Introduction to Ecology
Chapter 18
Organisms and Their
Environment
What is Ecology?
Ecology is the study of interactions
among organisms.
Determines relationships among living
and nonliving parts of the world within
the biosphere, or portion of Earth that
supports life.
ORGANISMS AND THEIR
ENVIRONMENT
I. ECOSYSTEMS: EVERYTHING IN
AN ECOSYSTEM IS CONNECTED.
AN ECOSYSTEM INCLUDES:
A. BIOTIC- ALL LIVING THINGS IN
AN ECOSYSTEM.
B - ABIOTIC- ALL NON-LIVING
THINGS IN AN ECOSYSTEM, SUCH
AS SOIL, AIR AND WATER.
Biotic factors
All the living things
that inhabit an
environment
Organisms depend
upon other living
things for food and
reproduction.
All living organisms
affect other living
organisms.
Abiotic factors
The nonliving parts of
an environment
Include air currents,
moisture, light,
temperature, and soil.
II. ORGANIZATION OF LIVING
THINGS:
A. ORGANISM- _A SINGLE
INDIVIDUAL
B. SPECIES- A GROUP OF
ORGANISMS THAT CAN
REPRODUCE AND PRODUCE
FERTILE OFFSPRING.
C. POPULATIONS- GROUP OF
INDIVIDUALS OF THE SAME
SPECIES_ LIVING IN THE _SAME
AREA.
D. COMMUNITIES- SEVERAL
DIFFERENT POPULATIONS_ THAT
INTERACT IN A SPECIFIC AREA.
E. BIOSPHERE – ALL
COMMUNITIES OF THE EARTH.
Levels of Organization
Single Individual
Population
Population-a group of organisms of
one species that interbreed and live
in the same place at the same time
May compete with one another for
food, water, mates, and other
resources.
Community
A collection of
interacting
populations.
A change in one
population in a
community will
cause changes
in the other
populations.
Ecosystem
An ecosystem is
made up of the
interactions
among the
populations in a
community and
the community’s
physical
surroundings, or
abiotic factors.
III. NICHE VS. HABITAT:
A. NICHE IS HOW AN ORGANISM
LIVES (WHAT IT DOES) INCLUDING
REPRODUCTION, TIME OF DAY IT
IS MOST ACTIVE, TYPE OF
SPECIES INTERACTIONS, ETC.
B. HABITAT IS WHERE IT LIVES.
Parts of an Ecosystem
Habitat-the
place where
an organism
lives out its
life.
Niche-the role and
position an organism has
in its environment.
Niche-might reveal what
food the organism eats,
how far it roams in search
of food, where it lives, etc.
Occupying different
niches reduces
competition among
organisms
IV. FIVE TYPES OF SPECIES
INTERACTIONS:
A. PREDATION- ONE ORGANISM
(PREDATOR) kills and eats another
(PREY). EXAMPLE: LION EATING
ZEBRA.
B. COMPETITION- _two species THAT
DEPEND ON THE same LIMITED
RESOURCE. EXAMPLES: TWO
FLOWERS NEEDING POLLINATION,
LIONS AND HYENAS NEEDING FOOD.
C. PARASITISM- ONE SPECIES
(PARASITE) THAT lives in or on another
(HOST) WITHOUT IMMEDIATELY
KILLING IT EXAMPLE: TICKS AND A
DOG.
D. MUTUALISM- A cooperative
partnership BETWEEN TWO
SPECIES THAT BENEFITS BOTH.
EXAMPLE: HUMANS AND
INTESTINAL BACTERIA.
E. COMMENSALISM- A
RELATIONSHIP BETWEEN TWO
SPECIES where one benefits but
the other is not harmed. EXAMPLE:
SHARK AND REMORA.
Predator and Prey
Relationship in
which one
organism kills
(predator) and
eats another
(prey)
Organisms fight
for survival
Competition
Two or more species dependant on
the same resource.
Parasitism
A symbiotic
relationship in
which one
organism
benefits at the
expense of
another
Mutualism
A symbiotic
relationship in
which both
species benefit.
Bees and birds visit
flowers in search of
pollen and nectar. In the
process flowers are
pollinated.
Commensalism
Symbiotic
relationship in
which one
species benefits
and the other
species is
neither harmed
nor benefited.
The Patella gets it food from the
plant, the Euklonia, which is not
harmed or damaged in the
process.
NUTRITION AND ENERGY FLOW
I. ENERGY FLOW IN ECOSYSTEMS
A. ALMOST all ORGANISMS
REQUIRE ENERGY FROM THE sun:
1. DIRECTLY- producers ( MAKES
THEIR OWN FOOD-autotrophs)
2. INDIRECTLY- consumers (DO
NOT MAKE THEIR OWN FOOD heterotrophs)
II. WHO EATS WHAT IN AN
ECOSYSTEM?
A. PRODUCER- MAKES ITS OWN
FOOD, EXAMPLES - plants, algae,
some bacteria
B. CONSUMER- Gets energy by
eating other organisms
1. Herbivore_ -EATS PRODUCERS,
EXAMPLES - COWS, SHEEP,
GRASSHOPPERS
2. Carnivore - EATS OTHER
CONSUMERS, EXAMPLES - LION,
WOLVES
3. Omnivore - EATS BOTH
PRODUCERS AND CONSUMERS,
EXAMPLES - HUMANS, BEARS, PIGS
4. Decomposer - BREAKS DOWN
DEAD ORGANISMS, EXAMPLES FUNGI AND BACTERIA
III. HOW ENERGY IS RELEASED?
A. Photosynthesis (chloroplast)CONVERTS ENERGY FROM THE
SUN TO SUGAR
6 CO2 + 6 H2O + SUNLIGHT 
C6H12 O6 + 6 O2
B. Respiration (mitochondria)CONVERTS SUGAR INTO ENERGY
C6H12 O6 + 6 O2  6 CO2 + 6 H2O
+
ENERGY
IV. ENERGY IS TRANSFERRED
THROUGH FOOD CHAINS, FOOD
WEBS, AND TROPHIC LEVELS
A. Food chain IS A SERIES OF
ENERGY TRANSFERS AS ONE
ORGANISM IS CONSUMED BY
ANOTHER. EXAMPLE - ALGAE
KRILL COD LEOPARD SEAL
KILLER WHALE
B. Food Web - MORE THAN ONE
FOOD CHAIN LINKED TOGETHER
Trophic Level_ - CHANGE IN
USEABLE ENERGY IN A FOOD
CHAIN/WEB,
MOST ENERGY AT THE BOTTOM
OF A TROPHIC LEVEL
V. WATER CYCLE:
A. SUNLIGHT CAUSES evaporation
& transpiration
B. WATER VAPOR COOLS AND
forms clouds
C. CLOUDS BECOME saturated
and precipitate
D. CYCLE repeats_
Source of Energy
Evaporation
Transpiration
Precipitation
Condensation
The movement through plants
The Clouds form
Transpiration
Precipitation
The rain falls
Evaporation
The vapor rises
Water Chemical Properties
-
-
H
H
Two atoms of
hydrogen
One atom of oxygen
o
+
Ground Water
VI. CARBON CYCLE:
A. CARBON DIOXIDE FROM
THE ATMOSPHERE IS USED IN
photosynthesis_
B. Oxygen_ IS RELEASED AS A BY
PRODUCT OF PHOTOSYNTHESIS
C. ORGANISMS TAKE IN OXYGEN
breath out_ CARBON DIOXIDE.
D. DECOMPOSING OF PLANTS
AND ANIMALS PRODUCES carbon
dioxide CO2__
E. BURNING OF _fossil fuels_
PRODUCES CARBON DIOXIDE
1990s values
VII. NITROGEN CYCLE:
A. NITROGEN GAS FROM THE
ATMOSPHERE IS ABSORBED INTO
THE ROOTS OF PLANTS BY
_nitrogen fixing bacteria_
B. ORGANISMS EAT plants
C. ANIMALS RELEASE AMMONIA
NH4 IN THEIR wastes
AMMONIA IS BROKEN DOWN INTO
NITROGEN BY decomposers
OTHER CYCLES:
SULFUR ,CALCIUM, PHOSPOROUS