Use dichotomous keys to identify and classify organisms.

A student uses a dichotomous key to identify an unknown organism. At the first branch, the key asks: 'Does the organism have a backbone?' The student observes that the organism has no backbone, jointed legs, and a hard outer skeleton. Which of the following groups is the organism most likely to belong to?

A student is using a dichotomous key to identify an unknown invertebrate specimen. At the first step, the key presents two contrasting statements: (A) Body segmented (B) Body not segmented The student observes that the specimen has a cylindrical body with visible rings running along its entire length. Use the dichotomous key approach to identify which statement the student should follow next, and explain why this observation supports your choice.

A student uses a dichotomous key to identify an unknown organism. At the first step, the key asks: 'Does the organism have a backbone?' The student observes that the organism has jointed legs, an external skeleton, and antennae. Which characteristic would the student use to answer this first branching question in the dichotomous key?

A student collects an organism from a garden and records its observable characteristics. Use the dichotomous key provided to identify the class and phylum of the organism.