What travel though a food chain or web

Which of the following examples can cause gene flow between populations? a. an increase in predators to a population of zebra b. a volcanic eruption that kills half of a population of mice c. bird droppings that contain seeds from a different location d. a person that sprays a toxin on a group of mosquitoes

What would be the most likely result if the ph of the stomach were increased to 5

What is a gene ? a) a section of a protein that codes for dna. b) the alternate version of a trait. c) the visible trait in the f1 generation. d) a section of dna that codes for a specific trait .