A controlled variable is not changed throughout an experiment. It is there so that the other variables being tested on can be better understood.
Answer:
the law of superposition is an axiom that forms one of the bases of the sciences of geology
Most likely two dominant recessive genes. For example - pp or one parent could have Pp
Answer
Villi is present on both of surface
Explanation
Intestine and lungs both have million of villi on the surface .In lungs and intestine villi increase the surface area but purpose is different . In lungs it is use for air exchange and in intestine it is use for food absorption .Both Villi of intestine and lungs are one cell thick and have maximum blood capillaries for food and air exchange respectively .