The vertebrates in which blood flows directly from respiratory organs to body tissues without first returning to the heart are the a. fishes b. birds c. mammals d. reptiles e. amphibians

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.

The cell membrane controls what enters and leaves the cell. which of the structures in the diagram below is the cell membrane? — f о

What are ways that ordinary people can to keep antibiotic resistance from getting worse?