What is the difference between a ZW sex-determination system and a XY-sex-determination system?

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What is the difference between a ZW sex-determination system and a XY-sex-determination system?

In: Biology

In XY, all female eggs have an X while the male sperm has an X or a Y. So sex is determined by the male sperm.

In ZW, all males are ZZ, while the female egg can be either a Z or a W. So sex us determined by the female ovum.

The X and Y look sort of like those letters on karyotypes (images of the chromosomes).

The X is much bigger than the Y. The Z is much bigger than the W.

So the Z is like the X, but the ZZ is male and the XX is female. The Y or W is the “newer” chromosome and is smaller.

edit: the Y is definitely “newer” in terms of evolution. I am not so certain with the ZW if it as clear.