The importance of random accumulation of small genetic changes sufficient to explain evolution

Origin of life from nonliving matter is known as

Fossil $X$ is older than fossil $Y$ if

Development of patagia in animals is an

In the developmental history of mammalian heart, it is observed that it passes through a two-chambered fish-like heart, three-chambered frog-like heart and finally four-chambered stage. To which hypothesis can this above cited statement be approximated