Name: Raniya Lee

PT 7.2: Ecosystems & Populations

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Learning Target
(HS-LS2-6): I can evaluate the claims, evidence, and reasoning that stable conditions
result in consistent populations within an ecosystem, while changing conditions can result
in a new ecosystem.

Guiding Questions
How do changes in the environment affect an ecosystem?

Task 1 - Yellowstone Wolves Introduction

The interactions of organisms in an ecosystem can either have a positive or negative affect on
the environment. In this performance task, you will evaluate the evidence of how the
reintroduction of the wolf population affected the ecosystem at Yellowstone National Park.
DIRECTIONS: Watch this video Wolves of Yellowstone and answer the following question:
What changes resulted from the reintroduction of wolves into this ecosystem?
Describe THREE changes that occurred.
1. Plants started growing faster than they were before

2. Rivers became stronger than they were before

3. There was more berries for bears

In your own words, explain what biodiversity is in an ecosystem. Include examples.

Biodiversity in an ecosystem is a large variety of different species that inhabit a
particular area. Meaning that there are a lot of different species of plants and
animals. For example, say we have a bunch/variety of different birds or snails, or a
variety of different plants. Like grasses, trees, or even bushes. Those are the

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 different varieties of species you might see in a biodiversity ecosystem.

DIRECTIONS: Answer the following questions. Refer to your PT 7.2 notes for the answers.
1. What is the term that describes all living things? Biotic

2. What is the term that describes all non-living things? Abiotic

3. Biodiversity is the variety of different __________ that inhabit a Species

particular area.

4. Give an example of a biotic factor and give an example of an Biotic: Animals

abiotic factor.
Abiotic: Soil

5. What is it called when a species is so important, the rest of the Keystone Species
ecosystem would suffer without it?

6. All of the physical, chemical, and biological factors that a Ecological Niche
species needs to survive are called what?

7. This is where an organism lives. Habitat

8. In certain populations, there are __________ __________ that cause Limiting Factors
organisms to die.

9. Which factor affects all organisms, regardless of population Destiny- Independent

size? Factors

10. Which factor affects certain organisms, depending on the Destiny - Dependent
population size? Factors

11. Explain an example of how a population (or ecosystem) has changed over time.
Populations have changed over time because there are water droughts in some areas

12. Explain one example of a density-dependent factor and how it affects organisms.
Density dependent factors are like wolves. Wolves are density dependent factors
because they can over kill other animals and the other animals will/can go extinct.

13. Explain one example of a density-independent factor and how it affects organisms.
Density independent factors are like wildfires. Wildfires are being seen a lot more
around the world because of climate change.

14. In class we discussed the book “The Lorax” by Dr. Seuss. Is the factor that affects the
organisms in that ecosystem density-dependent or density-independent? Explain.
I would say that it is density independent, because in the book the trees are getting cut
down because people wanted to use them for making sweaters and other different types
of clothing materials.

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15. IN YOUR OWN WORDS, explain what carrying capacity is and give an example.
Carrying capacity to me is when there is either not enough or is too much of something
around. Like if there were too many wolves and not enough bison or elk.

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Task 2 - Analyzing and Evaluating Graphs
DIRECTIONS: Observe the following graphs that show the change of various populations over
time and then answer the following questions. Your answers need to be 3-5 sentences.

1. What do you notice about the moose and wolf populations in the graph above? BE
DETAILED in your explanation.
I noticed that the wolf population would go up because there was a lot of moose. But
then when the wolves would eat too many of the moose the wolves would start to die
off because they didn’t have enough moose to eat.

2. Describe what you notice about the elk and bison population when the wolves were
absent, then reintroduced into Yellowstone National Park.
Wolves absent: They were both increasing

Wolves present: The moose would increase but then the elk would decrease

3. Based on this graph, what do you think would have happened if the wolves were not
reintroduced?

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 If the wolves were to not be reintroduced to the environment then I think that the
moose species would continue to increase and over-populate the environment
because then they would be eating all the food and then eventually eat it all.

4. Fill in the following venn-diagram with the similarities and differences between
density-dependent factors and density-independent factors. Remember, where the
circles overlap is where you put the similarities of the two topics.

● Competition: ● ● Affects all populations

animals competing in similar ways,
for resources. regardless of the
● Predation: animals population size.
being eaten by
● Unusual weather
predators.
● Natural disasters
● Parasitism: a
● Seasonal cycles
parasite lives in or
● Certain human
on another
activities
organism (the host)
and harms it.
● Disease: certain
diseases can infect
and kill an
organism, which
can also be passed
onto others

5. Identify the following factors as a biotic or abiotic factor:

Factor Biotic or Abiotic?

Grass Abiotic

Sun Abiotic

Fungus Biotic

Dirt Abiotic

Wind Biotic

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Task 3 - Analyzing Counter-Arguments
DIRECTIONS: Read these two articles & then create an argument about whether or not wolves
are a keystone species for the Yellowstone Ecosystem. Provide three key pieces of evidence
that support your argument. CITE YOUR RESOURCES!

Article 1: Has The Reintroduction Of Wolves Really Saved Yellowstone?

Article 2: Is the Wolf a Real American Hero?

Argument: In my opinion I think that wolves have saved Yellowstone National Park.
Because it says “Once upon a time, we exterminated the wolves from the
Rocky Mountain West, including the part that would soon become
Yellowstone National Park. We thought this was a good idea because wolves
frightened us, and also because they ate the domestic livestock we liked a lot
more.” I say that the wolves saved Yellowstone National Park because when
they realized that the elk population was expanding too much and eating all of
the young willow tree’s they knew that they needed to bring the wolves back
to Yellowstone National Park.

Evidence 1: In Article One, it says “Scientists discovered that without wolves present in
Yellowstone to hunt and kill prey, the elk population grew so large it ate up all
the young willow trees until there were none. This affected the habitat of
many other animals and plants in harmful ways and the ecosystem became
unbalanced. Or, as science puts it we caused a harmful ‘top-down trophic
cascade’ by removing an apex predator, the wolf, from the food web.“ Because
we removed the wolves from Yellowstone National Park the elk ate up all the
young willow trees and expanded their population more.

Evidence 2: In Article One, it says “It followed that returning the apex predator might
right that balance; and field biologists began to find some evidence for this
idea, even as popular support increased for bringing wolves back. So with
conservation ethics and ecological science in pretty good alignment, we
re-introduced the wolves to Yellowstone, where today they scare away the
hungry elk herds from the tasty young willows. Thanks to the wolf, balance
has been restored.” When they realized that the elk were eating all the willows
they put the wolves back into the Yellowstone National Park center. When
they put the wolf population back out the wolves scared off the hungry elk
herds from the willows.

Evidence 3: In Article One, it says “...”

Resource(s): My resources came from:

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Task 4 - Writing Prompt
DIRECTIONS: Write 2-3 paragraphs (5-7 sentences) that answers the following question:
How do changes in the environment affect an ecosystem?

Changes in the environment affect an ecosystem because…

MASTERY RUBRIC AND COMPLETION CHECKLIST

Learning Target
(HS-LS2-6): I can evaluate the claims, evidence, and reasoning that stable conditions
result in consistent populations within an ecosystem, while changing conditions can
result in a new ecosystem.

Guiding Question
How do changes in the environment affect an ecosystem?

1 Concerns (2) Goal Achieved (3) Exceeded Mastery (4)

(Similar to a C) (Similar to a B or B+) (Similar to an A or A+)

A score of 2 means you 1) Topic and Content ❏ Answered the challenge

did everything you were My argument has a question?
knowledgeable and ❏ Real-world examples or
supposed to but your applications used not from the
answer may have used thoughtful response to the
class activity.
some vocabulary learning target(s) and guiding ❏ Supported my argument with
incorrectly or your use question(s). information that was not
of evidence was unclear provided in class and cited
2) Use of Evidence and correctly.
or missing some
Analysis ❏ Used all score 4 vocabulary.
important details.
My argument is supported by
information from the You need at least 3 boxes
provided class resources checked from the above boxes
and class activities. to have a chance at earning a
grade of 4 if you got a 3 on
everything else.

IMPORTANT! Any information used that is NOT learned from class MUST be cited or
you will have to redo the assignment! You must use YOUR OWN WORDS.
Required Vocabulary: If you do not use ALL of the Score 2 words you will get NO CREDIT.

Score 2 Words Score 3 Words Score 4 Words

● Population ● Population ● Population

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● Ecosystem ● Ecosystem ● Ecosystem
● Habitat ● Habitat ● Habitat
● Environment ● Environment ● Environment
● Keystone species ● Keystone species
● Niche ● Niche
● Abiotic ● Abiotic
● Biotic ● Biotic
● Biodiversity
● Density-dependent factors
● Density-independent factors
● Carrying capacity