Students who demonstrate understanding can: 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.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
Adult fish, chickens, pigs and humans look very different, but their early embryos look surprisingly alike. At similar early stages, vertebrate embryos all have a tail and a series of folds in the neck region called pharyngeal arches. As development continues, these shared features follow different paths: in fish the neck folds become parts of the gills, while in mammals they become parts of the jaw, ear and throat.
Students analyze pictorial data, such as side-by-side drawings or photographs of embryos at several stages, and look for patterns of similarity. The key idea is that these early similarities reveal relationships that are not obvious when you compare the fully formed animals. Species whose embryos stay similar for longer are generally more closely related.
The comparison stays at the level of what the embryos look like, the gross appearance of anatomical structures, so students focus on careful observation and pattern-finding rather than on developmental genetics.
Human embryos never become fish. They share early structures with fish embryos, which then develop into different adult parts.
Early vertebrate embryos are similar, not identical, and the differences grow as development continues.
Embryology is one line of evidence. Scientists combine it with fossil and anatomical evidence to build a stronger case for relationships.
Drawings show fish, chicken, rabbit and human embryos at three stages. At stage 1 all four have a tail and neck folds. At stage 2 the rabbit and human still look very alike, while the fish and chicken look more different. At stage 3 all four look distinct. What can you infer?
Answer: All four share a common ancestor, and the rabbit and human are the most closely related because their embryos remain similar the longest.
Provide unlabeled embryo images and ask students to match each to its adult animal, then reveal answers and discuss what made it hard. Follow with a table where students record similarities and differences at each stage.
Assessment is limited to gross appearance, so practice precise observation language, such as 'both embryos show a tail and four neck folds at stage 1'.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: A) They share a common ancestor
Shared early structures are evidence of common ancestry.
Answer: D) Two closely related species
Closely related species share developmental patterns for longer.
Answer: embryo (also accepted: an embryo, embryonic stage)
An embryo is the early developing stage of an organism.
Answer: B) Jaw, ear and throat
The same embryonic structures follow different paths in different groups.
Answer: A) It reveals relationships that adult anatomy hides
Early similarities can show relatedness not obvious in adults.
Communicate scientific information that common ancestry and biological evolution are supported by multiple lines of empirical evidence.
A full lesson with slides, activities and an exit ticket on clues from embryo development, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-LS4-3 with an answer key, ready in about a minute.
Make a worksheet βTurn clues from embryo development into a quiz students answer online that marks itself, with a class summary for you.
Build a test βPictorial data, such as diagrams or pictures of embryos from different species at comparable stages.
Comparisons are limited to the gross appearance of anatomical structures during embryological development.