2. ECOLOGY
The first law of ecology
Everything is related to everything else
- Barry Commoner
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3. Components of the Environment
Lithosphere
Hydrosphere
Biosphere Atmosphere
Pedosphere (portion of earth that supports life)
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4. 4
ECOLOGY
Organism and its environment
The study of living organisms in the
natural environment
&
How they interact with one another, with
other living things and with nonliving
environment
5. Levels of Organization
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Organism
1st Level: Organism: An individual living thing
that uses energy, reproduces, responds, grows,
and develops.
6. Levels of Organization
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Population
2nd Level: Population: A group of organisms, all
of the same species, which interbreed and live in the
same place at the same time.
7. Community
3rd Level: Community: All the population of
different species that live in the same place at the
same time (same ecosystem).
8. Ecosystem
4th Level: Ecosystem: Populations of plants
and animals that interact with each other in a
given area with the abiotic components of that area.
(terrestrial or aquatic).
9. Ecosystem
A part of the environment which is self
sufficient independent & closed system
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10. Biological system is maintained by
3 groups of species
Producers (Autotrophs)
Consumers (Heterotrophs)
&
Decomposers / Recyclers / Scavengers
(ultimate consumers)
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23. Human System vs Ecosystem
Anthroposystem
● Very simple ecosystem;
max. 3 trophic levels
● Open system; minimal
recycling
● High efficiency of
transfer of biomass to
higher trophic level
● Monoculture; high
density
● Few favored species
encouraged; weeds
destroyed
● Static, highly unstable
● Few people feed the
rest-agriculture
Ecosystem
● Often highly complex
food webs
● Often closed systems
with significant
recycling
● Low efficiency of
transfer of biomass to
higher trophic level
● High biodiversity
● Natural balance in
species populations
achieved adapted to
conditions
● Robust, stable,
dynamic, adaptable,
evolving
24. Problems with Human Systems
● Dependent on very few species
○ 80% of world food from 15 species.
○ Human consume only 150 out of the estimated
50,000 edibles.
○ Out of 10,000 cereals, not one new has been
cultivated in the past 2000 yrs.
● Inherently unstable
○ Irish Great potato famine (1845-47) wind-
borne potato blight fungus; near total crop
failure
○ 1 million dead due to starvation, typhoid and
cholera
● Require constant inputs; pesticides, fertilizers,
etc.
● Prone to pest attacks and failures
● Pollute soil, air, water
● Soil degradation and topsoil loss
