1. How has sex originated ? 2. What are various types of meiosis ?

On the basis of period and site of occurrence meiosis is of three types −

• Gametic or terminal meiosis
• Zygotic or initial meiosis.
• Sporogenetic or intermediate meiosis.

Gametic or terminal meiosis

In gametic meiosis diploid individual forms haploid gametes by the process of meiosis. These haploid gametes fuse to form diploid zygote. This type of meiosis can be observed in animals.

Zygotic meiosis

In zygotic meiosis haploid gametes are formed by haploid individuals by the process of mitosis. The formed haploid gametes fuse to form diploid zygote which undergoes meiosis followed by mitotic division to form haploid adult. This type of meiosis is found in algae, fungi etc.

Sporogenetic Meiosis

In sporogenetic meiosis diploid sporocytes undergo meiosis to form haploid spores. Haploid spores germinate to form haploid gametophyte which produces haploid gametes by mitosis. These haploid gametes fuse to form diploid zygote. This type of meiosis is found in higher plants like gymnosperms.

Regards

Arun (askIITians forum expert)