In plain English: MS-LS4-1 is the NGSS middle school performance expectation that asks students to analyze data from the fossil record for patterns that show which life forms existed, how diverse they were, when they went extinct and how they changed. Students read the order of fossils in rock layers, assuming natural laws worked in the past as they do today. It is usually taught in grade 6, 7 or 8 life science.
Analyze and interpret data for patterns in the fossil record that document the existence, diversity, extinction, and change of life forms throughout the history of life on Earth under the assumption that natural laws operate today as in the past.
Clarification Statement: Emphasis is on finding patterns of changes in the level of complexity of anatomical structures in organisms and the chronological order of fossil appearance in the rock layers.
Assessment Boundary: Assessment does not include the names of individual species or geological eras in the fossil record.
Next Generation Science Standards · Disciplinary Core Idea: Biological Evolution: Unity and Diversity · Official standard
Students analyze data from the fossil record, the collection of all fossils found in rock layers around the world. A fossil is the preserved remains or traces (such as bones, shells, leaf prints, burrows or footprints) of an organism that lived long ago. Students look for four patterns: the existence of life forms (what lived), their diversity (how many different kinds lived at one time), their extinction (when a kind of organism died out everywhere and never appears again), and their change over time, especially changes in how complex (made of many connected parts) their body structures are. To put fossils in time order, students use the law of superposition: in rock layers that have not been folded or flipped, each layer is younger than the layer below it. This rests on the idea in the standard that natural laws operate today as in the past: sand and mud settle under gravity today, so they settled the same way long ago.
The NGSS Clarification Statement says: "Emphasis is on finding patterns of changes in the level of complexity of anatomical structures in organisms and the chronological order of fossil appearance in the rock layers." The Assessment Boundary says: "Assessment does not include the names of individual species or geological eras in the fossil record." So this page names large groups (such as fish or flowering plants) but never asks students to recall species names or era names. Rock layers, fossil types A-G and all counts are invented for teaching and labeled as invented. Ages in millions of years for large groups are real and rounded.
Learning Objectives
By the end of this lesson, students will be able to:
Use the law of superposition, and the idea that natural laws worked the same way in the past, to put fossils in time order
Read a table or chart of rock layers to show when kinds of organisms first appear and when they disappear
Count the kinds of fossils in each layer to describe changes in diversity, including sharp drops that mark extinctions
Describe changes in the complexity of body structures across layers, using means and counts
Judge whether fossil data are strong enough to support a claim about existence, extinction or change
Prior Knowledge Required
Students should already be comfortable with:
Fossils give evidence about organisms and environments of long ago 3-LS4-1
Rock layers and the fossils in them show how a landscape changed over time 4-ESS1-1
Show a clear jar in which the class has poured a cup of muddy water every Monday for three weeks, with a different color of sand each time (or a photo of one). Ask:
Warm-Up Prompt
"Which layer in the jar went in first? How do you know? A cliff by a river also shows layers. What would you have to assume to use the same thinking for the cliff?"
Collect answers. Students usually say the bottom layer went in first because sediment sinks. Write the key assumption on the board in plain words: "Gravity and settling worked the same way long ago as they do in our jar." Tell students this is the assumption named in the standard, and that today they will use it to read the history of life.
Direct Instruction15 minutes
Reading the fossil record. Define fossil, fossil record, rock layer (a sheet of rock that formed from sediment, the sand, mud or shell pieces that settle out of water or wind), the law of superposition, diversity, extinction and complexity. A relative age tells which of two things is older, without giving an age in years. Work through the examples below. For each one ask: "Which pattern does this show: existence, diversity, extinction or change?"
Superposition and natural laws (invented cliff)
A cliff shows four flat layers. From bottom to top: sandstone with ripple marks, gray shale with fish scales, limestone full of shells, and sandstone with fern leaf prints. Today, ripples form in sand on river bottoms, fine mud settles in quiet water, and shells pile up in shallow seas.
Result: Because sediment settled under gravity in the past just as it does now, the bottom sandstone formed first and the fern layer formed last. The order of the fossils, from oldest to youngest, is fish scales, then shells, then fern leaves. The rock types also tell us the environment changed from river to quiet water to sea to land.
Using a rate measured today (invented numbers)
Scientists measure that the bottom of a quiet lake collects about 2 mm of soft mud each year. A core (a long tube of mud pulled up from the lake bottom) is 1.2 m long. A leaf is found 0.5 m below the top.
Result: If the rate was the same in the past, the core holds about 1,200 mm ÷ 2 mm per year = 600 years of mud. The leaf was buried about 500 mm ÷ 2 = 250 years ago. This is the same assumption, natural laws operate today as in the past, used to estimate time.
Diversity and a mass extinction (invented quarry, Diagram 2)
In one quarry, the number of different kinds of shelled fossils in Layers 1-6 (oldest to youngest) is 3, 6, 11, 14, 4 and 9.
Result: Diversity rose from 3 to 14 kinds, then fell to 4: 14 - 4 = 10 kinds are missing, and 10 ÷ 14 ≈ 0.71, so about 71% of the kinds disappeared at once. If the same drop shows up at many sites around the world, it marks a mass extinction. Diversity then recovered to 9 kinds, and many of these are new kinds not found in lower layers.
Extinction of a whole group (real, rounded)
Trilobites were sea animals with jointed legs and a hard outer covering, distant relatives of today's insects and crabs. Their fossils are found in rocks from about 521 to about 252 million years old, at thousands of sites on every continent.
Result: The group existed for about 521 - 252 = 269 million years and became very diverse: more than 20,000 kinds have been named. No trilobite has ever been found in any rock younger than about 252 million years, anywhere on Earth. That worldwide pattern is the evidence that the group went extinct.
Change in complexity (invented numbers, real pattern)
Coiled-shell sea animals called ammonites had inner walls that met the shell along a wavy line called a suture line. In one invented set of layers, the mean number of folds in the suture line is 4, 6, 9, 14 and 20 in Layers 1-5.
Result: From Layer 1 to Layer 5 the number of folds rose from 4 to 20, which is 20 ÷ 4 = 5 times as many. The structure became more complex in younger layers. The real ammonite fossil record shows this same kind of pattern, from simple sutures to very folded ones.
Point out two cautions. First, change does not always mean more complex: some groups lost structures over time. Second, a fossil missing from one layer at one site does not prove extinction, because the organism may have lived elsewhere or left no fossils there. Extinction claims need many sites.
Guided Practice15 minutes
Pairs analyze an invented quarry wall with six undisturbed layers. Each letter stands for one kind of fossil. Students build a range chart, a chart with one bar for each kind of fossil that runs from the layer where it first appears to the layer where it last appears.
Invented data: fossil types found in each layer of one quarry
Layer
Fossil types found
Layer 6 (top)
C, F, G
Layer 5
C, F
Layer 4
B, C, E
Layer 3
B, C, D, E
Layer 2
A, B, D
Layer 1 (bottom)
A
Which layer is oldest? Which fossil type existed first?
For each type, write the layer where it first appears and the layer where it last appears. Draw the bars, then compare with Diagram 1.
Count the types in each layer. Which layer shows the greatest diversity?
Which types are missing from the top layer? What other data would you need before calling them extinct?
Discuss: Layer 1 is oldest, so type A existed first. Layer 3 has the most types (4). Types A, B, D and E do not reach the top layer; F and G appear only in the youngest layers. Before calling A, B, D or E extinct, a scientist would check many other sites for younger fossils of them.
Independent Practice10-15 minutes
Each student analyzes invented data on Group S, an invented group of extinct sea animals that stood on a stalk and caught food with feathery arms. The layers are in one undisturbed stack, Layer 1 at the bottom.
Invented data: Group S fossils in six layers
Layer
Kinds of Group S found
Mean number of arms per fossil
Layer 6 (top)
0
none found
Layer 5
3
16
Layer 4
6
12
Layer 3
4
10
Layer 2
2
8
Layer 1 (bottom)
1
5
Students write four sentences, one for each pattern: existence (when Group S first appears), diversity (where it peaks), extinction (what Layer 6 shows, and what is still needed to be sure), and change (how the arms changed). Each sentence cites numbers from the table.
Closure5 minutes
Return to the jar from the warm-up. Exit ticket: "Name the assumption that lets us read rock layers like the jar. Then describe one pattern from today's data (existence, diversity, extinction or change) and the numbers that show it."
Differentiation Strategies
For Struggling Students
Give a blank range chart with layers and fossil types already labeled, so students only shade the bars
Provide a four-box organizer labeled existence, diversity, extinction and change, with one sentence frame in each box
Pair the jar model with every rock layer table: point to the jar's bottom layer each time students decide which layer is oldest
For Advanced Students
Ask students to explain how a layer with no fossils of a group, between two layers that have them, could happen without extinction
Have students design a data table that would convince a skeptic that a group went extinct worldwide, not just at one site
Ask students to find a case where a structure became simpler over time and explain why change does not always mean more complex
Assessment Guidance
What to Look For
Check that students put layers in order using superposition and can say why the bottom layer is oldest (natural laws, such as gravity and settling, worked the same way in the past). Look for students who count kinds per layer to describe diversity, who use first and last appearances to describe existence and extinction, and who cite numbers when they describe change in a structure. Watch for students who treat a fossil missing at one site as proof of extinction, or who think every group always becomes more complex.
02
Classroom Activities
3 Activities
1
Sediment Jar Layers: Natural Laws Today
15 min on 3 daysGroups of 3-4
Groups build their own rock record in a jar to test the idea that natural laws operate today as in the past. Each day they add a scoop of sediment mixed with one shape of dried pasta (their "fossils"), let it settle, and measure the new layer. Then they use their jar to explain how geologists read real layers.
Procedure
Day 1: put 1 cup of a gravel, sand and soil mix and 6 elbow pasta pieces in a plastic jar, fill it two thirds with water, close the lid, shake for 10 seconds and let it settle overnight.
Day 2: gently pour in 1 cup of the mix with 6 shell pasta pieces. Do not shake. Let it settle.
Day 3: repeat with 6 bow-tie pasta pieces.
Each day, measure the thickness of the new layer in millimeters with a ruler held against the jar, and sketch where the gravel, sand and fine soil ended up.
Safety: plastic jars only, wipe up spills right away, and wash hands after handling soil.
Sample Data (invented)
Layer thickness after settling: Day 1, 22 mm; Day 2, 18 mm; Day 3, 25 mm. In each layer, gravel settled at the bottom, then sand, then fine soil on top.
Discussion Questions
Which pasta "fossils" are the oldest, and how can you tell without your notes?
What is the total thickness of the three layers? Which day made the thickest layer?
What would happen to the order if someone stirred the jar? What could do this to real rock layers?
Why do geologists assume that sediment settled long ago the way it settles in your jar?
Modification for Distance Learning
Students make the jar at home with a plastic bottle, soil and dried beans, or analyze the sample data and a teacher video of the jar.
2
Drill Core Card Sort
25 minPairs
Pairs receive 8 shuffled cards from an invented drill core, a long cylinder of rock cut out of the ground. Each card gives a depth and the fossils found there. Pairs sort the cards, build a time order, and describe how the complexity of life changed. The depths are invented; the order of the fossil groups follows the real worldwide pattern.
Core Cards (depths invented)
760 m: layered mounds built by single-celled organisms, no other fossils
640 m: soft-bodied, many-celled organisms preserved as imprints; no shells, bones or legs
590 m: small shells and animals with jointed legs
470 m: shells, bony plates of fish without jaws, and spores of the first land plants
400 m: fish with jaws, and small land plants with stems
300 m: bones of four-limbed animals and fern leaves
150 m: reptile bones, ferns and pine-like cones
40 m: mammal teeth, pollen of flowering plants and pine-like cones
Tasks
Sort the cards from deepest to shallowest. Which card is oldest?
Make a table with one row per card and columns for: one cell or many cells, hard parts (shells or bones), backbone, limbs.
Find the first card where each feature appears.
Write a claim about how the complexity of life changed from the oldest card to the youngest, with evidence from at least three cards.
Discussion Questions
Single-celled organisms appear on the deepest card. Are they missing from the shallower cards because they went extinct? (Hint: are there single-celled organisms alive today?)
Fish with jaws first appear at 400 m. Why does that mean they cannot be older than fish without jaws in this core?
Which card would you check at other sites before making a claim about the whole world?
Modification for Distance Learning
Post the cards as a slide in random order. Students drag them into order and fill in a shared feature table.
3
Timeline of Life on a Paper Strip
30 minGroups of 4
Groups build a scale timeline of the history of life on a strip of adding machine tape, using 1 mm for every 1 million years. The ages are real and rounded. The strip shows how long life existed before complex forms appeared in the fossil record.
Events to Mark (real ages, rounded)
Oldest fossils of single-celled life: about 3,500 million years ago
First large many-celled organisms: about 570 million years ago
Animals with shells and other hard parts become common: about 540 million years ago
First land plants: about 470 million years ago
First four-limbed animals: about 370 million years ago
First dinosaurs: about 230 million years ago; first mammals: about 200 million years ago
First flowering plants: about 130 million years ago
Extinction of all dinosaurs except birds: about 66 million years ago
First humans of our kind: about 0.3 million years ago
Procedure
Cut a strip 3.6 m long. Mark "today" 5 cm from one end.
Measure from "today" toward the other end: an event 570 million years ago goes 570 mm (57 cm) from the today mark.
Label each event and color the part of the strip with only single-celled life.
Discussion Questions
How far from the today mark is the oldest fossil? What fraction of the strip, from that mark to today, has only single-celled life?
Where are the events crowded together? What does that suggest about when complex life forms appeared?
How far from the today mark is the first human? Can you even see it with a meter stick?
Modification for Distance Learning
Students use a long hallway at home or a scaled drawing in a slide (1 cm for 100 million years) and share a photo.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Range Chart for the Guided Practice Quarry (Invented Data)
Each bar runs from the layer where a fossil type first appears to the layer where it last appears. Layer 1 is at the bottom and is the oldest. Bars that stop below Layer 6 belong to types not found in the youngest layer; bars that start high belong to types that appeared late.
Diagram 2: Kinds of Shelled Fossils in Each Layer of One Quarry (Invented Data)
Drawn to scale from the invented quarry in the worked examples. Diversity rises through Layer 4, then drops sharply in Layer 5 (red), the pattern that marks an extinction event, and partly recovers in Layer 6.
04
Homework Assignment
~30 min
MS-LS4-1 Homework: Reading the Fossil Record
Directions: Unless a problem says the ages are real, all layers and counts are invented for practice. In every stack, Layer 1 is at the bottom and the layers have not been folded or flipped. Show your calculations and cite numbers in every answer.
Part 1: Putting Fossils in Order (Problems 1-2)
A canyon wall has five layers. Layer 1: shells and worm burrows. Layer 2: shells and fish scales. Layer 3: fern leaves and reptile footprints. Layer 4: fern leaves, reptile footprints and mammal teeth. Layer 5: mammal teeth and leaves of flowering plants. (a) List the kinds of fossils in the order they first appear. (b) Which layer formed most recently, and what assumption lets you say so? (c) Shells are not found above Layer 2. Does this show that shelled animals went extinct? Explain, using what the rocks suggest about the environment.
Scientists measure that a river delta, the fan of sediment where a river enters the sea, builds up about 3 mm of sediment per year today. (a) About how many years would a 1.5 m layer of the same sediment take to form at that rate? (1 m = 1,000 mm.) (b) What assumption are you making? (c) Name one thing that could make your estimate wrong.
Part 2: Diversity and Extinction (Problems 3-4)
The number of kinds of fossil corals in seven layers of one reef, Layers 1-7, is 5, 8, 12, 15, 15, 3 and 7. (a) Make a bar graph. (b) Between which two layers is the largest drop, and how many kinds were lost? (c) What percent of the kinds were lost in that drop? (d) What would you need to check before calling this a mass extinction?
Real ages, rounded: the oldest dinosaur fossils are about 230 million years old, and fossils of dinosaurs other than birds stop at about 66 million years. The oldest fossils of humans of our kind are about 0.3 million years old. (a) For about how long did non-bird dinosaurs exist? (b) About how many times longer is that than the time humans of our kind have existed? (c) Mammal and bird fossils are common in younger layers at many sites. Explain why this makes the missing non-bird dinosaur fossils strong evidence of extinction.
Part 3: Change and Argument (Problems 5-6)
An invented group of fossil snails is found in four layers. Spines counted on four shells from each layer: Layer 1: 2, 3, 2, 3. Layer 2: 4, 3, 5, 4. Layer 3: 6, 7, 5, 6. Layer 4: 8, 9, 9, 10. (a) Find the mean number of spines in each layer. (b) Describe the change. (c) Is four shells per layer enough to support a strong claim? Explain.
A classmate says: "Rock layers might have formed in a totally different way long ago, so the order of fossils tells us nothing." (a) Give one observation from today that supports the idea that sediment settled the same way in the past. (b) The same order of first appearances (fish before four-limbed animals, four-limbed animals before mammals) is found in rocks on every continent. Explain why this pattern supports reading rock layers in order. (c) Write a respectful two-sentence reply to your classmate.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Reading Layers
Correct order of layers and fossils, with the reason (superposition and natural laws)
Correct order without a reason, or one error
Using Numbers
Correct counts, differences, means and percents, with work shown
One calculation error or missing work
Patterns
Names the pattern (existence, diversity, extinction or change) and supports it with data
Names a pattern but cites no numbers
Judging Evidence
Says what the data cannot show and what more evidence is needed
Makes a claim that goes beyond the data
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All layers and counts are invented unless a question says the pattern is real. In every stack, Layer 1 is at the bottom and the layers have not been disturbed. 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
In a stack of rock layers that has not been folded or flipped, which layer formed first?
Answer: C
By the law of superposition, each layer settled on top of the one below it, so the bottom layer formed first. Choice A reverses the order. Choices B and D use thickness and fossil count, which do not tell age.
Question 2 of 20 · Multiple Choice
Geologists watch sand and mud settle in layers on lake bottoms today. Why does this help them read rock layers that are millions of years old?
Answer: A
The standard's assumption is that natural laws operate today as in the past, so sediment settled under gravity long ago just as it does now. Choice B is a claim about speed with no evidence, choice C contradicts the layers themselves, and choice D is false: many rocks formed in places that are now dry land.
Question 3 of 20 · Multiple Choice
Invented data from one cliff, bottom to top: Layer 1 has fossil types P and Q; Layer 2 has Q and R; Layer 3 has R and S; Layer 4 has S and T. Which fossil type appears for the first time most recently?
Answer: D
Layer 4 is the youngest layer, and T first appears there. Choice A is the oldest type, the reverse of the question. Choice C, S, first appears in Layer 3, and choice B, R, in Layer 2.
Question 4 of 20 · Multiple Choice
Invented counts of different kinds of fossils: Layer 1, 4 kinds; Layer 2, 9 kinds; Layer 3, 15 kinds; Layer 4, 6 kinds. Which statement describes the diversity?
Answer: B
Diversity is the number of different kinds: 4, 9 and 15 show a rise, then 6 is a sharp drop. Choice A picks Layer 1, which has the fewest kinds. Choice C ignores the drop in Layer 4, and choice D ignores the changes.
Question 5 of 20 · Multiple Choice
Fossil type W (invented) is found in Layers 2-5 at 40 sites on three continents, but never in Layer 6 or any younger layer at any site. What is the best interpretation?
Answer: A
Many sites agree that W existed during Layers 2-5 and then disappears everywhere, which is the evidence for extinction. Choice C reverses the order: W is found below Layer 6, so it is older. Choices B and D offer explanations with no evidence, and they would not explain why the pattern is the same at all 40 sites.
Question 6 of 20 · Multiple Choice
Invented data: Layer 7 holds 24 kinds of shelled fossils, and Layer 8, just above it, holds only 6 kinds. What percent of the kinds disappeared?
Answer: C
24 - 6 = 18 kinds disappeared, and 18 ÷ 24 = 0.75, or 75%. Choice A is the percent that remained (6 ÷ 24). Choice B writes the number of kinds lost as if it were a percent. Choice D divides 18 by 6 instead of by the starting 24.
Question 7 of 20 · Multiple Choice
Real pattern, simplified: the oldest land plant fossils are stems with no leaves; younger layers add plants with small leaves, then plants with large leaves and branching veins, and the youngest layers add plants with flowers. What does this pattern show?
Answer: A
New, more complex structures (leaves, branching veins, flowers) appear in younger layers. Choice B reverses the pattern, choice C ignores the change, and choice D reverses the order of appearance.
Question 8 of 20 · Multiple Choice
Fossils of an invented group first appear in rocks 480 million years old and last appear in rocks 360 million years old. For about how long did the group exist?
Answer: B
The group existed from 480 to 360 million years ago: 480 - 360 = 120 million years. Choice A adds the two ages. Choices C and D give only one of the two ages, not the time between them.
Question 9 of 20 · Multiple Choice
At one site, fossil type K (invented) is found in Layers 1-3, is missing from Layer 4, and is found again in Layer 5. What is the best interpretation?
Answer: B
Because K is found again in Layer 5, it cannot have gone extinct earlier; it just was not preserved, or did not live at this spot, while Layer 4 formed. Choice A ignores Layer 5. Choice C breaks the law of superposition, and choice D ignores the older fossils in Layers 1-3.
Question 10 of 20 · Multiple Choice
Today, a river delta (invented) builds up about 4 mm of sediment per year. If the same process worked in the past, about how long did a 1.6 m layer of the same sediment take to form? (1 m = 1,000 mm.)
Answer: D
1.6 m = 1,600 mm, and 1,600 ÷ 4 = 400 years. Choice A multiplies 1.6 by 4. Choice B divides 1.6 by 4 without changing meters to millimeters. Choice C multiplies 1,600 by 4 instead of dividing.
Question 11 of 20 · Multiple Choice
Which evidence would best show that a fossil group went extinct?
Answer: C
Extinction means the group is gone everywhere, so the strongest evidence is its absence from all younger layers at many sites. Choices A and B use a single site, where a group can be missing for other reasons. Choice D is about size, not survival.
Question 12 of 20 · Multiple Choice
Which statement about change in the fossil record is accurate?
Answer: D
Rock layers of different ages hold different kinds of organisms, which shows that life forms changed over time. Choice A is false: some groups lost structures. Choice C contradicts the record, and choice B ignores the many kinds that appear in young layers.
Question 13 of 20 · Multiple Choice
Invented counts of kinds of fossil plants in five layers, oldest to youngest: 2, 5, 9, 14 and 20. By how many kinds did diversity increase from the oldest layer to the youngest?
Answer: A
20 - 2 = 18 more kinds. Choice B is only the count in the youngest layer. Choice C adds the first and last counts, and choice D divides 20 by 2, which tells how many times as many, not how many more.
Question 14 of 20 · Multiple Choice
At 50 sites on several continents, fossils of invented group M are found only in layers younger than the oldest fossils of invented group N. What is the best explanation?
Answer: C
The chronological order of first appearances, repeated at many sites, shows when each group came into existence: N first, M later. Choice A would put M fossils in lower, older layers, the opposite of what is found, and choice B describes fossils moving up through solid rock, which does not happen. Choice D is about rock hardness, which does not set the order.
Question 15 of 20 · Short Answer
Invented data, one cliff, bottom to top: Layer 1 has types U and V; Layer 2 has U, V and W; Layer 3 has V, W, X and Y; Layer 4 has W and Y. Describe one first appearance, one disappearance and the change in diversity, with evidence.
First appearances: W first appears in Layer 2, and X and Y first appear in Layer 3. Disappearances: U is last found in Layer 2, V and X are last found in Layer 3. Diversity (kinds per layer) is 2, 3, 4 and 2, so it rose to a peak in Layer 3 and then fell. Full credit cites layers for each pattern and notes that one cliff cannot prove extinction.
Question 16 of 20 · Short Answer
The standard says students interpret fossils "under the assumption that natural laws operate today as in the past." Explain what this assumption means for reading rock layers, and give one observation from today that supports it.
It means that processes such as gravity pulling sediment down, sand settling in rivers and mud settling in quiet water worked the same way long ago. So the lower layer in an undisturbed stack settled first and is older. Supporting observations: sediment settling in layers in lakes, at river deltas or in a jar; ripple marks forming in sand today that look like ripple marks in old rock. Full credit explains the assumption and links one modern observation to it.
Question 17 of 20 · Short Answer
Invented data: ribs counted on four fossil shells of one group in Layer 1 are 6, 8, 7 and 7. In Layer 4 they are 14, 12, 15 and 13. Find the mean for each layer and describe the change.
Layer 1 mean: (6 + 8 + 7 + 7) ÷ 4 = 28 ÷ 4 = 7 ribs. Layer 4 mean: (14 + 12 + 15 + 13) ÷ 4 = 54 ÷ 4 = 13.5 ribs. The shells in the younger layer have almost twice as many ribs, so this structure became more complex over time in this group. Full credit has both means and a sentence about change, and may note that four shells per layer is a small sample.
Question 18 of 20 · Short Answer
At one quarry, fossil type R (invented) is found in Layers 1-5 but not in the top layer, Layer 6. A student writes: "Type R went extinct after Layer 5." Evaluate the claim.
The claim goes beyond the data. One site cannot show extinction: R may have moved away from this spot, the environment here may have changed, or R may simply not have been preserved in Layer 6. To support extinction, the student needs data from many sites showing that no layer younger than Layer 5 holds R anywhere. Full credit says why one site is not enough and names the data needed.
Question 19 of 20 · Short Answer
Invented counts of kinds of fossil sea animals in six layers, oldest to youngest: 12, 15, 16, 3, 5 and 9. Identify the likely extinction event, find the percent of kinds lost, and describe what happened afterward.
The sharp drop is from Layer 3 (16 kinds) to Layer 4 (3 kinds): 16 - 3 = 13 kinds lost, and 13 ÷ 16 ≈ 0.81, or about 81%. Afterward diversity recovered to 5 and then 9 kinds. Full credit gives the drop, the percent and the recovery, and notes that the drop must appear at many sites to be called a mass extinction.
Question 20 of 20 · Short Answer
A student says, "The fossil record shows that living things have never changed." Use two different patterns in fossil data to respond.
Change: younger layers hold kinds of organisms and structures (for example, flowers, or more folded suture lines) that are not found in older layers. Extinction: whole groups are found in old layers and never in younger ones anywhere. Diversity also changes, with sharp drops and recoveries. Full credit uses two patterns, each tied to what is found in older and younger layers.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-LS4-1 mean?
MS-LS4-1 asks middle school students to analyze and interpret fossil data for patterns that show the existence, diversity, extinction and change of life forms over Earth's history. The code means Middle School, Life Science, core idea 4 (Biological Evolution: Unity and Diversity), performance expectation 1.
Is MS-LS4-1 taught in grade 6, 7 or 8?
It depends on the school. MS-LS4-1 is a middle school standard for grades 6-8, and it is usually taught in a life science unit on evolution, often together with MS-LS4-2 and MS-LS4-3. Some schools teach it next to the Earth science standard MS-ESS1-4 on rock layers and the geologic time scale.
What is the law of superposition?
It is the rule that in rock layers that have not been folded, flipped or broken, each layer is younger than the layer below it. It gives a relative age (older or younger) for the fossils in each layer, but not an age in years.
What does "natural laws operate today as in the past" mean in MS-LS4-1?
It means scientists assume that gravity, settling of sediment, and other natural processes worked the same way long ago as they do now. Because sediment settles in layers on lake and sea bottoms today, geologists can read old rock layers the same way: lower layers formed first.
If a fossil is missing from a layer, did the organism go extinct?
Not necessarily. An organism can be missing from one layer at one site because it lived somewhere else at the time, the environment changed, or its remains were not preserved. Extinction is supported when a group is missing from all younger layers at many sites around the world.
Do students need to memorize species names or geologic eras for MS-LS4-1?
No. The Assessment Boundary says assessment does not include the names of individual species or geological eras. Students should be able to read patterns in fossil data, such as the order of appearance and changes in complexity, using large groups like fish, mammals or flowering plants.
Why are there gaps in the fossil record?
Fossils form only under special conditions, such as quick burial in mud or sand. Soft-bodied organisms rarely fossilize, many rocks have been worn away by erosion, and many fossils have not been found yet. That is why scientists look for patterns that repeat across many sites.
Does the fossil record show that life always becomes more complex?
No. The fossil record shows that complex structures such as shells, backbones, limbs and flowers appear over time, but single-celled organisms are still very common today, and some groups lost structures over time. Change is the pattern; more complex is only one kind of change.
Are the data on this page real?
The rock layers, fossil types labeled with letters and all counts are invented for teaching and labeled as invented. The ages for large groups, such as the oldest fossils of single-celled life (about 3,500 million years) and the first flowering plants (about 130 million years), are real and rounded.
What comes after MS-LS4-1?
MS-LS4-2 compares the anatomy of modern and fossil organisms to infer relationships, and MS-LS4-3 compares embryos. In high school, HS-LS4-1 asks students to communicate how fossils, anatomy, embryos and DNA together support common ancestry and biological evolution.
07
Related Standards
5 standards
These standards connect to MS-LS4-1: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
3-LS4-1Prerequisite
Analyze fossil data for evidence of organisms and environments of long ago
Lesson coming soon
4-ESS1-1Prerequisite
Use patterns in rock layers and fossils to explain changes in a landscape
Lesson coming soon
Alongside
MS-ESS1-4Parallel
Explain from rock strata how the geologic time scale organizes Earth's history
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