Which of the following are types of gnotobiotic animals?

The types of gnotobiotic animals primarily include those that are axenic and defined flora. Gnotobiotic animals are specially managed to have known and controlled microbial populations. "Axenic" refers to animals that are completely free of any detectable microorganisms, making them ideal for studies that require a sterile environment. "Defined flora" refers to animals that have a known composition of specific microorganisms, which can be beneficial for research into the interactions between the host and these defined microbial communities.

Germ-free and semi-germ-free are also related concepts, but in the context of gnotobiotic classifications, the terms axenic and defined flora are more precise descriptors of the conditions these animals are raised under. This ensures a standardized basis for research where the influence of microorganisms can be systematically studied.

Normal flora and flora-free, as well as wild and domesticated classifications, do not pertain to the controlled microbial environments characteristic of gnotobiotic animals. Instead, these terms relate more to the general conditions or environments in which animals live, rather than the specific controlled biological states required for gnotobiotic research.