Unit 9: Ecology
Name:
Aim 49: Nutritional roles, food chains, and food webs
Date:
In every ecosystem, populations of different species are linked together, directly or indirectly, in a complex web of
interactions. Most of the interactions occur as organisms obtain their food. Each population has one or more specific roles
in the ecosystem. As a result, maintaining the ecosystem’s diversity is essential to its stability.
I.
Habitat vs. Niche
Because the world contains a wide variety of physical conditions, many different kinds of environments are available
to organisms.
a) Habitat: ________________________________________________
 Ex:
b) Niche: The _________________ that each species places in an ecosystem
(what an organism does, how it, how/where it obtains food etc.)
 Only _________ species at a time can occupy a particular niche. What happens if two species attempt to
fill the same role in an ecosystem? ______________________
1. Do these finches occupy the same habitat? _______________
2. Do these finches occupy the same niche? ________________
3. Do you expect there to be competition between these finches?
_________ Why?
4. What would happen if the Cape May Warbler and the BayBreasted Warbler began to occupy the same niche?
II.
Nutritional Roles in an Ecosystem
A. There are two types of nutrition in an Ecosystem
1) Autotrophic Nutrition
a.
Also known as: _______________________ or ______________________
b.
Definition: _________________________________________________ and ______________ the
sun’s _______________ through the process of _____________________________
c.
Example: ________________ and __________________
*Why are autotrophs considered the most important and most abundant organisms in an ecosystem?
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2) Heterotrophic Nutrition
a. Also known as: _______________________ or ______________________
b. Definition: must _______________________ food by _______________________ other organisms
c. Example: animals eating _______________ or other _________________
There are many types of heterotrophs in an ecosystem
TYPE OF
HETEROTROPH
DEFINITION
EXAMPLE
Only eat ______________________
1. HERBIVORE
2. CARNIVORES
Only eat _______________ (other animals)
a. Predators
a. ____________ & __________ their food (prey)
a.
b. Scavengers
b. Eat ______________ animals they find. They're
the “clean up crew” and are NOT DECOMPOSERS
b.
Eat both ______________ and ____________________
3. OMNIVORES
4. DECOMPOSERS
Break down, absorb, and _______________________
__________________ matter (dead organisms and wastes)
so they can __________________ these ________________
to the soil to be ______________________ by producers
III.
Food Chains
A. A food chain illustrates a _____________________ linear direction of energy flow in an ecosystem.
B. The main source of energy for life on Earth is the _____________
C. Example:


The arrows always point towards the _________________________
What do the arrows represent?
Which row in the chart correctly identifies characteristics that can be associated with the members of this food chain?
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IV.
Food Webs
A. Each organism usually feeds on more than one food source and each organisms may be fed on by more than
one organism
B. A food web shows the complex __________________________ food chains within an ecosystem
C. Why is a food web a better representation of feeing relationships than a food chain?
The organisms in an ecosystem are categorized into Trophic Levels
which are steps or levels in a food chain, web or pyramid
Nutrition/Role
Example
Trophic Level 1
Producers
Autotrophs
Grass
Trophic Level 2
Primary Consumer
Herbivore
Grasshopper
Trophic Level 3
Secondary Consumer
Carnivore
Snake
Trophic Level 4
Tertiary Consumer
Omnivore
Hawk
Based on the food web above:
1. Where does the energy come from to start this food web?
2. How many total food chains are there in this food web?
3. Name two organisms that belongs to more than one food chain:
4. Name an organism that is considered a secondary and a tertiary consumer:
5. Identify ALL of the:
a. Producers:
b. Primary consumers (herbivores):
c. Secondary consumers (carnivores):
d. Tertiary consumers (omnivores):
6. What organelle indicates that an organism carries out autotrophic nutrition?
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7. What important group of organisms in an ecosystem is missing from this web that should be labeled in the
blank space? _________________________. Give two examples:
8. What important abiotic factor is missing from this web?
9. What do the arrows represent?
10. Why do some organisms have multiple arrows pointing to them?
11. If the amount of carbon dioxide in the atmosphere were to decrease, which organisms would be one of the
first affected?
Why?
12. How do herbivores use the organic compounds produced by autotrophs?
13. If this ecosystem experienced a severe drought, explain what would happen to the snake population.
14. Explain why the deer population could remain relatively constant even though the number of edible tree parts
varies year to year.
15. How many food sources does the Hawk have?
16. Even though both the hawks and the owls both have two food sources, explain why the hawks would be less
likely to survive if a disease wiped out the mice.
17. What would happen if the number of hawks decreased?
18. If the Owl population were removed, make a prediction about what could happen to the:
a. Frogs:
b. Mice:
c. Crickets:
d. Hawks:
19. Explain what happens to the stability of an ecosystem if any organism increases, decreases or is removed & why
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