Chapter 18: Introduction to Ecology
Section 1 Vocabulary Pretest
1.
2.
3.
4.
5.
6.
7.
Ecology
Interdependence
Ecological Model
Biosphere
Ecosystem
Community
Population
A. Thin zone of Earth that supports
life
B. All organisms living in a certain
area
C. All the members of one species
in one area
D. Study of the relationship of
organisms and their environment
E. All living things depend on other
living things
F. All living and nonliving parts of
an environment
G. Used to study the complexity of
ecosystems
Answer Key
1.
2.
3.
4.
5.
6.
7.
Ecology
Interdependence
Ecological Model
Biosphere
Ecosystem
Community
Population
D
E
G
A
F
B
C
Ecology and Interdependence
• Ecology is the study of the interactions
between organisms and the living and
nonliving components of their
environment.
– Interdependence is a key theme
found throughout ecology.
– Living things depend on each other
in complex ways for survival.
– Ecological models can be
used to study this complexity.
Levels of Organization
• The hierarchy of environmental organization
from largest to smallest is: Biosphere,
Ecosystems, Communities, Populations,
and Organisms.
• Biosphere —thin zone of the Earth that
supports life.
– 20 km thick from the bottom of the ocean
to the lowest atmosphere.
– Three parts:
• lithosphere—land on the surface
• hydrosphere—water on the Earth
• atmosphere—air that surrounds Earth
Ecosystems
• Biosphere is made of many smaller parts called
ecosystems.
• Ecosystem—all living and nonliving parts of an
environment. Every ecosystem is able to support
itself and has both biotic and abiotic factors:
– Biotic factors—living organisms
– Abiotic factors—nonliving parts: air, water, sunlight,
soil, temperature, pH, humidity, salinity, oxygen
concentration, availability of nitrogen, etc. They are
not constant—vary from place to place and over time.
• Examples: pond, garden, riverbank, puddle of
water.
Communities and
Populations
• Each ecosystem is made up of
one or more communities.
– Community—all the organisms
living in a certain area.
Example: pond community
• Each community is made up of
populations.
– Population—all the organisms of
the same species living in the
same area.
Example: frogs in a pond
Section 2 Vocabulary Pretest
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Habitat
Biotic factor
Abiotic factor
Tolerance curve
Acclimation
Conformer
Regulator
Dormancy
Migration
Niche
Generalist
Specialist
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
Nonliving things
Living things
Place where an organism lives
Adjusting tolerance to abiotic factors
Cannot regulate internal conditions
Range of conditions that can be stood
Temporarily moving away
Temporarily not growing
Organisms job or role
Organism with narrow niche
Organism with broad niche
Can regulate internal conditions
Answer Key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Habitat
Biotic factor
Abiotic factor
Tolerance curve
Acclimation
Conformer
Regulator
Dormancy
Migration
Niche
Generalist
Specialist
C
B
A
F
D
E
L
H
G
I
K
J
Surviving in an Ecosystem
• Each organism has a limited range of
environmental conditions in which they can
survive.
– The range for a particular factor can be
measured using a tolerance curve
– Some organisms can adjust their tolerance to
abiotic factors through the process of
acclimation.
• Happens within an organism’s lifetime (not like
adaptation)
Strategies for Tolerance
• Two strategies exist to deal with
fluctuations in environments.
– Conformers—organisms who do not regulate
their internal conditions; they change with the
environment. Ex: ectothermic animals
– Regulators—organisms that use energy to
control some of their internal conditions.
Ex: endothermic animals
Escaping Unfavorable Conditions
• Sometimes, adjusting isn’t possible and
organisms must temporarily escape.
Ex: Lizard hiding in the shade
Seed dormancy or animal hibernation
Migration
Habitats and Niches
• Habitat—place where an organism
lives. It provides food, water, shelter,
and a place to reproduce. Example:
a woodpecker’s habitat is the trees in
a forest.
• Niche—everything an organism does
and everything it needs in its habitat.
It is often defined as an organism’s
job or role in its community.
Example: a woodpecker’s niche is
catching and eating insects.
Generalist vs. Specialist
• Generalist—species
with broad niches
– Ex: opossum (eats
almost anything)
• Specialist—species
with narrow niches
– Ex: koala (eats
eucalyptus leaves only)
Section 3 Vocabulary Pretest
1. Producer
2. Chemosynthesis
3. Gross primary
productivity
4. Biomass
5. Net primary
productivity
6. Consumer
7. Herbivore
A.
B.
C.
D.
An organism that eats food
An organism that makes food
An organism that eats plants only
An organism that uses chemicals to
generate energy
E. Rate at which biomass accumulates
F. Rate at which producers capture energy
from sunlight by producing organic
compounds
G. All organic material produced in an
ecosystem
8.
9.
10.
11.
12.
13.
14.
Carnivore
Omnivore
Detritivore
Decomposer
Trophic level
Food chain
Food web
H. An organism that eats both
producers and consumers
I. Model of the flow of energy
through an ecosystem
J. An organism that breaks down
organic material by causing decay
K. An organism that feeds on the
“wastes” of an ecosystem
L. An organism that eats other
consumers.
M. Many food chains combined
N. An organism’s position in a
sequence of energy transfers
Answer Key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Producer
Chemosynthesis
Gross primary productivity
Biomass
Net primary productivity
Consumer
Herbivore
Carnivore
Omnivore
Detritivore
Decomposer
Trophic level
Food chain
Food web
B
D
F
G
E
A
C
L
H
K
J
N
I
M
Energy and the Environment
• Sunlight—main source of energy in an ecosystem.
– In photosynthesis, plants change light energy from the
sun into chemical energy stored in food.
– Some of the plant’s food energy is used for their own
growth and reproduction. The rest is stored.
– Animals eat the plants and use the stored food for
energy for growth, reproduction and movement.
Ecological Classification of
Organisms
• Ecologists classify organisms into two
major groups according to the way they get
food:
– Producers—make food
– Consumers—eat food
Producers
• Producers—make or produce their own
food. Examples:
Some protists
All plants
Some bacteria
Types of Producers
• Photoautotrophs—use
solar energy
(photosynthesis) to
produce sugar
• Chemoautotrophs—use
energy stored in
inorganic molecules
(chemosynthesis) to
produce carbohydrates
Measuring Productivity
• Gross primary productivity—the rate at which producers
capture energy from sunlight by producing organic
compounds.
– Measured in biomass —organic material that has been produced in
an ecosystem
• Net primary productivity —rate at which biomass
accumulates
– Expressed in kcal/m2/yr or g/m2/yr.
– Calculated by: Gross primary productivity minus the rate of
respiration in producers.
The graph shows the net primary productivity varies between biomes.
The rainforest is 25 times greater than the desert of the same size.
Variations in light, temperature and precipitation account for the difference in
terrestrial biomes. Variations in light and availability of nutrients accounts for
differences in aquatic biomes.
Consumers
• Consumers—get food by eating other
organisms or organic wastes.
(Heterotrophs)
• Four types:
Herbivores—eat producers
Omnivores—eat producers
and consumers
Carnivores—eat other consumers
• Detritivores--feed on “wastes” (dead plants, animal
wastes, and dead animal carcasses.)
– A few are specifically classified as decomposers because they
cause decay and return important nutrients to the soil.
Detritivores
Decomposing Detritivores
Energy Flow
• Energy flow through an
ecosystem can be illustrated
using trophic levels (shows an
organism’s position in a
sequence of energy transfers)
• 1st level = producers
• 2nd level = herbivores
• 3rd and higher levels = predators
• Consumers are also grouped into feeding or
trophic levels according to the foods they eat.
• Many organisms feed at more than one level,
especially omnivores.
C1—first level consumers:
eat plants
C2—second level consumers:
eat C1 consumers
C3—third level consumers:
eat C2 consumers
Food Chains
• Food chain—model of the flow of energy
through the organisms of an ecosystem
– Source of energy is the sun.
– Arrows always point in the direction of the
flow of energy.
– Energy that flows through a food chain is not
recycled. Sunlight must continue to flow
through the biosphere to power the food chain.
A food chain from a typical meadow ecosystem.
C1
C2
C3
Food Webs
• Food web —many food
chains combine to form a
food web. It is generally a
better model because it
gives more information.
– The members of a food
web can be identified by
their trophic level.
– Many organisms function
on more than one trophic
level.
Which is a producer?
Which are C1 consumers?
Which are C2 consumers?
Which is a C3 consumer?
Which is a C4 consumer?
A complex food web from an aquatic ecosystem
Energy Pyramid
• An energy pyramid is a model that
shows how the amount of energy
decreases at each level of the food
chain.
– Some escape being eaten so their
energy is never transferred to the next
level.
– Animals gain only a small amount of
energy from the food they eat. Some
parts of prey cannot be broken down for
food (Ex: antlers and hoofs)
– Much of the energy is used up or is
released as heat energy.
– Therefore, fewer organisms can be
supported at each level of the pyramid.
A kilocalorie is a
measure of
energy. The
energy transfer
from one level
to the next is
about 10 %.
For example:
if there are
1,000 kcal at
one level, only
100 kcal are
transferred to
the next. Thus
each level can
support fewer
and fewer
organisms.
Cycles in Nature
• Many of the abiotic factors in an ecosystem
pass through cycles that allow the substances
to be used and reused.
• Four important cycles of abiotic substances
include:
–
–
–
–
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Water Cycle
• Water also passes through both living and
nonliving parts of the environment. The water
cycle is maintained by evaporation,
transpiration, condensation and precipitation.
• Evaporation = adds water as vapor to the atmosphere.
Water evaporates as water, soil, and living bodies heat up.
• Transpiration = evaporation of water from plants…causes
them to take in more water.
• Condensation = change of water from a gas to a
liquid…causes the formation of clouds in the water cycle.
• Precipitation = the return of water from the
atmosphere…the amount of water the atmosphere can hold
depends on temperature and air pressure…when clouds
become saturated with water vapor, precipitation falls.
– Types: Rain, snow, sleet, hail and fog
Carbon Cycle
• Photosynthesis and cellular respiration form the basis of
the carbon cycle.
• In the past 150 years, atmospheric carbon dioxide has risen
more than 30%..mostly due to the burning of fossil fuels
Nitrogen Cycle
• Air is 78% nitrogen gas. Most organisms cannot use nitrogen in this form.
• Nitrogen-fixing bacteria change nitrogen gas into nitrates which can be
used by living things to make proteins and nucleic acids.
– Live in the soil and on the roots of certain plants (beans, peas, clover
and alfalfa).
– Receive carbohydrates from plants and produce nitrogen for plants
– Release extra nitrogen into the soil.
• Decomposers--make the nitrogen from decaying organisms and wastes
available in the soil by turning it to ammonia (NH3) which changes in the
soil to ammonium (NH4+) in a process called ammonification.
• Soil bacteria turns ammonium into nitrites (NO2-) and nitrates (NO3-) in a
process called nitrification. Plants can use the nitrates and then animals
can eat the plants.
• Anaerobic bacteria return nitrogen to the air by breaking down soil
nitrates in the process of denitrification.
Phosphorus Cycle
• Phosphorus is necessary for healthy bones, teeth, and the formation of DNA
and RNA.
• The erosion of rocks is important in adding phosphorus to the soil and water.
• Excreted wastes and decaying organisms also add phosphorus to soil and
water.
• Plants absorb phosphorus. Animals get phosphorus from plants.