What type of blood is carried by the four major blood vessels entering/leaving the heart?

What are the two causes of density in deep current waters? a. salinity (how much salt) of the water and high temperaturesb. salinity (how much salt) of the water and low temperatures c. oxygen content of the water and high temperatures. d. oxygen content of the water and low temperatures

Which of the following are causes of evolutionary change? 1)genetic drift 2) natural selection 3) gene flow 4)mutation

How does the structure of fats enable them to hold so much energy?