A bell-shaped jellyfish drifting through water is an easy form to recognise. A life-cycle diagram may introduce a very different-looking attached stage, changing what it means to follow the same kind of animal through time.
The Smithsonian’s jellyfish life-cycle account describes medusae, larvae and polyps, with different routes between stages among groups. Many familiar jellyfish have an attached polyp stage that can produce new individuals asexually. The sequence is not identical for every species.
Follow the arrows carefully
Choose a diagram that identifies its organism. Number the stages and label what each arrow represents: development, attachment or reproduction. An arrow is not always a picture of one individual simply growing larger.
Notice whether the diagram repeats a stage or branches. That can be important when interpreting a population, because a reproduction step differs from the same individual changing shape.
For an original reading exercise, cover the stage names and describe each form from the drawing. Then restore the labels and compare the descriptions. The exercise can reveal how strongly the familiar bell shape has governed your idea of a jellyfish.
Keep the species or group name with your notes. A useful life-cycle sketch helps you understand the organism it describes; it should not become a universal template pasted onto every gelatinous creature photographed at sea.
Editorial illustration from this site’s image library; not documentary evidence of the example or object discussed.