Question

All multicellular organism start their life form a single cell called
A. Zygote
B. Egg cell
C. Sperm
D. None of the above

Answer 1

Hint: Cell is described as the basic structural and functional unit of living organisms. Some organisms are made up of single cells and they are called unicellular while many organisms are made up of multiple cells grouped together to form tissues and then organs. They are called multicellular organisms.

Complete answer: In sexual reproduction, there is formation of male and female gametes either by the same individual or by different individuals of the opposite sex.
In sexually reproducing organisms, gametogenesis is the process of formation of gametes through meiosis. The male gametes are called sperms while the female gametes are called egg cells in humans and other animals.
To reproduce sexually two similar or dissimilar gametes fuse together to give rise to a zygote. The zygote develops into a new organism. Sexual reproduction results in offspring that are not identical to their parents or among themselves as it involves the fusion of male and female gametes.
The formation of the zygote is a universal phenomenon that occurs in all sexually reproducing organisms. The life cycle of the organism and the environment to which it is exposed, decides the further development of zygote. In organisms such as Algae and Fungi, the zygote develops a thick wall that is resistant to desiccation and damage. Before germination, it generally undergoes a period of rest. A zygote is the vital link that ensures continuity of species between organisms of one generation and the next.
So, the correct answer is “Option A”.

Note: Embryogenesis refers to the process of development of an embryo from the zygote. During this process, the zygote undergoes cell division i.e. mitosis and cell differentiation. Cell division occurs through mitosis.