the expanded articular end of an epiphysis that is separated from the shaft by a narrower neck is called a

the sphincter muscles at the end of the digestive tract is the anus.

but there is no

i guess you forgot putting it.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.