MS-LS1-1: Investigating Evidence That Living Things Are Made of Cells
In plain English: MS-LS1-1 is the NGSS middle school performance expectation that asks students to conduct an investigation that gives evidence that living things are made of cells. Students use hand lenses and microscopes to tell living from nonliving samples and to show that some organisms are a single cell while others have many cells of different types. It is usually taught in grade 6, 7 or 8 life science.
Conduct an investigation to provide evidence that living things are made of cells; either one cell or many different numbers and types of cells.
Clarification Statement: Emphasis is on developing evidence that living things are made of cells, distinguishing between living and non-living things, and understanding that living things may be made of one cell or many and varied cells.
Next Generation Science Standards · Disciplinary Core Idea: From Molecules to Organisms: Structures and Processes · Official standard
Students collect their own evidence that living things are made of cells. A cell is the smallest unit that can carry out the jobs of life, and an organism is any single living thing. Students look at living, once-living and never-living samples with hand lenses and a microscope, test samples for signs of life over a few days, and estimate cell sizes from what they see. They compare single-celled organisms, which are one cell, with multicellular organisms, which are made of many cells, often of several different types.
The NGSS Clarification Statement says: "Emphasis is on developing evidence that living things are made of cells, distinguishing between living and non-living things, and understanding that living things may be made of one cell or many and varied cells." NGSS gives no Assessment Boundary for MS-LS1-1, so the lesson keeps the focus that statement sets: evidence for cells, living or not, and one cell or many. How the parts inside a cell work belongs to MS-LS1-2 and is not assessed here. All class data on this page are invented for teaching and labeled as invented; microscope field sizes are typical values for school microscopes. Students do the practice of conducting an investigation: they plan, observe, count, measure and argue from what they record.
Learning Objectives
By the end of this lesson, students will be able to:
Prepare a wet mount, find a sample at low power and calculate total magnification
Use microscope observations to decide whether a sample is made of cells
Distinguish living, once-living and never-living samples using cells plus other evidence such as growth and reproduction
Give evidence that some organisms are a single cell and others are many cells of different numbers and types
Estimate cell sizes and cell counts from the field of view and write a claim backed by evidence
Prior Knowledge Required
Students should already be comfortable with:
Plants and animals have internal and external structures that support survival and growth 4-LS1-1
Matter is made of particles too small to be seen 5-PS1-1
Dividing multi-digit whole numbers 6.NS.B.2
Reading a data table and recording observations in a science notebook
Put three things on the front table: a clump of live moss, a dry brown leaf from the ground and a piece of sidewalk chalk. Ask students to sort them before anyone touches a microscope:
Warm-Up Prompt
"Which of these is alive now, which was alive once, and which was never alive? What could you observe, today or over a few days, that would give evidence for your answer?"
List the evidence students suggest on the board (it moves, it grows, it is green, it needs water, it is made of tiny parts). Circle "made of tiny parts": today they test it. Keep the list, because the class returns to it in Closure.
Direct Instruction15 minutes
Key words. A cell is a tiny unit with an outer edge that holds its contents; every living thing is made of one or more cells. A microscope uses lenses to make small things look larger. Magnification is how many times larger the image looks: multiply the number on the eyepiece (the lens you look into) by the number on the objective (the lens just above the slide). The field of view is the round area you see through the eyepiece. Cells are measured in micrometers (µm): 1 mm = 1,000 µm. For the class microscopes, the field of view is about 4,500 µm across at 40×, 1,800 µm at 100× and 450 µm at 400× (measure yours with a clear ruler at 40×). Show Diagram 1, then work through the examples.
Total magnification
A microscope has a 10× eyepiece. A student switches to the 40× objective to look at cheek cells.
Result: Total magnification = 10 × 40 = 400×. The cells look 400 times wider than they really are.
Estimating cell size from the field of view
At 400× the field of view is 450 µm across. About 9 cheek cells fit in a row across it (Diagram 1).
Result: Each cell is about 450 µm ÷ 9 = 50 µm across. Every cell has its own outer edge, so the sample is many separate cells from one person.
One cell is the whole organism
At 100× (field of view 1,800 µm) a Paramecium from a pond culture is about one eighth as long as the field is wide. It swims, takes in food and backs away when it bumps into something.
Result: Length ≈ 1,800 µm ÷ 8 = 225 µm. It has one outer edge and no walls inside it, so the whole organism is a single cell, and it still does every job of a living thing.
Made of cells, but alive now?
Under the microscope, a dry brown leaf from the ground shows rows of empty, box-shaped cells. Kept on a wet paper towel for a week, it does not grow or turn green.
Result: The cells are evidence the leaf came from a living thing. The lack of growth is evidence it is no longer alive. Cells tell you "living now or once living," not "living now."
Many cells in one small organism
A moss leaf is about 1,500 µm long and 400 µm wide, only one cell thick. Its cells are about 60 µm long and 20 µm wide.
Result: 1,500 ÷ 60 = 25 cells along the length and 400 ÷ 20 = 20 across, so about 25 × 20 = 500 cells in one tiny leaf. The moss plant has many leaves, plus stems and root-like threads with other cell types.
After each example, ask: "What did the student observe, and what does it count as evidence for?" Stress two ideas. Seeing cells shows a sample is or was part of a living thing. Being one cell or many is a separate question, answered by looking for walls or edges inside the organism and for cells of different shapes.
Guided Practice15 minutes
Pairs read the invented results below from another class that looked at six samples. For each sample they decide: living now, once living, or never living; and, for the organisms, one cell or many.
Guided practice data (invented): six samples, observed at 100× and kept for 5 days
Sample
Cells seen?
What the cells look like
Change over 5 days
P
Yes
Single oval cells that swim; some pinch into two
Many more swimmers
Q
No
Rough white grains of different sizes
No change
R
Yes
Sheet of long green cells, side by side
New green tips grew
S
Yes
Box-shaped cells, brown and empty
No change
T
No
Smooth, even strands with no edges across them
No change
U
Yes
Flat, separate cells, each with one dark spot
Sample was used up on day 1
Sort the samples. Living now: P and R. Once living: S. Never living: Q and T. Sample U came from a living person, but the scraped cells alone cannot be tested for growth.
Count: 4 of the 6 samples show cells, and only 2 of those 4 show growth. Ask: why is "cells seen" not enough to call a sample alive now?
Which sample is a whole organism made of one cell? (P: each swimmer is one cell, and it reproduces by dividing.)
Write one sentence that uses samples P and R as evidence that living things are made of cells, either one cell or many.
Independent Practice10-15 minutes
Each student analyzes a new invented observation. A green thread from a pond, an alga (a simple plant-like living thing that grows in water) called Spirogyra, is viewed at 100×, where the field of view is 1,800 µm across. The thread crosses the whole field. Thin walls cross it at even spacing, splitting it into 15 equal box-shaped sections, each with a green spiral band inside. A second thread, kept in a sunny window, grows from 6 mm to 9 mm long in 4 days.
Students estimate the length of one section (1,800 µm ÷ 15 = 120 µm), decide whether the thread is one cell or many (many: each walled section is a cell), decide whether the cells are all one type (they look the same), and write a claim, evidence and reasoning paragraph that also uses the growth data. Ask them how this organism differs from a Paramecium.
Closure5 minutes
Exit ticket: "Name one observation that shows an organism is a single cell, and one that shows an organism has many cells of different types." Return to the warm-up list and ask which items the class now has real evidence for. Moss: cells and growth. Dry leaf: cells, no growth. Chalk: no cells, no growth.
Differentiation Strategies
For Struggling Students
Give a recording sheet with three columns (cells seen? changes over time? one cell or many?) and picture cards of each sample
Pre-focus one microscope at each station on the 10× objective so students can compare before they focus on their own
Use a sentence frame: "Sample ___ is ___ because I observed ___ and ___."
For Advanced Students
Ask students to measure the field of view at 40× with a clear ruler and calculate the field at 100× and 400× by proportion
Ask students to plan how they would tell a small many-celled organism from a large single cell under the microscope, and what they would sketch as proof
Ask students to estimate how many cells a whole moss plant has, stating every assumption they make
Assessment Guidance
What to Look For
Check that students name the observation, not just the conclusion ("I saw separate edges around each unit," not "it is alive"). Look for students who treat any tiny structure as a cell, such as chalk grains or thread fibers, and for students who think "made of cells" proves a sample is alive now. Listen for the difference between one cell that is a whole organism and one cell scraped from a many-celled body. Check every size estimate for the right field of view and for µm as the unit.
02
Classroom Activities
3 Activities
1
Living, Once Living or Never Living? Microscope Stations
30 minPairs
Pairs rotate through six stations, make or use a wet mount (a sample in a drop of water under a cover slip), find it at 40×, then move to 100× or 400×. At each station they sketch what they see, label the total magnification, and record whether they see cells.
Stations
1: one moss leaf pulled off with tweezers, in a drop of water
2: a drop from a live Paramecium culture
3: a small torn piece of a dry brown leaf, in a drop of water
4: your own cheek cells (see the safety notes), or a prepared slide of human cheek cells
5: a 1 cm piece of polyester thread
6: a pinch of crushed sidewalk chalk in a drop of water
Safety
Cheek cells are collected only with the teacher watching. Each student gently rubs the inside of their own cheek with the flat end of a new toothpick, smears it on their own slide and adds one drop of diluted blue food coloring. Used toothpicks go straight into the zip bag; nobody shares slides or toothpicks. The teacher collects the used slides and disinfects them before washing. Any student who prefers not to take part, or any class whose school does not allow cheek-cell sampling, uses the prepared slide of human cheek cells instead.
No blades are used: the teacher crushes the chalk, and students tear leaves by hand or with tweezers.
Carry microscopes with one hand on the arm and one under the base. Use plastic cover slips, report any broken glass to the teacher, and wash hands at the end.
Sample Data (invented)
One pair recorded: moss, many green cells side by side (100×); Paramecium, single swimming cells (100×); dry leaf, empty brown cells (100×); cheek, flat separate cells with one dark spot each (400×); thread, smooth strands with no edges across them (100×); chalk, rough grains of many sizes, no edges inside them (100×).
Discussion Questions
In the sample data, three stations held samples from something alive now (moss, Paramecium, a person) and three did not. Which observations alone could not tell those two groups apart?
The chalk grains and the cells both look like small separate pieces. What feature did the cells have that the grains did not?
The cheek cells came from a person, and the Paramecium is a whole organism. How is one cheek cell different from one Paramecium?
Modification for Distance Learning
Students use labeled micrographs (photos taken through a microscope) of the six samples from a free online microscope image collection, sort them in a shared slide, and record evidence for each choice.
2
One Cell or Many? Sizes and Cell Types
20 minGroups of 3
Groups first measure the field of view: at 40×, a clear plastic ruler shows the field is about 4.5 mm (4,500 µm) across. Since 100× is 2.5 times 40×, the field at 100× is 4,500 ÷ 2.5 = 1,800 µm. Then they compare three living samples and decide which are one cell and which are many cells, and of how many types.
Procedure
At 100×, estimate the size of one Paramecium and one Volvox ball by asking "how many would fit across the field?"
Look for walls or edges inside each organism. Count the kinds of cells you can tell apart by shape, size or color.
Look at the prepared slide of a plant root cross-section (a thin slice made by the supply company) and sketch every kind of cell you see.
Sample Data (invented)
Paramecium: about 8 fit across the 100× field, one cell, no inside walls. Volvox: a green ball about one quarter of the field across (about 450 µm), with hundreds of tiny green cells around the outside and 6 larger, darker cells inside, so 2 kinds of cells. Root slice: an outer layer of small flat cells, large round packed cells in the middle area, and small thick-walled tube cells in the center, so 3 kinds of cells.
Discussion Questions
Volvox is wider than a Paramecium. Does that make it one cell or many? What did you see that decided it?
Of the three samples, only the root slice showed three kinds of cells. Why might a bigger, more complex organism have more types of cells?
What would you need to look for to convince a skeptic that a Paramecium really is one cell?
Challenge Variation
Groups estimate how many tiny cells cover the outside of the Volvox ball: they count the cells along a short stretch of the edge in their sketch and scale up. They report the estimate as a range and explain why it is not exact.
3
Brine Shrimp Eggs: Is It Alive?
25 min, plus 5 min on each of 2 later daysGroups of 3-4
Dry brine shrimp eggs look like brown dust. Groups plan and run a test to decide whether the specks are alive, using tiny specks of crushed chalk as a never-living comparison. This is the investigation practice: they choose what to change, what to keep the same and what to record.
Procedure
Cup A: 500 mL of water with 2 level teaspoons (about 12 g) of non-iodized salt and a small pinch of eggs. Cup B: 500 mL of plain tap water and the same pinch of eggs. Cup C: salt water like Cup A with a pinch of chalk specks.
Keep all three cups side by side in the same warm room, out of direct sun.
Each day, take three 1 mL samples from each cup with a dropper, put each in a small petri dish, and count anything swimming at 40×.
Safety: use non-iodized salt only, never taste the water, and wash hands after handling the cups. At the end, offer the shrimp to a classroom fish tank as food or pour the cups into a sink; never release them outdoors.
Sample Data (invented)
Swimmers counted in three 1 mL samples. Cup A: day 0: 0, 0, 0; day 1: 3, 5, 4; day 2: 11, 9, 13. Cup B: day 0: 0, 0, 0; day 1: 0, 0, 0; day 2: 1, 0, 0. Cup C: 0 in every sample on every day. Diagram 2 shows the means.
Discussion Questions
The mean count in Cup A went up every day. What does that show about the specks in Cup A?
Cup C never had a swimmer. Why was it useful to include it?
Cup B had only one swimmer in nine samples. Does that prove the eggs in Cup B are not alive? What would you change or keep watching?
Modification for Distance Learning
Students analyze the sample data, draw their own bar graph, and record a short video explaining which cup gave the strongest evidence of life and why.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Estimating Cell Size from the Field of View (400×)
Cheek cells drawn to scale in a 450 µm field of view (the field at 400× on a typical school microscope). Nine cells fit in a row across the field, so each is about 50 µm across. Each cell has its own edge and one dark spot, which is evidence that the sample is many separate cells.
Diagram 2: Brine Shrimp Egg Test (Invented Data)
Mean number of swimmers in three 1 mL samples from each cup, drawn to scale from the invented data in Activity 3. Only the eggs in salt water hatched in large numbers; the chalk specks never produced a swimmer. Growth in numbers is evidence of life that cells alone cannot give.
04
Homework Assignment
~30 min
MS-LS1-1 Homework: Collecting Evidence for Cells
Directions: All data are invented for practice. Use these fields of view for a school microscope with a 10× eyepiece: 4,500 µm at 40×, 1,800 µm at 100× and 450 µm at 400×. Remember 1 mm = 1,000 µm. Show your math, and end each problem with a sentence that names your evidence.
Part 1: Magnification and Size (Problems 1-2)
A microscope has a 10× eyepiece and a 20× objective. (a) Find the total magnification. (b) The field of view gets narrower in the same proportion as the magnification gets larger. Use the 4,500 µm field at 40× to find the field of view at your answer to (a). (c) An amoeba from a pond culture stretches across about one third of that field. Estimate its length in µm. (d) The amoeba has one outer edge and no walls inside it. Is it one cell or many? Explain.
Duckweed is a tiny plant that floats on ponds. The top layer of one duckweed leaf is about 3,000 µm long and 2,000 µm wide, and its cells are about 50 µm by 50 µm. (a) About how many cells fit along the length, and how many across the width? (b) About how many cells are in the top layer? (c) Explain why the whole duckweed plant has more cells than your answer.
Part 2: Living or Not? (Problems 3-4)
Two green samples are scraped from a fish tank. Sample 1, from the glass, shows many separate round green cells, each about 10 µm across; on the glass, the green film grows from 2 cm² to 6 cm² in 5 days. Sample 2, a fleck from a green plastic plant, shows smooth green material with no edges inside it and no change in 5 days. (a) How many times larger did the green film get? (b) Which sample is living? Give two pieces of evidence. (c) Is the green film one organism made of many cells, or many single-celled organisms? What observation supports your answer?
A bag of dry lentils from the grocery store looks lifeless. Plan an investigation to test whether the lentils are alive. (a) What will you do to the lentils, and what will you use as a never-living comparison? (b) What will you keep the same for both? (c) What will you observe and record, and for how many days? (d) How could you show that a lentil is made of cells, and why is that alone not enough to show it is alive?
Part 3: One Cell or Many, and How Many Types (Problems 5-6)
Use these invented observations. Organism W: one cell about 150 µm long that swims with tiny hairs. Organism X: a chain of 20 identical box-shaped cells. Organism Y: a flat sheet of about 1,000 green cells that all look alike. Organism Z: a roundworm about 1 mm long, made of about 1,000 cells of several types: skin, muscle, gut and nerve cells. (a) Sort the organisms into: one cell; many cells of one type; many cells of more than one type. (b) Y and Z have about the same number of cells. What makes Z different? (c) Which organism must do every job of life inside a single cell?
A student claims, "Big plants are big because their cells are big." A class measured the surface cells of four plants (invented data): duckweed leaf 3 mm long, cells 50 µm; clover leaf 20 mm long, cells 55 µm; maple leaf 120 mm long, cells 45 µm; banana leaf 2,100 mm long, cells 60 µm. (a) How many times longer is the banana leaf than the duckweed leaf? (b) How many times larger is the banana leaf cell than the duckweed cell? (c) Write a claim, evidence and reasoning response to the student.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Calculations
Magnifications, sizes and counts correct, with µm or the right unit
Correct method with one arithmetic or unit error
Evidence for Cells and Life
Names specific observations (edges, walls, growth, reproduction) and says what each is evidence for
States a conclusion with general or missing evidence
Investigation Plan
Plan has a comparison, things kept the same, observations to record and enough time
Plan is missing a comparison or a clear list of observations
Claim, Evidence, Reasoning
Claim answers the question, cites data, and explains why the data support it
Claim and evidence given, but reasoning is missing
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All observations and data are invented for practice. Unless a question says otherwise, use these fields of view for a school microscope with a 10× eyepiece: 4,500 µm at 40×, 1,800 µm at 100× and 450 µm at 400×. 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 observation is the best evidence that a sample from a garden is made of cells?
Answer: C
Cells show up under a microscope as small units, each with its own outer edge. Choice B is not evidence of cells: green paint and green plastic have no cells. Choice A describes texture, which many nonliving things share, and choice D is about where it came from, not what it is made of.
Question 2 of 20 · Multiple Choice
A microscope has a 15× eyepiece and a 40× objective. What is the total magnification?
Answer: C
Total magnification is eyepiece × objective = 15 × 40 = 600×. Choice A adds the two numbers instead of multiplying. Choice B uses only the objective. Choice D adds an extra zero to the product.
Question 3 of 20 · Multiple Choice
At 400× the field of view is 450 µm across. About 15 plant cells fit in a row across it. About how wide is one cell?
Answer: B
Each cell takes up one fifteenth of the field: 450 ÷ 15 = 30 µm. Choice A gives the number of cells, not their size. Choice C subtracts 15 from 450. Choice D multiplies, which would make each cell larger than the whole field.
Question 4 of 20 · Multiple Choice
A tiny pond organism has one outer edge and no walls inside it. It swims, takes in food and splits into two. What is the best conclusion?
Answer: A
It is one cell (one edge, no inside walls), and it does the jobs of a living thing on its own, including reproducing, so it is a single-celled organism. Choice C fails because a cell taken from a larger animal does not swim off, feed and reproduce on its own. Choice D would need walls or edges inside it.
Question 5 of 20 · Multiple Choice
Under the microscope, a curl of wood shaving from a pencil sharpener shows rows of empty, box-shaped cells. What do these observations show?
Answer: D
Box-shaped cells are evidence the wood came from a living thing, a tree, but cells alone do not show it is alive now. Choices A and B treat "made of cells" as proof of life now; you would need growth or another sign of life. Choice C confuses cells with mineral grains, which have no edges or walls around separate units.
Question 6 of 20 · Multiple Choice
Potting soil contains perlite: small white bits of puffed-up volcanic rock. Which plan gives the strongest evidence about whether some other white specks in the soil are alive?
Answer: B
Watching many specks over days, next to never-living perlite kept in the same conditions, lets you see growth, movement or reproduction and compare. Choice A is one observation of one speck. Choice C gives an opinion, not evidence you collected. Choice D is too short for growth to show.
Question 7 of 20 · Multiple Choice
Which statement about many-celled organisms is supported by evidence from microscope slides?
Answer: B
Slices of roots, leaves and animal bodies show cells of different shapes in one organism, such as flat outer cells and long tube cells. Choice A is disproved by any slide with several kinds of cells. Choice C confuses the organism with one cell; it has walls or edges between its many cells.
Question 8 of 20 · Multiple Choice
A class tests four samples for 7 days (invented data). Which sample is most likely a single-celled organism?
Answer: C
Each unit is one cell, and the count rises, which shows reproduction, so each cell is a whole living organism. Choice A is many-celled (a sheet of cells). Choice B shows no cells. Choice D shows cells but no sign of life now, like a dead leaf.
Question 9 of 20 · Multiple Choice
A student says, "An amoeba is only one cell, so it cannot do everything a living thing needs to do." Which observation argues against this?
Answer: D
Moving, feeding and reproducing are jobs of a living thing, and the amoeba does them all as a single cell. Choice A is about size, not about what it can do. Choice B is evidence that it is one cell, not evidence that one cell can do everything. Choice C is about where it lives.
Question 10 of 20 · Multiple Choice
Why do students add a drop of diluted blue food coloring to cheek cells on a slide?
Answer: A
Cheek cells are almost clear, so a stain (a dye that colors cells) makes their edges and the dark spot inside them stand out. Choice C is wrong: a dye does not make cells grow. Choice B is wrong because the dye is for seeing, not for keeping cells alive.
Question 11 of 20 · Multiple Choice
Why should you find a sample with the 4× objective (40× total) before switching to the 40× objective?
Answer: B
At 40× the field of view is about 4,500 µm across, ten times wider than at 400×, so the sample is easier to find and center. Choice C reverses what higher power does. Choice A is wrong: cells show at every power, just smaller at low power.
Question 12 of 20 · Multiple Choice
A green alga grows as a chain of identical cells. One chain is 960 µm long, and each cell is about 80 µm long. About how many cells are in the chain?
Answer: A
Number of cells = 960 ÷ 80 = 12. Choice B subtracts 80 from 960. Choice C multiplies the two numbers. Choice D adds the two numbers.
Question 13 of 20 · Multiple Choice
A cell is 0.04 mm across. How wide is it in micrometers (µm)?
Answer: C
Since 1 mm = 1,000 µm, 0.04 mm = 0.04 × 1,000 = 40 µm. Choice A multiplies by 100 instead of 1,000. Choice B multiplies by 10,000. Choice D divides by 1,000 instead of multiplying.
Question 14 of 20 · Multiple Choice
Which slide would give the best evidence that one organism is made of several types of cells?
Answer: D
A slice across one organ of one plant shows several different cell shapes (outer cells, food-storage cells and tube cells), which is direct evidence of several cell types in one organism. Choice A shows many organisms, each a single cell. Choice C shows only one type of cell from one place in the body. Choice B has no cells.
Question 15 of 20 · Short Answer
Craft stores sell dried, dyed moss for decorations. Plan an investigation to test whether it is still alive. Name a comparison, what you keep the same, and what you will record.
Model plan: put craft-store moss and live moss from outdoors (the comparison) on wet paper towels in clear cups, in the same window, with the same water each day, for 1-2 weeks. Record new green tips, length of the stems and color each few days, and look at a leaf of each at 100×. Both will show cells, so the decision rests on growth: new growth means alive, none means once living.
Question 16 of 20 · Short Answer
At 100× the field of view is 1,800 µm across. A water flea (Daphnia) stretches across about two thirds of the field. Estimate its length. It has eyes, legs and a gut. Is it one cell or many? Explain.
Length ≈ 1,800 × 2 ÷ 3 = 1,200 µm (about 1.2 mm). It is many-celled: eyes, legs and a gut are body parts built from different kinds of cells, so its body must be made of many cells.
Question 17 of 20 · Short Answer
Explain why seeing cells in a sample is not enough to say the sample is alive now. Use a slice of cooked carrot as your example.
A slice of cooked carrot shows plant cells, so it is evidence the carrot was once living. Cooking killed the cells: the slice will not grow, divide or respond. To say a sample is alive now, you also need evidence such as growth, reproduction or movement over time.
Question 18 of 20 · Short Answer
A student looks at three parts of one bean plant (invented): root hair cells are long and thin, leaf surface cells are flat and wavy-edged, and the cells in the stem are long tubes. What does this show about the bean plant?
The bean plant is multicellular with several types of cells. One organism has cells of three different shapes, each in a different part, which supports the idea that many-celled organisms are made of different numbers and types of cells.
Question 19 of 20 · Short Answer
A rotifer, a tiny pond animal, is about one tenth of the 100× field of view (1,800 µm) long. Find its length. A Paramecium is a similar size. A classmate says, "They are the same size, so they must both be one cell." Respond.
Length ≈ 1,800 ÷ 10 = 180 µm. Size alone does not tell you how many cells an organism has. A rotifer has a mouth, a gut and a foot, made of many cells of different types, while a Paramecium has one outer edge and no inside walls. The evidence is the walls or edges between cells, not the size.
Question 20 of 20 · Short Answer
Tiny chalk specks in a drop of water jiggle constantly at 400×. Lee says the specks are alive because they move. Respond with evidence that a living sample would show.
Movement alone is not enough: very tiny particles of any material jiggle in water. The chalk specks show no cells (no edges or walls around units), and they do not grow or reproduce: their number and size stay the same for days. A living sample would show cells and changes such as growth or more organisms over time.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-LS1-1 mean?
MS-LS1-1 asks students to carry out an investigation that gives evidence that living things are made of cells, either one cell or many cells of different numbers and types. Students look at samples, decide what is and is not made of cells, and use what they see as evidence. The code means Middle School, Life Science, core idea 1 (From Molecules to Organisms: Structures and Processes), performance expectation 1.
What grade is MS-LS1-1 taught in?
It is a middle school standard for grades 6-8, and states and schools place it differently. Many teach it early in grade 6 or 7 life science, because it opens the study of cells, body systems and growth that later MS-LS1 standards build on.
Does MS-LS1-1 have an assessment boundary?
No. NGSS lists no Assessment Boundary for MS-LS1-1. The Clarification Statement sets the focus: evidence that living things are made of cells, telling living from nonliving things, and seeing that organisms can be one cell or many varied cells. The names and jobs of cell parts are the topic of MS-LS1-2.
What is the difference between single-celled and multicellular organisms?
A single-celled organism is one cell that does every job of life by itself, such as a Paramecium. A multicellular organism is made of many cells, from just a few to trillions, and its cells are often of different types, such as the root, stem and leaf cells of a plant.
Are viruses made of cells?
No. Viruses are not made of cells, and they can only make copies of themselves inside the cells of another organism. Scientists debate whether to call them living, so many teachers leave viruses out of this standard or treat them as a discussion question beyond this standard.
Can I teach MS-LS1-1 without microscopes?
Yes, partly. Hand lenses show cells in a few samples, such as thin moss leaves, and printed or online micrographs (photos taken through a microscope) can stand in for slides. Students still do the practice if they record observations, compare samples and argue from evidence, though looking at a real sample is stronger.
Is it safe to look at cheek cells in class?
Yes, with teacher supervision. Each student uses a new flat toothpick on their own cheek, puts the cells on their own slide, and drops the toothpick in a bag right away. Nobody shares slides or toothpicks, and everyone washes hands afterward. The only stain used is diluted blue food coloring, a household dye. Where cheek sampling is not allowed, a prepared slide of human cheek cells works just as well.
Why isn't "made of cells" the same as "alive"?
Because once-living things keep their cells for a while. A dead leaf, a wood chip or a cooked vegetable shows cells but will not grow or reproduce. Cells show that a sample is or was part of a living thing; other evidence over time, such as growth or reproduction, shows it is alive now.
What mistakes do students make with MS-LS1-1?
Common mistakes include calling any small grain a cell, thinking a moving speck must be alive, forgetting to multiply the eyepiece and objective numbers, and mixing up millimeters and micrometers. Some students also think one cell scraped from a body is a whole organism; ask whether it could feed and reproduce on its own.
How does MS-LS1-1 connect to other standards?
It is the first step in the middle school cell sequence. MS-LS1-2 asks how the parts of a cell help the whole cell work, and MS-LS1-3 asks how groups of cells form the body systems. In high school, HS-LS1-2 and HS-LS1-4 build on it with levels of organization and how cells divide.
07
Related Standards
5 standards
These standards connect to MS-LS1-1: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
4-LS1-1Prerequisite
Argue that plant and animal structures support survival, growth, behavior and reproduction
Lesson coming soon
Alongside
MS-LS1-2Parallel
Model how a cell works as a whole and how its parts contribute
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