Q.(a) Explain the different kinds of syngamy in living organisms. OR

(a) Syngamy is classified as isogamy, anisogamy or oogamy based on how similar the two fusing gametes are. (b) Active immunity is self-produced and long-lasting; passive immunity is borrowed and short-lived.

(a) Syngamy is the fusion of two gametes to form a zygote, and organisms show different kinds of syngamy depending on the nature of the fusing gametes. In isogamy, the two fusing gametes are morphologically similar in size, shape and structure (though physiologically distinct) -- seen in some algae and protists such as Chlamydomonas. In anisogamy, the two fusing gametes differ in size and/or motility, one usually being larger than the other -- seen in some algae and fungi. In oogamy, the two fusing gametes are strikingly different: a large, non-motile, nutrient-rich female gamete (the egg/ovum) fuses with a small, motile male gamete (the sperm) -- this is the type of syngamy seen in most higher animals (including humans) and higher plants. …