HS-LS2-7: Designing Solutions to Reduce Human Impacts on Ecosystems
In plain English: HS-LS2-7 is the NGSS high school performance expectation that asks students to design, evaluate and refine a solution that reduces the harm human activities such as urbanization, dams and invasive species do to the environment and to biodiversity. Students test designs against criteria and constraints, weigh trade-offs with data, and improve the design. It is usually taught in Biology or Environmental Science.
Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.
Clarification Statement: Examples of human activities can include urbanization, building dams, and dissemination of invasive species.
Next Generation Science Standards · Disciplinary Core Idea: Ecosystems: Interactions, Energy, and Dynamics · Official standard
Students act as designers. They start from evidence that a human activity harms an ecosystem, write a design goal with criteria and constraints, and then do the three things the performance expectation names: design a solution, evaluate it with data and a weighted decision matrix, and refine it after a test shows where it falls short. The lesson covers the three human activities the NGSS lists: urbanization (paved surfaces, stormwater runoff and roads), dams (blocked fish migration) and the spread of invasive species. Every solution is judged twice, once for the physical environment (water quantity and quality, habitat) and once for biodiversity (the number and kinds of species that persist).
The NGSS Clarification Statement says: "Examples of human activities can include urbanization, building dams, and dissemination of invasive species." HS-LS2-7 has no Assessment Boundary, so the lesson stays with what the performance expectation asks for and keeps the calculations to proportions, percentages and simple volumes. Every data set on this page is invented for teaching and labeled as invented, and every runoff coefficient is an assumed value stated with the problem. The one hands-on lab uses water, bagged potting soil, mulch and gravel only, with goggles, gloves and hand washing.
Learning Objectives
By the end of this lesson, students will be able to:
Use data to describe how urbanization, dams and invasive species change the physical environment and reduce biodiversity
Design a solution to one human impact and state measurable criteria and realistic constraints for it
Evaluate competing solutions with test data, cost figures and a weighted decision matrix, and explain the trade-offs
Refine a design after testing by identifying the part that failed a criterion and predicting the effect of the change
Distinguish evidence of a benefit to the environment from evidence of a benefit to biodiversity
Prior Knowledge Required
Students should already be comfortable with:
Evaluating competing design solutions for maintaining biodiversity and ecosystem services MS-LS2-5
Designing a method for monitoring and minimizing a human impact on the environment MS-ESS3-3
Criteria and constraints in engineering design MS-ETS1-1
Percentages, rates and area times depth as a volume
Show a map or photo of the school grounds and point to the nearest storm drain. Ask students where the water goes during a heavy rain.
Warm-Up Prompt
"Rain that falls on a forest mostly soaks in. Rain that falls on our parking lot runs into a storm drain and then into a creek. List two ways that difference could change the creek, and one living thing in the creek that could be harmed."
Collect answers on the board in two columns, environment (flooding, erosion, warm water, oil and sediment) and biodiversity (insects, fish, plants that disappear). Tell students that today they will design something that reduces the harm, then test and improve it.
Direct Instruction15-20 minutes
Three human activities and their impacts.Urbanization replaces soil and plants with roofs, roads and parking lots. Rain that cannot soak in runs off quickly, so creeks flood, banks erode and pollutants wash in, and roads split habitat and kill animals that cross them. Dams turn a flowing river into a lake, trap sediment, change water temperature and block fish that migrate upstream to spawn. Invasive species, carried to new places on boats, in cargo or in garden plants, can outcompete or eat native species. For each impact, a solution is judged on both the environment and biodiversity.
The design cycle. (1) Define the problem with criteria (what success means, with a number where possible) and constraints (limits such as cost, space and safety). (2) Design one or more solutions. (3) Evaluate them with test data, cost per unit of benefit and a weighted decision matrix, and name the trade-offs. (4) Refine: find the part that failed a criterion, change it and test again. Runoff volume is estimated as V = C × P × A, where P is rainfall depth, A is the area and C is the runoff coefficient (the fraction of the rain that runs off).
Urbanization: designing a parking lot surface
A 1,500 m² parking lot receives a 20 mm storm. Assume a runoff coefficient of 0.90 for asphalt and 0.30 for permeable pavers.
Result: Asphalt: 0.90 × 0.020 m × 1,500 m² = 27 m³ of runoff. Pavers: 0.30 × 0.020 × 1,500 = 9 m³. The pavers cut runoff by 18 m³, about 67%, which is evidence of a benefit to the environment (less flooding and erosion downstream).
Dams: evaluating and refining a fish ladder
Invented tagging data: 2,400 tagged adult fish reached the base of a dam in the first season after a fish ladder was built, and 1,560 were detected at the top. The design criterion is that at least 80% pass. Engineers then added a stronger attraction flow at the ladder entrance. The next season, 2,050 of 2,500 tagged fish passed.
Result: First design: 1,560 ÷ 2,400 = 65%, which fails the criterion. Refined design: 2,050 ÷ 2,500 = 82%, which meets it. Testing located the weak part (fish could not find the entrance), and the refinement targeted that part.
Invasive species: evaluating a removal program
Invented plot data for an invasive plant in a woodland: before removal, 4 removal plots had 6, 5, 7 and 6 native plant species per 1 m², and 4 control plots had 6, 7, 5 and 6. Two years after hand removal, the removal plots had 9, 11, 10 and 12 native species, while the control plots (no removal) still had 6, 7, 5 and 6.
Result: Removal plots: mean 6.0 before, 10.5 after, a gain of 4.5 species. Control plots: mean 6.0 before and after. Because the controls did not change, the gain is evidence that removal benefits biodiversity, not just a good year for all plots.
Weighted decision matrix
A city compares three stormwater solutions for one street, scoring each from 1 (poor) to 5 (excellent). Weights: runoff reduction 3, habitat value 2, cost 2, maintenance 1. Rain gardens score 4, 5, 4, 3. Permeable pavement scores 4, 1, 3, 3. An underground storage tank scores 5, 1, 2, 4.
Result: Rain gardens: 3(4) + 2(5) + 2(4) + 1(3) = 33. Pavement: 12 + 2 + 6 + 3 = 23. Tank: 15 + 2 + 4 + 4 = 25. Rain gardens win, mainly on habitat value; the tank removes the most runoff but adds nothing for biodiversity.
Cost per unit of benefit
A rain garden costs $6,000 and holds 12 m³ of runoff per storm. A green roof of about 1,200 m² costs $180,000 (about $150 per m²) and holds 18 m³ per storm.
Result: Rain garden: $6,000 ÷ 12 m³ = $500 per m³. Green roof: $180,000 ÷ 18 m³ = $10,000 per m³. The rain garden is twenty times as cost-effective for runoff, but the green roof uses no ground space, so the constraints of the site can still favor it.
After each example, ask: "Which number is the evidence? Is it evidence about the environment, about biodiversity, or both? What would you change next?" Point out that a solution can meet one criterion and fail another, which is why designers weigh trade-offs instead of looking for a perfect answer.
Guided Practice15 minutes
Pairs analyze the invented stream survey in the table and in Diagram 1. Each stream was sampled the same way for mayflies, stoneflies and caddisflies, insects that need clean, cool, oxygen-rich water and are food for fish.
Guided practice data: 8 invented streams
Stream
Impervious cover (%)
Sensitive insect taxa
A
2
24
B
5
22
C
8
19
D
12
14
E
18
10
F
25
7
G
33
5
H
40
4
Describe the pattern. Every stream at or below 8% impervious cover has at least 19 taxa, and every stream at or above 12% has at most 14.
Turn the pattern into a quantitative design criterion for a new neighborhood, for example: "effective impervious cover stays at or below 10%."
A planned 50-hectare subdivision will pave or roof 30% of its area (15 ha). If some impervious area drains into rain gardens instead of pipes, it no longer counts as effective. Solve 0.30 × (1 - f) = 0.10: f = 2/3, so 10 ha of the 15 ha must drain to infiltration features.
Name one constraint that could make this design hard to build, and one piece of monitoring data that would show whether it protects the stream's biodiversity.
Independent Practice10-15 minutes
Each student evaluates and refines a road design. An invented 5 km stretch of highway through forest averaged 36 deer-vehicle collisions per year. The state added wildlife fencing along the road and two underpasses. In the first year after the change there were 9 collisions, and 7 of them happened within 200 m of the two ends of the fence. Cameras recorded 1,150 animal crossings through the underpasses, by deer, coyotes and bobcats.
Students (1) compute the reduction in collisions (1 - 9/36 = 75%), (2) state which data are evidence for the environment and which are evidence for biodiversity, (3) find the weak part of the design from the data (7 of the 9 remaining collisions, about 78%, were at the fence ends), and (4) propose a refinement, such as extending the fence or adding escape ramps at the ends, with the data they would collect to test it.
Closure10 minutes
Exit ticket: "Pick one of today's three human activities. Write one criterion with a number, one constraint, and one piece of data that would tell you the solution needs to be refined." Return to the warm-up columns and ask students to move each impact to the solution that addresses it.
Differentiation Strategies
For Struggling Students
Give a design brief template with blanks for the problem, two criteria, two constraints, the test and the refinement
Provide a partly filled decision matrix so students first multiply weight by score for one option before scoring the others
Use one human activity (urbanization) for all practice before moving on to dams and invasive species
For Advanced Students
Ask students to change one weight in a decision matrix and find the smallest change that makes a different solution win, then explain what that says about the decision
Have students design a monitoring plan with a control site and a before-after comparison for a solution of their choice
Ask students to combine two solutions (for example rain gardens plus permeable pavement) and argue whether the combined benefit is simply the sum of the parts
Assessment Guidance
What to Look For
Strong work names the human activity and the specific harm, gives criteria with numbers and units, and separates criteria (what success means) from constraints (limits). Evaluations use data, cost per unit of benefit or a weighted matrix, and they name at least one trade-off. Refinements target the part of the design that failed a criterion and predict what the next test will show. Watch for solutions judged only on cost, claims of benefit with no comparison or control, and students who treat a benefit to water quality as proof of a benefit to biodiversity without species data.
02
Classroom Activities
3 Activities
1
Runoff Tray Lab: Design a Low-Impact City Block
30 minGroups of 3-4
Each group models a city block in an aluminum roasting pan, propped 5 cm high at one end, with a spout at the low end. Half of the pan must stay "pavement" (a clear plastic sheet). Groups design the other half, pour a 1,000 mL test storm from a watering can, measure the runoff, and refine their design once.
Design Brief
Criterion: at most 400 mL of the 1,000 mL test storm leaves the spout within 2 minutes.
Constraint: at least half the pan stays pavement (the block still needs a parking area), and each group may use at most 2 cups of soil, 1 cup of mulch and 1 cup of gravel.
Sketch the design and predict the runoff before you build it.
Procedure and Safety
Wear safety goggles and disposable gloves while handling soil, mulch and gravel. Use bagged potting soil and store-bought mulch only, never soil from roadsides or unknown sites, and keep the potting soil damp so it does not make dust.
Test the all-pavement pan first as the control. Pour the 1,000 mL slowly over 30 seconds with the sprinkler head, collect the runoff in the tub, and read the volume in the measuring jug after 2 minutes.
Build and test your design, record the runoff, then make one change and test again.
Wipe up spills at once so no one slips, keep water away from electrical outlets and devices, pour used water and soil outside on a planted area (not down the sink), and wash hands with soap at the end.
Sample Data (invented)
All pavement: 930 mL. Half pavement, half bare soil: 560 mL. Half pavement, half mulched soil: 470 mL. Refined design, with a gravel trench along the downhill edge of the pavement that catches runoff before it reaches the spout: 340 mL. Diagram 2 shows these results.
Discussion Questions
The mulched-soil design failed the criterion and the refined design met it. Which part of the design did the refinement change, and why did that part matter?
The pavement still sends water toward the spout in every design. How does the gravel trench deal with that?
What does the pan model leave out about a real city block? Name one limit of the model.
Modification for Distance Learning
Students run the test at home with a disposable baking pan, a zip-top bag as pavement and potting soil, with an adult's permission, or they analyze the sample data above and post a refined design sketch with a predicted runoff.
2
River Council: Evaluating Solutions for an Old Dam
25 minGroups of 5 (one role each)
An invented 70-year-old dam on a river blocks a run of migrating fish and traps sediment behind it. It also stores water for a small town. Each group acts as a river council and evaluates three solutions: a fish ladder, trap-and-haul (catching fish below the dam and trucking them upstream), and removing the dam. Roles: fisheries biologist, town water manager, farmer who irrigates from the reservoir, river recreation guide, and city budget officer.
Fish ladder: fish passage 3, river habitat and sediment 2, water supply 5, cost 4.
Trap-and-haul: fish passage 2, river habitat and sediment 1, water supply 5, cost 3.
Dam removal: fish passage 5, river habitat and sediment 5, water supply 1, cost 2.
Procedure
Each role argues for a weight from 1 to 3 for each criterion. The group agrees on one set of weights and records the reasons.
Compute the weighted total for each solution. Start with the sample weights fish passage 3, habitat 2, water supply 3, cost 2, then use your own.
Change the water-supply weight to 1 and recompute. Record whether the winner changes.
Write a recommendation that names the winner, the trade-off it accepts, and one refinement that would reduce its weakest score.
Discussion Questions
With the sample weights the fish ladder wins (36, against 32 for removal and 29 for trap-and-haul). With the water-supply weight at 1, dam removal wins. What does that tell you about how the council's values shape the "best" solution?
Trap-and-haul scores lowest under both sets of weights. Is there any situation where it could still be the right first step?
Which criteria are about the environment and which are about biodiversity? Is any criterion about both?
Modification for Distance Learning
Assign roles in breakout rooms and share the scoring card as a spreadsheet that computes the totals, so groups can test several sets of weights quickly.
3
Stop the Spread: Refining a Boat Inspection Plan
20 minPairs
Zebra mussels are an invasive species that spread between lakes on boats and trailers and can crowd out native mussels. An invented lake with three boat ramps ran a first-season inspection plan. Pairs analyze the season's data, find where the plan failed, and refine it within a fixed staff budget.
Season 1 Data (invented)
Plan: inspectors at the main ramp only, 8 a.m. to 4 p.m.
Boats launched: main ramp 2,400, north ramp 900, south ramp 700 (4,000 in all). About 30% of launches at the main ramp happened before 8 a.m.
Boats inspected: 1,600, all at the main ramp. Boats found carrying mussels or plant fragments: 32.
Constraint: the budget pays for 16 inspector-hours per day, and each ramp needs someone present to inspect.
Procedure
Compute the share of all boats inspected (1,600 ÷ 4,000 = 40%) and the share of inspected boats that carried mussels or plant fragments (32 ÷ 1,600 = 2%).
Identify the two biggest gaps in the plan from the data.
Refine the plan: decide how to spend the 16 inspector-hours across ramps and hours of the day, and add one low-cost measure (for example, a locked gate at a small ramp or a self-service cleaning station).
Write the criterion your refined plan should meet in Season 2, and the data you will collect to check it.
Discussion Questions
The north and south ramps had no inspectors, so 1,600 of the 4,000 boats (40%) launched there without any check. Why is that a bigger gap than the 2% of inspected boats that carried mussels?
How does the early-morning data change when inspectors should start?
Is the number of boats found with mussels good evidence that the plan protects native species? What other data would you want?
Challenge Variation
Pairs compare their refined plan with another pair's plan using the same criterion, and argue which one is more likely to keep the invasive species out of the lake.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Sensitive Stream Insects Against Impervious Cover
Invented survey of 8 streams, drawn to scale. Streams whose watersheds have more roofs and pavement have fewer kinds of pollution-sensitive insects, and the drop is steep between about 8% and 12% cover. Designers can turn a pattern like this into a quantitative criterion for new development, such as keeping effective impervious cover at or below 10%.
Diagram 2: Runoff Tray Lab Results Against the Design Criterion
Invented sample data from Activity 1, drawn to scale. Every tray received a 1,000 mL test storm. The mulched-soil design (470 mL) still failed the 400 mL criterion, so the group refined it with a gravel trench that catches water running off the pavement, and the refined tray (340 mL) met the criterion.
04
Homework Assignment
~30 min
HS-LS2-7 Homework: Design, Evaluate and Refine
Directions: All data sets, prices and scores are invented for practice, and every runoff coefficient is an assumed value given in the problem. Show each calculation with units. For every design question, state at least one criterion and one constraint, and end each problem with a sentence that says whether the evidence is about the environment, biodiversity, or both.
Part 1: Designing for Urban Runoff (Problems 1-2)
A school roof of 800 m² drains into a storm pipe. Assume a runoff coefficient of 0.95. (a) Find the volume of runoff from a 30 mm storm, in m³ and in liters. (b) A rain barrel holds 200 L. How many barrels would capture the whole storm? (c) Use your answer to argue whether barrels alone meet a criterion of "capture all runoff from a 30 mm storm" within a constraint of fitting along one wall of the school, and design a better combination.
A green roof is tested on a 20 mm storm. Design 1 has 5 cm of growing medium and holds back 8 mm of rain; Design 2 has 10 cm and holds back 14 mm. The criterion is to hold back at least 60% of a 20 mm storm. The constraint is that the roof can carry at most 120 kg/m² of wet growing medium, and the wet medium has a density of 1,500 kg/m³. (a) Find the percent held back and the load in kg/m² for each design. (b) Does either design meet both the criterion and the constraint? (c) Assume retention rises in a straight line with depth. Would an 8 cm layer meet both? (d) Propose a refinement and say how you would test it.
Part 2: Evaluating Solutions for Dams and Invasive Species (Problems 3-4)
Scientists counted fish species upstream of a small dam for 3 years before it was removed (4, 4 and 5 species) and for 3 years after (8, 10 and 11). A similar nearby river whose dam stayed in place had 5, 5 and 6 species in the same "before" years and 6, 5 and 6 in the "after" years. In the first year after removal, the water downstream was muddy for several months. (a) Find the mean number of species before and after on each river. (b) Evaluate the claim "Removing the dam increased biodiversity upstream." Why does the second river matter? (c) Name the trade-off shown by the muddy water, and whether it is an environmental or a biodiversity cost.
A lake manager compares three ways to control an invasive floating plant. Weights: effectiveness 3, low harm to native species 3, cost 2, speed 1. Scores from 1 to 5: mechanical harvesting 3, 4, 2, 4; herbicide 5, 2, 4, 5; biological control (a plant-eating insect) 4, 4, 5, 1. (a) Compute each weighted total and name the winner. (b) Recompute with the speed weight raised to 3. Does the winner change? (c) Before releasing an insect as biological control, what evidence should the manager require so the solution does not create a new invasive species problem?
Part 3: Refining and Arguing (Problems 5-6)
A fish ladder must climb a 6.0 m dam, and fish in this river can jump at most 0.30 m from one pool to the next. Each pool is 3.0 m long. (a) How many pool steps does the ladder need, and how long is it if it runs in a straight line? (b) The riverbank beside the dam has only 40 m of space. Refine the layout so the ladder fits without changing the step height. (c) In the first test, 1,020 of 1,500 tagged fish passed. The agency's criterion is 85%. Does the ladder meet it, and what would you investigate next?
A developer can build 160 homes on a 40-hectare forest in two ways. Plan A spreads the homes out and leaves eight separate 1-hectare patches of forest. Plan B clusters the homes and leaves one connected 20-hectare forest. Invented surveys of similar sites found an average of 2 forest-interior bird species in 1-hectare patches and 9 in 20-hectare patches. (a) What percent of the forest does each plan keep? (b) Use the data to argue which plan better protects biodiversity, and name one environmental benefit of the same plan. (c) Propose one refinement to the better plan and the evidence you would collect to evaluate it.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Design
Solution targets the named impact, with a numerical criterion and a realistic constraint
Solution given, but the criterion has no number or the constraint is missing
Evaluation with Data
Correct calculations with units; compares options or uses a control and names a trade-off
Calculations mostly correct, but no comparison, control or trade-off
Refinement
Identifies the part that failed and predicts the result of a specific change and how to test it
Suggests a change without linking it to the failed criterion or a test
Environment and Biodiversity
Correctly labels evidence as about the environment, biodiversity or both
Treats all benefits as the same kind of evidence
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All data sets, prices and scores are invented, and each runoff coefficient is an assumed value given in the question. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
A town wants a design that reduces flooding from a new shopping center. Which statement is a constraint rather than a criterion?
Answer: C
A constraint is a limit on the possible solutions, such as a budget. Choices A, B and D describe what success looks like, so they are criteria. Choice B is easy to mistake for a constraint because it contains a minimum, but it sets a target for biodiversity rather than ruling any design out.
Question 2 of 20 · Multiple Choice
A 600 m² parking lot receives a 40 mm storm. Assume a runoff coefficient of 0.85. About how much water runs off?
Answer: B
V = C × P × A = 0.85 × 0.040 m × 600 m² = 20.4 m³. Choice A forgets the runoff coefficient (it assumes all rain runs off). Choice C uses 0.15, the fraction that soaks in. Choice D converts 40 mm to 0.40 m instead of 0.040 m.
Question 3 of 20 · Multiple Choice
Why do fish biologists count tagged fish both at the base of a dam and at the top of its fish ladder?
Answer: A
Passage efficiency is the number detected at the top divided by the number that reached the base, so both counts are needed. Choice C claims more than the counts can show, and choice B needs a species survey, not a tag count.
Question 4 of 20 · Multiple Choice
A refined fish ladder is tested: 1,200 tagged fish reach the base of the dam and 840 are detected at the top. What is the passage efficiency?
Answer: D
840 ÷ 1,200 = 0.70 = 70%. Choice A is the share that failed to pass. Choice B divides the wrong way (1,200 ÷ 840 ≈ 1.43). Choice C reads 840 as a share of 1,000.
Question 5 of 20 · Multiple Choice
An invasive vine is pulled from 5 plots in a park. Which additional data would best show that the removal, and not the weather, caused native plants to return?
Answer: D
Untreated control plots show what would have happened without removal. If they stay the same while removal plots gain native species, the gain is linked to removal. Choices B and C measure effort, not the outcome for biodiversity.
Question 6 of 20 · Multiple Choice
Two designs are scored from 1 to 5 on two criteria. Wildlife value has weight 3 and cost has weight 1. Design P scores 2 for wildlife and 5 for cost. Design Q scores 4 for wildlife and 2 for cost. Which design wins, and by how much?
Answer: C
P: 3(2) + 1(5) = 11. Q: 3(4) + 1(2) = 14, so Q wins by 3. Choice D adds the raw scores without weights (P 7, Q 6), which ignores that wildlife value counts three times as much as cost. Choice A has the right gap but swaps the two totals.
Question 7 of 20 · Multiple Choice
A bioswale (a planted ditch that soaks up runoff) is designed to absorb a 25 mm storm, but in testing it overflows during storms above 15 mm, and the soil stays waterlogged for days. What is the best refinement to test next?
Answer: B
The test data point to the part that failed: water is not draining into the ground, so the refinement changes drainage and is tested again. Choice C ignores the criterion. Choice A removes the habitat value, and choice D repeats the design without addressing the cause.
Question 8 of 20 · Multiple Choice
A city paves over a meadow for a new parking lot. Which change to the nearby creek is an impact on the environment rather than directly on biodiversity?
Answer: A
Peak flow and erosion are physical changes to the environment. They can lead to biodiversity loss, but choices B, C and D are the biodiversity changes themselves, measured as fewer kinds of organisms.
Question 9 of 20 · Multiple Choice
Which statement best explains how a dam can reduce biodiversity in a river?
Answer: C
A dam blocks passage and turns flowing water into a still reservoir, changing temperature and trapping sediment, so species adapted to a flowing river decline. Choice B is backward: the reservoir behind a dam is slower, not faster. Choice D ignores the changes in flow and sediment downstream.
Question 10 of 20 · Multiple Choice
Zebra mussels spread between lakes mainly on boats and trailers. Which solution targets the pathway of spread?
Answer: B
Inspection and cleaning stop mussels before they enter the lake, so it acts on the pathway. Choice C monitors the harm but does not prevent it, and choice A treats a different part of the ecosystem.
Question 11 of 20 · Multiple Choice
A school planted native flower strips along its fields. Invented surveys found 12 bee species before planting and 18 two years later. What is the percent increase?
Answer: D
The increase is 6 species, and 6 ÷ 12 = 0.5 = 50%. Choice B divides by the new count (6 ÷ 18). Choice A reports the raw change as a percent, and choice C divides 18 by 12 and reads the ratio 1.5 as 150% without subtracting the original.
Question 12 of 20 · Multiple Choice
To remove an invasive fish from a small lake, managers plan a treatment that also kills the native fish for one season. Native fish will then be restocked from a nearby lake. How should a council weigh the loss of native fish when it evaluates this plan?
Answer: A
Evaluation weighs trade-offs over time: losing the native fish for one season is a real cost to biodiversity, but the invasive fish would keep harming native species every year if it stayed. Choice B draws a general conclusion from one cost. Choice C throws away the rest of the evidence. Choice D ignores that the native fish are part of the biodiversity the plan is meant to protect.
Question 13 of 20 · Multiple Choice
Rain garden X costs $4,800 and holds 16 m³ of runoff per storm. Rain garden Y costs $9,000 and holds 20 m³. Which is more cost-effective for holding runoff?
Answer: B
X: $4,800 ÷ 16 = $300 per m³. Y: $9,000 ÷ 20 = $450 per m³. Lower cost per unit of benefit is more cost-effective. Choice A judges by total benefit and ignores cost, and choice C swaps the two values.
Question 14 of 20 · Multiple Choice
A company says: "Our new culvert design helped fish. After we installed it, we saw lots of fish in the stream." What is the biggest weakness of this evidence?
Answer: C
Evidence of a benefit needs a comparison: before and after, or a treated and an untreated site, with counts rather than "lots". Choice D proposes a different design instead of evaluating the evidence for this one.
Question 15 of 20 · Short Answer
A new two-lane road will cut through a forest used by deer, salamanders and foxes. Write one quantitative criterion and one constraint for a solution that reduces the road's impact on wildlife, and name the design you would test first.
Sample answer. Criterion: animal-vehicle collisions on the new road stay at least 80% below those on a similar unfenced road, measured over one year. Constraint: the solution must fit within the road budget and must not close the road to traffic. Design: wildlife fencing that guides animals to underpasses, with a small tunnel for salamanders. Full credit needs a number and unit in the criterion and a real limit in the constraint.
Question 16 of 20 · Short Answer
A garage roof of 150 m² will drain into a rain garden. Assume a runoff coefficient of 0.90. The design must hold the runoff from a 25 mm storm, and the rain garden can pond water 0.15 m deep. What is the smallest area the rain garden can have?
Runoff = 0.90 × 0.025 m × 150 m² = 3.375 m³. Area = volume ÷ depth = 3.375 ÷ 0.15 = 22.5 m². A design slightly larger than this adds a margin for heavier storms.
Question 17 of 20 · Short Answer
A river group releases native freshwater mussels at 3 sites after cleaning out an invasive clam. Invented counts of live native mussels per 10 m² after one year: cleaned sites 14, 11, 17; three uncleaned sites where the same number were released: 5, 3, 4. Evaluate the evidence that removing the invasive clam helped the native mussels.
Mean at cleaned sites = (14 + 11 + 17) ÷ 3 = 14 per 10 m²; mean at uncleaned sites = (5 + 3 + 4) ÷ 3 = 4. The same number were released everywhere, and every cleaned site beat every uncleaned site, so the data support the claim. The sample is small (3 sites each), so repeating the test at more sites would make the evidence stronger.
Question 18 of 20 · Short Answer
A fish ladder's first test gave 62% passage against a criterion of 80%. Tag detectors show that almost every fish enters the ladder, and most of the fish that fail turn back at the same pool, where the water drops 0.45 m to the next pool. Every other step drops 0.30 m. What should the designers refine, and what result would show the refinement worked?
The weak part is that one step: fish find and enter the ladder, but the 0.45 m drop is higher than the others, and most failing fish turn back there. Refine it by splitting the drop into smaller steps, for example by adding a pool so no drop is more than 0.30 m. The refinement worked if the next season's tagging shows at least 80% of the fish that reach the base pass the ladder, and the detectors no longer show fish turning back at that pool.
Question 19 of 20 · Short Answer
A council scores two solutions for an urban creek from 1 to 5. Criteria and weights: flood reduction 2, habitat 2, cost 1. A concrete channel scores 5, 1, 3. A restored floodplain park scores 4, 5, 2. Compute both totals. Then raise the flood-reduction weight to 4 and compute again. Does the winner change?
Weights 2, 2, 1: channel = 10 + 2 + 3 = 15; park = 8 + 10 + 2 = 20, so the park wins. Weights 4, 2, 1: channel = 20 + 2 + 3 = 25; park = 16 + 10 + 2 = 28, so the park still wins. The park's lead shrinks from 5 to 3 points: its habitat score makes the decision robust to this change.
Question 20 of 20 · Short Answer
A new wastewater plant removes most of the nutrients a town used to release into a lake. Give one piece of evidence that would show a benefit to the environment and one that would show a benefit to biodiversity, and explain why the first does not prove the second.
Environment: lower nitrogen and phosphorus levels, fewer algae blooms, or higher dissolved oxygen in summer. Biodiversity: more native fish, insect or plant species counted in the lake in standard surveys. Cleaner water makes it possible for species to return, but they may not, for example if they cannot reach the lake or an invasive species blocks them, so species counts are needed.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-LS2-7 mean?
HS-LS2-7 asks high school students to design, evaluate and refine a solution that reduces the impact of a human activity on the environment and on biodiversity.
The code reads: HS (high school), LS2 (the life science core idea Ecosystems: Interactions, Energy, and Dynamics), performance expectation 7. Students do engineering work inside a biology topic: they test a design, compare it with others and improve it.
What human activities does HS-LS2-7 include?
The Clarification Statement names urbanization, building dams and the spread of invasive species as examples.
Other activities with clear ecosystem impacts, such as roads, farming runoff or overfishing, also fit, as long as students design, evaluate and refine a solution. This lesson uses all three official examples.
Is HS-LS2-7 biology or environmental science?
It is a life science standard, so it is usually taught in Biology, and it also fits naturally in Environmental Science.
It sits in the ecosystems unit, often after students study biodiversity and ecosystem stability (HS-LS2-6), and it pairs well with the engineering design standards HS-ETS1-2 and HS-ETS1-3.
What is the difference between evaluating and refining a solution?
Evaluating judges how well a solution meets its criteria and constraints; refining changes the solution to fix what the evaluation found.
An evaluation uses test data, costs and trade-offs, often in a weighted decision matrix. A refinement targets the weak part, such as a fish ladder entrance that fish cannot find, and is tested again.
How do you tell an impact on the environment from an impact on biodiversity?
Environmental impacts are changes to the physical surroundings; biodiversity impacts are changes in the number and variety of living things.
Faster runoff, warmer water and muddier streams are environmental. Fewer kinds of insects, fish or plants are biodiversity. A solution can fix the first without fixing the second, so good evaluations measure both.
What is a weighted decision matrix?
It is a table that scores each solution on each criterion, multiplies each score by a weight that shows how much that criterion matters, and adds the results.
The highest total wins, but students should also test how the result changes when a weight changes. If a small change in weights flips the winner, the decision depends on values, and the group should say so.
Does HS-LS2-7 have an assessment boundary?
No. The NGSS gives no Assessment Boundary for HS-LS2-7.
Assessments usually ask students to work with a given problem and data: propose a design, judge solutions against criteria and constraints, and suggest a refinement. The math stays at percentages, rates and simple volumes.
What are common mistakes students make with HS-LS2-7?
A common mistake is to propose a solution without saying how anyone would know whether it worked.
Others include mixing up criteria and constraints, judging a solution only by cost, claiming a benefit with no before-and-after or control data, and treating cleaner water as proof that species have returned.
Is there a safe hands-on lab for HS-LS2-7?
Yes. A runoff tray lab uses water, bagged potting soil, mulch and gravel in aluminum pans to model a city block.
Students wear goggles and gloves, keep the soil damp so it does not make dust, wipe spills at once, keep water away from outlets, dispose of muddy water outside and wash their hands. Avoid soil from roadsides or unknown sites.
How does HS-LS2-7 connect to other standards?
It builds on the middle school standards MS-LS2-5 and MS-ESS3-3 and leads to HS-LS4-6, where students use a simulation to test a solution for biodiversity.
It runs parallel to HS-ESS3-4, which evaluates or refines technology that reduces human impacts on natural systems, and to the engineering design standards.
07
Related Standards
5 standards
These standards connect to HS-LS2-7: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-LS2-5Prerequisite
Evaluate competing designs for maintaining biodiversity and ecosystem services
NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.
