2. The meaning of the word ecology was given by German Biologist Hackle
Ecology is the scientific study of the interactions between organisms and
their environment. The term comes from the Greek 'study of house', or
the study of the place we live in.
Ecology includes the study of interactions organisms have with each
other, other organisms, and with abiotic components of their
Topics of interest to ecologists include the diversity, distribution, amount
(biomass), and number (population) of particular organisms, as well as
cooperation and competition between organisms, both within and among
. Ecosystems are composed of dynamically interacting parts including
organisms, the communities they make up, and the non-living
components of their environment.
3. Organismal ecology looks at how individuals interact with their
environment, which is made up of biotic (living)
and abiotic (non-living) components.
The environment is made up of two factors:
Biotic factors- all living organisms inhabiting the Earth
Abiotic factors- nonliving parts of the environment (i.e.
temperature, soil, light, moisture, air currents)
4. Within the discipline of ecology, researchers work at five
broad levels, sometimes discretely and sometimes with
E. and biosphere
Let's take a look at each levels:-
Organism: Organismal ecologists study adaptations,
beneficial features arising by natural selection, that allow
organisms to live in specific habitats. These adaptations can
be morphological, physiological, or behavioral.
5. Population: A population is a group of organisms of the
same species that live in the same area at the same time.
Population ecologists study the size, density, and structure of
populations and how they change over time.
Ecosystem: An ecosystem consists of all the organisms in
an area, the community, and the abiotic factors that influence
that community. Ecosystem ecologists often focus on flow of
energy and recycling of nutrients.
Biosphere: The biosphere is planet Earth, viewed as an
ecological system. Ecologists working at the biosphere level
may study global patterns—for example, climate or species
distribution—interactions among ecosystems, and phenomena
that affect the entire globe, such as climate change.
6. An ecosystem includes all of the living things (plants,
animals and organisms) in a given area, interacting with
each other, and also with their non-living environments
(weather, earth, sun, soil, climate, atmosphere).
The study of ecosystems mainly consists of the study of
certain processes that link the living, or biotic,
components to the non-living, or abiotic, components.
There are many examples of ecosystems -- a pond, a
forest, an estuary, a grassland. The boundaries are not
fixed in any objective way, although sometimes they
seem obvious, as with the shoreline of a small pond.
7. Nutrient cycling:
◦ Movement of chemical elements from the
environment into living organisms and from them
back into the environment through organisms live,
grow, die and decompose.
◦ Energy is required to transform inorganic nutrients
into organic tissues of an organism.
◦ Energy is the driving force to the work of ecosystem.
◦ It refers to the particular pattern of inter-relationships
that exists between organisms in an ecosystem.
9. All living things need to feed to get energy to grow, move
and reproduce. But what do these living things feed on?
Smaller insects feed on green plants, and bigger animals
feed on smaller ones and so on.
This feeding relationship in an ecosystem is called a food
Food chains are usually in a sequence, with an arrow used
to show the flow of energy. Below are some living things
that can fit into a food chain.
A food chain is not the same as a food web.
A food web is a network of many food chains and is more
11. • They have a predominance of trees that are interspersed with
large number of species of herbs, shrubs, climbers, lichens algae
& a variety of wild animals & birds.
• Depending upon the climatic conditions forests can be of
different types :
1. Tropical Rain Forest
2. Tropical Deciduous forests
3. Tropical Scrub Forests
4. Temperate Rain Forests
5. Temperate Deciduous Forests
6. Evergreen Coniferous Forests
12. The Carbon Cycle:-
• The carbon cycle is very important to all ecosystems, and
ultimately life on earth. The carbon cycle is critical to the
• Living tissue contains carbon, because they contain
proteins, fats and carbohydrates. The carbon in these (living
or dead) tissues is recycled in various processes.
Let's see how this cycle works using the simple sketch below:
13. Human activities like heating and cars burning fuels
(combustion) give off carbon into the atmosphere. During
respiration, animals also introduce carbon into the atmosphere
in the form of carbon dioxide.
The Carbon dioxide in the atmosphere is absorbed by green
plants (producers) to make food in photosynthesis.
When animals feed on green plants, they pass on carbon
compounds unto other animals in the upper levels of their food
chains. Animals give off carbon dioxide into the atmosphere
Carbon dioxide is also given off when plants and animals die.
This occurs when decomposers (bacteria and fungi) break
down dead plants and animals (decomposition) and release the
carbon compounds stored in them.
14. The Nitrogen Cycle
• Nitrogen is also key in the existence of ecosystems and food
chains. Nitrogen forms about 78% of the air on earth. But
plants do not use nitrogen directly from the air. This is
because nitrogen itself is unreactive, and cannot be used by
green plants to make protein.
• Nitrogen gas therefore, needs to be converted into nitrate
compound in the soil by nitrogen-fixing bacteria in soil, root
nodules or lightning.
• To understand the cycle better, let us consider the diagram
15. 1. Nitrogen is introduced into the soil by precipitation (rain, lightning).
2. Nitrates don’t only come from Nitrogen in the air. They can also be obtained by the
conversion of ammonia, commonly used in fertilizers by nitrifying bacteria in the soil.
Some root nodules can also convert nitrogen in the soil into nitrates.
3. Plants build up proteins using nitrates absorbed from the soil.
4. When animals like cows, eat these plants, they, in turn, use it to build animal
5. When these animals (cows) poop, pee or die, the urea, excreta or carcass are
broken down by decomposers and the nitrogen is re-introduced into the soil in the
form of ammonia.
6. Nitrates in the soil can also be broken down by denitrifying bacteria (in specific
conditions) and sent into the air as nitrogen. This process can help make the soil
infertile because it will lack the nitrates needed for plant use
o Once nitrogen gets back into the air, the cycle continues.
• Borman, F.H. and G.E. Likens. 1970. "The nutrient cycles
of an ecosystem." Scientific American, October 1970, pp
• Wessells, N.K. and J.L. Hopson. 1988. Biology. New York:
Random House. Ch. 44.
• Bailey, Robert G. (2009). Ecosystem Geography (Second
ed.). New York: Springer. ISBN 978-0-387-89515-4.
• Chapin, F. Stuart; Pamela A. Matson; Harold A. Mooney
(2002). Principles of Terrestrial Ecosystem Ecology. New
York: Springer. ISBN 0-387-95443-0.
• Gurevitch, Jessica; Samuel M. Scheiner; Gordon A. Fox
(2006). The Ecology of Plants (Second ed.). Sunderland,
Massachusetts: Sinauer Associates. ISBN 978-0-87893-