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ECOSYSTEM
ORGANIZATION
And POPULATIONS
OVERVIEW
Ecosystem Organization
 Ecology
is the study of the
interactions of organisms with
one another and their physical
environment.
Ecosystem Organization

Every organism has a habitat,
where organism lives, and a
niche, role or job of organism in
the ecosystem.
Ecosystem Organization
 The
interactions of
the organisms may
be studied as
populations,
communities,
ecosystems or the
entire biosphere.
Ecosystem Organization
 Organism
is a single
living thing.
Ecosystem Organization
 Population
is the number
of individuals of the same
species in the same place
at the same time.
Factors That Control
Population Growth
 Populations
don’t grow indefinitely
because of Limiting Factors.
 The
major limiting
factors are
FWSS:
– Food
– Water
– Shelter
– Space
Other Factors That Control
Population Growth
Other Limiting
Factors:
 Competition
 Predation
 Parasitism
 Crowding
 Natural disasters
 Disease
What dynamics might be
involved in predicting
population growth?
 Population
Size
 Population Growth Rate
 Carrying Capacity
 Limiting Factors
Population Size
 Number
of
individuals in a
population
 Growth occurs
when the
birthrate is
greater than
the death rate.
Population Growth Curves
Exponential growth:
Population
increases by a
constant
proportion per
unit of time
 At this growth rate
the population
exhibits a Jshaped curve

70
60
50
40
Exponential
30
B
20
10
Lag
0
A
0
1
2
3 4
Time
5
6
Population Growth Curves


At this growth rate the
population exhibits an
S-shaped curve.
K (carrying capacity) =
maximum population
size that an
environment can
support
600
500 K carrying capacity
K
400
Population

Logistic growth:
Population increases
rapidly for a period of
time, its growth begins
to slow, and ultimately,
growth stops.
stabilization
300
200
100
exponential
0
lag
0
10
20
Time (in days)
30
Natural Selection
and Populations

Relate the five concepts of natural
selection to Logistic Graph.
Genetic variation
 Numbers increase
 Competition
 Survival of the
fittest
 Descent with
modification

Event A
Event B
Event C
Event D
Ecosystem Organization
 Community
is all of the
different populations
living in a given area
and time.
Biodiversity

Number of
different
species living
within an
ecosystem.
How Biodiversity Impacts
Population Growth
6 forces that cause populations to evolve:
 Mutation – ultimate source of all variation
 Migration – movement of organisms from one
population to another, creates gene flow.
 Nonrandom mating – when individuals prefer to
mate with others of their own genotype, inbreeding
is an example.
 Genetic drift – random change in response to their
environment.
 Natural selection –Survival of the fittest.
 Extinction- species that have disappeared
permanently.
Ecosystem Organization
 Ecosystem
is all of the
communities (biotic) and
all of the physical factors
(abiotic) in an area.
Biotic & Abiotic Factors
Biotic =

Living organisms
Abiotic =


Nonliving
Include air, water,
temperature, moisture,
light, and soil.
Ecosystem Organization
 Biosphere
is all of the
areas on Earth where
organisms live.
Energy Flow in
Ecosystems
 Energy
flows
into the
biological
world from
SUN, the
ultimate
source of all
energy.
Producers
 Producers
are
autotrophs…
they can make
their own food
through
photosynthesis or
chemosynthesis
 Plants, some
bacteria, and
algae
Consumers
 Eat
other
organisms to
obtain energy;
 also known as
heterotrophs
 Example:
cows,
humans…
Decomposers
Consume organic
wastes (feces, urine,dead
leaves or bodies)
 Receive energy from
every other type
 Responsible for the final
step in the food chain
 Example:
Earthworms, maggots,
fungi, and some bacteria
