Name: ________________________________
Period: _________
Date: ________
UNIT 4 Test Review
ENERGY FLOW THROUGH ECOSYSTEMS
1. Define the following terms
Ecology - study of living interactions with living or non living things
Species - 2 animals that can produce fertile offspring
Population – same species same area
Community – all populations in the same area (living things)
Ecosystem – area including living and nonliving things
Abiotic – a non-living factor in an ecosystem
Biotic – a living factor in an ecosystem
Abiotic Interaction – an interaction in an ecosystem that occurs between a living organism and a nonliving object
Biotic Interaction – an interaction in an ecosystem that occurs between two living organisms
Resource – A factor in an ecosystem that affects communities that can run out
Condition - A factor in an ecosystem that affects communities that can not run out
Autotroph(Producers) – Any organism that gets its energy from non-living sources (ex. sun, chemicals)
Heterotroph(Consumers) - Any organism that gets its energy from consuming other living sources (ex. sun, chemicals)
Food Chain – A diagram that shows the movement of energy through an ecosystem using one organism per trophic
level
Food Web - A diagram that shows the movement of energy through an ecosystem using more than one organism per
trophic level
Herbivore – A consumer that eats producers
Carnivore – A consumer that eats other consumers
Omnivore – A consumer that eats both producers and other consumers
2. Fill in the Blanks below
All deer living in New hope is an example of a __species population_________________________
All deer, raccoons, etc. living in New hope is an example of a _____community______________________
All animals, plants, rocks soil, weather etc. in New hope is an example of an ____ecosystem_________________
3. What is the difference between a condition and a resource? Resources can be used up
4. What is the difference between a heterotroph and an autotroph? Heterotroph gets energy from living sources
Autotroph – non living sources
5. What is the difference between a food web and a food chain?
Food chain – 1 per trophic level
Food web – more than one
6. What are the two laws of Thermodynamics?
1 energy can not be created or destroyed
2 energy transfers are not 100% efficient
7. What is the 10% rule? How does it relate to food webs?
Only 10% of the energy at one trophic level moves to the next when an organism is consumed. This limits the
number of trophic levels in an ecosystem
8. What happens to the 90% of the energy that does not make it to the consumer ?
Some energy is used as an animal hunts/gathers its food. Some energy is used to consume and digest the food.
Some energy is not processed and remains in the chemical bonds of the waste product.
9. A lion eats a wildebeest. A wildebeest eats grass. How much energy does a lion get indirectly from 1,000 J of
grass?
10 J
10. Draw a food web with at least three trophic levels below and at least two organisms on each level. Label each
species as follows
a.)
b.)
c.)
d.)
trophic level
autotroph or heterotroph
producer, primary consumer or secondary consumer
herbivore, carnivore, omnivore
11. From your food web above, which trophic level would have the biggest organisms? Why?
Top, they must be big to catch and consume smaller things. They also need to cover large areas to find food because
as you move up the trophic levels organisms become scarce.
12. From your food web above and based on the 10% rule, which trophic level would have the biggest population?
Why?
1st trophic level. You need many small things to feed a big thing due to energy loss. Organisms at the
bottom trophic levels have the best resources in the smallest area. In order to survive as a species, they often have
adapted and developed high reproduction rates.
13. Describe step by step what would happen if a new extremely efficient herbivore was introduced into your food
chain above.
The competing herbivore populations would decrease. The producer population could decrease or even be wiped out
due to over-consumption by the new herbivore. The carnivore population could decrease if it can not eat the new
herbivore, …
14. Why are top carnivores a good indicator of an ecosystems health?
They are the last in line to receive energy. Any problems that occur in the food web below them can affect their
population. In addition, they are the most effected by biomagnification.
15. a. What is biodiversity? The amount of species in an ecosystem
b. How does biodiversity effect the stability of an ecosystem? More biodiversity the more options for consumers.
The more options, the better the ecosystems ability to adapt to the changes.
c. Which would be more stable, a rainforest or the arctic tundra?Why? Rainforest because there are more species
MATTER FLOW THROUGH ECOSYSTEMS
16. Define the following terms
Pollutant - any substance that has a high concentration and is in the "wrong" ecosystem at the "wrong" time
Pesticide - a substance used to kill pests
Pest - any organism that a person finds harmful or inconvenient
Bioaccumulation - The build up of a chemical pollutant in a single organism on a single trophic level
Biomagnification (Bioacculmulation) - The concentration of a pollutant as it is passed up the trophic levels by
consumers
17. List and describe the four major types of pollutant sources. Include the possible negative effects of each.
Fertilizers - Released by farmers to increase crop growth. Cause Eutrophication(Algal Blooms) and fish death
Pesticides - Released by farmers to increase crop yield. Runoff and get absorbed by organisms. Biomagnification
leads to species death.
Sewage - Nutrients and chemicals released into rivers. Can result in Eutrophication or biomagnification.
Landfills and Industry - chemicals released into rivers. Can result in biomagnification.
18. What are the six major problems with pesticides?





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Can enter the food chain by being eaten directly or through runoff
Move through the food chain as organisms eat each other
Take a long time to break down
Can be fat soluble not water soluble (stay in the body)
Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species
Can cause birth defects and cancer in
19. Using your food web from question 10, determine which organism would be affected the most by a pesticide.
Explain why the top trophic level is affected the most. Which organism from your web should you eat to keep your
toxin intake to a minimum.
The secondary consumer will experience the greatest affect because he will receive the highest concentration of
pollutant. This is because Biomagnification takes place. When a consumer absorbs the material of its food source it
begins accumulating toxins in its system. The amount of toxin is multiplied by the number of organisms that are
consumed. In order to consume the least amount of toxin you should eat from the 1st trophic level.
20. What are the three conditions that a chemical pollutant must meet in order to biomagnify? Explain why each
condition must be met.
 The pollutant must be “long-lived”. And can not be broken down easily. - It must stay active long enough to
make its way through the food chain.
 The pollutant must be concentrated by producers. (Bioaccumulation) - If the substance is not absorbed and
stored in the producers then it has no way of getting into the food chain to begin with.
 The pollutant must be fat-soluble. - water soluble pollutants are eliminated by the bodies excretory system and
will not be passed on when one organism consumes another.
21. Farmers buy pesticides that are highly toxic, fat soluble, and long lived. Why would farmers want each of these
traits?
Highly toxic - kills a larger percentage and a larger variety of pests
Fat soluble - Does not wash away in the rain as easily
Long lived - Does not need to be reapplied frequently
22. Environmentalists want rules that only allow pesticides that are less toxic, water soluble, and short lived. Why do
environmentalists like each of these traits?
less toxic - does not kill a variety of pests. Targets a particular species.
Water soluble - Does not remain in organisms so it will not biomagnify
Short lived - Will not remain in soil and continue to accumulate high concentrations
23. Explain why a farmer can not use the same pesticide on his crops every single year?
If a pesticide does not kill 100% of a bug it is because a number of them are immune to the pesticide. They will pass
this gene on to their offspring and all be immune the next year.