The crocodile has the most complicated blood circulation of all vertebrates. They do have four chambers in their heart yes as well as two ventricles which is very unusual in reptiles.
I expect crocodiles adapted to have a heart like this, because they evolved from smaller reptiles which don’t have a four chambered heart. Crocodiles would have had to adapt their hearts because they are an unusual reptile in that they spend a lot of their time in water. Their special heart is a good adaptation for living in water because it means that when the crocodile is underwater it’s heart rate can slow right down to one or two beats per minute. This helps reduce blood flow and save oxygen. Then when the crocodile comes back above water it’s heart rate speeds right up to normal speed again within a matter of seconds.
I actually had to google this – I didn’t know crocodiles had a 4 part heart. Even use who have gone to University still learn something new every day!!!
Birds, which evolved from reptiles, also have four chambers in their hearts, but most reptiles, like lizards, only have three chambers. These three-chambered hearts send a mixture of oxygen-containing and not-oxygen-containing blood around the body each time.
Four chambered hearts allow the animal to separate the oxygenated blood from the blood without oxygen. This makes the blood circulation more efficient – you don’t waste energy sending the blood with no oxygen around the body.
Crocodiles are large, and since they spend time underwater, need to be able to keep their body well stocked with oxygen without wasting energy. As crocodiles became larger, they probably would have struggled with a 3-chamber heart, and this would have led to them adapting and evolving to have a 4-chamber heart.
answered on 20 Mar 2014:
I am more of a botanist (studier of plants) than a Herpetologist (studier of reptiles and amphibians)
But I have checked what you young ladies have explained (very well ) below. And I have learnt something new!