MS-LS1-6: Photosynthesis, Matter Cycling and Energy Flow
In plain English: MS-LS1-6 is the NGSS middle school performance expectation that asks students to construct an explanation, based on evidence, of the role of photosynthesis in moving matter and energy into and out of organisms. Students trace carbon dioxide and water into sugar and oxygen, and light energy into food energy that leaves as heat. It is usually taught in grade 6, 7 or 8 life science.
Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms.
Clarification Statement: Emphasis is on tracing movement of matter and flow of energy.
Assessment Boundary: Assessment does not include the biochemical mechanisms of photosynthesis.
Next Generation Science Standards · Disciplinary Core Idea: From Molecules to Organisms: Structures and Processes · Official standard
Students construct explanations, backed by evidence, of the role photosynthesis plays in moving matter and energy into and out of organisms. They trace matter: carbon dioxide from the air and water from the soil become sugar and oxygen, the sugar builds the plant or becomes food for animals, and the atoms eventually return to the air. They trace energy: light energy is stored in sugar, moves into animals as food, and leaves organisms as heat. Evidence comes from seedlings grown in light and dark, potted and hydroponic plants, algae jars with an oxygen sensor and food energy values. Data sets are invented for teaching unless labeled as standard values.
The NGSS Clarification Statement says: "Emphasis is on tracing movement of matter and flow of energy." The Assessment Boundary says: "Assessment does not include the biochemical mechanisms of photosynthesis." So students work with the inputs and outputs and with where matter and energy go, and never with the chemical steps inside the leaf. Students do the practice of constructing explanations: they analyze data, count atoms, compare masses and write claims with evidence and reasoning.
Learning Objectives
By the end of this lesson, students will be able to:
Name the matter (carbon dioxide, water, sugar, oxygen) and energy (light, stored food energy, heat) that go into and out of a plant in photosynthesis
Use atom counts and mass data to show that photosynthesis rearranges matter without creating or destroying it
Use evidence from seedlings, potted plants and algae to explain that most of a plant's mass comes from carbon dioxide and water, using light energy
Trace matter and energy from photosynthesis into animals that eat plants, and explain why matter cycles while energy flows
Prior Knowledge Required
Students should already be comfortable with:
Plants get the materials for growth mainly from air and water 5-LS1-1
Energy in animals' food was once energy from the sun 5-PS3-1
Matter is made of atoms and is conserved when it changes MS-PS1-5
Show a small acorn next to a photo of a full-grown oak tree that weighs several tonnes.
Warm-Up Prompt
"The oak grew from an acorn that weighed about 5 grams. Where did all the rest of the tree's matter come from? And where did the energy the tree used to grow come from? Write your best guess for each, and one observation that could test it."
Record answers in two columns: "matter" and "energy". Many students say the soil supplies the matter; keep that idea on the board, because the evidence in the lesson tests it.
Direct Instruction15-20 minutes
Key words.Matter is anything that has mass and takes up space, and it is made of atoms. Energy is the ability to cause change, such as motion or warming. Photosynthesis is the process in which plants, algae and some microorganisms use light energy to turn carbon dioxide and water into sugar, giving off oxygen:
carbon dioxide + water + light energy → sugar + oxygen, or with formulas, 6CO2 + 6H2O → C6H12O6 + 6O2.
Tracing matter. The atoms are rearranged, not created or destroyed, so the mass going in equals the mass coming out. Sugar is the plant's food: it is stored, used to build new plant material, or broken down to release energy. When an animal eats the plant, that matter moves into the animal. Animals and plants both break down sugar and give off carbon dioxide and water, which plants can use again, so matter cycles. Tracing energy. Light energy is stored in sugar. It moves into animals in food and is used for growth, motion and warmth, and it leaves organisms as heat, so energy flows through and does not come back as light. The steps inside the leaf are beyond this standard. All data on this page are invented for teaching unless they are labeled as standard values.
Counting atoms and mass (matter)
Use the formula equation. Count the atoms on each side. Then use these masses: a plant that makes 60 g of sugar uses 88 g of carbon dioxide and 36 g of water and gives off 64 g of oxygen.
Result: Left: 6 C, 12 H, 18 O (12 in CO2 + 6 in H2O). Right: 6 C, 12 H, 18 O (6 in sugar + 12 in O2). Mass: 88 + 36 = 124 g in and 60 + 64 = 124 g out, so no matter is lost or created.
Seedlings in light and dark (matter needs light energy)
Pea seeds from one packet weigh 0.25 g each when dried. Half are grown in light and half in a dark cupboard, with the same soil and water. After 3 weeks the seedlings are dried and weighed: 0.42 g each in light and 0.16 g each in the dark. See Diagram 2.
Result: Light: 0.42 - 0.25 = 0.17 g gained. Dark: 0.25 - 0.16 = 0.09 g lost. Without light there is no photosynthesis, so the dark seedlings use up the food stored in the seed and cannot add new matter.
Potted tree and soil (matter comes from air and water)
A lemon tree grows in a pot for 3 years and gains 2.0 kg. The dried soil in the pot weighs 10.00 kg at the start and 9.98 kg at the end.
Result: The soil lost only 0.02 kg, which is 1% of the 2.0 kg gained. So about 99% of the new matter came from somewhere else: carbon dioxide from the air and water taken in by the roots.
Energy in food came from the sun (energy)
A medium apple has about 19 g of sugar. A standard value for food energy is about 4 Calories (food energy units) per gram of sugar.
Result: 19 × 4 = 76 Calories. That energy was light energy, stored in sugar by the apple tree's leaves. When a person eats the apple, the energy moves into the person and is used for moving, growing and staying warm, and it leaves the body as heat.
Matter and energy into and out of an animal
A caterpillar eats 2.0 g of leaf (dry mass) in one day. Of that, 0.6 g becomes new caterpillar body, 0.5 g leaves as droppings, and the rest is broken down to release energy and leaves as carbon dioxide and water.
Result: 2.0 - 0.6 - 0.5 = 0.9 g leaves as carbon dioxide and water, which plants can take in again (matter cycles). The energy released from that 0.9 g is used and leaves the caterpillar as heat (energy flows).
After each example, ask: "What is the matter here, and where does it go? What is the energy, and where does it go?" Use Diagram 1 to sort each arrow into matter (solid) or energy (dashed).
Guided Practice10-15 minutes
Pairs analyze invented data from three clear plastic jars of pond water, each closed with a lid and holding an oxygen sensor. Jar A has green algae and sits under an LED lamp. Jar B has the same amount of algae but is wrapped in foil. Jar C has pond water with the algae filtered out and sits under the lamp. No animals are in the jars. Readings are dissolved oxygen in milligrams per liter (mg/L).
Guided practice data (invented): dissolved oxygen, mg/L
Jar
Start
After 4 hours
A: algae, light
8.0
10.4
B: algae, dark (foil)
8.0
7.4
C: no algae, light
8.0
8.0
Find the change in oxygen in each jar. Mark each one as a rise, a fall or no change.
Which jar is the control, and what does it rule out?
Explain the change in Jar A using the word equation. Which matter left the algae, and what energy did they use?
Jar B fell even though nothing was eating the algae. What were the algae doing with their stored sugar, and what did that use up?
Write a claim, evidence and reasoning statement about the role of light in photosynthesis.
Independent Practice10-15 minutes
Each student writes an explanation from new invented data. Potatoes are underground stems that store food made in the leaves. A farmer grew potato plants of one variety in three rows. In row 1 the leaves got full sun. In row 2 half of each plant's leaves were covered with shade cloth. In row 3 most of the leaves were trimmed off early in the summer.
Independent practice data (invented): potatoes harvested per plant
Row
Leaves
Mass of potatoes (kg)
1
all leaves in full sun
1.5
2
half the leaves shaded
0.9
3
most leaves removed
0.3
Students explain the pattern, trace the matter in a potato back to the air and the soil water, and trace the energy in a potato back to the sun. They finish by saying where that matter and energy go when a person eats the potato.
Closure5 minutes
Exit ticket: "Name the two kinds of matter that go into a leaf for photosynthesis and the two that come out. Then name the energy that goes in and one way energy leaves the plant." Return to the warm-up columns and ask students to cross out or keep the idea that the oak's matter came from the soil, citing one piece of evidence.
Differentiation Strategies
For Struggling Students
Give a two-color highlighter routine: one color for matter words and one for energy words in every data set
Provide a fill-in flow diagram with empty boxes for the two inputs, two outputs and one energy input
Use whole-number masses first (like 88 + 36 = 60 + 64 in the first worked example) before decimals
For Advanced Students
Ask students to explain why the oxygen in an algae jar rises in light but would level off if the jar were left in light for many days
Have students use the formula equation to find the mass of oxygen given off for any mass of sugar, and test their rule on a new value
Ask students to design an investigation that separates the effect of light from the effect of warmth from the lamp
Assessment Guidance
What to Look For
Check that students keep matter and energy apart: light is never an input of matter, and atoms never "turn into energy". Look for explanations that name both inputs and both outputs, use mass or atom counts as evidence, and follow the sugar into the plant's body or into an animal. Listen for students who say the plant's mass comes from the soil, or who draw energy arrows that loop back to the plant.
02
Classroom Activities
3 Activities
1
Light Box or Dark Box: A Seedling Investigation
15 min setup, 15 min data dayGroups of 3-4
Groups grow sweet corn seedlings in two identical pots, one on a sunny windowsill and one inside a closed shoebox, and compare them after 14 days. The investigation tests whether light is needed for a plant to add matter.
Procedure
Soak 12 sweet corn seeds in water overnight. Plant 6 seeds 2 cm deep in each of two pots with the same potting soil.
Put one pot on a sunny windowsill and the other in a shoebox with the lid on, in the same room. Give both 30 mL of water every other day.
On day 14, measure each seedling's height, note its color, and cut all seedlings in a pot at the soil line and weigh them together on a kitchen scale. Divide by the number of seedlings.
Safety: wash hands after handling soil, and do not eat treated seeds.
Sample Data (invented)
Day 14, mean per seedling. Window: 18 cm tall, green, 2.4 g. Shoebox: 24 cm tall, pale yellow, 1.5 g.
Discussion Questions
The shoebox seedlings were taller but lighter. Which measurement, height or mass, tells you more about how much new matter the plant added? Why?
Where did the matter in the shoebox seedlings come from, if they could not do photosynthesis?
Predict what will happen to the shoebox seedlings after another three weeks in the dark, and explain using energy.
Modification for Distance Learning
Students grow the two pots at home with dried beans or peas from the kitchen, post photos with a ruler on day 7 and day 14, and enter heights and masses in a shared class table.
2
Carbon Passport and Energy Tokens: A Moving Model
20 minWhole class
Each student carries one "carbon atom passport" through five stations and gets it stamped at each one: Air, Leaf, Plant body, Rabbit, Air again. Energy is modeled with paper tokens that start at the Leaf station and are dropped into a "heat" bin along the way. The model shows that matter cycles back to the air while energy flows through and leaves as heat.
Model Rules
At the Leaf station, each group of 4 students receives 10 light-energy tokens, now stored in sugar.
At the Plant body station, the plant uses 4 tokens to live and grow: they go into the heat bin. The other 6 stay stored in the plant.
At the Rabbit station, the rabbit eats the plant and gets those 6 tokens. It uses 5 to move and stay warm (heat bin) and stores 1 in its body.
At the last station, the carbon passport returns to Air as carbon dioxide breathed out by the rabbit. Tokens never go back to the Leaf station.
Discussion Questions
Count the tokens in the heat bin and the tokens still stored in the rabbit for one group. Do they add up to the 10 that entered at the Leaf?
Your carbon passport ended where it started. Could your energy tokens do the same? Why not?
Where in a real plant does the rabbit's carbon dioxide go next?
Modification for Distance Learning
Students move a game piece across a printed five-station board, keep the energy tokens as tally marks, and post a photo of their finished passport with a one-paragraph explanation.
3
Evidence Gallery: Air, Water or Soil?
20 minGroups of 3-4
Four posters around the room each show one invented data set. Groups rotate every 4 minutes and decide whether each poster supports, weakens or does not test the claim "Most of a plant's mass comes from carbon dioxide and water, using light energy." Then each group writes one explanation that uses at least three posters.
The 4 Posters (invented data)
Poster 1, hydroponic tomato: a tomato plant grows with its roots in water with dissolved minerals, and no soil. Its dry mass rises from 1 g to 41 g in 8 weeks, while the minerals added weigh 1.6 g in all.
Poster 2, closed bottle garden: a plastic bottle with its cap screwed on, holding moist soil and a small fern weighs 812 g on day 1 and 812 g on day 60, and the fern is still green and growing.
Poster 3, soil test: two pots of the same soil, one with a bean plant and one without, are dried and weighed after 6 weeks: 2.000 kg and 2.004 kg.
Poster 4, carbon dioxide and growth: seedlings in air with extra carbon dioxide, with the same light and water, gain 30% more dry mass than seedlings in normal air.
Discussion Questions
On Poster 1, the minerals added up to much less than the dry mass the plant gained. What must the rest of the mass be made of?
On Poster 2, the bottle's mass did not change while the fern grew. Explain how that can happen if no matter enters or leaves the bottle.
Which poster is the strongest evidence that carbon dioxide is one of the materials? Which one does not test the claim at all?
Challenge Variation
Groups design a fifth poster: an investigation that would weaken the claim if the claim were wrong. They say what result they would expect if plants really took most of their mass from the soil.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Matter and Energy Into and Out of a Plant
A flow model of photosynthesis in a leaf. Solid arrows show matter: carbon dioxide and water go in, oxygen goes out, and sugar is stored, builds the plant or becomes food for animals. Dashed arrows show energy: light energy goes in and is stored in sugar, and energy leaves as heat when the plant uses its sugar or as food eaten by animals.
Diagram 2: Pea Seedlings Gain Mass Only in the Light
Invented data from the worked example, drawn to scale. Seedlings grown in light weigh more than the seed they came from, so they added new matter. Seedlings grown in the dark weigh less than the seed, because they used up the seed's stored food without making more.
04
Homework Assignment
~30 min
MS-LS1-6 Homework: Tracing Matter and Energy Through Photosynthesis
Directions: Data sets are invented unless labeled as standard values. Use about 4 Calories per gram of sugar or starch. Show your calculations, and end each problem with an explanation that traces matter, energy or both into and out of the organism.
Part 1: Tracing Matter (Problems 1-3)
For every 30 g of sugar a plant makes by photosynthesis, it uses 44 g of carbon dioxide and 18 g of water and gives off 32 g of oxygen. (a) Show that the mass in equals the mass out. (b) How many grams of carbon dioxide and water does the plant use, and how much oxygen does it give off, to make 90 g of sugar? (c) Explain why a plant can gain a lot of mass while the soil it grows in barely changes.
A sweet potato vine grows in a jar of water with dissolved minerals and no soil. In 6 weeks its dry mass increases by 12 g, while the minerals it took up weigh 0.5 g. (a) How many grams of the gain did not come from the minerals? (b) What percent of the gain is that? (c) Name the two materials that most of the gain came from, and say how each got into the plant.
A clear plastic jar with a lid holds pond water and water plants, with no animals. An oxygen sensor reads 7.0 mg/L at sunrise, 9.4 mg/L at sunset and 8.2 mg/L at the next sunrise. (a) Find the change during the day and during the night. (b) Explain both changes. (c) Over the full 24 hours, did the plants add or remove oxygen overall? What does that tell you about whether they made more sugar than they used?
Part 2: Tracing Energy (Problems 4-6)
A 150 g serving of sweet corn has about 28 g of sugar and starch. (a) About how many Calories of food energy is that? (b) Trace that energy from where it started to where it is used in your body. (c) Where does the energy finally go?
A class model says: of 100 units of energy in the grass a grasshopper eats, 30 units leave in its droppings, 55 are released as heat as the grasshopper lives and moves, and the rest is stored in new body tissue. (a) How many units are stored? (b) Can the 55 units of heat be used again by the grass? Explain. (c) The grasshopper also breathes out carbon dioxide. Can those carbon atoms be used again by the grass? Explain the difference between (b) and (c).
In an invented study, seedlings were grown for 2 weeks under three conditions. Change in dry mass per seedling: light with normal air, +1.8 g; light with air that had most of its carbon dioxide removed, +0.3 g; dark with normal air, -0.2 g. (a) Which condition shows that light energy is needed? (b) Which shows that carbon dioxide is one of the materials? (c) Write an explanation of the role of photosynthesis that uses all three results.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Calculations
Correct masses, percents and energy values with units for every part
Correct method with one calculation or unit error
Tracing Matter
Names carbon dioxide and water going in, sugar and oxygen coming out, and where the sugar goes next
Names the inputs and outputs but does not follow the matter further
Tracing Energy
Follows light energy into sugar, into food for other organisms and out as heat, and says energy is not recycled
Traces energy part of the way, or treats energy as matter
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Data sets are invented. Use about 4 Calories per gram of sugar or starch where needed. 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
Which two kinds of matter does a plant take in and use for photosynthesis?
Answer: D
Photosynthesis uses carbon dioxide from the air and water from the soil. Choice A lists the products, not the inputs. Choice B includes sunlight, which is energy, not matter.
Question 2 of 20 · Multiple Choice
A student says a tree's mass comes mostly from the soil. Which observation argues best against that idea?
Answer: A
If the soil lost only a few grams while the tree gained kilograms, almost all the new matter came from somewhere else: carbon dioxide and water. Choice B shows that soil nutrients help, not that they make up the mass. Choice C describes roots but measures nothing about mass.
Question 3 of 20 · Multiple Choice
Which statement about energy in photosynthesis is correct?
Answer: C
Photosynthesis stores light energy in sugar. Choice A breaks the rule that energy is not created. Choice B mixes up energy and matter: carbon dioxide is an input made of atoms, not a form of energy.
Question 4 of 20 · Multiple Choice
In 6CO2 + 6H2O, how many oxygen atoms are there in all?
Answer: B
Six CO2 have 12 oxygen atoms and six H2O have 6, so 12 + 6 = 18. Choice A counts only the carbon dioxide. Choice C counts only the water. Choice D counts 2 oxygen atoms in each water molecule as well.
Question 5 of 20 · Multiple Choice
A plant uses 22 g of carbon dioxide and 9 g of water to make 15 g of sugar. How much oxygen does it give off?
Answer: A
Mass in is 22 + 9 = 31 g, and mass out must also be 31 g, so oxygen = 31 - 15 = 16 g. Choice B is the total mass in, not the oxygen. Choice C subtracts the sugar from the carbon dioxide only (22 - 15).
Question 6 of 20 · Multiple Choice
Algae in a jar wrapped in foil made the oxygen in the water go down. What best explains this?
Answer: D
In the dark there is no photosynthesis, but the algae keep breaking down stored sugar for energy, and that uses oxygen. Choice B is the opposite of the data. Choice C treats light, which is energy, as if it could become matter.
Question 7 of 20 · Multiple Choice
Which sentence correctly describes matter and energy in a meadow with grass and rabbits?
Answer: C
Atoms are used again and again: carbon dioxide breathed out by a rabbit can be taken in by grass. Energy enters as light, moves through food and leaves as heat, so it flows rather than cycles. Choice A swaps the two. Choice B says energy cycles, which it does not.
Question 8 of 20 · Multiple Choice
A snack bar has 24 g of sugar and starch. Using about 4 Calories per gram, how much food energy is that?
Answer: B
24 × 4 = 96 Calories. Choice A adds the numbers. Choice C divides 24 by 4. Choice D multiplies by 10 instead of 4.
Question 9 of 20 · Multiple Choice
Which result is the best evidence that a plant needs light to add matter?
Answer: D
Dry mass measures the matter in the plant, so a gain in light and a loss in the dark ties new matter to light. Choice B is about height, which can rise without new matter. Choice A shows a color change but no measurement of matter.
Question 10 of 20 · Multiple Choice
A student's model of photosynthesis shows light going in, carbon dioxide going in, and sugar and oxygen coming out. What is missing?
Answer: A
Water is the second input of photosynthesis, taken in through the roots. Choice B is wrong: heat is a way energy leaves, and light is the energy input. Choice D lists a product as an input.
Question 11 of 20 · Multiple Choice
How does matter made by photosynthesis get into a rabbit?
Answer: B
Animals get matter, and the energy stored in it, by eating plants or other animals. Choice C describes photosynthesis, which rabbits cannot do. Choice A is wrong because sugar is not a gas in the air.
Question 12 of 20 · Multiple Choice
To test whether algae give off oxygen in the light, which jar is the best control?
Answer: C
A jar with no algae under the same light shows whether the oxygen change comes from the algae or from something else, such as the light warming the water. Choices A, B and D still contain algae, so they cannot show what happens without them, and Choice A also changes both warmth and light at once.
Question 13 of 20 · Multiple Choice
A seed weighs 0.30 g dry. After 3 weeks in light the dried seedling weighs 0.58 g, and a seedling from the same packet grown in the dark weighs 0.19 g. How much matter did the seedling in light add?
Answer: A
0.58 - 0.30 = 0.28 g. Choice B compares the two seedlings (0.58 - 0.19) instead of comparing the seedling with its seed. Choice C is how much the dark seedling lost (0.30 - 0.19). Choice D adds the seed and the light seedling.
Question 14 of 20 · Multiple Choice
A deer eats leaves. Later, a carbon atom from those leaves is breathed out by the deer. Where can that carbon atom go next?
Answer: D
The deer breathes out the carbon atom in carbon dioxide, and a plant can take it in for photosynthesis, so matter cycles. Choices A and C confuse matter with energy: atoms do not turn into energy or heat in living things.
Question 15 of 20 · Short Answer
Using 6CO2 + 6H2O → C6H12O6 + 6O2, how many carbon dioxide and water molecules does a plant need to make 2 sugar molecules, and how many oxygen molecules does it give off?
Double every number: 12 CO2 and 12 H2O make 2 C6H12O6 and give off 12 O2. Check carbon: 12 in and 2 × 6 = 12 out.
Question 16 of 20 · Short Answer
A student runs a race after eating a bowl of oatmeal. Trace the energy she uses from where it started to where it ends up.
Light energy from the sun was stored in sugar and starch by photosynthesis in the leaves of oat plants. The energy moved into the student when she ate the oats. Her body broke down the food to release the energy, used it to move her muscles, and it left her body as heat. The energy flows one way; it does not return to the sun or the plants.
Question 17 of 20 · Short Answer
Invented data: a lidded plastic jar with algae under an LED lamp went from 7.5 to 9.1 mg/L of oxygen in 3 hours, and a foil-wrapped jar of the same algae went from 7.5 to 7.1 mg/L. Find both changes and explain them.
Light: +1.6 mg/L. Dark: -0.4 mg/L. In light, the algae did photosynthesis, made sugar and gave off oxygen faster than they used it. In the dark there was no photosynthesis, so they only used oxygen to break down stored sugar for energy.
Question 18 of 20 · Short Answer
An orange has about 12 g of sugar. About how many Calories of food energy is that (about 4 Calories per gram), and where did that energy come from?
12 × 4 = 48 Calories. The energy came from sunlight: the orange tree's leaves stored light energy in sugar by photosynthesis, and the sugar moved into the fruit.
Question 19 of 20 · Short Answer
A student's food web model shows energy arrows going from the sun to grass, from grass to a rabbit, and from the rabbit back to the grass. Explain what is wrong and how to fix it.
Energy does not cycle. The arrow from the rabbit back to the grass should be removed, and an arrow should show energy leaving the rabbit (and the grass) as heat. A matter arrow can go from the rabbit back to the grass, because the rabbit breathes out carbon dioxide and its droppings and body are broken down, so atoms return to the plant.
Question 20 of 20 · Short Answer
A potted geranium gained 40 g of dry mass in one season, while the dried soil in its pot lost 0.5 g. Find how much of the gain did not come from the soil and explain where it came from.
40 - 0.5 = 39.5 g, which is about 99% of the gain. It came from carbon dioxide from the air and water from the soil, which photosynthesis turned into sugar, using light energy. The plant then used the sugar to build new leaves, stems and roots.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-LS1-6 mean?
MS-LS1-6 asks students to build an explanation, using evidence, of how photosynthesis moves matter and energy into and out of organisms. Students trace carbon dioxide and water into sugar and oxygen, and light energy into food energy. The code means Middle School, Life Science, core idea 1 (From Molecules to Organisms: Structures and Processes), performance expectation 6.
What is the assessment boundary for MS-LS1-6?
The official Assessment Boundary says: "Assessment does not include the biochemical mechanisms of photosynthesis." Students need the inputs, the outputs and where matter and energy go, not the chemical steps inside the leaf. The Clarification Statement puts the emphasis on "tracing movement of matter and flow of energy."
What goes into and out of photosynthesis?
Carbon dioxide and water go in as matter, and light goes in as energy. Sugar and oxygen come out. The sugar stores the energy, and the plant uses it to grow, to store food or to get energy for its own life.
Do students need the chemical equation for MS-LS1-6?
A word equation is enough to trace matter and energy, but the formula equation, 6CO2 + 6H2O → C6H12O6 + 6O2, lets students count atoms and see that none are lost. Counting atoms fits the standard; the steps between the two sides do not.
Where does a plant's mass come from?
Mostly from carbon dioxide in the air and water, not from the soil. Potted-plant and hydroponic data show that the soil or minerals supply only a small part of the mass. Students are often surprised by this, so it is worth testing with evidence.
What is the difference between matter cycling and energy flow?
Matter cycles: the same atoms move from air to plant to animal and back to air, again and again. Energy flows: it enters as light, is stored in food, is used by organisms and leaves as heat, and it does not return as light. Diagrams should show matter arrows that loop and energy arrows that leave.
Is MS-LS1-6 only about plants?
No. The standard says "into and out of organisms", so it includes the animals that eat plants. Matter and energy made available by photosynthesis move into animals as food, and leave them as carbon dioxide, water, droppings and heat. Algae and some microorganisms also do photosynthesis.
What classroom-safe labs work for MS-LS1-6?
Seedlings grown in light and in a closed box, potted plants weighed with their soil, and algae jars with an oxygen sensor all work with simple materials. None need flames or strong chemicals. Data sets like the ones on this page help when a lab cannot run.
Do plants use oxygen too?
Yes. Plants break down some of their sugar for energy, day and night, and that uses oxygen and gives off carbon dioxide, just as animals do. In light, photosynthesis usually gives off more oxygen than the plant uses, so the overall change is an increase. The details of that process are taught in MS-LS1-7.
How does MS-LS1-6 connect to other standards?
It builds on 5-LS1-1 (plants get their materials mostly from air and water) and 5-PS3-1 (energy in food was once energy from the sun). It leads to MS-LS1-7, on how food is broken down and rebuilt, and to MS-LS2-3, on matter and energy in whole ecosystems. In high school, HS-LS1-5 models how light energy becomes chemical energy.
07
Related Standards
6 standards
These standards connect to MS-LS1-6: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
5-LS1-1Prerequisite
Argue that plants get materials for growth chiefly from air and water
Lesson coming soon
5-PS3-1Prerequisite
Model that energy in animals' food was once energy from the sun
Lesson coming soon
Alongside
MS-LS2-3Parallel
Model the cycling of matter and flow of energy among parts of an ecosystem
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