What evidence is there from fossils to suggest that reptiles lived before mammals?
Because the skeletons of what we believe to have been reptiles have been found deeper in the earth than the skeletons of what we believe to have been be mammals.
What are the differences between the mammals amphibians reptiles birds and fish circulatory systems?
I suggest you get a copy of Homer Smith's book: From Fish to Philosopher. Start with fish; they don't need a separate pulmonary system (they have gills), to amphibians who have a 3 chambered heart, up to mammals and birds who require essentially two completely separate systems for pulmonary and systemic circulation.
There is very little evidence for any plant life in the Precambrian Period. There is evidence in the form of stromatolites (found near Shark Bay in Australia) for bacteria. Some controversial fossils from the 1.25 billion year old Hatakai Shale from the Grand Canyon in the USA suggest that there was plant life in the Precambrian. Creationalist often use this as evidence that evolution is not true.
Monotremes lay eggs. Monotremes include just the platypus and the echidna. However, it is a fallacy to suggest that their ancestors were reptilian. This is pure theory, and not backed up by any evidence. Fossil evidence shows, for example, that the platypus is largely unchanged compared to its ancient, larger ancestor.
Some suggest that Triceratops fossils are actually the fossils of young Torosaurus. However, Triceratops were extremely common and existed before Torosaurus did. If Torosaurus were adult Triceratops, their should be fossils of Torosaurus that were as old as the oldest fossils of Triceratops. Thus, I don't think that Torosaurus was the same as Triceratops.
There is research evidence to suggest that in some breeds higher temperatures can determine the sex of a chicken just as it does in some reptiles. However, since the eggs are incubated under a hen, and not in the ground, the hen will keep the eggs at a steady 100F and the sex of the chick will depend on its genetics.