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Cycads, a mostly tropical phylum of gymnosperms, evolved about 300 million years ago and were dominant forms during the Age of the Dinosaurs. Though their sperm are flagellated, their ovules are pollinated by beetles. These beetles get nutrition by eating pollen and microsporophyll tissue and shelter within the male cones (they are dioecious). Upon visiting megasporophylls on nearby female plants, which become attractively aromatic and warm (but are not palatable), the beetles transfer pollen to the exposed ovules. Cycad megasporophyll tissues synthesize neurotoxins, some of which is transferred to the seeds, that are effective against most animals, including humans.
-Which feature of cycads distinguishes them from most other gymnosperms?
I. They have exposed ovules.
II. They have flagellated sperm.
III. They are pollinated by animals.

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Quizplus · Accepted Answer

I is incorrect because many gymnosperms have exposed ovules. II is incorrect because some other gymnosperms, such as ginkgoes, also have flagellated sperm. III is correct and distinguishes cycads from most other gymnosperms, which are wind-pollinated.

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