Explain the events upto double fertilisation after the pollen tube enters one of the synergids in an ovule of an angiosperm.
Fertilization process is the unique feature of the angiosperm life cycle. By the two sperms, one fertilizes with the egg for the formation of the zygote which is known as Syngamy; and the other sperm combines with the secondary nucleus which is known as the triple fusion to form the triploid nucleus (3n) that is calles primary endosperm nucleus in the large central cell of the embryo sac. And then the combination of two male gametes with the different nuclei of the embryo sac is known as double fertilization.
First, the fertilized egg becomes the zygote and then get developed into the embryo. After the division of primary endosperm nucleus, it gives endosperm. It is rich in nutrients so that it can take proper care of the developing embryo.
Double Fertilization:
And, as a result of the triple fusion, the primary endosperm nucleus is formed. It divides primarily to the zygote and forms the endosperm.
Fill in the blanks:
(a) Humans reproduce __________. (asexually/sexually)
(b) Humans are__________. (oviparous/viviparous/ovoviviparous)
(c) Fertilization is __________ in humans. (external/internal)
(d) Male and female gametes are __________. (diploid/haploid)
(e) Zygote is __________. (diploid/haploid)
(f) The process of release of the ovum from a mature follicle is called__________.
(g) Ovulation is induced by a hormone called the __________.
(h) The fusion of male and female gametes is called _____________.
(i) Fertilisation takes place in _____________.
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between fetus and uterus is called ____________.