Aristotle - male provides the form, female provides the matter, the embryo has then a potential to become an adult human which it then actualises. Serious problem for the ancient world - how to arrange animals into groups. Aristotle - first system that actual gives a reasonable classification of animals. Rather than being based on organs of movement, as previous tries were, Aristotle uses reproduction. Main groups are the viviparous, which bear live offspring, the oviparous with perfect or imperfect eggs, down to the insects with larvae.
Animals are then divided up into genus and species.
This system was a hierarchy of perfection, man naturally being considered the most perfect. Modern system of classification dates from Linnaeus in the eighteenth century. Possible course - heart first organ to form in the embryo's that Aristotle examined. Galen and anatomy. Galen, c130 - c200, the most famous doctor in antiquity.