The correct statement(s) about sex determination in animals are:
- The mechanism of sex determination varies with different animal species.
The other statements are incorrect:
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In many species, such as mammals, males are XY and females are XX, but this is not true for all animals. Many animals have different mechanisms of sex determination (e.g., ZW/ZZ system in birds, environmental factors in reptiles).
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The SRY gene is present in males of certain species (like most mammals) and is critical for male sex determination; however, not all animal species have this gene, and some species have different pathways for sex determination altogether.