Which scientist’s theory greatly influenced charles darwin? sigmund freud thomas malthus friedrich nietzche herbert spenser

What do animals wth echolocation have in common other than echolocation

Out of the seven main animal groups (fish, mammals, birds, insects, reptiles, amphibians, and arachnids), how many contain members with internal backbones? a. 5 b. 3 c. 7 d. 1

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.