Why does a species of animal need to continue to undergo natural selection?

The pharynx is the structure in the body that serves as a pathway of both air and food. how does the body make sure that food does not get into the lungs? the salivary glands secrete enzymes that pull food out of the air pathway. the small intestine pushes the air out of the digestive system. the pancreas breaks down food in the air pathway. the epiglottis closes the air pathway so that food will not enter it.

Methane gas created by a cows flatulence especially in a large herd is a greenhouse gas. true or false.

How can we use spectral lines of light coming from the superclusters to identify which is receding from earth at the slowest rate.