Mississippi Science MAQ.6.3

ScienceGrades 9–12Marine and Aquatic Science I & II

The Standard

Develop a dichotomous classification key to be used in the identification of sample aquatic invertebrates.

2026 Mississippi College- and Career-Readiness Standards for Science · Invertebrate Consumers

Teacher's field guide

What Students Need to Do: Students examine aquatic invertebrates and choose features they can see, such as jointed legs or hinged shells. They write paired choices that lead to an identification, then test the key on each sample.
What Mastery Looks Like: A student writes a key with two clear, contrasting choices at every step. A classmate can follow it to identify each sample without guessing or reaching a dead end.
Common Misconceptions: Students may write choices that overlap, such as 'has legs' and 'has a hard shell,' both of which fit a crayfish. They may count claws as extra legs or sort by color, which can vary between individuals.
How to Assess It: Show photos of a pond snail, freshwater mussel, dragonfly nymph, and crayfish. Ask students to write a two-choice key and trace the path that identifies the nymph.

Lesson moves

Give pairs four specimen photo cards to sort by jointed legs, then by leg count or shell type, before writing paired choices.
Ask partners why 'has a shell' cannot separate a snail from a mussel, then have them write a choice that can.
Swap keys between pairs; use new photos of the same four animals to find unclear choices, then revise them.
Print a mock stream sample tally sheet; have students identify photographed invertebrates with their keys and record how many of each appear.

Free download

A ready-to-print activity worksheet aligned to MAQ.6.3, with an answer key for the teacher on its own page. No account needed.

PDF, US Letter, prints cleanly in black and white.

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