What does the statement lack genetic variation mean (in science) 7th grade

What two fields of study provide the core information that is used to classify organisms?

Facilitates growth and change in neurons and the migration of neurons to different sites in the brain

What can be said about farmers in highly developed countries? a) they have little or no negative impact on the environment. b) they practice subsistence agriculture. c) they are able to incorporate polyculture into their farming practices. d) they utilize organic farming techniques on a regular basis. e) they rely on large amounts of energy from fossil fuels.