Reproduction in Organisms Test - 18

Sexual reproduction in mammals involves cyclic changes during which ovum is released. In primitive animals it is called oestrus cycle and in in primates including human being it is called menstrual cycle.

The outer layer of pollen grain is called exine, which is made of spropollenin. It is very hard natural substance having no effect of enzyme. It helps the pollen grain to survive in adverse environmental condition.

Transfer of male gametes into female genital tract is called insemination. Semen contains glucose, protein along with sperms. Insemination occurs during coitus.

During sexual reproduction male and female gametes are fused together to form zygote. The gene from two different sources mix together and develops some new features in new progeny. The new traits help the organisms to survive in adverse condition also.

Ovulation is the process of release of ovum from ovary. Menstrual cycle begin with menstrual bleeding. Increase in FSH and LH hormone leads to release of ovum from ovary in the middle of menstrual cycle. In human female ovulation occurs on the 14-15th day of beginning of menstrual cycle.

Unisexual flower contain either male or female reproductive parts so there is no chance of autogamy. It may have geitonogamy occurring on different flower of same plants.

Egg and antipodal cells are haploid structure as they are formed by meiosis cell divisions in which number of chromosome reduce to half. This kinds of division occurs only during gamete formation.

Wind is the most common means of pollination in flowering plants. The pollen grain must be light and dry and in large number to facilitate pollination. Flower with one or few ovules are pollinated by wind to ensure fertilisation.

Reproduction in plants involves certain events in particular order starting from pollination to transfer pollen grain from anther to stigma followed by Syngamy and fertilisation. Zygote is the product of fertilization that undergoes embryogenesis to form seed and fruit.

Zygote is the product of fusion of male and female gametes. Large number of cells is formed by mitotic division that arrange into layer. The single layered hollow spherical structure is called blastula.