Free Biodiversity and Variety of Life MCQs with Answers

1981. Megaspores are produced from the megaspore mother cells after:

• A. Mitotic division
• B. Formation of thick wall
• C. Differentiation
• D. Meiotic division

Explanation: In angiosperms, microsporogenesis i.e., formation of microspores (or pollen grains) occurs by the meiotic divisions of diploid microspore mother cells (or pollen mother cells ). Microsporogenesis takes place in the anther. Megasporogenesis i.e. formation of megaspores occurs by the meiotic divisions of diploid megaspore mother cells. Megasporogenesis takes place in the ovule.

1982. What is the function of germ pore?

• A. Emergence of radicle
• B. Absorption of water for seed germination
• C. Initiation of pollen tube
• D. Release of male gametes

Explanation: In a pollen grain, exine is thin or absent at certain places. These areas may have thickened intine or deposition of callose. They are called germ pores (if rounded) or germinal furrows (if elongated). After pollination, the pollen grain on the stigma absorbs water and nutrients from the stigmatic secretion through its germ pores. The tube or vegetative cell enlarges and comes out of pollen grains through germ pore to form a pollen tube

1983. Plants with ovaries having only one or a few ovules are generally pollinated by:

• A. Bees
• B. Butterflies
• C. Birds
• D. Wind

Explanation: Anemophily is an abiotic means of pollination by wind and, being non­directional, a wasteful process as the pollen would reach the stigma through wind is a hit­or­miss affair. During the transit of pollen through wind, a considerable amount of pollen is lost because it never reaches a proper stigma. To stand this loss, anemophilous plants have to produce enormous quantities of pollen. Anemophily is also associated with reduction in the number of ovules per ovary. Some models predict that plants benefit from numerous inexpensive flowers distributed throughout the inflorescence, each with a single ovule or a few ovules. In grasses there is just one ovule per ovary. This is to increase the probability of successful pollination of each ovule

1984. Nucellar polyembryony is reported in species of:

• A. Citrus
• B. Gossypium
• C. Triticum
• D. Brassica

Explanation: In nucellar polyembryony, some of the nucellar cells surrounding the embryo sac start dividing. Then it protrudes into the embryo sac and develop into the embryos. In such species, each ovule contains many embryos. Occurrence of more than one embryo in a seed is referred as polyembryony. Nucellar polyembryony is found in many of the Citrus and mango varieties

1985. Wind pollination is common in:

• A. Legumes
• B. Lilies
• C. Grasses
• D. Orchids

Explanation: Wind pollination is common in grasses because they typically have small, inconspicuous flowers that lack showy petals and nectar to attract pollinators. Instead, grasses rely on the wind to carry their lightweight pollen from one flower to another.

1986. In angiosperms, functional megaspore develops into:

• A. Embryo sac
• B. Ovule
• C. Endosperm
• D. Pollen sac

Explanation: In angiosperms, the functional megaspore develops into the embryo sac, which is a structure within the ovule that contains the female gametophyte (egg cells).

1987. What does the filiform apparatus do at the entrance into ovule?

• A. It brings about the opening of the pollen tube
• B. It guides the pollen tube from a synergid to the egg
• C. It helps in the entry of the pollen tube into a synergid
• D. It prevents the entry of more than one pollen tube into the embryo sac

Explanation: Within the embryo sac three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which plays an important role in guiding the pollen tubes into the synergid. Three cells are at the chalazal end and are called the antipodals. The large central cell, has two polar nuclei.

1988. Through which cell of the embryo sac, does the pollen tube enter the embryo sac?

• A. Egg cell
• B. Persistent synergid
• C. Degenerated synergids
• D. Central cell

Explanation: The pollen tube enters into the embryo sac at the micropylar end. This entry may be between egg and one synergid or between wall of embryo sac and synergid or through one synergid. So one synergid is always degenerated to allow the entry of the pollen tube.

1989. In angiosperms, pollen tube liberate their male gametes into the:

• A. Central cell
• B. Antipodal cells
• C. Egg cell
• D. Synergids

Explanation: On reaching of pollen tube inside the embryo sac, the 2 male gametes are discharged through a sub­terminal pore in pollen tube. The contents of pollen tube are discharged in the synergid and the pollen tube does not grow beyond it in the embryo sac. Further the cytoplasm of pollen tube is restricted to chalazal end of this synergid cell.

1990. In grasses, what happens in the microspore mother cell for the formation of mature pollen grains?

• A. One meiotic and two mitotic divisions
• B. One meiotic and one mitotic division
• C. One meiotic division
• D. One mitotic division

Explanation: Grass is a monocot plant. Primary sporogenous cell gives rise to microspore mother cells or pollen mother cells. Each MMC on reduction division gives rise to 4 microspores or pollens and this formation of microspores or pollens is called microsporogenesis. Karyokinesis is of successive type. The successive type of cytokinesis is common in monocots. Here both meiotic I and II nuclear divisions are followed by wall formation and it leads to isobilateral tetrad.