Posted by By: Maximus Addington and Amelia Dell
The objective covered that this project intends to go into great depth on is comparing and contrasting hearts in the animal kingdom. In order to go into more detail than what was covered in lecture this project illustrates the specific anatomical layout and consequent difference observed between the hearts of fish, octopuses, frogs, humans, crocodiles, and birds.
As background, the journey to the modern human heart starts with the protozoans, which compose the foundation for the tree of life approximately 3.8 billion years ago. We then journey up the tree of life to the first multicellular organism containing a primitive coelom approximately 800 million years ago. From there we move on to Ecdysoa and Deuterostoma, two organisms belonging to the phylum Bilateria, containing the first peristatic tubular heart with a single contracting mesoderm layer. This heart likely contained a single trabeculated ventricle and a single atrium that evolved later to form a resemblance to the modern fish heart. This peristaltic heart soon underwent a rapid structural diversification that led to the aspects of the modern heart we see today including a conduction system, unidirectional circulation, etc. This rapid diversification was primarily due to the ancestral network of genes associated with the ancient heart structure that expanded through the addition of new genetic networks and gene duplication. As a result, the primitive heart previously described underwent a rapid evolution leading from a two-chambered heart with one atrium and one ventricle in the gnathostome fish; to a three-chambered heart with two atria in amphibian tetrapods; to a four-chambered heart in crocodiles, alligators, birds, and fish. The images above demonstrate the modern layout of these species/organisms.
3.8 million years ago, human hearts began with protozoans, then later evolved into the Ecdysoa and Deuterostoma, two multicellular organisms belonging to the phylum Bilateria, which contained the first peristatic tubular heart with a single contracting mesoderm layer. Genes associated with this ancient heart structure expanded through the addition of new genetic networks and gene duplication, resulting in the peristaltic heart undergoing rapid structural diversification. This led to the evolution of a conduction system and unidirectional circulation seen in the modern human and mammalian heart, as well as different numbers of heart chambers found in other animal Orders.