Because there is genetic variation among the newly reproduced organism.
<span>The water that leaves the body as exhaled
air, sweat or urine is ultimately extracted from blood plasma and the
organs/glands which are important in regulating water output are the kidneys,
hypothalamus and endocrine glands. The kidney has a remarkable ability to
dilute or concentrate urine according to an individual’s changing physiological
needs and to regulate electrolyte excretion. Moreoever the hypothalamus is
located in the brain and links the nervous and endocrine systems to each other.
In addition, the endocrine glands secrete their porducts and hormones directly
into the blood rather that through duct and the major glands of the endocrine
system include hypothalamus. Endocrine glands secrete chemicals such as saliva
or sweaat and secrete hormones directly into the blood stream. </span>
D, death & birth rates are at an equilibrium causing population to be constant
Blood has further to travel in larger, more complex animals
