MS-LS4-3: Comparing Embryos to Find Hidden Relationships
In plain English: MS-LS4-3 is the NGSS middle school performance expectation that asks students to analyze pictures and diagrams of embryos from several species and compare patterns of similarity in how they develop. Shared early features reveal relationships that the fully formed adults do not show. It is usually taught in grade 6, 7 or 8 life science.
Analyze displays of pictorial data to compare patterns of similarities in the embryological development across multiple species to identify relationships not evident in the fully formed anatomy.
Clarification Statement: Emphasis is on inferring general patterns of relatedness among embryos of different organisms by comparing the macroscopic appearance of diagrams or pictures.
Assessment Boundary: Assessment of comparisons is limited to gross appearance of anatomical structures in embryological development.
Next Generation Science Standards · Disciplinary Core Idea: Biological Evolution: Unity and Diversity · Official standard
Students analyze pictures of embryos, organisms in their earliest stage of development, before they hatch or are born, and compare how different species develop. Embryological development is the series of changes an embryo goes through as it grows. Students look for patterns in pictorial data (drawings and photographs) and find that early embryos of species with very different adult bodies can share structures, such as a tail and a row of neck ridges (called pharyngeal arches: bulges on the sides of the neck region). Shared early structures point to a shared ancestor, and they can reveal a relationship that the fully formed anatomy (the adult body) hides. For some sea animals, the clue comes from the larva, the young form that hatches from the egg and keeps developing before it takes the adult shape; the page labels these cases as larvae.
The NGSS Clarification Statement says: "Emphasis is on inferring general patterns of relatedness among embryos of different organisms by comparing the macroscopic appearance of diagrams or pictures." The Assessment Boundary says: "Assessment of comparisons is limited to gross appearance of anatomical structures in embryological development." Gross appearance means the visible shape of body parts, so every comparison on this page uses what can be seen in a picture, never cells, chemicals or DNA. Facts about real embryos and larvae are real and simplified, and the drawings are simplified outlines, not to scale. Data sets labeled invented were written for practice.
Learning Objectives
By the end of this lesson, students will be able to:
Read drawings and photographs of embryos and record the visible structures at each stage
Compare embryos of several species at the same stage and describe which structures they share
Explain how shared early structures can reveal relationships that adult anatomy hides
Use counts and percents of shared features in pictorial data to decide which species are most closely related
Judge whether a pictorial comparison is fair, for example whether the stages match
Prior Knowledge Required
Students should already be comfortable with:
Organisms have life cycles that include birth, growth and reproduction 3-LS1-1
Homologous structures in adults are evidence of common ancestry MS-LS4-2
Show photos of an adult barnacle on a rock and an adult clam side by side, then a photo of a crab. Ask:
Warm-Up Prompt
"A barnacle has a hard shell and spends its adult life stuck to a rock, like a clam. Which animal do you think it is related to, the clam or the crab? What evidence could settle the question if the adults are not enough?"
Record votes. Explain that scientists once classified barnacles with clams and snails because of their shells, and that pictures of the young barnacles changed their minds. The class will see why in the worked examples.
Direct Instruction15 minutes
Embryos as evidence. Define embryo, embryological development, larva, neck ridges (pharyngeal arches), somites (a row of small blocks along the back of an embryo that later form the backbone and back muscles), limb buds (small bumps that grow into legs, arms, wings or fins) and gross appearance. Show Diagram 1, then work through the examples. For each, ask: "What do the adults look like? What do the young stages share? What relationship do the young stages show that the adults hide?"
Four vertebrate embryos at one stage (real, Diagram 1)
Pictures of early embryos of a zebrafish, a turtle, a chicken and a pig, each at the stage when limb or fin buds first appear. The adults look nothing alike: fins and gills, a shell, feathers, hair.
Result: All four embryos show the same visible structures: neck ridges, a row of somites, limb or fin buds and a tail. The embryos are not identical: the zebrafish body lies on a large yolk, and the pig has only a small yolk sac. The shared structures suggest that all four inherited one early body plan from a common ancestor, which makes them all vertebrates (animals with backbones).
The turtle shell starts late (real)
An adult turtle's shell makes it look unlike any other reptile. Early turtle embryos look like lizard or bird embryos at the same stage, with no shell at all. Later, a ridge grows along each side of the back, and the ribs grow outward into it to build the shell.
Result: Because the shell appears only after a shared early stage, turtle embryos show what the adults hide: turtles develop from the same early body plan as other reptiles and birds, and the shell was added to that plan.
Sea squirt larva (real, Diagram 2)
An adult sea squirt is a soft bag stuck to a rock, with two openings for water. Its larva swims like a tiny tadpole, with a muscular tail, a stiff rod (notochord) along the tail and a nerve cord along its back.
Result: A stiff rod and a nerve cord along the back, with a tail, are structures that vertebrate embryos also have. The larva shows that sea squirts are related to animals with backbones, a relationship the adult bag shape gives no hint of. As the larva settles, it loses the tail and the rod.
Barnacle larva (real)
An adult barnacle builds a shell of hard plates and stays stuck to one spot. Its larva, which hatches from the egg, is a tiny swimmer with one eye and three pairs of jointed legs, shaped like the larvae of shrimp and crabs.
Result: The larva matches the young of crabs and shrimp, not of clams or snails, so barnacles are related to crabs and shrimp. Scientists moved barnacles to that group in the 1830s after studying these larvae. A second clue was already in the adult: its feathery feeding legs are jointed, but the shell had hidden it.
Address two ideas. First, embryos do not replay the adult forms of their ancestors: a chicken embryo is never a tiny adult fish. It shares early structures, which then develop in different ways. Second, some drawings published in the 1870s made embryos of different animals look more alike than they are. Photographs show real differences in size, shape and yolk, but the shared structures, such as neck ridges and a tail, are real.
Guided Practice15 minutes
Pairs use Diagram 1 and the table below. The early rows describe the embryos in Diagram 1; the adult rows list outside features people notice in the adults. A 1 means the feature is present.
Real features, simplified: early embryos and adults of four vertebrates
Feature
Zebrafish
Turtle
Chicken
Pig
Embryo: neck ridges
1
1
1
1
Embryo: tail
1
1
1
1
Embryo: somites
1
1
1
1
Embryo: limb or fin buds
1
1
1
1
Embryo: large yolk
1
1
1
0
Adult: gills
1
0
0
0
Adult: paired fins
1
0
0
0
Adult: four limbs (or two legs and two wings)
0
1
1
1
Adult: shell
0
1
0
0
Adult: feathers
0
0
1
0
Adult: hair
0
0
0
1
Adult: beak
0
1
1
0
For the zebrafish and the pig, count the embryo features that both have (both 1). Then count the adult features that both have.
Do the same for the turtle and the chicken.
Which pair shares more as embryos than as adults? Which features explain the difference?
Write a claim about how the zebrafish and the pig are related, and say why the embryo rows are better evidence for it than the adult rows.
Discuss: the zebrafish and the pig share 4 embryo features but none of the listed adult features, so the relationship is hidden in the adults. The turtle and the chicken share all 5 embryo features and 2 adult features (limbs and a beak). Ask: "The adult rows leave out features such as a backbone and jaws. How would adding them change the counts?"
Independent Practice10-15 minutes
Each student analyzes a set of picture descriptions for a flounder, a flatfish that lies on one side on the sea floor. Show photographs of each stage if available.
Picture set: how a flounder develops (real, simplified)
Stage
What the picture shows
Young larva
Swims upright, with one eye on each side of its head, like other young fish
Changing larva
One eye has moved partway over the top of the head
Young flounder
Both eyes on one side; it lies on its blind side on the sea floor
Adult
Flat, lopsided body with both eyes on the upper side
Students answer: (1) Which stage looks most like a typical fish such as a trout? (2) What relationship does the young larva show that the adult hides? (3) Why must scientists compare the young larva with young larvae of other fish, not with adults? Each answer cites a stage from the table.
Closure5 minutes
Return to the barnacle vote from the warm-up and reveal the answer with the barnacle example. Exit ticket: "Name one animal from today whose relatives are hidden in its adult body. Describe the young stage that reveals them, and say what structure gives it away."
Differentiation Strategies
For Struggling Students
Give a picture checklist with small icons for neck ridges, tail, somites and limb buds, so students tick what they see in each picture
Compare only two species at a time, at one stage, before adding more
Use a sentence frame: "As embryos, ___ and ___ both have ___. As adults, they ___. This suggests ___."
For Advanced Students
Ask students to explain why a shared feature at the earliest stage tells less than a shared feature that appears later in only some species
Have students find photos of the same embryo at three stages and make their own labeled comparison chart
Ask students to argue whether larvae count as evidence from embryological development, and to defend their view with the barnacle case
Assessment Guidance
What to Look For
Check that students compare embryos at matching stages, name visible structures (neck ridges, tail, somites, limb buds), and use shared early structures as evidence of a common ancestor. Look for students who can say what the adult anatomy hides and why the embryo reveals it. Watch for the ideas that embryos are tiny copies of ancestral adults, that all embryos are identical, or that a difference in yolk or size rules out a relationship.
02
Classroom Activities
3 Activities
1
Embryo Picture Card Sort
25 minGroups of 3-4
Groups receive 12 shuffled picture cards, 3 stages each of a shark, a salamander, a lizard and a rabbit, with no labels. Teachers print them from a reliable embryology image collection or draw simplified outlines like Diagram 1. Groups first sort the cards by stage, then by species, and record what they used to decide.
What the Cards Show (real, simplified)
Early stage (all four): curled body, neck ridges, a row of somites, small limb or fin buds and a tail.
Middle stage: buds are longer and the head is taking shape; the shark's buds are becoming fins, the others' buds are becoming legs with paddle-shaped ends.
Late stage: the shark has fins and gill slits; the salamander has feathery gills and four legs; the lizard has four legs, scales and a long tail; the rabbit has outer ears, a short tail and fingers and toes.
Tasks
Sort into three stage piles. Then try to sort each pile by species. Record how many cards in each pile your group placed correctly.
Make a table of the visible structures on each card.
Find the stage at which the species are hardest to tell apart, and the stage at which they become easy.
Discussion Questions
Which stage pile was hardest to sort by species, and which structures made it hard?
The rabbit's tail is short as an adult. What did its tail look like on the early card, and what does that suggest?
Why is it important that all four early cards show the same stage?
Modification for Distance Learning
Post the 12 pictures in a shared slide in random order. Groups drag them into a 3-by-4 grid and type the features they used.
2
Brine Shrimp Larvae and the Barnacle Question
20 min, plus a 1-2 day waitPairs
Pairs hatch brine shrimp, small crustaceans (the group that includes crabs and shrimp), and look closely at the young that hatch. They compare the larvae they see with a drawing of a barnacle larva to test the claim that barnacles belong with crustaceans, not with clams.
Procedure
Teacher setup: dissolve about 2 level teaspoons of non-iodized salt in 500 mL of room-temperature water and add a small pinch of brine shrimp eggs. Keep the cup in a warm room, out of direct sun, for 1-2 days.
Put one drop of water with larvae in a petri dish and look with a hand lens or a microscope at low power.
Sketch one larva. Count its eyes and its pairs of legs, and note its body shape.
Put your sketch next to the barnacle larva drawing and list what matches.
Safety: never taste the water; wash hands afterward. At the end, give the brine shrimp to a classroom fish tank or pour them down the sink; never release them outdoors.
What Students Should See
A tiny orange swimmer with one dark eye and three pairs of jointed legs that row it through the water. The barnacle larva drawing shows the same plan: one eye and three pairs of jointed legs, with a triangle-shaped shield.
Discussion Questions
How many matches did you find between the brine shrimp larva and the barnacle larva?
A clam larva is a tiny swimmer with a ring of beating hairs and no legs. Which larva does the barnacle larva match?
Why did scientists need to see the larvae before they could classify barnacles correctly?
Modification for Distance Learning
Use a short video of hatching brine shrimp and a labeled photo of a barnacle larva. Students post a side-by-side sketch with their list of matches.
3
Hidden Relatives Gallery Walk
25 minGroups of 3
Three posters each show an adult and its young stage. Groups spend 6 minutes at each poster, record what the young stage shares with other animals, and write the relationship the adult hides. Groups then vote on which poster gives the strongest evidence.
Posters (real, simplified)
Crab: the adult keeps its short tail folded tightly under its body. A late crab larva has a long, straight tail held out behind it, like a shrimp's or a lobster's.
Sea star: the adult has five arms arranged in a circle, with no left or right side. Its larva swims with a left side and a right side, like most other young animals.
Crab parasite: a parasite related to barnacles lives inside crabs as an adult and looks like a soft, shapeless sac with no legs, shell or eyes. Its larva has one eye and three pairs of jointed legs, like a barnacle larva.
Recording Sheet
Adult features: what does the adult look like?
Young-stage features: what visible structures does the young stage have?
Hidden relationship: which animals does the young stage resemble, and what does that suggest?
Discussion Questions
Which poster shows the biggest difference between the adult and the young stage?
At which poster would the adult alone lead you to the wrong group? Explain.
All three posters use larvae, not embryos inside an egg. Is the evidence the same kind as in Diagram 1? Why or why not?
Challenge Variation
Groups make a fourth poster for an animal of their choice whose young stage reveals a hidden relative, using photos from a reliable source, and explain the visible structures that reveal it.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Early Embryos of Four Vertebrates
Simplified outline drawings based on real embryos at about the stage when limb or fin buds first appear; not to scale (real embryos at this stage are a few millimeters long). All four show neck ridges, a row of somites, buds and a tail. They also differ: the zebrafish lies on a large yolk ball, the turtle and the chicken have large yolks, and the pig has only a small yolk sac.
Diagram 2: A Sea Squirt Larva and Adult
Simplified drawings of real structures, not to scale. The swimming larva has a tail with a stiff rod (notochord) and a nerve cord along its back, structures also found in vertebrate embryos. The adult, fixed to a rock, has lost the tail and the rod; it keeps slits in its throat that filter food from the water.
04
Homework Assignment
~30 min
MS-LS4-3 Homework: What Embryos Reveal
Directions: Facts about real embryos and larvae are real and simplified. Problems 2 and 4 use invented data from picture sets and say so. In every answer, name the visible structures you compare and the stage you are describing.
Part 1: Reading Embryo Pictures (Problems 1-2)
Pictures of early embryos of a lizard, a bat and a sparrow all show neck ridges, a tail and two pairs of limb buds. Later, the bat's front limb buds grow very long fingers with skin between them, the sparrow's front limb buds become wings with only a few short finger bones, and the lizard's become legs with five clawed toes. (a) List the structures shared at the early stage. (b) At what point do the three start to look different? (c) Explain what the early similarity suggests about the three animals.
Invented data from a picture set: early embryos of species 1 and 2 share 6 of 6 listed features; species 1 and 3 share 5 of 6; species 1 and 4 share 2 of 6. As adults, species 1 and 2 share 1 of 6 listed features, species 1 and 3 share 4 of 6, and species 1 and 4 share 1 of 6. (a) Write each early and adult match as a percent, to the nearest whole percent. (b) For which pair does the adult anatomy hide the relationship most? (c) Which species is most likely the closest relative of species 1? Explain.
Part 2: Hidden Relationships (Problems 3-4)
Coqui frogs of Puerto Rico lay eggs on land, and no tadpole ever swims out. Inside the egg, the embryo grows a broad tail and limb buds; the tail shrinks before hatching, and a tiny frog climbs out. (a) Which structure in the coqui embryo is not found in the adult? (b) What does that structure suggest about the coqui's ancestors? (c) Why would this relationship be hard to see from the adult alone?
Invented data: in a set of 10 pictures showing matching stages, duck and chicken embryos look alike in 8 stages, chicken and alligator embryos in 5, and chicken and pig embryos in 3. (a) Which animal is most closely related to the chicken, based on these data? (b) Sketch a branching diagram for the four animals. (c) Explain why the number of stages alike is a reasonable way to compare relationships.
Part 3: Explaining the Evidence (Problems 5-6)
In a chicken embryo at about day 6 or 7, pictures of the wing bud show three separate finger shapes. In the adult wing, the tip looks like one stiff piece covered by feathers. (a) What does the embryo picture show that the adult wing hides? (b) Which other animals have front limbs with separate fingers? (c) Write one sentence that uses this evidence to explain a relationship.
Write a paragraph of 100-150 words explaining why scientists use embryos and larvae to find relationships between species. Use at least two examples from this unit, say what structure each one reveals, and name one limit of this kind of evidence.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Reading Pictures
Names the visible structures and stages correctly
One structure or stage misread
Comparing
Compares matching stages and identifies shared and different structures
Compares, but mixes stages or lists only similarities
Using Numbers
Correct percents and counts, with work shown
One calculation error
Explaining Relationships
Explains what the young stage reveals that the adult hides, with reasoning about common ancestry
States a relationship with little reasoning
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Facts about real embryos and larvae are simplified; data sets marked invented were written for practice. 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
What is an embryo?
Answer: A
An embryo is an organism in its earliest stage, before it hatches or is born. Choice B describes an adult, choice C a fossil, and choice D a young animal after birth.
Question 2 of 20 · Multiple Choice
Pictures show that early embryos of a trout, a gecko and a hamster all have neck ridges and a tail. What does this suggest?
Answer: C
Shared early structures are evidence that the three inherited a body plan from a common ancestor. Choice A is false: the adults look very different. Choice B is about habitat, and choice D is about size, neither of which the pictures show.
Question 3 of 20 · Multiple Choice
Invented data: in a set of drawings, early embryos of species R and S share 6 of 8 listed features, while the adults share 2 of 8. How many percentage points higher is the early match?
Answer: B
6 ÷ 8 = 75% and 2 ÷ 8 = 25%, so the early match is 75 - 25 = 50 percentage points higher. Choice A subtracts the counts without making percents. Choice C divides 6 by 2, and choice D adds the two percents.
Question 4 of 20 · Multiple Choice
Why can embryos show relationships that the adults hide?
Answer: A
Structures inherited from a common ancestor often appear early and then develop differently or disappear, so the adults can look unrelated. Choice B is false: adults keep many ancestral features. Choices C and D are false: embryos differ, and related adults can look very different.
Question 5 of 20 · Multiple Choice
Invented pictorial data: embryos of species P and Q look alike through Stage 4 of 5, while embryos of P and R look alike only through Stage 1. Which conclusion is best supported?
Answer: B
Embryos that stay alike for more stages suggest a more recent common ancestor, so P and Q are likely closer. Choice A reverses the evidence. Choice C goes far beyond the data, and choice D ignores the shared early stage.
Question 6 of 20 · Multiple Choice
An adult frog has no tail and breathes with lungs, but frog embryos and tadpoles have a tail and gills. What does this suggest?
Answer: D
A tail and gills in the young stage point to ancestors that had them, the same structures fish have. Choice A ignores that tadpoles use their tails and gills to swim and breathe. Choice B is false: tadpoles grow into frogs, and choice C does not happen.
Question 7 of 20 · Multiple Choice
Two species have very different adult bodies. Which data would best test whether they are closely related, as MS-LS4-3 describes?
Answer: C
MS-LS4-3 compares pictures of embryos across species, and matching stages make the comparison fair. Choices A, B and D describe adult color, diet and behavior, which unrelated species can share.
Question 8 of 20 · Multiple Choice
An invented picture display shows embryos of species A and B on days 2, 4, 6 and 8. They look alike on days 2, 4 and 6 and differ on day 8. For what fraction of the stages shown do they look alike?
Answer: D
They look alike at 3 of the 4 stages shown, which is 3/4. Choice A is the fraction of stages where they differ. Choice B divides by the last day number (8) instead of the number of stages, and choice C turns the fraction upside down.
Question 9 of 20 · Multiple Choice
In a picture set, lizard and chicken embryos both have a tail at an early stage, but only the lizard keeps a long tail as an adult. Which statement is best?
Answer: B
A structure shared early in development points to a common ancestor; afterward it develops differently, staying long in the lizard and becoming a short bony tail in the chicken. Choice A ignores the evidence of the embryo's tail. Choice C goes far beyond the data, and choice D ignores a pattern that repeats across many species.
Question 10 of 20 · Multiple Choice
The Assessment Boundary limits comparisons to gross appearance. Which observation is about gross appearance?
Answer: D
Neck ridges can be seen in a picture of the whole embryo, so they are part of its gross appearance. Choices A, B and C need lab tests of cells or molecules, which are beyond this standard.
Question 11 of 20 · Multiple Choice
Which pair would you expect to have embryos that stay alike for the most stages?
Answer: C
A robin and a sparrow are both birds, the most closely related pair, so their embryos should stay alike longest. The other pairs come from different groups of vertebrates (choices A, B and D), so their embryos should start to differ sooner.
Question 12 of 20 · Multiple Choice
Invented data: in pictures of 10 stages, embryos of species M and N look alike in the first 7 stages, and embryos of M and O in the first 3. Which statement is best?
Answer: A
M and N stay alike for 7 - 3 = 4 more stages, so they are likely more closely related. Choice B picks the wrong pair, choice C uses the total number of stages, and choice D picks the wrong pair and uses one count instead of the difference.
Question 13 of 20 · Multiple Choice
Larvae of clams and of some sea worms look alike: tiny top-shaped swimmers with a belt of beating hairs. The adults look nothing alike. What do the larvae suggest?
Answer: A
A shared, unusual larva shape is evidence of a common ancestor, even when the adults differ. Choice B confuses relationship with one animal turning into another. Choice C is false because the larvae grow into different adults, and choice D ignores the pattern.
Question 14 of 20 · Multiple Choice
Which statement about embryos and evolution is accurate?
Answer: D
Related species inherit early developmental features from common ancestors. Choice A is an old idea that has been rejected: embryos share early structures with relatives, not the adult forms of ancestors. Choice B is false, since fish, birds and insects have embryos too, and choice C ignores real differences.
Question 15 of 20 · Short Answer
Invented pictorial data, early to late stages: species 1 and 2 share neck ridges, a tail and limb buds at Stage 1; at Stage 2 both still have tails, but only species 1 has fins; at Stage 3 they share nothing on the list. Species 3 shares neck ridges and a tail with species 1 at Stage 1 only. Describe the pattern and what it suggests.
All three share early features at Stage 1, which suggests a common ancestor. Species 1 and 2 stay alike longer (they still share a tail at Stage 2), so they are likely more closely related to each other than either is to species 3. Full credit compares the stages in order and links staying alike longer to a closer relationship.
Question 16 of 20 · Short Answer
You have photographs of embryos of a frog, a newt and a goldfish at 5 matching stages. Describe how you would use them to decide which two are most closely related.
List the visible structures (neck ridges, tail, somites, limb or fin buds, gills, eyes) in each photograph. For each pair, record at which stages they look alike and count the shared structures at each stage. The pair that stays alike for the most stages and shares the most structures is likely the most closely related. Keep the stages matched, and use the same list of structures for every pair. Full credit has a feature list, a fair comparison across matching stages, and a rule for deciding.
Question 17 of 20 · Short Answer
Invented data from a picture set: early embryos of species T and U share 5 of 6 listed features; the adults share 1 of 6. Find both percents, to the nearest whole percent, and explain what they show.
Early: 5 ÷ 6 ≈ 0.83, about 83%. Adults: 1 ÷ 6 ≈ 0.17, about 17%. The embryos share far more than the adults, so a relationship that is hard to see in the adults shows up in the embryos. Full credit gives both percents and explains that the shared early structures are evidence of a common ancestor.
Question 18 of 20 · Short Answer
A student compares a picture of an early embryo of species A with a picture of a late embryo of species B. She concludes that A and B are not related because the pictures look very different. Evaluate her reasoning.
The comparison is not fair because the stages do not match: a late embryo has already developed species-specific structures, while an early embryo has not. She should compare both species at the same early stage (and then at matching later stages) before deciding. Full credit names the stage mismatch and the fix.
Question 19 of 20 · Short Answer
In the guided practice table, the pig embryo has no large yolk, while the zebrafish, turtle and chicken embryos do. Does this difference mean the pig is unrelated to the others? Explain.
No. The yolk is the embryo's food store, and pig embryos are fed through the mother instead, so they need only a small yolk sac. The pig embryo still shares the neck ridges, tail, somites and limb buds with the others, so the shared structures point to a common ancestor and the yolk difference reflects a different way of feeding the embryo. Full credit names the shared structures and explains why the yolk difference does not rule out a relationship.
Question 20 of 20 · Short Answer
A scientist finds a new deep-sea animal (invented for this question). The adult is a soft, legless tube fixed to the sea floor. Its larva swims with one eye and three pairs of jointed legs. Explain what the scientist should conclude and what other pictorial data would help.
The larva matches the young of crustaceans such as barnacles, brine shrimp and crabs, so the animal is most likely a crustacean, even though the adult shows no jointed legs. Other helpful pictures: later larval stages, to see whether it passes through the same stages as barnacle larvae, and close-ups of the adult for any hidden jointed parts. Full credit links the larval structures to a group and names more pictorial evidence.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-LS4-3 mean?
MS-LS4-3 asks middle school students to analyze pictures of embryos from several species, compare patterns of similarity in their development, and identify relationships that the adults do not show. The code means Middle School, Life Science, core idea 4 (Biological Evolution: Unity and Diversity), performance expectation 3.
What is the Assessment Boundary for MS-LS4-3?
Assessment of comparisons is limited to gross appearance of anatomical structures in embryological development. Students compare what can be seen in pictures, such as neck ridges, tails and limb buds, and are not assessed on cells, genes or chemistry.
What grade is MS-LS4-3 taught in?
It is a middle school standard for grades 6-8, usually taught in a life science unit on evolution together with MS-LS4-1 (the fossil record) and MS-LS4-2 (anatomy). The exact grade depends on the school.
Do human embryos have gills?
No. Early human embryos, like other vertebrate embryos, have neck ridges (pharyngeal arches) with grooves between them. In fish these ridges develop into gill supports; in mammals they develop into parts of the jaw, ear and throat. The ridges are shared, but only fish turn them into gills.
Is it true that embryos replay the evolution of their ancestors?
No. That idea, popular in the 1800s, has been rejected. Embryos do not pass through the adult forms of their ancestors. Related species share early structures, which then develop in different ways.
Were the old embryo drawings faked?
Some drawings from the 1870s made embryos of different animals look more alike than they really are. Modern photographs show real differences in size, shape and yolk. They also confirm that the key shared structures, such as neck ridges and a tail, are real, so the evidence does not depend on the old drawings.
Why does MS-LS4-3 talk about relationships not evident in the fully formed anatomy?
Because adults can hide their relatives. A barnacle's shell makes it look like a clam, and an adult sea squirt looks like a bag, but their young stages show that barnacles are crustaceans and that sea squirts are related to animals with backbones.
Can larvae be used as evidence for MS-LS4-3?
Many textbooks include larvae, the young stages that hatch from the egg and keep developing, because they are part of an animal's development. This page uses vertebrate embryos for the main data and labels every larva example, so teachers can decide how much to use.
What lab works for MS-LS4-3 in a middle school classroom?
A picture card sort of embryos at three stages needs only printed images. Hatching brine shrimp with salt water lets students see a live crustacean larva in a day or two, with a hand lens or a microscope, and compare it with a barnacle larva.
What comes after MS-LS4-3?
In high school, HS-LS4-1 asks students to communicate how embryos, anatomy, fossils and DNA together support common ancestry. MS-LS4-3 gives them practice with the embryo part of that evidence.
07
Related Standards
5 standards
These standards connect to MS-LS4-3: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
3-LS1-1Prerequisite
Model that organisms have unique and diverse life cycles with birth, growth and death
Lesson coming soon
4-LS1-1Prerequisite
Argue that internal and external structures support survival, growth and reproduction
Lesson coming soon
Alongside
MS-LS4-2Parallel
Explain anatomical similarities and differences to infer evolutionary relationships
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