MS-LS4-3: Comparing Embryos to Find Relationships
Also called NGSS MS-LS4-3 · Topic: Natural Selection and Adaptations · Life Science
The Official Wording
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.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What MS-LS4-3 Means in Plain English
Middle schoolers study drawings or photos of embryos from several species, such as fish, chickens, pigs and humans, and look for shared features. Early embryos of very different animals look surprisingly alike, which hints at relationships that the grown animals hide.
Students compare only what the pictures show, the overall shape of body parts as they form, not genes or cell details. This adds to bone comparisons (MS-LS4-2) and leads to DNA and anatomy evidence for common ancestry in high school (HS-LS4-1).
MS-LS4-3 I Can Statements
- I can describe features that early embryos of different species share.
- I can spot when embryos look more alike than the adults do.
- I can use embryo patterns to explain which animals are related.
MS-LS4-3 Worked Example
A card-sorting activity built from printed embryo pictures at matched early and later stages.
Which features do fish, chicken, pig and human embryos share at an early stage?
Set It Up: Picture cards showing each animal's embryo at an early stage and a later stage, a data table and a pencil.
- Lay out the four early-stage cards side by side.Four curled shapes, hard to tell apart
- Look for a tail and record which embryos have one.Tail: all four
- Look for the row of folds behind the head, called pharyngeal arches.Pharyngeal arches: all four
- Repeat both checks with the later-stage cards.Fish keeps the folds as gills, the others reshape them
- Rank the pairs by how long they stay alike.Pig and human stay alike longest
All four early embryos have a tail and pharyngeal arches, and the two mammals stay similar the longest.
Why it works: Shared early features come from a common ancestor's way of developing, and species that stay alike longer share a more recent ancestor.
Common Mistakes with MS-LS4-3
Thinking human embryos grow gills
“Human babies have gills before they are born.”
Try this: Human embryos have folds in the neck region like fish embryos do, but in humans those folds become parts of the jaw, ear and throat.
Comparing embryos at different stages
An early fish embryo set beside a nearly formed chick
Try this: Line up embryos at matching stages of development so differences come from the species, not from how far along each one is.
Saying alike means identical
“The embryos are exactly the same, so the animals are the same.”
Try this: Embryos share a general body plan but already differ in small ways. Similar means related through ancestry, not identical or the same species.
Where MS-LS4-3 Fits
Practice MS-LS4-3
Quick Check
- A chick embryo and a human embryo both have a tail early on. What could that suggest?
- Why compare embryos when you could just compare adults?
- Two species' embryos stay alike longer than a third species' embryo. What does that tell you?