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The fish heart evolved before the amphibian heart and is its evolutionary predecessor. The heart's complexity can be traced back to even simpler versions in animals like annelids (earthworm) and other organisms with what is basically a one-chambered heart. The "additional" chambers evolved over time by mutations on the genes that determined the heart's development. Any mutation to the structure of the heart that gave the organism an advantage (additional chambers prevent back flow and greatly improve efficiency of oxygen and heat, which is increasingly necessary to progressively "higher" organisms which have higher metabolic demands for both) increased that organisms chance of reproducing. An interesting testament to the theory that mammals and birds last common ancestor was reptilian is that while we both have 4 chambered hearts, they are oriented in different directions (deoxygenated blood enters our right atrium, but their left atrium). Crocodilians are the only reptiles that also have a four chambered heart, which bares more similarity to those of birds (this model of four chambered heart probably evolved before birds and crocs had their evolutionary split) but with some unique features specific to crocs. If I missed anything or am mistaken, please let me know.
R.DLM The more correct answer is that it reflects the difference between using gills and using lungs to oxygenate the blood. All animals must "expose" their blood to a more oxygen-rich environment in order to create the gradient that moves carbon dioxide out and oxygen in. Because the fish uses the surrounding water to do this, it doesn't need the double system that animals with lungs need. "Double system" means that there is a circulation system to the lungs and to the body, both of which are a closed loop with the heart as the common central point. The physiology is actually quite complex; in fact, it is irreducibly complex. By that, I mean that you just don't randomly mutate and develop another chamber in the heart. To go from the single circulation of the fish heart to the double circulation of the 3 or 4 chambered heart requires a completely new pathway for fluid flow, including valves, veins-to-arteries connections, coordinated heart muscle contraction, new pressure differentials and means to control them (read nerves and centers in the brain0, and the list goes on and on with both major and minor requirements to "change" from 2 chambers to 3. It is very tempting to look at the hearts of different animals and conclude that the more complex "evolved" from the less complex. In fact, even the 2 chambered heart of the fish is remarkably complex. Trying to go from 2 chambers (living in water) to 3 chambers (living out of the water) involves more than one nonfunctional intermediate form (read: lethal to the organism), so it is incorrect to say that the amphibian heart evolved from the fish heart. Even given eons of time, this could not have happened in a Darwinian fashion! Here's a link that explains it in more detail if you're interested: http://www.ideacenter.org/contentmgr/showdetails.php/id/1113 Bottom line answer: fish have 2 chambers because they use gills to perform the CO2-oxygen exchange, and all creatures with lungs have 3 or 4 chambers to perform the same exchange. Or, stated differently, they are that way because that's the way they are - almost as if it were designed that way, eh? And please remember that this is a very oversimplified answer. I encourage you to go beyond this site and seek more detailed answers. Anatomy and physiology are phenomenally complex studies, far more so than we think about day to day!
What else can I help you with?
What amphibians live near the ocean?
Amphibians can not live in the ocean. Even though they are able to swim they do not have the capability to live in such large bodies of water. Amphibians would also dehydrate in salt water since they can't some-regulate.
Does a goat have a backbone?
yes, a horse has a back bone. its a vertebrate. of course how would you ride one if they didn't
Is a fish an amphibian reptile or mammal?
Penguins are not amphibians. Penguins are Flightless Birds.
What would happen if a sharks heart failed?
The shark heart would fail which wouldn't be able to eat or pump blood which then the shark would die
Why is a shark a fish and not a mammal?
fish. if its a mammal it would have either be warm blooded,have hair,fur,or wool,give live birth,and breathe wit lungs
Are mammles vertibrates or in vertibrates?
Mainly, amphibians and fish are vertebrates, and are not mammals. An example of a mammal who is also a vertebrate would be a shrew.
Are gorillas the largest amphibian?
Gorillas are not amphibians, they are mammals. And before you ask, no they are not the largest mammal. The largest would be the blue whale
How would you know if one things has life?
Its heart would be working and the mammal would be active. Tip: , Always check the heart!
What class of vertebrates has a heart with two atria and one ventricle?
Any class of vertebrate with a three-chambered heart has two atria and one ventricle. An example would be amphibians such as frogs.
What kind of vertebrate is the tundra most suitable for?
Mammals and birds both do well in the tundra. Fish, reptiles and amphibians--not so much. The best answer would probably be 'warm blooded'.
What is the main form of animals?
There is no one main form of animal, but there are a few that are most common. Mammals, amphibians, and reptiles are the most well known. If there was any ONE form of animal though, it would probably be the mammal.
What would happen to an ecosystem if there were no honey bees and amphibians?
the honeybees would not give out honey and amphibians would not eat insects then we could not survive
How many people own amphibians?
i would say about 34% of the earths people own amphibians.
Where is the talest mammal in the world?
The African giraffe would be the tallest mammal.
What is the doctor of Amphibians?
A doctor that treats amphibians would be a veterinarian, specifically a veterinarian that has specialized in reptile and amphibian medicine.
What do amphibians have that bony fish do not?
Well they have limbs and lungs, which I would consider more complex.
How important is the cardiovascular system?
Without this system, human life would not exist (not to mention mammals, reptiles, amphibians, and all other animals which require a heart and blood vessels for survival).
