SEEd Standards

Standard BIO.1.1: Plan and carry out an investigation to analyze and interpret data to determine how

biotic and abiotic factors can affect the stability and change of a population. Emphasize stability and

change in populations’ carrying capacities and an ecosystem’s biodiversity. (LS2.A, LS2.C)

Standard BIO.1.5: Design a solution that reduces the impact caused by human activities on the

environment and biodiversity. Define the problem, identify criteria and constraints, develop possible

solutions using models, analyze data to make improvements from iteratively testing solutions, and

optimize a solution. Examples of human activities could include building dams, pollution,

deforestation, or introduction of invasive species. (LS2.C, LS4.D, ETS1.A, ETS1.B, ETS1.C)

Additional Standards

Writing Standard 1: Write arguments to support claims in an analysis of substantive topics or texts,

using valid reasoning and relevant and sufficient evidence.

Unit Overview

In this unit, students will investigate how changes in an ecosystem affect the stability of populations.

Specifically, they will explore how dams affect the abiotic factors of an ecosystem, which in turn affects

native fish populations. They will then act as water managers and examine a group of dams. Based on

a budget and information about each dam, they will then propose a plan detailing which dams to

rehabilitate, which to remove, and which to maintain.

Performance Expectations

● Students will construct an explanation for how changing conditions alter abiotic and biotic

factors in an ecosystem and may result in a new ecosystem.

● Students will construct an argument that the stability of populations is affected by changes to

both biotic and abiotic parts of the ecosystem. This argument is supported by evidence and

uses the claim, evidence, reasoning format.

● Students will design, evaluate, and refine a solution for reducing the impacts of human

activities on the environment and biodiversity.

STABILITY OF POPULATIONS

Time

Part 1: 45 min

Part 2: 60 min

Part 3: 60 min

Background Information

Change is inevitable in nature. Ecosystems have to cope with sudden changes like hurricanes and

long-term changes like ice ages. Healthy ecosystems can withstand the stress caused by change, and

populations of organisms can recover. Stressed ecosystems handle change poorly; populations in

these ecosystems are already fragile or out of balance and may respond to change with population

spikes or crashes. Sometimes, an ecosystem is so fragile that it cannot recover from change.

Changes to ecosystems occur frequently. They

can be natural changes, such as a lightning strike

causing a wildfire, or a hurricane. Many changes

are caused by humans. Overfishing, habitat

fragmentation, and pollution can greatly affect an

ecosystem and the organisms in it.

Changes to an ecosystem can also be positive or

negative. Fires can be devastating, but in some

ecosystems, they are necessary. Some trees can

only reproduce after a fire: the intense heat opens

up their cones, releasing seeds. Humans can

cause positive change in an ecosystem through

wildlife management, reintroducing native

species, or planting native plants. On the other

hand, changes such as an oil spill or overfishing

are negative. They cause a decrease in

populations that can unbalance the ecosystem.

We can find many examples of changes to ecosystems in Utah. In these lessons, students will focus

on river dams. Dams can have many societal benefits such as flood control, power generation, and

recreation. However, they also have a dramatic impact on the environment.

Dams disrupt sediment flow. In normal conditions, rivers transport sediment downstream. When a

dam is built, sediment can no longer flow downstream and begins to pile up behind the dam. This not

only harms the dam and requires expensive dredging to remove the sediment, but it also causes

erosion downstream from the dam. Without an influx of new material, riverbanks and beds begin to

erode away.

Some tree species produce serotinous cones.

These cones are covered in resin that must be

melted in the intense heat of a wildfire before

the cone can open and release its seeds.

Once released, the seeds are then dispersed

by wind or gravity.

Dams alter water temperature. When water hits the dam, it slows down and spread out, forming a

reservoir. The surface of the reservoir heats up in the sun, while the deep waters stay very cold. When

water is released from the dam, it affects downstream temperatures of the river system. Some dams

release deep water from the reservoir, which sends cold water downstream that can delay fish

spawning. Other dams release warm surface water from the reservoir, which can warm temperatures

downstream and harm cool-water species.

Dams also act as a barrier to fish movement up and down the river, which can cut off access to vital

habitat and spawning areas. Fish ladders are designed to help fish pass up and over dams, but their

effectiveness is mixed at best.

Human activity has the greatest impact on the amount and

quality of wildlife habitat in many areas of the world. Wildlife

habitat can be destroyed or its quality diminished as a result

of urban sprawl, agricultural practices, pollution, habitat

fragmentation, or introduction of invasive species. People

can also have a positive impact on wildlife populations

through improvement and protection of habitat or

ecosystems. Responsibly selecting and caring for pets can

reduce the spread of invasive species. Properly draining and

drying a boat between bodies of water prevents the transport

of invasive mussels. Planting trees and shrubs and providing

sources of food and water in individual yards is one way

people can help wildlife.

Humans have the unique ability to choose to have a positive

impact on an ecosystem. Supporting policies that promote

healthy habitats and increasing awareness about human

impacts on the environment are powerful ways to create

positive changes for ecosystems.

Humans, for good or ill, have the

greatest impact on ecosystems.

Preparation

Reserve the computer cart or computer lab (optional).

Materials

● Dam Dilemma worksheet (digital form; printable)

● Sticky notes

● 3 giant sticky notes

● Markers

● Videos (The Dam Dilemma, Hydropower 101, and Remove the Dams to Save the Salmon?)

Investigative Phenomena

● Yacyreta Dam Impact (still image; swipeable image)

○ This image is part of the “Images of Change” series by NASA. These satellite images

show the Paraguay-Parana River before and after the construction of the Yacyreta

Dam. The first image (left) was taken May 25, 1985. The second image (right) was

taken June 7, 2010.

Gathering,

Tell the students that you’d like to share a photo that you saw recently. You noticed something

interesting about the photo and you would like to hear their thoughts. Display the image of the Yacryeta

Dam. Alternatively, you have the students pull up the swipeable image of the dam on their own devices

and swipe back and forth between the two images. Ask the students to record their observations and

questions in their science notebook.

Have the students discuss their observations in small groups. You can use this time to visit each group

and add to their discussion as needed. What features do the students recognize in the images?

Emphasize similarities and differences. Ask what they think may have caused the change.

Allow students to share their observations and questions with the class. List their questions on the

board. Draw attention to any questions or observations about changes in the ecosystem. For example,

students may observe that the images seem to be the same location. They may also observe that the

label on the swipeable image provides some clues that may explain the differences in the images.

Make connections with the student’s prior knowledge about dams and rivers.

As a class, the students will investigate how dams alter an ecosystem and how those changes affect

organisms in the ecosystem. To begin, they will explore more about dams: why do humans build dams

and what are the consequences, both positive and negative?

Reasoning

On the three giant sticky notes, write “Why do we build dams?”, “What are positive effects of

dams?”, and “What are negative effects of dams?”. Post the giant sticky note posters around the

room.

Give each group a stack of sticky notes. Ask them to share what they already know about dams by

writing answers to the three questions on sticky notes and sticking them to their corresponding

poster. If they see another small sticky note with the same or similar answer to their own, they

should stack their sticky note on top of the one that’s already there. Give them a few minutes to do

so. Encourage group discussion. (For remote learning, you can do this activity with a shared

document. Create one page or sheet for each question and have students type in their responses.

You can also use breakout rooms in your virtual platform to allow groups to discuss.)

When they’ve finished, share some of the common answers from each poster. Tell the students that

they will have the opportunity to add to the posters or revise their responses later.

Tell the students that they will be watching three short videos about dams and answering some

questions about them. Links to the videos and the questions are contained in the Dam Dilemma

worksheet, which you can print out or assign digitally. This is a great homework or remote learning

assignment: do the introductory assignment at the end of class (or at the beginning of an at-home

learning day) and then assign the video activity for your students to complete at home. Alternatively,

you can book a computer cart or lab and do the activity in class.

Share the Dam Dilemma worksheet digitally with the students. The links to the videos are included.

As they watch the video segments, have the students fill in the worksheet questions (the document

is saved as a form so the questions can be answered digitally). If you are using printed worksheets,

be sure to share the video links as well.

Communicating

During your next class period, ask the students to revisit the questions on the large sticky note posters.

Pass out sticky notes and give them time to write new information and new answers based on their

learning. Have them stick their answers to the appropriate poster like before (or add to the shared

document if learning remotely).

As a class, discuss how their understanding of dams has changed (or hasn’t changed). Show them the

phenomenon image and their list of questions. Do they have any new observations or questions about

the phenomenon to add? Emphasize questions about the ecosystem and changes that the ecosystem

may have experienced after dam construction.

Assessment Opportunities

Do student sticky note answers show a deeper or more nuanced understanding of dams, their

purposes, and their effects?

Extension Activity

As an extension, you can have students build and test a water turbine or water wheel. Give them

some basic building materials (recyclables like plastic bottles, cans, and cardboard work well) and an

axle for their turbine to rotate on, such as a rod, dowel, or pipe. Challenge them to build and test a

wheel or turbine that will spin when water is poured over it. Give them time to test and refine their

designs.

Preparation

Reserve computer cart or lab.

Print Westwater Dam Final Report worksheet for each student (or group).

Watch this short instructional video.

Materials

● Westwater Dam Lesson PowerPoint (Google Slides; PowerPoint Download)

● Westwater Dam Final Report worksheet (digital form; printable)

Gathering

Display the list of student questions about the phenomenon. Point out any questions related to

ecosystem changes or potential impacts to wildlife. Tell the students that they will investigate these

questions by playing the part of fishery biologists in a virtual river survey.

In groups, they will go through the Westwater Dam Lesson slides. These slides are available online

as a Google Slides presentation or as a PowerPoint download. Select which version is best for your

students.

The PowerPoint file is stored in Google Drive but needs to be downloaded and run in Microsoft

PowerPoint to appear properly. This lesson will have them collect data about a variety of research

sites on the fictional Westwater River before and after the construction of the dam. They will then

use this data to determine the effect of the river on humpback chub spawning habitat. As they go

through the lesson, they will use the information to answer the questions on the Final Report

worksheet.

The PowerPoint lesson contains interactive elements such as textboxes where students can input

answers. In order for these elements to work properly, content such as macros must be enabled

(when saving the file, be sure to save as a macro-enabled .pptm file). When opening the

presentation, a security warning should pop up near the top of the screen warning that some active

content has been disabled. Instruct students to click the button that says “Enable Content”.

While there are fillable textboxes in the PowerPoint, all of the information is collected in the

worksheet as well. You only need to collect their worksheet to see their answers.

The PowerPoint gives students directions for how to interact with the lesson, so it can be assigned

(along with the accompanying worksheet) for asynchronous, at-home learning.

Ideally, students will go through the lesson with their group. Some slides have prompts for group

discussions. However, students can also go through the lesson and complete the accompanying

worksheet on their own.

The first part of the lesson (worksheet questions 1-3) is a virtual survey of Westwater River. Students

will fill in missing information while learning about abiotic factors in the river that are affected by

dam construction.

Reasoning

In the second part of the lesson, students will need to use the data from the river survey sites to

make predictions about humpback chub populations. Based on the information about each site,

students will determine whether each site is a suitable humpback chub spawning habitat based on

requirements provided in the worksheet. They will then compare the number of spawning sites

before dam construction to the number of spawning sites after dam construction.

Students should determine that there are fewer suitable spawning sites after dam construction.

Based on this information, the students will be prompted to make a prediction about how this might

affect humpback chub populations in Westwater River. They will be asked to use the claim, evidence,

reasoning format. Because there are few sites to lay eggs, students can reasonably predict that chub

populations will decline.

You may want to review with your students how to construct an explanation/argument in the claim,

evidence, reasoning format.

Claim: generally, the claim is the answer to a question. In this case, how might a reduction in spawning

sites affect humpback chub populations?

Evidence: observational (I noticed) or empirical (I measured) data that supports the claim.

Reasoning: how the evidence supports the claim. This “closes the circle” of your argument.

For example, “Fewer spawning sites will make humpback chub populations decline (claim). Humpback

chub will only lay their eggs in certain conditions. When we looked at the data, there were 3 sites where

humpback chub could spawn before the dam built. After the dam was built, there was only 1 spawning

site left. (evidence). If there are fewer places to lay eggs or if the eggs are less likely to survive because

the conditions are wrong, then there will be fewer baby fish and the chub population will decrease

(reasoning).”

Communicating

After completing the virtual river survey, the lesson will ask them to move on to a review of data from

a 3-year fish survey on humpback chubs. They will answer some questions in the worksheet about

the data and have to write an argument for whether the data supports their prediction about chub

populations. Once again, they will be instructed to use the claim, evidence, reasoning format. The

data shows a decline in the estimated population size for humpback chubs in Westwater Canyon

over a three-year period.

Assessment Opportunities

Read the students’ responses on the worksheet. Do their answers show an understanding that

changes to the ecosystem can alter the number of organisms it can support (in this case, that fewer

spawning sites lowers the river’s carrying capacity for humpback chub)?

Preparation

Share the Water Management Activity file with your students digitally or print a copy for each group.

Materials

● Water Management Activity (digital form; printable)

Gathering

Tell the students that now that they know more about dams and their effects (both positive and

negative), they will have the opportunity to act as water resource managers for the Westwater River

system. There are directions for this activity on the first two pages of the Water Management Activity

packet so students can work independently, but go over their task and instructions as a class if

possible.

Water managers make decisions around the control and movement of water in order to make

optimum use of this resource. This includes maintaining water quality and quantity and ensuring

water supply for agriculture, industry, and domestic use. Water managers must balance societal

needs and ecological needs.

When water managers make decisions, they have to consider society’s objectives. Some possible

objectives are:

Restore habitat

Reduce yearly maintenance costs

Increase hydroelectric power production

As a class or in groups, discuss what kinds of objectives and goals they want to have for their river

system. Remind them to balance societal (human) needs with ecological needs. For example, what

kinds of services do they want the river to provide? This could include power, irrigation, clean water,

and recreation. Emphasize long-term sustainability for both human and animal populations.

Have the students record their goals/objectives on the first page of the Water Management Activity.

The activity contains profiles for 5 different dams on the Westwater River system. Each one has its

own unique circumstances and challenges. Their task as water managers is to access all the dams

and decide whether to remove, rehabilitate, or maintain the dam. As in real life, they will have a

limited budget to work with and each choice they make has an associated cost. Their goal is to

create a plan for the river system to address the goals and objectives established by the class/group.

In order to help them, they will use a scoring system to rate each dam. (Water managers often use

complex mathematical algorithms to help them measure the benefits and drawbacks of maintaining

or removing a dam. In this lesson, the students will use a very simplified system.) The system

measures two criteria: societal impact and ecological impact. The higher the score, the more positive

the impact.

Each dam has a starting score for both its societal impact and ecological impact. By choosing to

remove or rehabilitate the dam, students can spend their budget to alter the scores. The final and

least expensive option, maintaining the dam, does not alter the dam’s original scores.

For each dam, students will have to make a choice to remove, rehabilitate, or maintain. These

options cannot be combined. For example, if a student chooses to remove the dam, they cannot also

purchase a dam upgrade from the Rehabilitate option. Below is a brief overview of each option.

Remove

For a set cost, the dam is removed from the river. The removal option will list pros and cons of

removal, as well as how the site score will be altered. For example:

Cost Pros Cons

$1.25

million

+2 Societal: gain white-water rafting, kayaking

and fishing

+1 Societal, +1 Ecological: lower risk of algal

blooms

-2 Societal: lose swimming

beaches and boating

-2 Societal: lose irrigation for

9,000 acres of farmland

Notice that this option has both a positive and a negative societal impact. By combining all the

impact score pros and cons, the overall change to the original score is -1 Societal, +1 Ecological. If

the dam’s original score was Societal: 2, Ecological:-1, then removing the dam would change the

score to Societal: 1, Ecological: 0.

Rehabilitate

The rehabilitate option will provide a menu of “upgrades” for students to choose from, each with an

associated cost and score adjustment. To rehabilitate, students must purchase at least one of these

options. They can purchase more than one if their budget allows.

For example:

Upgrade 1 Description Cost Outcome

Dam

Repairs

Reinforce the structure of the

dam and repair damage

$1.2 million +1 Societal: reduce risk of dam

failure

By purchasing a fish ladder, students can increase the societal score of the dam by one.

Maintain

In the maintain option, the dam is left as is with no changes. There is a small cost for regular

maintenance and the societal/ecological impact scores do not change.

Reasoning

After the students have made their choices, they will go through and score their dams on the score

sheet after the dam profiles. They will calculate the final score for their dam site by adding or

subtracting points from the starting score for their removals or rehabilitations. The students should

plot the final score for societal impact on one line and ecological impact on the other line (starting

scores are already marked). Ask them to draw an arrow from their starting score to their final score

so they can see how the impact changes based on their decisions. (If students are using the digital

form, there are option buttons on the number line that the students can click to show their final

scores. They will not draw the arrow if using the digital form.)

Societal Impact

Ecological Impact

This provides the students with a simple way to visualize the effects of their management decisions.

They will also be asked to calculate their average scores by adding up all the scores in a single

category and dividing by the number of dams (5). After plotting all of their scores, they will turn to the

last page of the activity.

Communicating

On the last page of the activity, the students will have to report on how well their plan meets the

societal goals and objectives they established at the beginning on the lesson. Arguments should be

written using the claim, evidence, reasoning format.

For example, “The changes to dam 1 helped support our goal to restore habitat and our goal to keep

people safe (claim). The dam started with scores in the poor/very poor range. By removing the dam,

we increased the societal impact to ‘good’ and the ecological impact to ‘fair’ (evidence). When we

removed the dam, we met our goals by restoring 30 miles of fish habitat and by reducing the risk of

flooding for the nearby town (reasoning).”

Assessment Opportunities

Read the arguments the students wrote in their science notebooks. Their answers should follow the

claim, evidence, and reasoning format. Their answers should show an understanding of how their

choices affect the river system. They will be able to identify how their solutions reduce the negative

impacts of dams and identify any constraints (budget, technology, etc.).

Looking for more ways to explore, discover, and learn? Check out these free resources below*!

Dams

This short reading from National Geographic includes vocabulary terms and the history of human-

built dams.

Impact of Dams on Native People Case Study

With a mix of text, images, and interviews, this interactive lesson from the Smithsonian National

Museum of the American Indian helps students explore how dams affect indigenous peoples and

cultures.

Water in Utah

Did you know that Utah is the 2nd driest state in the country? Explore all the ways humans and

animals use water in our state. Be sure to check out the video about toxic algae blooms in the “Eyes

on Science” section.

*External links are provided for informational purposes only; they do not constitute an endorsement by

LLPA nor is LLPA responsible for the accuracy, legality, or content of the external site.