What five groups are commonly used to categorize wild animals?

The five groups are fish, amphibians, reptiles, birds and mammals. In addition, we called these wild animals vertebrates, they have backbones.

Some of the characteristics they have to determine their group :

Fish : has slimy scales, use gills for breathing.

Amphibians: has moist skin, young ones use gills for breathing, older ones uses lungs and their skin.

Reptiles: has dry scales, internal fertilization and lay eggs.

Birds: has feather covering their body, has wings.

Mammals: has hair covering their body, uses lungs for gas exchange and has mammary glands for feeding the young.

Genetic engineering is the answer.