 One of the major themes of life is
Interdependence, which states that
organisms are dependent on one
another & their env’t
 ECOLOGY – The study of the
interactions of living organisms w/
one another and w/ their env’t
I. Introduction
A. Groups of Organisms
1. Population – group of organisms of the
same species living in a particular place
at a particular time.
a. Species: a group of organisms that
look alike, are genetically similar, &
can reproduce
b. In biology, these organisms will
interbreed & mate w/in the population
c. Examples:
2. Community – Different populations that live
in the same area & interact with one another
--Example: Marine community
3. Biome/Ecosystem – Communities of living things
interacting with each other AND with their physical env’t.
-- Example: Tropical Rainforest, Desert, Savannah, Tundra
4. Biosphere – All the life supportive env’ts and
organisms on this planet.
B. Three important characteristics of every
population:
1. geographic distribution (i.e. the area
being inhabited)
2. size & density (# of organisms in an area
and how are they dispersed)
3. growth rate (i.e. do they grow, stay the
same, or decrease in size)
 growth: 1. when birth > death
2. immigration – move into pop.
 decrease: 1. when birth < death
2. emigration – move out of pop.
C. Organisms in a Population are Dispersed
 Dispersion – How individuals w/in Pop. are
arranged
1. Clumped – Individuals are bunched
together into clusters
2. Even/Uniform – Individuals are located at
regular intervals
3. Random – location is self-determined
II. Predicting population growth
 Considers Carrying Capacity – The Pop. size
that an env’t can sustain. Affected by
predators,
prey, resources, etc.
 Pop. < carrying capacity = rapid growth
 Pop. reaches carrying capacity = growth
stops (death rate = birth rate)
 Two basic types of growth…
a. Exponential growth curve
- unlimited resources
- predators are few or
non-existent
b. Logistic model
- declining resources
(i.e. competition)
- increases in # of predators
Limits to Growth within a Population
 Limiting resources – growth depends on
those resources needed for survival
(ex. food, water, shelter)
 Limiting Factors – factors that cause
population growth to stop by depleting
limiting resources
(ex. Disease, hunting, natural disaster,
deforestation, climate)
III. Types of Populations
A. r-strategists – Exhibit exponential
growth when conditions allow
(Ex: cockroaches, fruit flies)
B. K-strategists – Population is usually
near the carrying capacity
(Ex: whales, humans)
IV. Population Genetics: How Populations Evolve
 There are a variety of factors that affect
how a population evolves (Hardy-Wein.):
1. Mutations – Very slow, affects are seen over
long period of time (source of variations)
Ex: cancer, bacteria strains
2. Gene Flow – Migration, mov’t in/out of Pop.
3. Non-random Mating (selection): inbreeding
4. Genetic Drift – certain genes only found in
1 or 2 indiv. (small Pop. affected most)
5. Natural selection – “survival of the fittest”
-- strongest individuals will pass on traits
COMMUNITIES
What is Community Ecology?
The study of how populations of organisms
(living in a small area) interact with each other
I. Characteristics of Communities
A. Community Interactions
 Populations of organisms often interact
w/ each other in complex ways.
1. Predator-Prey Interaction
- Predation – one organism (predator)
captures & feeds on another (prey)
2. Competition – when organisms compete
with each other for resources (food/shelter)
3. Symbiosis – any relationship in which two
organisms live closely together. Four types:
a. mutualism - when both organisms benefit
b. commensalism - when one benefits and the
other is unaffected
c. amensalism - when one is harmed & the
the other is unaffected
d. parasitism - when one benefits & the other
is harmed
effects on organism 2
BENEFIT HARM
effects on
organism 1
NO
EFFECT
BENEFIT
mutualism predation/ commensalism
parasitism
HARM
predation/ competition amensalism
parasitism
NO
EFFECT
commensalism amensalism
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B. The Ecological Niche
1. The ecological position of a species in a
community. The “role” it plays in the
community & larger ecosystem
(ex. An animals place in the food web)
2. Includes the physical and biological
conditions needed to survive.
(ex. food source, temp, live near water…)
Ecosystems
(a.k.a. Biomes)
A “Community” of living things together WITH the physical env’t.
(how populations interact with each other AND their
environment)
I. What is an Ecosystem?
 The living organisms are known as biotic
factors
 The physical (i.e. non-living) aspects are called
abiotic factors (e.g. water, soil, climate, temp.)
 Together, these factors determine the survival,
growth & productivity of organisms & the
ecosystem
 Organisms create a habitat within an ecosystem
II. Energy Flow
 All living things require energy for metabolism and
growth
 The flow of NRG determines what kind & how many
organisms
an ecosystem
can support
A.
Producers
(a.k.a. Autotrophs)
1. The primary source of NRG is the sun
2. All life depends on organisms that can capture
solar NRG and convert it to chemical NRG (i.e.
glucose) during photosynthesis
3. Thus, they produce their own NRG and food
for other organisms
B. Consumers (a.k.a. Heterotrophs)
 organisms that must rely on other organisms for
food and NRG
PHOTOSYNTHESIS
Sun + 6CO2 + 6H2O  C6H12O6 + 6O2
C. Trophic Levels
1. a group of organisms that obtain their NRG
from a common source
2. NRG moves from one level to another
3. There are five levels…
1. Lowest level: Primary producers
(a.k.a. photosynthesizers)
Plants
Algae
Some bacteria
2. Level two: Primary consumers
 Eat the primary consumers
 known as Herbivores
Caterpillars
Grasshoppers
Mice
Geese
Cows
3. Level three: Secondary consumers
 Eat the primary consumers
 known as Carnivores – eat the herbivores
4. Level Four: Tertiary consumers
a. Top carnivores – eat all other animals
b. Omnivores – eat plants & animals
5. Level Five: Detritivores (a.k.a. decomposers)
- a class of consumers that obtain their NRG
from the organic wastes & dead bodies
produced at all trophic levels.
Bacteria
Worms
Fungi
Decomposers: worms, fungi,
bacteria help to recycle
nutrients and elements
II. Energy Flow Through an Ecosystem
 Exploring Feeding Relationships
A. Food Webs
a. interconnected network of food chains that
traces the directional flow of NRG in an eco.
b. animals feed at several levels, thus NRG
doesn’t flow in straight paths.
Food Web
B. Ecological Pyramids
1. Diagrams that show the relative amounts
of NRG and matter contained within
each trophic level.
2. Three types of pyramids:
ENERGY PYRAMIDS
1. organisms use NRG to metabolize, thus, much of their NRG is lost as heat
during biochemical reactions (can’t be used)
2. 10% RULE: only 10% of the NRG available at one trophic level is
transferred to organisms at the next level.
Energy Loss
Biomass Pyramid
(total amount of living tissue at each level)
Pyramid of Numbers
(shows the number of individual organisms at each troiphic level)
III. Ecosystem Cycles
 in addition to NRG, organisms need other
inorganic substances to fxn
 Although NRG flows in one direction;
carbon & other inorganic substances are
constantly recycle
 Biochemical cycle – substances pass
from nonliving env’t (e.g. soil, atmosphere)
to living things, & back to nonliving env’t
 Four critical substances needed to sustain
health of an ecosystem: C, N, P, H2O
A. The Water Cycle
1. Water vapor condenses and falls as precipitation
2. Some seeps into soil and becomes ground water (below surface)
3. Most runs-off surface back to oceans & lakes
4 Sun heats oceans & lakes and water evaporates back into the
atmosphere (transpiration – the evaporation of water from plants)
B. The Carbon Cycle
* carbon forms the backbone of all organisms
1. How is CO2 taken out of atmosphere?
 Photosynthesis
 CO2 is used by plants & algae to build GLUCOSE
 Consumers will get their carbon by eating other
organisms or their remains
2. How is C returned to the atmosphere as CO2?
a. Cellular Respiration by organisms:
6O2 + C6H12O6  6CO2 + 6H2O
b. Combustion
-- dead organisms decompose and form oil & coal
(i.e. fossil fuels) underground…humans BURN
-- humans also cut down and burn forests
c. Volcanic activity
The Carbon Cycle
C. The Nitrogen Cycle
* 78% of atmosphere is N2, but also in DNA, RNA, proteins
1. Though abundant, it can’t be used as a gas from the air.
Needs to be converted into a usable form (i.e. ammonia,
NH3), in a process called, nitrogen fixation
 done by bacteria in roots of plants and in soil
2. When organisms decompose, nitrogen is also put into
the soil as ammonia, which can be used by producers
3. Nitrification – ammonia is converted into nitrates (NO3-)
by different bacteria in soil
4. Denitrification – nitrates are converted back into
nitrogen
gas which is released back into atmosphere
The Nitrogen Cycle
D. The Phosphorus Cycle (for DNA/RNA)
* different b/c atmosphere doesn’t play a role
1. On Land:
 Phophorus exists primarily as phosphate (PO43-)
found in soil deposits, which can be absorbed by
plants & then eaten by consumers
 Consumers decompose & release phosphate back
into ground to be taken up by producers
2. In Ocean
 Phosphate also found in ocean sediment. When
erosion from land occurs or these sediments break
down, phosphate released into ocean & dissolved.
 Then taken up by algae, eaten by consumers, and
excreted back into ocean
The Phosphorous Cycle
IV. Nutrient Limitations
 The 4 cycles are imported b/c they provide ecosystem
w/ nutrients
 Primary productivity – the rate at which producers use
these nutrients to create organic matter.
 Short supply of any nutrient will slow growth and p
productivity (why farmers use fertilizers)
 Aquatic systems may get too much nutrient leading to
build up of algae, known as an algal bloom, which can be
bad if not enough consumer to keep in equilibrium
Human Impact on
the BIOSPHERE
1. Acid Rain – The acidified precipitation
that results when sulfur-rich smoke
combines w/ water vapor to produce
sulfuric acid
 The smoke is a result of power plants
burning fossil fuels (coal & oil),
as well as car exhaust
2. Ozone Depletion
a. Ozone (O3) – the layer of the
atmosphere that protects living
organisms from harmful UV
light
b. Ozone depletion results from CFC breakdown
1. CFC’s (ChloroFluoroCarbons) – molecules
containing chlorine, fluorine, and carbon
2. Sources:
Coolant systems
Aerosols
Foaming Agents
3. When CFC’s are released into the atmosphere,
UV radiation breaks the bonds, thus releasing
chlorine atoms which break down ozone
3. Global Warming
 The Greenhouse Effect –
The warming of the atmosphere due to
greenhouse gases (CO2, methane, nitrous oxide)
 Short wave solar NRG pass thru atmosphere
and hits earth
 Some is absorbed; some is reflected back into
the atmosphere as long wave radiation
 This radiation can’t pass thru clouds or CO2
 It is absorbed or reradiated back to earth
 Thus, earth is heated
 This is similar to a “greenhouse”
a. The greenhouse effect is enhanced by the burning of fossil
fuels and vegetation, which releases C into the atmosphere.
The C combines with O2 to form CO2
b. CO2 concentration and thus global temp has steadily
increased over the last 150 years (industrial revolution)
c. Future concerns?
1. Sea level rising (due to melting of glaciers and ice
caps)
2. Changes in weather patterns (severe weather)
II. Ecosystem Damage
A. Daily Environmental Damage
1. Chemical Pollution (in air, lakes,
oceans) kills wildlife & aquatic life
2. Agricultural Chemicals
 pesticides (DDT), herbicides, fertilizers
 Biological Magnification
 Chemicals breakdown
slowly in env’t and
collect in animal tissues
 Concentration of
chemical is increased
as it passes up thru
the food chain
3. Consumption/Destruction of resources
a. Species extinction: due to habitat loss (ex. deforestation
b. Loss of topsoil: due to overgrazing
c. Ground water:
1. Loss due to watering lawns, leaky faucets
2. Pollution b/c of improper chemical waste disposal
4. Human Population
a. possibly the single greatest threat
b. Its continued exponential growth will cause an increase
in waste, depletion of resources and habitat
c. however, new technology is allowing for better
sanitation,
recycling, medical care, etc.
III. Environmental Solutions
 Reduce global pollution
1. Stop CFC production
2. Restricted use of DDT and asbestos in U.S.
3. Reduce air pollution by decreasing
emissions of CO2, sulfur dioxide, soot
4. Better sewage facilities
5. Conserve energy (car pooling)
6. Recycle