Question

Double fertilization is exhibited by
A. Angiosperms
B. Gymnosperms
C. Algae
D. Fungi

Answer 1

Hint: Different types of plant exhibit different modes of fertilization. Fertilization refers to the fusion of gametes leading to formation of zygote and embryo. In double fertilization fusion takes place two times.

Complete answer:
Double fertilization is a process in which one of the male sperm fuses with the female egg and the other female egg and the other male sperm fuses with the two polar nuclei. Double fertilization is a characteristic feature of angiosperms. It is important because it requires the fusion of male gametes which helps in avoiding polyembryony.
-In angiosperms: The carpel/pistil is termed as the female sex organ of the flower which consists of an ovary having many ovules. Within the ovule is present the female gametophyte called the embryo- sac. Each embryo sac has an egg cell and egg apparatus with synergids, antipodal cells and the polar nuclei which fuses and results in a secondary nucleus. All the cells are haploid in nature.
After formation of pollen grains in the anthers pollination takes place. Then the pollen grains with the process of germination gives two male gametes that are incorporated in the embryo sac through the pollen tube. The zygote is developed by the union of one male gamete with the egg and the endosperm is developed by the union of another male gametes with two polar nuclei. This event is known as double fertilization.
-Gymnosperms are the plants such as conifers whose seeds are not enclosed in an ovary. Double fertilization is absent in gymnosperms.
-Algae reproduce by vegetative, asexual and sexual methods.
-Fungi reproduce asexually by budding, fragmentation or by spores.

Hence, the correct answer is option (A).

Note: The formation of pollen grains to the ovules is called pollen pistil interaction. Each pollen tube gives two male gametes. The male gametes and the egg cells, synergids, three antipodal cells and two polar nuclei are all haploid. After the process of fertilization the zygote formed is diploid and the primary endosperm formed is triploid.