Question

11. The extinct "cycadeoids" differ from the modern extant cycads by having ______________.

A. primary tissues but no secondary tissues

B. unisexual pollen and seed cones

C. different morphology of the guard cells in the epidermis

D. flowers instead of cones

12. Cycads are dioecious, meaning that ______________.

A. there are no reproductive structures known

B. the plants drop their leaves each fall

C. there are separate male and female plants

D. they have male and female cones on the same plant

13. Unlike the seed cone of pines, the seed cone of cycads such as Cycas revoluta is ______________.

A. a complex structure, a branch of modified branches (microsporophylls)

B. a simple structure, a branch of modified leaves (megasporophylls)

C. a complex organism, a modified gametophyte

D. none of the above are correct

14. In cycads, as in all other gymnosperms, a pollen tube is ______________.

A. lacking, the sperm swim freely to the egg

B. extremely long, usually more than 15 cm in length

C. a means of transferring the pollen grain to the stigma

D. one of the most important evolutionary advances in seed plants

15. Cycad fossils are ______________.

A. unknown

B. known from the late Permian

C. abundant in the Devonian, but scarce in later Periods

D. never found with cones or seeds

Answer 1

11. The extinct “cycadeoids” differ from the modern extant cycads by having unisexual pollen and seed cones.

12. Cycads are dioecious, meaning that – C. There are separate male and female plants.

Pollen are produced by males cones which are carried by abiotic or biotic factors such as wind to female cones (both on different plants).

13. Unlike the seed cone of pines, the seed cone of cycads such as Cycas revolute is a simple structure, a branch of modified leaves (megasporophylls).

The female cone is comprised of modified leaves which we call as megasporophylls. These produce ovules which are fertilized by the pollen from the male cone plants.

14. In cycads, as in all other gymnosperms, a pollen tube is – a means of transferring the pollen grain to the stigma.

The pollen tube is known as haustorial. It absorbs nutrients from the female nucleus and grows on the tissues of the female sporophyte. It provides a pathway for the multiflagellated binucleated sperm to swim towards the egg.

15. Cycad fossils are known from the late Permian.

Cycads are basically gymnosperms which dominated during the Jurassic and Cretaceous period which came after the Permian period.