Name: Classification of Animals
Uploaded: 2019-07-19
Duration: 5 min 49 s
Description: Adaptations have led to complexities in organisms leading to similarities and dissimilarities. This becomes the basis of classification. Learn it here!

Question

Show the gradual changes in the gross anatomy of the heart in Fish, Amphibia, Reptilia and Mammalia.

Accepted Answer

The gradual changes in the gross anatomy of the heart in Fish, Amphibia, Reptilia and Mammalia:

Vertebrate hearts have muscular chambers called atria and ventricles.

Atria- collect blood from the body; contract and deposit blood in ventricles.

Ventricles- contract and discharge blood to the body.

Two chambered hearts:

Earliest vertebrate hearts with one atrium and one ventricle. Example: Fish hearts.

Three chambered hearts:

This type of heart is in class Amphibia and Reptilia.

Amphibians rely on cutaneous gas exchange, on gills, on lungs or on all three modes because the sources of oxygenated and deoxygenated blood vary, heart structure varies as well.

When a frog dives, a sphincter at the base of the pulmonary artery constricts, resulting in reduced blood flow to the lung and increased flow to the skin. Thus, while a frog is submerged, loss of pulmonary respiration is somewhat offset by increased cutaneous respiration.

As reptiles evolved, so did their hearts. This type of heart has two atria and one ventricle. Early reptiles had a 3 chambered heart just like the amphibians.

As they became more active, a 'septum' began to appear in their hearts. The septum evolved to divide more and more of the heart. Most reptiles today have a fairly significant septum.

In a few reptiles, like crocodiles, the septum completely divided the heart.

This four-chambered heart was passed on to the most successful descendants of the reptiles, the birds and mammals.

Four chambered hearts:

The members with this type are most advanced, birds and mammals possess this type of heart.

The ventricle is completely divided into two so that the heart is four-chambered. These have two atria and two ventricles. Separation of O₂ rich and O₂ poor blood maximizes O₂ levels in the blood.

In birds, the sinus venosus is reduced to a small but still anatomically discrete area.

In mammals, the sinus venosus is reduced to a patch of Purkinje fibres, or sinoatrial node (pacemaker), in the wall of the right atrium.

Show the gradual changes in the gross anatomy of the heart in Fish, Amphibia, Reptilia and Mammalia.

Important Questions on Classification of Diversity of Life : Taxonomy

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