Question

Use the information to answer the following question. 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 shelter from the microsporophylls. Upon visiting megasporophylls, the beetles transfer pollen to the exposed ovules. In cycads, pollen cones and seed cones are borne on different plants. Cycads synthesize neurotoxins, especially in the seeds, that are effective against most animals, including humans. Which feature of cycads distinguishes them from most other gymnosperms?

Answer 1

1. They have flagellated sperm.

2. They are pollinated by animals.

Step-by-step explanation:

In other types of gymnosperms when pollen grains land on the ovulate cones, they grow a long pollen tube. By the time this tube reaches the archegonia, about 15 months after pollination, the male gametophyte is fully mature. The pollen tube enters through the micropyle. The sperm nucleus divides in two, and the pollen tube discharges two sperm. One sperm nucleus degenerates, the other fertilizes the egg. It takes the female gametophyte about 15 months to mature, and about the same time for the pollen tube of the male gametophyte to reach it.

Most gymnosperms undergo pollination by wind, in contrast plants with "true flowers" (angiosperm) will use the help of an animal to pollinate their flowers.