Which has a lower density - dark coloured scoria or light coloured pumice?

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 are some characteristics of a free enterprise economy?

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point