Why are Birds and Reptiles with abundant yolk sac polyspermic? I was given an explanation that birds and reptiles are polyspermic because they have an abundant yolk sac. But how does it explain the thing? Chicken as an adult is not using in my opinion yolk as an energy source. Yolk is used during embryogenesis as the primary energy source with blastula and gastrula -stages and during organogenesis, since the embryo needs proteins and energy somewhere. **How does abundant yolk sac make birds and reptiles polyspermic?**

My professor says that

> The yolk sac is not connected to the mechanism of polyspermy or monospermy. [Amount of yolk inside the oocyte is then again.] The oocytes of reptiles and birds are yolk rich - polylecithal for instance.

where lecithal = yolk containing and some pieces of information about here.