Add -er or -or to the verbs to make nouns: keep, teach, help, direct, present, invent, act, visit.
keeper, teacher, helper, director, presenter, inventor, actor, visitor.
What is the word? 'How many of a type of animal there are in the world.'
population
What is the word? 'If a type of animal, bird or plant is this, it is disappearing and in danger.'
endangered