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Name ___________________________________________
Ecosystems EOG Review Guide
Factors in an Ecosystem:
An ____________________ includes all the _______________ (living) and ____________________ (nonliving)
parts of an environment as well as the interactions among them.
Each ecosystem contains different ____________________________, or the place where an organism lives,
that supply the same basic needs of air, warmth, water, and food. How an organism acts within its ecosystem
is called its __________________. There are many roles in an ecosystem, but __________________________
between species usually results in only one species occupying a niche at any one time. Often, organisms with
similar needs will divide resources to reduce competition (ex: birds eat insects during the day, bats eat them at
night).
The maximum size of a population is called the ___carrying capacity________________________________.
Human action (development, industrialization, pollution, farming, over hunting, overgrazing, clear cutting,
introduction of foreign species, soil erosion) often has negative consequences for the ecosystem (and humans
too).
Relationships in an Ecosystem:
Match each name of a relationship between organisms with its correct description:
_____ Predation
_____ Mutualism
_____ Commensalism
_____ Parasitism
_____ Competition
A. The organisms are rivals for resources.
B. One organism derives benefit, the other is unaffected.
C. One organism derives benefit at the other’s expense.
D. One organism preys on another.
E. Both organisms gain some advantage from the interaction.
When two organisms interact closely, this is called _____symbiosis_________________________.
Identify the type of relationship explained in each scenario: commensalisms, mutualism, parasitism, or predation.
Scenario
Type of Relationship
Explain your answer
A mite lives in the base of the eyelashes of
people who use mascara. It feeds on the
mascara; it does not seem to harm people.
A coyote captures, kills, and eats a rabbit.
The flower of the yucca plant provides the
only location where the yucca moth can lay
her eggs. In the process, the moth pollinates
the yucca flower.
Bacteria that live on the surface of our teeth
require sugar from our food to survive. A by
-product of their metabolism (body
processes) decays the enamel of teeth.
Nitrogen -fixing bacteria live in the roots of
some plants. They provide nitrogen in a form
the plants need and obtain a “home” and
nourishment from the plants.
Aspen trees provide shade for small spruce
and fir trees. These would not grow as well
in direct sunlight.
Insects lay their eggs in the buds of spruce
trees. The insect larvae live off the plant
material and prevent the bud from
developing normally.
Food Webs & Food Chains:
Every organism needs to obtain _____________________ in order to live. For example, plants get energy
from the sun, some animals eat plants, and some animals eat other animals.
A __________________________________ is the sequence of who eats whom in a biological community (an
ecosystem) to obtain nutrition. A food chain starts with the ___________________ energy source, usually the
sun or boiling-hot deep sea vents. The next link in the chain is an ___________________ that makes its own
food from the primary energy source -- an example is photosynthetic plants that make their own food from
sunlight (using a process called _____________________________) and chemosynthetic bacteria that make
their food energy from chemicals in hydrothermal vents. These are called ___________________________ or
primary producers.
Next come organisms that eat the autotrophs; these organisms are called ___________________________ or
primary consumers -- an example is a rabbit that eats grass. The next link in the chain is animals that eat
herbivore - these are called ___________________________ consumers -- an example is a snake that eats
rabbits. In turn, these animals are eaten by larger predators -- an example is an owl that eats snakes. The
tertiary ____________________________ are eaten by quaternary consumers -- an example is a hawk that
eats owls. Each food chain ends with a top _______________________________ and animal with no natural
enemies (like an alligator, hawk, or polar bear).
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Make a food chain with a producer and 3 consumers:
The _____________________ in a food chain show the flow of energy, from the sun or hydrothermal vent to a
top predator. As the energy flows from organism to organism, ____________________ is lost at each step. A
network of many food chains is called a _____________________________________________.
Circle the autotrophs and Bubble-cloud the heterotrophs in the following food web. List examples of:
Primary Consumers (3) ____________________
__________________________________________
Secondary Consumers (3) __________________
__________________________________________
Tertiary Consumers (3) ____________________
__________________________________________
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The populations of organisms in a food web are all connected. Although there is intense competition between
animals, there is also interdependence. When one species goes ___________________, it can affect an entire
chain of other species. What could happen within the food web above if the grasshopper population was
suddenly decreased due to a disease (that only kills the grasshoppers)?
The _____________________________________ of an organism is the position it holds in a food chain, or a
feeding level in an ecosystem.
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The 1st trophic level (A) consists of _________________.
Name the 2nd trophic level (both names)
__________________ and _______________________.
What is the 3rd trophic level called? _________________
What is the 4th trophic level called? _________________
When any organism dies, it is eventually eaten by detrivores
(like vultures, worms and crabs) and broken down by
___________________________ (mostly bacteria and
fungi), and the exchange of energy continues.
In any food web, energy is ______________ each time one organism _____________ another. Because of
this, there have to be many ________________ plants than there are plant-eaters. There are more
_____________________ than heterotrophs, and more ____________________________ than meat-eaters.
Each level has about ______% of the energy available to it because most of the energy is used by the
organisms at each level and is not passed on to the next level.
The Carbon Cycle:
The amount of __________________ on Earth does not change. Matter is ____________________ from
organisms to the ___________________________ and back again.
Use arrows to show the way in which carbon moves among the air, the ground, and plants and animals in
the carbon cycle. Then label each arrow to show the process (see key). The first one has been done for you.
There will be 10 more arrows to draw and label.
CO2 in atmosphere
A
Bacteria & Fungi
Animals
Green Plants
Coal, Oil and Gas
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A – Photosynthesis
B – Respiration
C – Consumption
D – Decomposition
E – Combustion (burning)
F - Compression
Use the diagram about the Carbon Cycle to complete the following paragraph:
Carbon __________________________ is taken from the atmosphere by ________________________, which
convert it to glucose by the process of ______________________________. During _____________________
_______________________________, these molecules are broken down and _______________ is released in
the ___________________________. Carbon is also returned to the atmosphere when __________________
break down ______________________________________, dead plants, and animals. If organic compounds
are not broken down, they may become compressed and converted into ______________________________.
The _______________________ of these fossil fuels release carbon into the atmosphere.
The Nitrogen Cycle:
Most of Earth’s nitrogen is in the ____________________________. All living things use nitrogen to make
______________________ such as proteins, but most organisms cannot use
_______________________________________________.
Use the diagram below to identify the events that take place in the Nitrogen Cycle.
1. A natural process converts nitrogen from the atmosphere into forms that are useful to a variety of
organisms through the process of ____________________________________________.
5. Some _____________________________ perform nitrogen fixation. ___________________________ can
also cause this process to occur.
4. _________________________________ takes nitrogen from nitrates and other compounds in the soil and
_____________________ it as nitrogen gas back into the atmosphere.
6. When a plant or animal dies, the remains ______________ and become part of the soil. The nitrogen in the
remains is recycled and can be used by plants.
Human activities also add nitrogen to the __________________. Many ________________________ contain
nitrates. When fertilizers are _____________________ on soil, the nitrogen content of the soil
______________________________.
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