Name ___________________________________________________________
Test Date ____________________
UNIT 4 – ECOLOGICAL STUDIES
I.
INTRODUCTION TO ECOLOGY
(pp. 63, 64, 98-104)
A. Introduction
Ecology is the study of interactions between organisms and their environment; therefore the study of ecology
includes biotic, or _______________ factors, as well as abiotic (______________________) factors.
B. Levels of Organization
1. __________________ - a group of similar organisms that can interbreed and produce fertile offspring
2. ___________________ - a group of organisms that belong to the same species and live in one area. The area in
which an organism lives is known as its ____________________.
3. ___________________ - many different species of organisms living in the same _________________
4. __________________ - a community and the ________________ factors that affect it
5. ___________________ - a group of ecosystems that have the same climate and similar _____________________
6. ___________________ - Earth
II. “THE STUDY OF . . . “
Ecologists spend large amounts of time investigating interactions between ____________ and _________________
factors. It is important that ecologists have an understanding of experimental design. An experimental design that is
flawed does not produce valid results or justifiable _____________________.
A. Laboratory Investigations - There are a variety of ways to conduct a laboratory investigation depending on the
desired outcome.
1. Comparative – A ________________________ of two or more things; for example, comparing plant cells with
animal cells under the microscope
2. Descriptive – Observational lab in which quantitative (_____________________________) and qualititative
(_________________________________________) information is obtained; for example, Seed Journal
3. Experimental – Designed experiment that follows the _______________________________________. Clearly
defined _____________ and test group(s).
B. The Scientific Method (pp.3-15)
The term, “scientific method” is misleading because it actually refers to a process that is neither reserved for ecologists
and other scientists, nor a methodical set of steps to be followed in a specific order. Instead, it is an ______________
pattern of thinking to solve everyday problems.
III. A CLOSER LOOK AT THE SCIENTIFIC METHOD
A. ________________________________
B. Forming a ________________________
A hypothesis is a _____________________________________________________________
C. Setting Up a Controlled _____________________
To test a hypothesis or find an answer to a question, a scientist will usually set up a controlled experiment. A
controlled experiment usually consists of two groups:
1. Control – Set-up used as a _______________________________________________________________
2. Experimental Group – Group in which all conditions are kept the same except for a ___________________. A
variable is a ________________________________________________. Only ______ factor should be
changed in each experimental group. This change is designed to ____________________________________.
a. Manipulated (independent) variable – factor that is _________________________________________
b. Responding (dependent) variable – condition that is ____________________________________________
D. Collecting Data
Data from an experiment should be presented in a concise and organized manner. Often __________ are used as a
visual representation of the results. The types of graphs used most often to illustrate results are:
1. ____________ Graph – Used to show relationship of a part to a whole
2. _____________ Graph – Used when independent variable isn’t continuous; for example, absorbency of different
brands of paper towels
3. ____________ Graph – Used when ___________________ variable is continuous; for example, time. A line
graph most clearly shows the relationship between the independent & dependent variables in an experiment. In a
line graph, the manipulated (independent) variable is plotted on the _____ axis and the responding (dependent)
variable is plotted on the ___ axis.
Manipulated (Independent) Variable:
_____________________________
Responding (Dependent) Variable:
__________________________
E. Analysis and Conclusion
After collecting data, a scientist must analyze the data and form conclusions based on the following questions:
1. Do the results ___________ or __________________ the ____________________________?
2. Is the experimental set-up _____________?
a. Was there a large enough ______________________?
b. Although no experimental set-up can be perfect, were the ________________________________ minimized?
c. Was there only _______________________________ tested?
3. Is the experiment ________________________?
F. Constructing a Theory
A scientific theory is an explanation that has been ___________________ many times by many different
____________________. Although a theory has been confirmed by repeated experiments, it may eventually be
_______________________.
IV. ENERGY FLOW
(pp. 67-73)
All living things require energy. The ultimate source of energy for the earth is the __________.
A. Autotrophs – “_________________________”. They are also known as _________________. Most producers
capture energy from the sun in a process called _________________________. Photosynthesis takes place in the
___________________________ of plant cells. The equation for photosynthesis is
__________________________________________________________________________________________.
B. Heterotrophs – Organisms that have to _______________________ are called heterotrophs or _______________.
There are several categories of consumers:
1. Herbivores – Eat _______________________________________________________
2. Carnivores – Eat ________________________________________________________
3. Omnivores – Eat ________________________________________________________
4. Detritivores – Obtain energy from ______________ bodies of plants and animals; for example, ____________
______________________________________
5. Decomposers – Break down _________________ matter. Most decomposers are in Kingdom
___________________ or Kingdom ____________________.
C. Energy in a Cell – All organisms (_______________________ and _________________________) must convert
_____________ energy present in _______________ and other food molecules into usable energy. This conversion
process is known as ___________________ and the end-product is a re-chargeable “battery” used by all cells for
energy known as _____________. Most ATP is produced through the process of ___________________________.
The equation for cellular respiration is
______________________________________________________________________________________.
V. ENERGY FLOW – A COMPARISON OF PHOTOSYNTHESIS & CELLULAR RESPIRATION (p. 232)
PHOTOSYNTHESIS
CELLULAR RESPIRATION
Function
Cell Location
Occurs In
Reactants
Products
Overall Reaction
VI. TRACING ENERGY FLOW
A. Trophic Levels - Each step in the pathway of energy flow is known as a __________________________. The first
trophic level is always a ____________________. The 2nd trophic level is known as the primary (1 o) ____________
and may be an ____________________ or ____________________. The last step is always a
_________________________.
B. Food Chains – A food chain illustrates how energy is transferred
by showing ________________________________
_________________________________________.
The arrows show the direction of _________________________.

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?
C. Food Webs – Typically feeding relationships are more complex than illustrated in a food chain. Most organisms eat
___________________________________________________ and ___________________________________ a
variety of organisms. These interconnected pathways are more accurately 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.
D. Ecological Pyramids – Although in theory, a food ____________ or food ___________ can consist of unlimited
numbers of __________________________, in actuality this does not take place. On average, only ________% of
the energy stored in an organism is passed to the next trophic level. ________% of the energy is either used by the
organism to maintain ____________________ or lost as ___________ to the environment. Because of this, most
food chains typically consist of only _____ or ______ trophic levels. Ecologists use ______________________ to
represent the amount of ________________ or _______________ at each _____________________________.
Pyramid of Numbers
VII. NUTRIENTS IN AN ECOSYSTEM
(pp. 74-80)
Unlike energy from the sun, nutrients are only available to an ecosystem in specific quantities and must be
_________________ within and between ecosystems. Nutrients may become a _____________________________
when they are depleted. Organisms require nutrients to ___________________________________________________.
Although all nutrients, including ____________, are re-cycled, there are a few nutrient cycles that are especially important.
A. Water Cycle
B. Carbon Cycle – Organisms require carbon to make _______________________, _____________,
_________________, and __________________________. Carbon dioxide in the atmosphere is taken up by
____________ and _____________ for ___________________. (Algae are autotrophic, unicellular organisms
with cell walls made of cellulose and chloroplasts that belong to kingdom ______________.). They produce
glucose for _______________________________. Humans and other _________________ eat plants & algae, or
they eat other organisms who have eaten plants & algae. The carbon from glucose is returned to the atmosphere
as __________, a waste product of cellular respiration. In addition, erosion, burning of _____________________,
and _____________________ recycle carbon.
C. Nitrogen Cycle – Organisms require nitrogen to build ________________ and ____________________.
The _________________ is mostly nitrogen, but only ____________________ produce the _________________
needed to convert nitrogen from the atmosphere to a useable form, a process known as _____________
___________________. After nitrogen fixation is carried out by bacteria in soil, the nitrogen compound in the soil
is then absorbed by ______________ and used to make __________ and ___________________. When other
organisms ___________________________________, they can re-use the nitrogen to build their own ____________
and _____________________. When organisms die, _______________________ return the nitrogen to the soil
where it may be taken up by _________________ again or returned to the atmosphere by other ______________.
UNIT 5 – ECOLOGICAL STUDIES
D. Phosphorus Cycle - All organisms require phosphorus for _____, _______, _______, and the
____________________________ of the cell membrane. Phosphorus is found in soil and rocks, absorbed by the
____________ of plants, where it is transported through the rest of the plant by the ________________.
______________________ eat plants, which is then returned to the soil
E. Nutrient Limitation – When nutrients are scarce in an ecosystem, they are described as __________________
_________________. This imposes restrictions on the number of organisms, an organism’s growth, and the
______________________________ of the system. For example, run-off from fertilized fields can trigger algae
blooms in aquatic systems.
VIII. ECOLOGICAL SUCCESSION (pp. 94-97)
Ecosystems are constantly changing in response to natural and human disturbances. As an ecosystem changes, older
Inhabitants gradually die out and new organisms move in, resulting in further changes in the community. Ecological
succession refers to a series of _____________________ changes that occur in a _____________________ over time.
A. Primary Succession – Occurs following destruction of ___________; for example, after _________________
eruption, glaciers melting
 First species to populate area known as ____________________ species
 Lichens are the most common pioneer species after a volcano because they are capable of growing on bare
rock. A lichen is a ____________ and ______________ living together. Cyanobacteria are
____________________ bacteria. In a lichen, the cyanobacteria provides _________ for the fungus and
the fungus provides _________ and _____________________ for the cyanobacteria.
B. Secondary Succession – Occurs when a disturbance of some kind changes an existing community without
removing the ____________; for example, ___________, clearing land.
IX.
ECOSYSTEM INTERACTIONS
(pp. 90-93)
Ecosystems are influenced by a combination of _____________ factors and _______________ factors. Together they
determine the health of an ecosystem and its _____________________.
A. The Niche - The role an organism plays in its _________________ is its _____________. An organism’s niche is
comprised of _________ and ___________ factors, for example, the type of food it eats, how it obtains its food,
the way it is food for other organisms, how & when it reproduces, its physical living requirements to survive, etc.
B. Interactions Within a Community – Community interactions have a powerful effect on an ecosystem:
1. Competition – Competition occurs when organisms are attempting to use the same __________________ at the
same time. Each different species within a community must have its own ___________.
 Competitive Exclusion Principle – No two species can occupy the same ________ in the same
__________________ at the same time.
2. Predation – The organism that does the killing and eating is the ________________ and the food organism is the
_____________.
3. Symbiosis – A relationship in which two organisms _______________________________________ is described
as symbiosis. There are three main types of symbiotic relationships:
a. Mutualism – Both organisms ____________. For example, virtually all plant roots have mycorrhizae – a
________________ that resides within the plant roots. Fungus enhances absorption of _____________ and
______________ in roots; plant provides ______________ for the fungus.
b. Commensalism – In commensalism, only one organism benefits, but the other organism ________________.
For example, barnacles are small ___________________ that often attach themselves to whales. They do not
harm the whales, and the barnacles benefit from the _________________________________________.
c. Parasitism – In parasitism, only one organism benefits and the other organism is ______________ by the
relationship. The organism that is harmed is known as the _______. Examples of parasites include
___________________________________________________________________.
X.
POPULATIONS WITHIN AN ECOSYSTEM
(pp. 124-127)
Populations within an ecosystem cannot have unlimited growth. There are conditions that have an impact on
population size known as ________________________. Limiting factors may described as density-dependent or
density-independent.
A. Density-Dependent Limiting Factors – Density-dependent factors depend on population size; for
example, __________________ and availability of _____________, ____________________, and
_______________________.
B. Density-Independent Limiting Factors – These are factors that affect all populations the same way,
regardless of size. Examples include _____________________________________, _______________
__________________, and human activities such as ________________________________________
___________________________________________________________________________________
C. Climax Community – A climax community is a ______________ community with very little population
growth or decline. Each ecosystem has a ___________________________, a certain number of
organisms that can exist _______________________. When the carrying capacity is exceeded,
resources become a ______________________________, and population numbers _______________.