Name ____________________________________________________
Test Date _________
UNIT 4 –ECOLOGY
I. INTRODUCTION TO ECOLOGY
(pp. 63, 64, 98-104)
A. Introduction
 Ecology is the study of interactions between organisms and their environment
 includes biotic, or _living___ factors
 and abiotic or _non-living_____ factors
 biotic factors and abiotic factors determine the health of an ecosystem and its _inhabitants
B. Levels of Organization
a. Species
b. Population
c. Community
d. Ecosystem
e. Biome
See Unit I- Intro to
Biology Notes
II. ENERGY IN AN ECOSYSTEM
(pp. 67-73)
 The ultimate source of energy for most life on earth is the _sun__
A. Autotrophs
 Self-feeders
 also known as _producers
 Most producers capture energy from the sun in a process called _photosynthesis_
B. Heterotrophs
 have to _obtain food
 also known as consumers
 There are several categories of consumers
1) Herbivores – Eat _producers (plants)
2) Carnivores – Eat _other consumers (animals)
3) Omnivores – Eat _producers & consumers
4) Decomposers – Break down _organic______ matter. Most are found in Kingdoms Eubacteria & Fungi
C. Energy in a Cell
 All producers__ and _consumers must convert _chemical energy present in _glucose into usable energy
 This is known as _metabolism
 The end-product is known as _ATP
 Most ATP is produced through the process of __cellular respiration
 The equation for Cellular Respirations is: C 6 H 12 O 6 + O 2 → CO 2 + H 2 O + ATP
III. ENERGY FLOW –
A COMPARISON OF PHOTOSYNTHESIS & CELLULAR RESPIRATION (p. 232)
Function
Cell Location
Occurs In
Reactants
Products
Overall Reaction
PHOTOSYNTHESIS
CELLULAR RESPIRATION
Use energy from sun to make glucose
Chloroplasts
Autotrophs
CO2 + H2O + energy
C6H12O6 + O2
CO2 + H2O + energy → C6H12O6 + O2
Release energy from glucose to make ATP
Mitochondria
Heterotrophs AND Autotrophs
C6H12O6 + O2
CO2 + H2O + energy
C6H12O6 + O2 → CO2 + H2O + energy
IV. Energy Flow in an Ecosystem
 Energy flows in _one_ direction
 CANNOT be recycled
 energy is captured by producers and converted to _glucose in _photosynthesis then used by the plants or
eaten by _consumers_______ to make _ATP
A. Trophic Levels
 step in the pathway of energy
 first trophic level is always a _producer
 2nd trophic level is known as the primary (1 o) _consumer may be herbivore____ or _omnivore
 last step is always a _decomposer
Energy (Sun) _ → __Producer____ → _1˚ Consumer (herbivore or omnivore)____ →2˚ Consumer (carnivore or
omnivore)_ → _Decomposer
B. Tracing Energy Flow
1. Food Chains
 illustrates how energy is transferred by showing _feeding relationships
 arrows show the direction of _energy transfer – means “is eaten by”
 consist of only _3___ or _4__ trophic levels

Which organism acts as a secondary consumer?

According to this food chain, which organism could be
described as an herbivore?

Which organism is the producer?

What are two terms that could be used to describe the hawk?
2. Food Webs



are more complex than a food chain
Most organisms eat & and _are eaten by a variety
of organisms
interconnected pathways are shown in a food web
According to this food web . . .

How many different producers are there?

Is the grasshopper a producer, primary, or secondary
consumer?

Is the grasshopper an herbivore, carnivore, or
omnivore?

What organism(s) acts as the decomposer?

Give an example of an organism in this food web that acts as secondary and tertiary consumer.

If all the squirrels in the community perished, would the hawk be able to survive? Explain.

If the grass was destroyed, which organism would be most directly affected? Explain.
3. Ecological Pyramids
 _10%__% of the energy stored in an organism is passed to the
next trophic level.
 _90___% of the energy is either used by the organism to
maintain _homeostasis____ or lost as _heat__ to the
environment
 Used to represent amount of _energy_____ or _matter__ at
each _trophic level
IV. ECOSYSTEM INTERACTIONS
(pp. 90-93)
A. The Niche
 The role an organism plays in its _community
 comprised of _biotic____ and _abiotic___ factors
 example:
o the type of food it eats
o how it obtains its food
o the way it is food for other organisms
o how & when it reproduces
o its physical living requirements to survive
B. Interactions Within a Community
1. Competition
o organisms are attempting to use the same _resources at the same time
2. Predation
o Predator killing and eating prey
3. Symbiosis
o A relationship in which two organisms _live very closely together
1. Mutualism Both organisms _benefit
 example, clown fish (Nemo) & sea anemone
2. Commensalism
 one organism benefits, the other organism _is not helped nor harmed
 example: barnacles on whales
3. Parasitism
 one benefits and the other is _harmed
 example: tapeworms, hookworms, ticks, lice
IV. POPULATIONS WITHIN AN ECOSYSTEM
(pp. 124-127)
 limiting factors- conditions that have an impact on population size
A. Density-Dependent Limiting Factors
 depend on population size
 example: competition__ and availability of _food___, _water__, and _sunlight
B. Density-Independent Limiting Factors
 affect all populations the same way, regardless of size
 Examples: unusual weather___, _natural disasters and human activities: cutting down trees, damming
rivers, etc
C. Climax Community
 a _stable___ community with very little population growth or decline
 carrying capacity__, a certain number of organisms that can exist successfully
 carrying capacity is exceeded, resources become a limiting factor______, and population numbers
_decline
IV. NUTRIENTS IN AN ECOSYSTEM
(pp. 74-80)
 only available to an ecosystem in specific quantities and must be _recycled_
 Nutrients may become a _limiting factor when depleted
 require nutrients to _build biomolecules, cells, tissues, etc
A. Carbon Cycle
 make _carbohydrates___, _lipids_, _proteins____, and _nucleic acids______
 taken up by _plants____ and _algae___ for photosynthesis
 CO2 is a waste product of cellular respiration
 Erosion, burning of _fossil fuels__, and _decomposition____ recycle carbon
B. Nitrogen Cycle
 require nitrogen to build _proteins____ and _nucleic acids
 atmosphere___ is mostly nitrogen
 only _bacteria can convert nitrogen from the atmosphere to a useable form, known as _nitrogen fixation
 absorbed by _plants__ and used to make _proteins & nucleic acids
 other organisms _eat plants and algae can re-use the nitrogen to build their own proteins___ and _nucleic
acids
 decomposers_____ return the nitrogen to the soil
C. Water Cycle
 Precipitation
 Evaporation
 Transpiration
 Condensation