Principles of Ecology
TSW identify the levels of
classification within ecology and
differentiate between food chains
and food webs
What is ecology?

The study of the
interactions of
organisms with
one another and
with their
physical
surroundings
Levels of Organization
(Broadest to most specific)
6.
5.
4.
3.
2.
1.
Biosphere
Biome
Ecosystem
Community
Population
Individual
6. Biosphere

Contains the part
of the earth in
which ALL life
exists (including
land, air, water,
and atmosphere)
5. Biome


A group of
ecosystems that
have the same
climate and
similar dominant
communities
Can you think of
any biomes?
4. Ecosystem

A collection of all of the organisms
that live in a particular place, together
with their nonliving, or physical
environment
3. Community

All the
populations of
organisms living
in a defined area
– Can be one
inch of soil or
and entire
forest
2. Population

A group of individuals that belong to
the SAME SPECIES and live in the
same area
1. Individual

One organism of
a particular
species
What keeps populations
from growing without end?

Limiting interactions
– Densitydependent
– Densityindependent
Density-dependent Factor


Factor that depends directly on the
size of a population
Examples:
– Disease (esp. parasitism)
– Predation
– Competition for space and resources
– Crowding and stress
Density- independent
Factor


Limiting factor that affects all
populations in a similar way,
regardless of population size
Examples:
– Temperature and climate changes
– Natural disasters
– Chemical pollutants
Simple Interactions

Food chain: a
series of steps in
which organisms
transfer energy
by eating or
being eaten
Trophic Levels



Producers: Organisms that make their
own food from inorganic sources
1º consumer: aka Herbivores, get
food/energy by feeding DIRECTLY on
producers
2º consumer: Feed on 1º consumers
Ecological Pyramids

Diagram showing the relative amounts
of energy/matter contained within
each trophic level in a food chain/food
web
3 Types of Pyramids



Energy: Lose actual energy as you
move up the pyramid
Biomass: Most mass is found at the
bottom of the pyramid
Numbers: Most individuals are found
at the bottom of the pyramid
Rule of 10

Only about 10% of the energy
available within one trophic level is
transferred to organisms at the next
level
Food Web


When the feeding relationships among
the various organisms in an ecosystem
form a network of complex
interactions
Link all food chains together