Students who demonstrate understanding can: Apply scientific ideas to construct an explanation for the anatomical similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships.
Clarification statement: Emphasis is on explanations of the evolutionary relationships among organisms in terms of similarity or differences of the gross appearance of anatomical structures.
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
Compare a human arm, a bat wing, a whale flipper and a cat's front leg. They do very different jobs, yet inside each one is the same basic arrangement: one upper bone, two lower bones, a cluster of wrist bones and finger bones. Structures like these, built on the same plan, are evidence that the organisms share a common ancestor. The more anatomical features two organisms share, the more closely related they are likely to be.
Students apply this idea to construct explanations about relationships among modern organisms and between modern and fossil organisms. A fossil whale with small hind legs, for example, links modern whales to land-dwelling ancestors. Differences matter too: over many generations, a shared structure can be modified for flying, swimming or running.
The emphasis is on the gross appearance of anatomical structures, the bones and body parts you can see and compare, rather than on molecules or DNA.
A bird wing and an insect wing both allow flight but are built very differently. Relatedness is judged by underlying structure, not by what the part does.
Humans and other apes share a common ancestor that lived long ago. No living species is the ancestor of another living species.
Related organisms can look very different because shared structures have been modified over many generations for different ways of life.
Modern whales have flippers and tiny, unattached hip bones. A fossil animal had four legs, a long tail and a skull shape like a whale's. Explain what these features suggest.
Answer: Shared limb and hip structures, plus a whale-like fossil with legs, are evidence that whales are related to land mammals through a common ancestor.
Give students labeled outline drawings of several vertebrate forelimbs and have them color-code matching bones. Then show a structure with a similar function but a different build, such as an insect wing, to sharpen the difference between structure and function.
Assessment asks for explanations of relationships using gross anatomy, so require students to name the specific shared feature they are using as evidence.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: D) They share a common ancestor
The same underlying structure is evidence of inheritance from a shared ancestor.
Answer: A) A wolf and a dog, which share very similar skeletons
Wolves and dogs share nearly identical skeletal structures. The other pairs share function or shape, not underlying structure.
Answer: homologous (also accepted: homologous structures)
Homologous structures share an underlying plan because of common ancestry.
Answer: C) As evidence linking birds to reptile-like ancestors
Fossils with mixed features help show how groups are related.
Answer: D) The shared structure was modified over many generations for different uses
Common structures were adapted for flying, swimming or running over time.
Analyze and interpret data from fossils to provide evidence of the organisms and the environments in which they lived long ago.
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 anatomical evidence of relatedness, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-LS4-2 with an answer key, ready in about a minute.
Make a worksheet βTurn anatomical evidence of relatedness into a quiz students answer online that marks itself, with a class summary for you.
Build a test βNo. The emphasis is on similarities and differences in the gross appearance of anatomical structures.
Yes. The standard includes comparisons between modern organisms and between modern and fossil organisms.