In the walls of the heart, two layers of tissue form a sandwich around a thick layer of muscle called the .

This is an active transport mechanism by which cells pump sodium and potassium ions against the concentration gradient

Which of the following is caused by reproductive isolation within a species? a. a decrease in gene flow b. an increase in genetic flow c. a decrease in genetic drift d. an increase in gene flow

Which statement does lola need to correct, and why? a) statement 1 because spiral galaxies do not havearmsb) statement 2 because the bulges contain mostlyyoung red stars.c) statement 3 because the arms are made of mostlyyoung blue and blue-white stars.d) statement 4 because spirals galaxies contain littleto no dust.(c)