Which is the vital link that ensures continuity of species between organisms of one generation and the next?
A. Sexual reproduction
B. Embryo
C. Zygote
D. Fertilisation

Hint: Fertilisation is the most important step in the sexual reproduction of living beings. This process involves the union of two haploid cells which are the female and male gametes and results in the development of a diploid zygote. This zygote is liable for the genetic constitution of progeny.

Complete step-by-step answer:
The formation of the zygote is universal in all sexually reproducing organisms. Apart from thallophytes, the zygote undergoes mitosis and generates an embryo that will eventually grow into a new individual. A zygote is formed because of the fusion of two gametes I.e female and male reproductive cells through the process of fertilisation. The zygote is composed of two sets of chromosomes consisting of genetic information which is transmitted to a new generation. In multicellular beings such as animals and plants, the zygote undergoes cell division and eventually makes up the organism. The zygote comprises 23 chromosomes each from both the parents, i.e. 46 chromosomes in all. A zygote is called a vital link between two generations. A zygote is the resulting structure of fertilisation that is formed because of the fusion of two haploid gametes.

Therefore the correct answer is option C.



Note: Zygote gives rise to the embryo. The zygote splits to form cells which further form tissues and eventually the whole organism. Oscar and Richard Hertwig were the first researchers to detect the development of animal zygotes. In organisms with external fertilisation, the zygote is developed in the external medium (usually water), however, in those exposing internal fertilisation, the zygote is developed within the body of the organism.