Question

The two extinct lines of the gymnosperms which are regarded as an ancestral stock from which the modern gymnosperms might have originated are?
A. Cordaitales and Bennettitales
B. Cycadales and Coniferales
C. Ginkgoales and Cycadales
D. Gnetales and Coniferales

Answer 1

Hint: The gymnosperms are plants that produce naked seeds. Gymnosperm is derived from the Greek words "gymnos" (meaning "naked") and "sperma" (meaning "seed") (meaning seed). They are a group of seed producing plants that includes conifers, cycads, ginkgo, and gnetophytes. There are over $$1000$$ species of gymnosperm present. It is known that the gymnosperms originated in the late carboniferous period.

Complete explanation:
Option A Cordaitales and Bennettitales: Cordaitales are an extinct species of woody plants that is suspected to be the early conifers. It is also hypothesized that corditales may have given rise to the conifers, ginkgos and cycads. Bennettitales is another extinct order of seed plants that appeared in the Permian period and became extinct towards the end of the Cretaceous period. The morphologies of bennettitales are very similar to the present day cycads.
Option A is correct.
Option B Cycadales and Coniferales: Cycads are present day gymnosperms which may have originated from Cordaitales and Bennettitales. They feature a thick, woody trunk with huge, tough, evergreen pinnate leaves on top. Coniferales are the most dominant gymnosperms. They are economically very important as they are the source of valuable timber and pulp.
Option B is incorrect.
Option C Ginkgoales and Cycadales: Ginkgoales is an order of gymnosperm containing only one species which is Ginkgo biloba in the present day. The ancestor of ginkgoales first appeared in the middle Jurassic period. It is already known that cycadales are present day gymnosperms.
Option C is incorrect.
Option D Gnetales and Coniferales: Gnetales is the order of gymnosperms that includes tropical evergreen trees, shrubs and lianas. Some of the gnetales are present till date. They are found in Africa, South America and Southeast Asia. It is already known that coniferales are widely distributed gymnosperms and of huge economic importance.
Option D is incorrect.

Therefore, Option A. Cordaitales and Bennettitales is the correct answer.

Note:
The other extinct group of gymnosperms include the Lyginopteridopsida, Gigantopteridales, Pentoxylales, Caytoniales, Glossopteridales and Voltziales. Today there are only four major lineages of gymnosperm seed plants present. They are Cycadopsida (the cycads), Ginkgopsida (ginkgos), Coniferopsida (conifers) and Gnetopsida (gnetophytes). There is a hypothesis that the angiosperms may have evolved from seed ferns of cycadeoid related gymnosperms which are the extinct gigantopterids.