HS-LS1-2: Modeling the Hierarchy of Interacting Systems in Organisms
In plain English: HS-LS1-2 is the NGSS high school performance expectation that asks students to develop and use a model of how a multicellular organism is organized in levels, from cells to tissues, organs and organ systems, and how those systems interact to carry out functions such as nutrient uptake, water delivery and movement. It is usually taught in Biology.
Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.
Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.
Next Generation Science Standards · Disciplinary Core Idea: From Molecules to Organisms: Structures and Processes · Official standard
Students develop and use models of how a multicellular organism is organized in levels: cells form tissues, tissues form organs, organs work together in organ systems, and organ systems interact so the whole organism can carry out a function. The official example is the center of the lesson: an artery, an organ of the circulatory system, depends on elastic tissue and smooth muscle to deliver the right amount of blood. Students build a working artery model, time a nerve-to-muscle response, trace water through a celery stalk, analyze invented blood-flow data, and critique and revise hierarchy models.
The official Clarification Statement reads: "Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system." The Assessment Boundary reads: "Assessment does not include interactions and functions at the molecular or chemical reaction level." So every model in this lesson stops at the level of cells and above. How cells release energy, how nerve signals pass from cell to cell chemically and how hormones act on cells are beyond this standard and do not appear in any activity, homework or quiz item.
Learning Objectives
By the end of this lesson, students will be able to:
Develop a model that shows the levels of organization in a multicellular organism (cells, tissues, organs, organ systems, organism) and use it to explain one function
Use a model of an artery to explain how elastic tissue and smooth muscle together deliver and regulate blood flow within the circulatory system
Use a model to trace how two or more systems interact in nutrient uptake, water delivery in a plant, or movement in response to a nerve signal
Analyze data and calculate organism-level quantities, such as blood pumped per minute and reaction time, with units, and use them to test a model
Predict how a failure at one level of organization affects the other levels, and revise a model when evidence does not fit
Prior Knowledge Required
Students should already be comfortable with:
The body is a system of interacting subsystems made of groups of cells MS-LS1-3
Living things are made of cells, either one cell or many types of cells MS-LS1-1
Sensory receptors send messages to the brain, which leads to a response MS-LS1-8
Plants take in water through roots and lose water vapor from leaves
Rates and unit conversions, such as milliliters to liters and centimeters to meters
Show a short clip or photo of someone pulling a hand back from a hot pan. Students write alone for two minutes, then compare with a partner.
Warm-Up Prompt
"You touch a hot pan and your hand jerks away before you even feel the pain. List every part of your body that took part, from the fingertip to the arm. Which of those parts would you call cells, which tissues, and which organs? Which systems had to work together?"
Collect answers in a list on the board without sorting them yet. Students usually name the skin, nerves, brain, spinal cord, arm muscles and bones. Point out that the list mixes levels (a nerve, a muscle, the nervous system) and tell the class that by the end of the lesson they will sort it into a model with levels and arrows between systems.
Direct Instruction20 minutes
Part 1: The levels. Build the hierarchy on the board from the bottom up, with a plant example next to each animal example:
Cells are the smallest living units. In a multicellular organism, cells are specialized: a muscle cell can shorten, a root hair cell has a long extension that takes in water.
Tissues are groups of similar cells that work together: muscle tissue, the lining of the intestine, the water-carrying xylem tissue of a stem.
Organs are made of several tissues working together: the heart, an artery, a leaf, a root.
Organ systems are organs that work together for one main function: the circulatory system, the digestive system, a plant's root system and shoot system.
The organism depends on its systems interacting. No system works alone: the muscles that move a leg need blood from the circulatory system and signals from the nervous system.
Part 2: The official example, an artery. Project Diagram 1. An artery is an organ. Its wall has elastic tissue, which stretches when the heart pushes blood in and springs back between beats, so blood keeps moving between heartbeats instead of arriving in spurts. It also has smooth muscle, which tightens to narrow the artery or relaxes to widen it, so it controls how much blood reaches the organs downstream. Nerves signal the smooth muscle, so the nervous system and the circulatory system interact. Work through the examples below.
Hierarchy model: walking
Build the levels for the function "a person walks up a hill."
Result: Cells: muscle cells shorten. Tissue: skeletal muscle tissue. Organ: a thigh muscle, which also contains connective tissue, nerves and blood vessels. Systems: the muscular system pulls on the skeletal system, the nervous system signals when to contract, and the circulatory system delivers blood. Organism: the person climbs.
Official example: the artery
Explain how an artery depends on elastic tissue and smooth muscle to deliver the proper amount of blood.
Result: Elastic tissue stretches during each heartbeat and recoils between beats, keeping blood flowing steadily. Smooth muscle narrows or widens the artery, raising or lowering the amount of blood that reaches an organ. If either tissue fails, the artery (organ) cannot do its part in the circulatory system.
Quantitative model: blood delivered per minute
At rest, a student's heart beats 70 times per minute and pushes out 75 mL of blood per beat (typical resting values). How much blood does the heart deliver to the arteries each minute?
Result: 70 beats/min × 75 mL/beat = 5,250 mL/min = 5.25 L/min. The heart (an organ) and the arteries (organs) together deliver this blood to every tissue.
Quantitative model: timing a nerve signal
In the hot-pan response, a signal travels from the fingertip to the spinal cord and back out to the arm muscles, a path of about 1.5 m, at about 60 m/s. How long does the signal spend traveling?
Result: 1.5 m ÷ 60 m/s = 0.025 s, or 25 milliseconds. The hand moves before the brain registers pain, because the spinal cord sends the signal back to the muscles directly.
Plant model: water delivery
A leafy sunflower shoot in a potometer takes up 3.0 mL of water in 60 minutes. With its leaves removed, the same shoot takes up 0.6 mL in 60 minutes (invented data).
Result: 3.0 ÷ 60 = 0.05 mL/min with leaves; 0.6 ÷ 60 = 0.01 mL/min without. Water loss from the leaves (organs of the shoot system) draws water up the xylem tissue of the stem, so removing the leaves cut the rate to one fifth.
Close Part 2 by sorting the warm-up list into levels together. Ask: which two systems interact in the hot-pan response? (Nervous and muscular, with the skeletal system as the levers.)
Guided Practice15 minutes
Pairs analyze the invented data below, which follow the pattern shown in physiology textbooks, and compare them with Diagram 2. Values are liters of blood per minute delivered to each group of organs.
Blood flow to organs in one person at rest and during hard exercise (invented data, L/min)
Organs
At rest
Hard exercise
Skeletal muscles
1.0
12.0
Digestive organs
1.4
0.5
Kidneys
1.1
0.5
Brain
0.7
0.7
Skin
0.5
1.5
Heart muscle
0.3
0.8
Total
5.0
16.0
How many times more blood does the heart pump per minute during exercise? (16.0 ÷ 5.0 = 3.2 times.)
What percent of the total goes to the skeletal muscles at rest and during exercise? (1.0 ÷ 5.0 = 20% at rest; 12.0 ÷ 16.0 = 75% during exercise.)
Which organs receive less blood during exercise, and which receive the same? (The digestive organs and the kidneys receive less; the brain receives the same 0.7 L/min.)
Use the artery model to explain how the flow can rise to one organ and fall to another at the same time. (Smooth muscle in the arteries to the leg muscles relaxes, widening them; smooth muscle in the arteries to the digestive organs tightens, narrowing them. Nerve signals control both.)
Push students to name the level of each part of their explanation: heart (organ), smooth muscle (tissue), circulatory and nervous systems (organ systems), the runner (organism).
Independent Practice10-15 minutes
Students develop their own model for nutrient uptake. The model must show at least four levels for the small intestine (for example, lining cells, the lining tissue with its folds, the small intestine as an organ, the digestive system), at least one arrow to the circulatory system, and the organism-level result. Then they use the model to answer in writing: if the muscle tissue in the intestine wall stopped contracting, which level would fail first, and how would that affect nutrient delivery to a leg muscle? Collect the models to check for the errors listed in the assessment guidance.
Closure5 minutes
Exit ticket: (1) Put these in order from smallest to largest: organ system, cell, organ, tissue, organism. (2) Name one way the nervous system and the circulatory system interact in an artery. (3) Draw one arrow between two plant organs that shows water delivery, and label it.
Differentiation Strategies
For Struggling Students
Give a hierarchy template with five labeled boxes and a word bank for each level
Start from one familiar function (walking) and add one level at a time, bottom to top
Use the physical artery model from Activity 1 before the diagram, so the tissues have a concrete meaning
For Advanced Students
Ask students to compare the hierarchy in a plant and an animal and name one way they differ
Ask students to use the blood-flow data to argue whether the brain's constant supply is evidence of regulation
Ask how feedback keeps body conditions stable when systems interact (connects to HS-LS1-3)
Assessment Guidance
What to Look For
Strong models show every level in the right order, name a real part at each level, and use arrows to show at least two systems interacting to carry out one named function. In the artery example, students should give each tissue a job (elastic tissue keeps flow steady, smooth muscle controls the amount) and say what happens to the organ and the system if a tissue fails. Watch for these errors: listing tissues as organs or systems as organs, models with no interactions between systems, arrows with no function named, and calculations without units. Explanations at the molecular or chemical level are not required and should not be graded.
02
Classroom Activities
3 Activities
1
Build a Working Artery Model
25 minPairs
Pairs pump water through a stiff tube and through a tube with a stretchy section to model elastic tissue, then pinch the tube with a binder clip to model smooth muscle. They measure how much water is delivered and relate each part of the model to a level of organization.
Safety
Work over a tray or sink and wipe up spills right away
Wear safety goggles: water can spray from a loose connection
Use latex-free balloons if anyone has a latex allergy
Procedure
Fill a squeeze bottle (the heart) with water and push 1 m of clear tubing (the artery) onto its spout
Squeeze 20 times at a steady pace, one squeeze per second, with the free end in a graduated cylinder. Watch whether water keeps flowing between squeezes. Record the volume
Tape a long thin balloon over the free end of the tubing, snip a small hole in its far end, and repeat. The balloon is the elastic tissue
Clip a binder clip halfway across the tubing (smooth muscle tightening) and repeat 20 squeezes
If the Lab Does Not Work: Sample Data
Invented results for 20 squeezes: stiff tubing, 400 mL, and flow stopped between squeezes; tubing with the balloon section, 400 mL, and water kept dripping out between squeezes; tubing with the clip, 260 mL.
Discussion Questions
What did the balloon section change about the flow between squeezes? Which tissue in a real artery does the same job?
In the sample data, how much water was delivered per squeeze with and without the clip? (20 mL and 13 mL.) By what percent did the clip reduce delivery? (35%.)
Which level of organization is the tubing? Which level is the whole setup of bottle and tubing?
What does this model leave out about a real artery?
Modification for Distance Learning
Students use the sample data to compute delivery per squeeze and percent change, then draw a labeled model that maps each part of the setup to a tissue, an organ or a system.
2
Reaction Time: Systems Working Together
20 minPairs
Pairs measure reaction time with a dropped ruler and model the pathway from the eye to the finger muscles. They compare a normal trial with a distracted one and use the result to decide which part of the model takes the most time.
Procedure
One partner holds a 30 cm ruler at the 0 mark, just above the other partner's open thumb and finger. Without warning, the holder drops it and the catcher pinches it as fast as possible
Record the catch distance in centimeters. Do 5 trials
Repeat 5 trials while the catcher counts backward from 100 by 3s out loud (the distraction)
Convert each mean distance to a time with t = √(2d ÷ g), using d in meters and g = 9.8 m/s²
If the Lab Does Not Work: Sample Data
Invented catch distances for one student. Normal: 18, 15, 17, 16 and 14 cm. Distracted: 22, 24, 21, 23 and 25 cm.
Discussion Questions
What are the mean distances and reaction times in the sample data? (Normal: 16 cm, about 0.18 s. Distracted: 23 cm, about 0.22 s.)
Draw the pathway as a model: eye (sense organ), nerves, brain, spinal cord, nerves, arm and finger muscles, bones. Which systems does it include?
The distraction slowed the response. Which part of the model does that point to, and why?
A nerve signal travels about 1 m in 0.02 s. Why is the measured reaction time so much longer?
Variation: Touch Signal
Instead of watching the ruler, the catcher closes their eyes and the holder taps the catcher's shoulder at the moment of release. Compare the times and discuss which sense organ starts each pathway.
3
Tracing Water Delivery in a Plant
25 min plus 60 min waitingSmall groups (3-4)
Groups place celery stalks in colored water, one with leaves and one with its leaves removed, and measure how far the color travels. They use the results to model how the leaf, stem and xylem tissue work together to deliver water.
Safety
The teacher trims the celery ends with a knife; students use plastic knives for cross sections
Food coloring stains skin and clothing: wear aprons or old shirts and goggles
Procedure
Put 100 mL of water and 10 drops of blue food coloring in each of two cups
Place one freshly trimmed stalk with leaves in the first cup and one stalk with all leaves removed in the second. Set both in the same bright spot
After 60 minutes, cut each stalk into 1 cm slices from the bottom up and record the highest slice with blue dots
Look at a slice with a hand lens. Sketch where the blue dots appear
If the Lab Does Not Work: Sample Data
Invented results after 60 minutes: the color rose 9 cm in the stalk with leaves and 3 cm in the stalk without leaves.
Discussion Questions
What was the rate of rise for each stalk in the sample data? (0.15 cm/min and 0.05 cm/min, so 3 times faster with leaves.)
The blue dots form a ring near the outside of each slice. What tissue are they, and what level of organization is the stalk?
Why did the leaves speed up delivery? Draw an arrow model from the cup to the air.
What part of a whole plant's water delivery system is missing from this setup?
Modification for Distance Learning
Students run the celery test at home with a glass and food coloring, or use the sample data, and upload a photo or sketch of their model.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: The Artery as a Model of Hierarchy
Left: each level of organization is built from the level below, using the official artery example. Right: a simplified cross-section of an artery wall (not to scale; in real arteries elastic fibers also run through the muscle layer). The elastic tissue stretches and recoils with each heartbeat to keep blood flowing, and the smooth muscle tightens or relaxes to control how much blood reaches the organs downstream.
Diagram 2: Where the Blood Goes During Exercise
Bars are drawn to scale for the invented data in Guided Practice. During hard exercise the heart pumps 3.2 times as much blood, and arteries to the skeletal muscles widen while arteries to the digestive organs and kidneys narrow. Flow to the brain stays the same.
04
Homework Assignment
~30 min
HS-LS1-2 Homework: Modeling Interacting Systems
Directions: Show calculations with units. In every model, label each part with its level of organization (cell, tissue, organ, organ system, organism) and use arrows to show how parts and systems interact. Use g = 9.8 m/s² where needed. All data sets are invented for practice.
Part 1: Building Hierarchy Models (Problems 1-2)
Sort these into levels of organization: a stomach muscle cell, the stomach, the digestive system, the lining of the small intestine, a red blood cell, the circulatory system, the heart, a person. Then draw a model that shows how the digestive and circulatory systems work together to deliver nutrients from a meal to a leg muscle. Label at least four levels.
Use the artery model. (a) With age, the elastic tissue in large arteries can become stiffer. Predict what happens to blood flow between heartbeats, and explain your prediction with the model. (b) On a hot day, smooth muscle in the arteries that supply the skin relaxes. Predict what changes and how the change helps the organism. (c) For each change, name the level of organization where it starts and one level it affects.
Part 2: Using Models with Data (Problems 3-4)
A cyclist's heart beats 60 times per minute at rest and pushes out 80 mL per beat. During a hard climb it beats 150 times per minute and pushes out 110 mL per beat. (a) Find the blood delivered per minute in liters for each condition. (b) How many times greater is delivery during the climb? (c) Name three organ systems that must interact to keep the cyclist moving uphill, and give one interaction between two of them.
In a ruler-drop test, a student's catch distances when watching the ruler were 25, 27, 26, 24 and 28 cm. When the partner tapped the student's shoulder at release (eyes closed), they were 13, 14, 12, 15 and 11 cm. (a) Find each mean distance and convert it to a reaction time with t = √(2d ÷ g). (b) Draw the pathway model for each condition. (c) Use your models to suggest why the times differ in this data set.
Part 3: Testing and Revising Models (Problems 5-6)
A leafy geranium shoot in a potometer took up 4.8 mL of water in 2 hours. The undersides of all its leaves were then coated with petroleum jelly, which blocks the pores there, and it took up 0.9 mL in the next 2 hours. (a) Find each rate in mL per minute. (b) By what percent did the rate drop? (c) Use a model of the shoot system (leaves, stem, xylem tissue) to explain the result.
A student's model of "how the body moves an arm when a ball is thrown at you" shows: Organism → Organ → Cell → Organ system → Tissue, with a single box labeled "muscles." (a) Identify two problems with the model. (b) Draw a revised model with the levels in order and at least three systems, with arrows that show how they interact. (c) Use your revised model to predict what would happen during a long game of catch if the nerves and muscles of the arm were healthy but an artery supplying the arm muscles were partly blocked.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
No Credit (0 pts)
Levels of Organization
All parts placed at the correct level, in order
One or two parts at the wrong level
Levels missing or out of order
Interacting Systems
Arrows show at least two systems interacting for a named function
Systems shown but interactions unclear or unlabeled
Only one system, or no arrows
Calculations
Rates, flows and times correct with units
Correct method with one error or missing units
Calculations missing or wrong method
Use of Evidence
Predictions and revisions explained with the model and the data
Prediction given but reasoning incomplete
No link between data and model
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Choose an answer or write your own, then open the explanation to compare. Your score updates as you go, and Reset quiz clears it for another attempt. Use g = 9.8 m/s² where needed. All data are invented.
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
Which list goes from the smallest level of organization to the largest?
Answer: A
Cells form tissues, tissues form organs, organs form organ systems, and systems make up the organism. Choice B puts tissue below cell, but a tissue is made of cells. Choice D puts organ below tissue, but an organ is built from several tissues.
Question 2 of 20 · Multiple Choice
Which of these is an organ?
Answer: C
A leaf is built from several kinds of tissue that work together, which makes it an organ. Choice A is one cell. Choice B is a tissue. Choice D is an organ system made of stems, leaves and flowers.
Question 3 of 20 · Multiple Choice
Two tube models of an artery are pumped by the same squeeze bottle at one squeeze per second. Between squeezes, water keeps flowing out of tube Q but stops flowing out of tube P (invented observations). Which conclusion is best supported?
Answer: D
Flow that continues between pushes means part of the push was stored in a wall that stretched and then recoiled, which is the job of elastic tissue. Choice B is not supported: a clip would lower the amount delivered, but flow would still stop between squeezes. Choice C is wrong: the bottle models the heart and the tubes model arteries.
Question 4 of 20 · Multiple Choice
Smooth muscle in the wall of an artery that supplies the stomach tightens. What happens?
Answer: A
When smooth muscle in the wall tightens, it narrows the artery and reduces flow to the organs it supplies. Choice B describes the smooth muscle relaxing. Choice C confuses the artery with the heart, a separate organ.
Question 5 of 20 · Multiple Choice
A student's heart beats 80 times per minute and pushes out 70 mL of blood per beat. How much blood does it deliver per minute?
Answer: B
80 beats/min × 70 mL/beat = 5,600 mL/min = 5.6 L/min. Choice A drops a zero in the multiplication. Choice C adds the two numbers instead of multiplying. Choice D divides 70 by 80.
Question 6 of 20 · Multiple Choice
A nerve signal travels 0.9 m from a toe to the spinal cord at 60 m/s. How long does the trip take?
Answer: C
Time = distance ÷ speed = 0.9 m ÷ 60 m/s = 0.015 s, or 15 milliseconds. Choice A multiplies distance by speed. Choice B divides speed by distance, which does not give a time. Choice D moves the decimal point.
Question 7 of 20 · Multiple Choice
Invented data: after a large meal, blood flow to a person's digestive organs rises from 1.2 L/min to 2.0 L/min while total blood flow stays about the same. Which explanation fits the hierarchy model?
Answer: D
Total flow is about the same, so blood was redistributed, which is what smooth muscle in artery walls does. Choice B would raise the total flow, but the data say it stayed about the same. Choice A has no support: organs do not make blood.
Question 8 of 20 · Multiple Choice
A ruler is caught after falling 19.6 cm. Using t = √(2d ÷ g) with g = 9.8 m/s², what is the reaction time?
Answer: B
2 × 0.196 m ÷ 9.8 m/s² = 0.04 s², and √0.04 = 0.20 s. Choice A forgets the square root. Choice C leaves out the factor of 2 (√0.02 ≈ 0.14). Choice D uses 19.6 cm without converting to meters (√4 = 2).
Question 9 of 20 · Multiple Choice
Oxygen from the air reaches a working leg muscle. Which two organ systems must interact for this to happen?
Answer: C
The respiratory system brings air into the lungs, and the circulatory system carries oxygen from the lungs to the muscle. Choice A involves moving the leg, not delivering oxygen. Choice D leaves out both the system that takes in air and the one that carries blood.
Question 10 of 20 · Multiple Choice
Which model best shows water delivery in a tomato plant?
Answer: B
Water enters the root system, moves up through xylem tissue in the stem, and leaves through the leaves as water vapor. Choice A reverses the direction. Choice D sends water from the roots back into the soil before it reaches the stem.
Question 11 of 20 · Multiple Choice
A student's model of "delivering the right amount of blood to a working muscle" shows only the heart. What is the most important addition?
Answer: D
The heart sets the total flow, but arteries control how much of it reaches each organ, and nerves signal the smooth muscle, so two systems and several tissues are involved. Choice A is wrong: blood is not made in the lungs. Choice B gives the skeleton a job it does not do.
Question 12 of 20 · Multiple Choice
Invented potometer data: a leafy shoot takes up 0.03 mL of water per minute in still air and 0.06 mL per minute with a fan blowing on it. Which conclusion is best supported?
Answer: A
The fan speeds water loss from the leaves, and uptake doubled from 0.03 to 0.06 mL/min, which links leaf and stem function. Choice C cannot be tested here: a potometer shoot has no roots. Choice D is contradicted by the doubled rate.
Question 13 of 20 · Multiple Choice
Which sequence models the response when you see a ball coming and raise your hands?
Answer: C
The sense organ detects the ball, nerves carry the signal to the brain, the signal returns through the spinal cord and nerves to the muscles, and the muscles pull on the bones. Choices A and D run the pathway backward, and choice B starts the response before anything is detected.
Question 14 of 20 · Multiple Choice
The nerves that serve a person's arm are damaged, but the arm muscles are healthy. What does the hierarchy model predict?
Answer: B
Movement needs the nervous and muscular systems to interact; without signals, healthy muscles do not contract when the person decides to move. Choice C ignores the interaction between systems. Choice D has no link to damage in one arm.
Question 15 of 20 · Short Answer
During a hard workout, a runner's heart beats 120 times per minute and pushes out 95 mL per beat. Her resting delivery is 5.0 L/min. Find her delivery during the workout in L/min and how many times greater it is than at rest.
120 × 95 = 11,400 mL/min = 11.4 L/min. 11.4 ÷ 5.0 = 2.28 times the resting delivery. The heart (organ) pumps more, and arteries to the working muscles widen, so the extra blood goes where it is needed.
Question 16 of 20 · Short Answer
In a celery test (invented data), color rose 6.3 cm in 45 minutes in a stalk with leaves and 2.7 cm in 45 minutes in a stalk without leaves. Find both rates and explain the difference with a model.
With leaves: 6.3 ÷ 45 = 0.14 cm/min. Without leaves: 2.7 ÷ 45 = 0.06 cm/min. Water lost from the leaves draws water up through the xylem tissue of the stem, so the leaves (organs) and the stem (organ) work together as the shoot system; without leaves, delivery slows.
Question 17 of 20 · Short Answer
Develop a hierarchy model for water delivery in an oak tree. Give one example at each of the five levels.
Cells: xylem cells (or root hair cells). Tissue: xylem tissue. Organs: roots, the trunk and leaves. Organ systems: the root system and the shoot system. Organism: the oak tree. Arrows: water moves from the soil into the root system, up through xylem in the trunk, and out of the leaves as water vapor.
Question 18 of 20 · Short Answer
When a person is frightened, arteries to the digestive organs narrow while arteries to the leg muscles widen. Use the artery model to explain how this happens and why it helps the organism.
Smooth muscle in the walls of arteries to the digestive organs tightens, narrowing them, while smooth muscle in arteries to the leg muscles relaxes, widening them. Nerve signals control both, so the nervous and circulatory systems interact. More blood reaches the leg muscles, which helps the person run or react, while digestion can wait.
Question 19 of 20 · Short Answer
A student catches a dropped ruler at 14, 16, 15, 13 and 17 cm (invented data). Find the mean distance and the reaction time with t = √(2d ÷ g), g = 9.8 m/s².
Mean = 75 ÷ 5 = 15 cm = 0.15 m. t = √(2 × 0.15 ÷ 9.8) = √0.0306 ≈ 0.17 s.
Question 20 of 20 · Short Answer
An artery that supplies part of the heart muscle becomes blocked. Use the hierarchy model to predict the effects at each level, from cells to organism.
Cells: heart muscle cells beyond the blockage receive no blood and can die. Tissue: that area of heart muscle tissue stops contracting. Organ: the heart pumps less blood. Organ system: the circulatory system delivers less blood to every organ. Organism: the person may become weak or be in danger. A failure at one level spreads to every level above it.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-LS1-2 mean?
HS-LS1-2 asks students to develop and use a model of the hierarchical organization of interacting systems in multicellular organisms. In practice, students show how cells form tissues, tissues form organs, organs form organ systems, and how those systems work together to carry out functions such as nutrient uptake, water delivery and movement in response to nerve signals.
What is the official example in HS-LS1-2?
The Clarification Statement gives an artery that depends on elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system. It works well as an anchor because one organ shows two tissues, two jobs and a link to a whole system.
Does HS-LS1-2 include cellular respiration or how nerve signals work chemically?
No. The Assessment Boundary says assessment "does not include interactions and functions at the molecular or chemical reaction level." Keep models at the level of cells, tissues, organs and systems. Cellular respiration is its own standard (HS-LS1-7).
Is HS-LS1-2 only about the human body?
No. The standard says multicellular organisms, so plants count too. Water delivery through roots, xylem tissue in the stem and leaves is one of the functions the Clarification Statement names, and plant examples help students see that the hierarchy is general.
What counts as a model for HS-LS1-2?
A labeled hierarchy diagram, a flow diagram with arrows between systems, a physical model such as tubing that acts like an artery, or a simple mathematical model such as blood pumped per minute. A strong model shows levels and interactions, and students use it to explain or predict.
Is HS-LS1-2 taught in Biology or Anatomy?
It is usually taught in high school Biology or Life Science, often after cells and before homeostasis (HS-LS1-3). Anatomy and Physiology courses go into much more detail on each system than this standard requires.
What mistakes do students make with levels of organization?
Frequent ones are calling a tissue an organ, calling an organ a system, drawing systems as separate boxes with no interactions, and naming a function without saying which parts carry it out. Ask students to label every box with its level and every arrow with what it carries.
How do I get students to use the model, not just draw it?
Ask for predictions: what happens if the elastic tissue stiffens, if a nerve is damaged, or if leaves are removed from a shoot. Then give data that tests the prediction, such as blood-flow numbers or potometer readings, and ask students to revise the model if the data do not fit.
Are these labs safe for a regular classroom?
Yes, with simple steps. The artery model uses water, tubing and balloons over a tray, the reaction-time test uses only a ruler, and the celery test uses food coloring and plastic knives. Wear goggles, wipe spills, use latex-free balloons when needed, and let the teacher do any cutting with a sharp knife.
How does HS-LS1-2 connect to other standards?
It builds on MS-LS1-3, where students argue that the body is a system of subsystems. It links back to HS-LS1-1, where proteins let specialized cells do their jobs, and forward to HS-LS1-3, where feedback between interacting systems keeps conditions inside the body stable.
07
Related Standards
5 standards
These standards connect to HS-LS1-2: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-LS1-3Prerequisite
Argue with evidence that the body is a system of interacting subsystems of cells
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