SHORT QUESTIONS OF GYMNOSPERMS
1. Give occurrence of Gymnosperms.
Ans: Gymnosperms are naked seeded plants. Gymnosperms are a group of ancient plants. They become dominant in the Jurassic period. Most of the gymnosperms are evergreen trees. Some shrubby plants are also found in this group. They have worldwide distribution. They are most abundant in the temperate region. The fossils of gymnosperms are found near coal and oil deposits.
2. How do fertilization and seed formation occur in gym nos perms?
Ans: Pollen tube carries male gametes to egg (oosphere). Fertilization occurs and diploid oospore is formed. Oospore is the beginning of gametophyte generation. The oospore gives rise to the embryo. Prothalial tissues provide nourishment to developing embryo. Integument is transformed into the seed coat The unutilized prothalial cell becomes endosperm.
3. What is meant by Ferns with seeds?
Ans: The primitive gymnosperms like Cycas are much identical with Pteridophytes (ferns). They were taken as Pteridophytes for long time. They were called Ferns with seeds.
4. Give two resemblances between gymnosperms and pteridophytes.
Ans: Both have regular alternation sporophytic and the gametophytic generations. Their sporophyte is dominant and forms the main plant body. Gametophyte is reduced to prothellus. Both are heterosporous
5. Give two differences between gymnosperms and pteridophytes.
Ans: There is no seed formation in the Pteridophytes. But present in gymnosperms. The male cells or sperms are carried by pollen-tube to the archegonia in the gymnosperms. But pollen tube is absent in Pteridophytes.
6. Give two similarities between gymnosperms and angiosperms.
Ans: They are similar in their external morphology, i.e., the
differentiation into root stem and leaves. Both have identical internal anatomy. Cambium is present in gymnosperm and dicot angiosperms.
7. Give two differences between gymnosperms and angiosperms.
Ans: The reproductive structures of angiosperms are flowers, those of gymnosperms are cones. In angiosperms, the seeds are enclosed by true carpels and at maturity, a carpel forms a fruit. It is absent in gymnosperms.
8. Name of order of gymnosperms.
Ans: Cycadofilicales, Bennettitales, Cycadales, Cordaitales, Ginokoales and Gnetales.
9. Which plant is called living fossil? Why?
Ans: Cycas is called a living fossil. It has several characters
common with the Ptcridophytes.
10. What are coralloid roots? Give their advantage to plant.
Ans: Cycas produces coralloid roots. Coralloid roots are short tufts and dichotomously branched roots. These roots contain an endophytic alga in the inner part of their cortex. Sometimes, bacteria are also present in the cortex. Bacteria fix nitrogen.
11. What are transfusion tissues? Give their function.
Ans: Transfusion tissues are present around mid ribs. They cause lateral conduction in the leaf.
12. How is microspore germinate in Cycas?
Ans: The microspore cut off lateral prothalial cell towards one side of the spore. The larger cell then cuts off a small generative cell adjacent to the plothalial cell. It itself becomes tube cell. The microspore is liberated at this stage. Spores are dispersed by wind.
13. How does fertilization occur in Cycas?
Ans: Pollen grain reaches the archegonial chamber by pollination.
The wall of the pollen grain protrudes towards the archegonial chamber. The pollen grain bursts and release antherozoids into the archegonial chamber. Antherozoid enters the oosphere. Male nucleus unites with the oosphere nucleus. Fertilized oosphere secretes a thick wall and becomes the oospore. Oospore develops embryo.
14. Give occurrence and common species of pinus.
Ans: The genus Pinus has about 90 species. It has world wide in distribution. They are mostly present in the temperate regions. Four species of pinus are found in Pakistan: Pinus wallichiana; Pinus halepensis; Pinus roxburghii; Pinus gerardiana.