Name ______________________________________________________________________________ Test Date________________
UNIT XII –ECOLOGY
I. WHAT IS ECOLOGY? (Pgs 32 – 37)
A. _____________________ is the study of the interaction among and between organisms and their environment. Interactions within
the biosphere produce a web of interdependence between organisms and the environment in which they live. It is this
interdependence of life on Earth that contributes to an ever-changing, or dynamic, biosphere.
B. Levels of Organization
Species - A group of similar organisms so similar to one another that can interbreed and produce _________________________.
Populations - Groups of organisms that belong to the same species and live in the same area (__________________________).
Community – The assemblage of different _________________________________________ that live together in a defined area.
Ecosystem – all the organisms that live in a particular place, together with their _____________________, or physical, environment.
Biome - is a group of ecosystems that have the same __________________ and similar dominant ________________________.
Biosphere – highest level of organization; includes all the ______________________ & ______________________ components.
II. ENERGY FLOW (Pgs 41 – 44)
All living things require _______________________. The ultimate source of energy for all living things on Earth is the ___________.
A. Producers– Organisms that are able to capture energy from _____________________ or ________________________ and use
it to produce food are known as autotrophs. They use energy from the environment to fuel the assembly of simple inorganic
compounds into complex organic molecules. (Ex. carbs, lipids, proteins, nucleic acids) Because these organisms make their own
food, they are also known as _______________________________________. The amount of organic matter that the
photosynthetic organisms of an ecosystem produce is called ______________________________________________________.
 Some producers capture light energy from the sun and transform it into the chemical energy of organic molecules in a
process called _____________________________. Photosynthesis takes place in the ______________________________
of plant cells. The equation for photosynthesis is: ___________________________________________________________
 Other producers are able to capture energy stored in the chemical bonds of molecules to make food in a process called
___________________________________________.
Examples of autotrophs: plants, algae, kelp, plankton, and some bacteria (cyanobacteria).
B. Consumers – Organisms that rely on other organisms for their energy/food supply are called heterotrophs or ______________.
There are several categories of consumers.
1. Herbivores – eat only plants or __________________________…. Ex. deer, cow, caterpillars
2. Carnivores – eat animals (other consumers)……..Ex. snakes, owls, coyotes
3. Omnivores – eat both plants and animals……Ex. humans, bears
4. Detritivores – obtain energy from dead bodies of plants and animals. Ex. mites, earthworms, snails, crabs, vultures
5. Decomposers - cause decay by the breakdown of organic matter & releases the nutrients back to the environment to be
used again by other organisms. Ex. Kingdom _______________________________________________________________
C. Feeding Relationships – Energy flows through an ecosystem in one direction; it
cannot be __________________. Energy flow begins with the ____________, is captured
by ________________________, then transferred to various _______________________.
Ecologists assign every organism in an ecosystem to a ____________________________,
which is a step in the pathway of energy flow and is determined by the organism’s source
of energy.
 1st or lowest trophic level = __________________________________________
 2nd trophic level = _________________________________________and may be
an _________________________________________________.
 3rd trophic level = ___________________________________, animals that eat other
consumers (herbivores or omnivores).
 Many ecosystems contain a 4th trophic level, consisting of carnivores that consume
other carnivores – these are called ______________________________________.
 Ecosystems also contain ___________________________ at the end, which serve a
primary purpose of decomposition, or replenishing the ecosystem with important
_______________________________ from dead organisms.
D. Illustrating Energy Flow – There are several illustrative techniques used by ecologists to show energy flow in an ecosystem.
1. Food Chains – A series of __________________ steps beginning with a producer, illustrating the transfer of energy through
organisms eating and being eaten. The arrow in a food chain always means “is consumed by”. Food chains are organized
into trophic levels.
Example: sun  grass(producer)  grasshopper(1˚consumer)  lizard(2˚consumer)  owl(3˚consumer)
Example: sun  cattail(producer)  caterpillar(1˚consumer)  frog(2˚consumer)
2. Food Webs – In most ecosystems, energy does not follow simple linear pathways because organisms have a tendency to
eat a ___________________ of organisms and are eaten by a _________________ of organisms. This creates a complicated,
_______________________ path of energy called 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.
E. Ecological Pyramids – diagrams that show the relative amounts of ______________________ or ________________________
contained within each trophic level in a food chain or food web.
1. Energy Pyramid – there is no limit to the # of trophic levels that a food chain can support; however, there is a slight
drawback to having many trophic levels. Only part of the energy (approximately ______%) that is stored in one trophic level
is passed on to the organisms in the next trophic level. This is because organisms have to __________ much of the energy
(______%) that they consume for life processes in order to maintain homeostasis (cell respiration, movement, reproduction);
and some is released or lost to the environment as _______________. Therefore, at each trophic level, the energy stored by
the organism is about one-tenth of that stored by the organisms in the level below. Because of this, most food chains
typically consist of only 3 or 4 trophic levels. (more levels = less energy available)
III. CYCLES OF MATTER (Pgs 45 – 49)
Nutrients In An Ecosystem – 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 recycled, there are a few nutrient cycles that are especially important.
A. Water Cycle – Water enters the atmosphere in the form of water vapor. Water vapor then condenses falls to ground in form of
rain or snow. Some of this precipitation becomes runoff from the ground and collects in rivers, lakes, streams, oceans. The rest
evaporates and condenses into clouds in the atmosphere. Rainfall then sends water back to earth taken up by the roots of
plants to be used for photosynthesis. Water then moves into the atmosphere by evaporating from the leaves
(________________________________________) through openings called __________________________________)
B. Carbon Cycle – Organisms require carbon to make organic
molecules like carbs, lipids, proteins, & NA’s. Four main
processes move carbon through its cycle:
1. Biological processes like______________________
_________________________________________,
decomposition.
2. Geochemical processes like ___________________
& __________________________________activity
(atmosphere & oceans)
3. Mixed biogeochemical processes like
___________________________________ and
_______________________ of dead organisms and
their conversion under pressure into coal and
petroleum (____________________________) –
these store C underground.
4. Human activities – mining,
_____________________________ forests, burning
fossil fuels (release CO2 into atmosphere)
C. Nitrogen Cycle – Organisms require nitrogen to build
_____________________ and _________________ acids.
The atmosphere is very rich in nitrogen gas, or N2; however,
most organisms are unable to use that gas because the two
nitrogen atoms in a molecule of N2 are connected by a triple
covalent bond. Only bacteria produce the _______________
needed to convert nitrogen from the atmosphere to a useable
form. They do this through a process known as
____________________________________. After nitrogen
fixation is carried out by bacteria in soil, the nitrogen
compound is then absorbed by plants and used to make
proteins. When organisms die, decomposers return the
nitrogen to the soil where it may be taken up by producers
again or returned to the atmosphere by other soil bacteria,
through a process called ____________________________.
D. Phosphorus Cycle – It is an important component of __________________________________. Phosphorus is found in soil and
rock as calcium phosphate, which dissolves in water to form phosphate ions (PO4). This phosphate is absorbed by the roots of
plants and used to build ATP and DNA. Heterotrophs that eat the plants reuse the organic phosphorus, and then when these
animals die and decay, the bacteria in the soil convert the phosphorus from the organic molecules back into PO4.
E. Nutrient Limitation – when an ecosystem is limited by a single nutrient that is scarce or cycles very slowly. This can limit an
organism’s growth & have an impact on the ____________________________________ of an ecosystem. Ex. Open oceans are
normally nutrient-poor compared to the land – 1/10,000 the amount of N found in soil. Runoff from heavily fertilized fields can
result in an __________________________________, which if there aren’t enough consumers to eat the algae, it can disrupt the
equilibrium of an ecosystem.
IV. WHAT SHAPES AN ECOSYSTEM?
A. Biotic & Abiotic Factors (Pg 35)
Ecosystems are influenced by a combination of biological (___________________) and physical (__________________) factors.
Together biotic and abiotic factors determine the health of an ecosystem and its productivity.
Biotic – all the ______________________ factors; trees, mushrooms, bacteria, disease, competition, algae, predators, prey, etc
Abiotic – all the ________________________ factors; temp, pH, precipitation, humidity, wind, nutrient availability, soil type, sun.
B. The Niche (Pg 38)
A niche is an organism’s way of making a living (_______________ that it plays in its community). It is comprised of physical and
biological factors, like the type of food it eats, how it obtains its food, the way it is food for other organisms, how and when it
reproduces, its physical living requirements to survive, etc. No two species share the same niche in the same habitat at the same
time – this is known as the _________________________________________________________________________________.
Ex. – you can have 3 species of North American warblers in the same spruce tree – but they will feed at different elevations & in
different parts of the tree.
C. Community Interactions (Pgs 38 – 40)
Community interactions, such as _______________________________, ___________________________, and various forms of
____________________________________, can have a powerful effect on an ecosystem.
1. Competition –when organisms of the same or different species attempt to use an ecological _________________________
(H2O, nutrients, light, food, or space) in the same place at the same time. Direct competition often results in a winner and a
loser (who fails to survive).
2. Predation – interaction in which one organism captures and feeds on another organism. The organism that does the
killing/eating is called the predator, and the food organism is the prey. Predators have specialized ways to go about
capturing and killing their prey.
3. Symbiosis – relationship in which two species _______________________________________ – “living together”.
Three main types of symbiotic relationships:
a. Mutualism – both species ______________________.
Ex- flowers & insects; Nitrogen fixing bacteria and plants; E.coli in the large intestine; alligator and plover birds.
b. Commensalism – only ________________ organism benefits, & the other organism is neither helped nor harmed.
Ex. barnacles on a whale’s skin, sea cucumber and pear fish
c. Parasitism – only one organism benefits, & the other organism is ______________________ by the relationship. The
organism that is harmed is known as the host.
Ex. – tapeworms, fleas, ticks, lice
D. Ecological Succession (Pgs 62 – 64)
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, causing further changes in the community.
Ecological succession – a series of predictable ____________________ that occurs in a community ____________________.
1. Primary Succession – Occurs on surfaces where __________________ exists. Ex: after volcanic eruption, glaciers melting
a. First species to populate the area is called the ____________________________________.
b. ____________________ is the most common pioneer species after a volcano because they are capable of growing on
bare rock. A lichen is a fungus and a cyanobacterium living together. Cyanobacteria are photosynthetic bacteria. In a
lichen, the cyanobacteria provides food for the fungus and the fungus provides water and minerals for the
cyanobacteria. As lichen grows, it helps to break up the rocks. When lichen die they add organic material to help form
soil to support plants.
2. Secondary Succession – Occurs when a disturbance of some kind changes an existing community without removing the
____________________________. Ex: clearing land, plowing, wildfires.
a. Ecologists believe that succession in a given area proceeds in predictable stages ending with a mature, stable
community, referred to as a __________________________________.