENVIORNMENTAL FACTORS

¡ Also called ecological factors or ecofactors.

¡ Any factor, abiotic or biotic, that influences the living organism.

CLASSIFICATION OF ECOLOGY

¡ Ecology is a broad discipline comprising many sub-disciplines.

Under this system the subjects studies:

¡ Ecophysiology: examines how the physiological functions of

organisms influence the way they interact with the environment, both
biotic and abiotic.
¡ Behaviour ecology: examines the role of behaviour that enables the
animal to adapt its environment.
¡ Population ecology: studies the dynamics of populations of a single
species.
¡ Community ecology (or synecology): focuses on the interactions
between species within an ecological community.
¡ Ecosystem ecology: study the flow of energy and matter through biotic
and abiotic components.
 Biosphere

Biome

Ecosystem
LEVELS OF ECOLOGICAL
ORGANISATION Community

Population

species
 Organism

Organ

Tissue
LEVELS OF ECOLOGICAL
ORGANIZATION Group of cells

Cells

Macro Molecules
LEVELS OF BIOLOGICAL ORGANIZATION

Three levels of biological organization

v Individual organism
v Population
v Community
Population: A group of individuals of the same species inhabiting the
same area.

Biomes at the largest scale, communities are known as biomass.(A

community of plant and animals living together in particular climate).

Tropical rain forest Tropical grassland

LEVELS OF ECOLOGY

¡ Organismal ecology: deals with features of individual organisms in

response to envn.

¡ Population ecology: deals with population growth and how and why a
population changes over time.
¡
Community ecology: deals with the composition, organization and
development of ecological communities.
¡ Autecology: an ecological study of an individual or a population or
entire species.

¡ Synecology (community ecology): study of ecological community.

ECOLOGY SOME TERMS:

¡ Flora: all the plants of an area

¡ Fauna: all the animals of an area
¡ Biota (Biological community): fauna + flora of the area
¡ Biome: Biota + non-living environment
¡ Biosphere: largest biome
¡ Biosphere is defined as the part of the earth occupied by living organisms.
It includes land, water and atmosphere.
ECOSYSTEM (ECOLOGICAL SYSTEM)
¡ A physically defined space comprising all the organisms which are
interacting with one another and with their physical environment and
act as a functional unit.

Pond/lake ecosystem
 ECOSYSTEM (ECOLOGICAL SYSTEM)
¡ A.G Tansley coined the term “ecosystem”. He defined an
ecosystem as a system resulting from the integration of all
living and non-living factors of the environment. He then
regarded the ecosystem as a complex system of not only
living beings but also the interaction of living beings with
physical factors so that the cycle of nature like energy flow
and flow of material may be maintained.

¡ The other names are biocoenosis, microcosm,

geobiocoenosis and holocoen
¡ According to Eugene P. Odum “ the ecosystem or
ecological system is the basic functional unit of the
organism and their environment interacting with each
other and within their own components.”

¡ k/a father of modern ecology.

ECOSYSTEM
• Ecosystem is the functional unit of nature in which creatures interact with
one another and their surroundings.

• Ecosystems are self-regulating and self-sustaining landscape units that can

be either terrestrial or aquatic. Deserts, forests, and grasslands are examples
of terrestrial ecosystems. Freshwater (ponds, lakes, streams) and saltwater
(marine estuaries) aquatic habitats exist.

¡ Biosphere is the largest ecological system. It includes all the organisms

present in the hydrosphere, lithosphere and atmosphere up to 13 km. it also
includes all the biotic and abiotic factors. It is also called the ecosphere.
 FEATURES OF ECOSYSTEM
vAll ecosystems are open systems

vThe boundary can be real or arbitrary.

vEcosystems have a temporal dimension- change through time.

vAn ecosystem has spatial dimension- could be of any type.

vComplex, self organizing and self regulated dynamic system.

vInterconnected by flow of energy and cycling of material.

vUltimate source of energy-sun.

TYPES OF ECOSYSTEM

Lotic Lentic
ARTIFICIAL ECOSYSTEM

Artificial Ponds Cropland(cultivated land)

NATURAL ECOSYSTEM
CONSTITUENTS OF ECOSYSTEM
The ecosystem can be divided into two main components
1. Abiotic component : living component of an ecosystem
v Physical
v Chemical
2. Biotic component: non-living component of an ecosystem
v Autotrophs (Producers): photoautotrophs/chemoautotrophs
v Heterotrophs: consumer/decomposers
ABIOTIC COMPONENTS

¡ Includes climate of a given region, inorganic substances like P, H, S,

O, etc and organic components like carbohydrates, protein and lipids.
 BIOTIC COMPONENTS

¡ There are two types of biotic components on the basis of nutrition

¡ Autotrophs: they synthesize organic compounds from simple inorganic components

from the environment. They are the ultimate source of organic compounds for all ono-
autotrophic organisms. Therefore also called producers They are of two types
¡ Photoautotrophs: use inorganic components in the presence of light for the synthesis of
food.
¡ Depends on chlorophyll-like pigments. eg- all green plants.
¡ Chemoautotrophs: use chemical energy to convert inorganic compounds into organic
matters. eg- nitrifying bacteria, and purple sulfur bacteria.
HETEROTROPHS

¡ Heterotrophs are the organism which cannot synthesize the

organicnutrients they need to and get them by feeding on producers. Eg,
fungi, animals etc.

¡ There are two types of heterotrophs on the basis of mode of food intake-

1. Consumer: that intake food by a process ingestion.

2. Decomposers: that intake food by the process of absorption.
CONSUMERS

¡ Consumers, or heterotrophs, are organisms that

consume other organisms to obtain their energy.
¡ Different types based on food habits:
1. Herbivores: Consumers that eat only producers
are herbivores like cows, sheep, deer, and
grasshoppers.
2. Carnivores: Consumers that eat only the flesh of
other animals are carnivores. Like tigers, hyenas,
polar bears, etc.
3. Omnivores: Consumers that eat both producers and
consumers are omnivores. Humans, bear etc.

4. Detritivores: heterotrophs that deeds on detritus.

Detritus are the dead bodies and waste products of
living and once-living or decomposing organic matter.
E.g.- earthworm, dung beetles.
CLASSIFICATION OF CONSUMERS

Consumers can also be classified based on feeding or trophic levels.

¡ Primary consumers (i.e. herbivores)
¡ Secondary consumers (i.e. primary carnivores)
¡ Tertiary consumers (i.e. secondary consumers)
5. Decomposers: Heterotrophs that gain their energy from breaking
down dead organisms and in carrying out they use the natural
process of decomposition e.g., bacteria and fungi.

Decomposition by decomposers is an oxidative process

Complex simple organic mineralization water soluble

organic compounds inorganic
Compounds nutrients

Both decomposers and detritivores derive nutrition from dead organic

matter. The difference is that detritivores eat organic matter and
decomposers secrete the enzymes to digest the organic matter and then
absorb the resulting molecules.
PRODUCTIVITY (PRODUCTIVITY)

¡ Productivity in an ecosystem can be defined as the rate at which the

biomass increases per unit area/volume.

¡ We measure the productivity of an ecosystem on the basis of the following:

1. Primary productivity
2. Secondary productivity
BIOMASS
¡ Biomass is the amount of organic matter present at any given time in
unit area/volume.

¡ Wet biomass: mass of living matters including its water content.

¡ Dry biomass: mass of living matter after it has been dried.

STANDING CROP

¡ The total biomass of photosynthetic autotrophs present in unit

area/volume at a given time.
PPRIMARY PRODUCTIVITY
¡ The rate at which biomass is produced per unit area/volume by producers.

¡ Expressed in terms of weight of carbon (g-2 yr-1) or equivalent calories (kcal m-

2 yr-1).

¡ Primary productivity can be divided into-

1. Gross primary productivity (GPP)
2. Net primary productivity (NPP) (also termed as net assimilation)
GROSS PRIMARY PRODUCTIVITY (GPP)

¡ The total amount of CO2 fixed to organic carbon by photoautotrophs

per unit time (i.e., total rate of photosynthesis) is called GPP
NET PRIMARY PRODUCTIVITY (NPP)
¡ A proportion of fixed organic carbon is respired away by the
photoautotrophs. A considerable amount of GPP is utilized by plants
in respiration.
¡ The total amount of organic carbon that is oxidized by the
photoautotrophs per unit of time is autotrophic respiration (RA).
¡ Net primary productivity (N.P.P.) is the amount of stored organic
matter in plant tissues after respiratory utilization.
NPP=GPP-R (R=Respiration + Metabolic activities).
Or GPP=NPP+R
¡ NPP represents the actual rate of production of new biomass which is
available for consumption by heterotrophic organisms.
SECONDARY PRODUCTIVITY

¡ It refers to the biomass production rate by consumers (herbivores).

¡ Not divided into gross and net primary productivity.
¡ Depends on NPP
Net Community productivity (NCP)
Rate of storage of organic matter not used by the heterotrophs.
NCP = GPP-RA-RH
FACTORS AFFECTING NPP

1. In terrestrial ecosystem:
v Growing season length
v Precipitation
v Temperature
v Solar radiation
v Nutrient availability
¡ Egs. NPP

¡ Region with increased rain fall: NPP

¡ Tropical rain forest:

¡ Warm and cold region:

¡ Solar radiation

¡ Nutrient availability
2. In aquatic ecosystem: depends on 2 important factors:

v Light
v Nutrient available