Name ________________________________
Date ____________________ Hour _____
O3 STUDY GUIDE:
1. Analyze the following food web: What parts are good? What parts are wrong or missing?
Good/Correct Parts of the Food Web:
Most arrows point in the correct direction
Variety of trophic levels represented- decomposers,
producers, primary and secondary consumers
Wrong/Missing Parts of the Food Web:
No Energy Source = Sun
No Soil
Trophic levels are not organized well
Some of the relationships are incorrect
2. Describe at least three ways that humans are impacting (positively or negatively) the nutrient cycles,
(carbon, and nitrogen). (Think about the cycles and describe ways that humans could change parts of it
and the results of those changes!) Make sure you describe, not just list the activity and the result in
terms of how they affect the carbon and nitrogen cycles.
• Use of fossil fuels is increasing the nitrogen and CO2 in the atmosphere faster than plants and soil pull
those out of the atmosphere, contributing to global warming and smog.
• Habitat destruction reduces the number plants and trees available for reclamation of CO2 and nitrogen
fixation.
• Use of fertilizers increases nitrogen in water sources due to run-off and disrupts the balance of
organisms/nutrients in those ecosystems.
• Increased nitrogen in the atmosphere also contributes to acid rain which affects organism survival and a
shift in chemical balance in soils and water.
3. What is symbiosis? Symbiosis is a close long term relationship between two organisms where at least
one benefits. By close relationship, these organisms are either living together or coming into frequent
contact.
List and define the three types of symbiosis. Also, describe a real-world example of each relationship.
a.
Parasitism- One organism benefits and the other organism is hurt, but does not usually kill the
host organism. Examples: Mistletoe/Spruce, Mouse/Flea, Deer/Tick
See Good Buddies handout for details of examples
Make sure you describe the relationships and not just list them. (I’ve only listed them here so you’ll
have to describe in more detail on the exam.)
b. Commensalism- One organism benefits and the other is unaffected. Silverfish/Army Ant,
Barnacle/Whale, Maribou Stork/Bee.
c.
Mutualism- Both organisms benefit. Ant/Aphid, Ostrich/Gazelle, Oxpecker/Rhinoceros
4. It has been a particularly good year for timber wolf reproduction. Make a list of relationship changes
you can expect as a result of the increase in wolf population in this ecosystem. I’ve listed a food chain
for you to use and done an example.
Sun Æ Lake Vegetation Æ Moose Æ Timber Wolf
a. The moose population will go down because there are more timber wolves to feed.
ANSWERS MAY VARY
b. Increased vegetation due to decreased grazing.
c.
Decreased wolf population due to declining moose herd.
5. Describe how a newly created island in the Pacific would change over time. (You should describe
possible changes in succession.) Include some possible detail.
This situation is an example of primary succession. First lichen/fungi would colonize the cooled lava,
breakdown the rock and produce soil. Once soil is established small quick growing plants would
colonize and be succeeded by grasses and seedling with better root systems. Eventually larger plants
would grow and animals such as insects and birds might migrate to the island.
After 10,000 years, a typhoon hits the land, what type of succession has just happened?
The process of secondary succession would eventually repopulate the island with a variety of organisms.
It is secondary succession because soil already exists after a typhoon comes through.
6. Diagram the nitrogen cycle.
See Powerpoint Presentation
N2
Fertilizer
Production
Lightning
Denitrification
(GAS
)
Nitrogen
Crops
Fixation
Sheep
Legume
Nitrogen-Fixing
Bacteria in
Decomposers
soil &
roots
What role do decomposers play in the nitrogen cycle?
Decomposers breakdown organic material and return nitrogen to the soil in a form plants can use
(ammonia).
What role do legumes play in the nitrogen cycle?
Legumes have a symbiotic nitrogen-fixing bacteria living on their roots. This nitrogen-fixing bacteria
“fixes” nitrogen into a useable form for plants - turn ammonia from waste products into nitrates.
Make note of the relationship between bacteria and legumes vs other plants.
7. What is biological magnification?
Biological magnification is the amplification of a substance (toxin) in organisms through consumption of
contaminated organisms in their food web/chain. The concentration increases as you move up the pyramid.
Small fish ingest mercury in the water and have a low concentration of contamination but are eaten by larger
fish which consume many small fish and therefore have a higher concentration of mercury. This process
continues to increase contamination levels as you move up the food chain.
• Why are pregnant women sometimes warned to eat only 1 meal of fish a week?
Mercury and other pollutants may affect development of the baby if the woman consumes contaminated
fish.
8. In an ecosystem, why are there always going to be more producers than herbivores? Why are there
more herbivores than carnivores? (Your answer should include a discussion of ENERGY.)
Producers have unlimited energy available from the sun to produce the food that they need. As we move up the
food pyramid, only 10% of the energy consumed by that level is available for the next level. Therefore the
amount of energy available to the herbivores is greater than that available to the carnivores. The amount of
energy available determines how many organisms an ecosystem can support.
Energy is the limiting factor as you move up the pyramid. Plants do not grow to fill the need of herbivores.
9. What is photosynthesis?
The production of food (sugars) by plants/algae from water, sunlight and carbon dioxide.
• What is cellular respiration?
The use/breakdown of energy (sugars) by organisms (plants and animals) that produces carbon dioxide and
water.
•
What is the connection between photosynthesis and cellular respiration? (Hint: Consider the
carbon cycle.)
Photosynthesis recaptures the carbon emitted by energy consumption (cellular respiration) to reclaim it for
future use. (Photosynthesis pulls carbon out of the atmosphere and transforms it to a sugar. One of the ways
that carbon returns to the atmosphere is through cellular respiration – when cells are burning that sugar.)
Match the term with the definition:
1. _B The maximum population a community
can tolerate for an extended period.
2. __D__ Anything that keeps a population from
over-growing the resources available.
3. __A_ A sequence of communities over time.
B. Carrying Capacity
4. __G_ The first species to inhabit a lifeless area.
D. Limiting Factors
5. __E_ The type of succession that occurs after
a volcano erupts.
6. __C_ Role of an organism in its ecosystem.
E. Primary succession
7. __F_ The type of succession one would expect
after a tornado devastates an area.
A. Succession
C. Niche
F. Secondary Succession
G. Pioneer species
10. What are some examples of limiting factors for plants?
Limiting factors for plants include adequate soil, water and available sunlight as well as climate conditions.
Consider habitat needs as well as means of death.
• What are some examples of limiting factors for animals?
Limiting factors for animals include the availability of food sources (vegetation or prey), habitat needs
(feeding, shelter, travel ways) and water, presence of predators.
Consider habitat needs as well as means of death.
11. Review your deadly links lab. Copy your answer for number 2 here.
Pesticides in the ecosystem my lead to illness, developmental or reproductive defects or death depending on
the type of pollutant, concentration of contamination and the degree of biological magnification.
12. If an ecosystem has enough food for 15 squirrels, does that mean that 15 squirrels will be living in that
ecosystem? (Include the idea of carrying capacity in your answer.)
Despite having enough food resources for 15 squirrels, those resources may not distribute evenly due to
competition. Additionally, there may be other limiting factors such as the presence of predators, disease or
other habitat needs (shelter, water, travel ways) that decrease the number of squirrels the ecosystem can
support (carrying capacity).
13. Decomposers play a valuable role in ecosystem health. Describe at least 2 key things decomposers do.
(HINT: think about energy pyramids, nutrient cycling, etc.)
Decomposers such as bacteria, breakdown organic materials for use by other organisms (plants) and convert
wastes into useable components (ammonia to nitrates).
Lichen and fungi aid in the creation of soil by breaking down rock and adding organic materials.
14. Why are nitrogen-fixing bacteria so important? EXPLAIN in the context of the nitrogen cycle.
Nitrogen fixing bacteria breakdown ammonia into nitrites and nitrates, returning nitrogen to the soil and
producing it in a form plants can use. Nitrogen-fixing bacteria make the vast amount of atmospheric nitrogen
useable to plants.