The 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 from the pollen and are sheltered from the microsporophylls. Upon visiting megasporophylls, the beetles transfer pollen (containing the flagellated sperm) to the exposed ovules. In cycads, pollen cones and seed cones are borne on different plants. Which feature of cycads distinguishes them from most other gymnosperms?
Answer:The Cycad tree is the sporophyte.They have flagellated sperm.
Explanation:
During pollination, the contents of the megaspore divide to form many–celled gamateophyte called the endosperm and archegonium. There is a micropyle opening with a sticky fluid, which traps the wind-borne male gametophyte (microspores) which,at this time is made up of prothallus cell;an antheridial cell and a large tube cell. The trapped microspore is sucked into the archegonia chamber. Antherizoids are released, but only one penetrates each oospore and fuses with the female nucleus. The zygote is formed in the ovule and the later develops into seed.The diploid seed germinates into a new sporophyte plant and the life cycle begins again. Examples of cycad include Cycas circinalis ,Cycas celebrical and Cycas revoluta
