What do the vessels that are carrying oxygen-poor blood
back to heart have that stops
blood from flowing
backwards?
A. thick muscular walls
B. valves
C. hemoglobin
D. SA nodes

Abiology teacher asks students to give examples of genetic variations that support the idea that changes in a population’s environment affect genetic variation. which is the least supportive example? a.changes in genetics in human populationsb.antibiotic resistance in bacteria populationsc.pesticide resistance in garden insectsd.changes in the color of the peppered moth population in england