- Aug 22, 2015
- Reaction score
- 38°29′ North 121°26′ West
Just to pick a nit…
What this meme says about “all vertebrates” is true of nearly all mammals, but not of all vertebrates.
In some other animals, including some other vertebrates, sex determination takes place differently.
In birds, for example, and in some reptiles, there's a ZW determination system, in which it is the heterogametic combination ZZ that is male, and the homogametic combination ZW that is female.
In some animals, chromosome patterns don't even figure into sex determination. In crocodilians, sex determination is based on the temperature at which the eggs gestate—higher temperatures produce males, while lower temperatures produce females.
And I know that there are some fish in which it is common for an organism to change form one sex to the other during the course of its life.