What is the proper label for number 5 on this diagram of the heart?

Because of renal immaturity in infants, it is important to teach parents not to give their infant plain water until age:

Which of the following is true of human male reproduction?

Anxiety, disorientation, confusion, and possible depression felt when one is placed in a new and unfamiliar culture is termed:

What traits make invasive species like periwinkle vine able to so easily invade?

In the food chain oat grass -> mule deer -> human -> mountain lion, the human is a(n) ______.

Gross Motor development is: 

Match each organization with its most characteristic role in global economics.

Which element is most important to scientists doing radiometric dating?

A population of shore crabs varies in the length of their walking legs, which they use to attach themselves to rocks when waves hit.  When the weather gets particularly harsh causing powerful waves (e.g. from a strong storm), the crabs with the longer legs are able to hold on tight, but the crabs with the shorts legs are more likely to die.  What mechanism of evolution is this?