Simplify the following text for a Grade 9 native English-speaking person.
Original: A carapace is a dorsal ( upper ) section of the exoskeleton or shell in a number of animal groups , including arthropods such as crustaceans and arachnids , as well as vertebrates such as turtles and tortoises .
Simplified: A carapace is a dorsal section of an exoskeleton or shell in a number of animal groups .