Fertilisation - Fusion of Sex Cells

Fertilization involves the fusion of an egg cell from a female with a sperm from a male, leading to embryo development. Mammals use internal fertilization, fertilizing a few eggs, while plants and marine creatures use external fertilization, potentially fertilizing millions of gametes.

What is the typical number of eggs fertilized by mammals?

What can be the number of gametes fertilized at once by plants and marine creatures?