Question

•An anthropologist discovers the fossilized heart of an extinct animal. The evidence indicates that the organism's heart was large, well-formed, and had four chambers, with no connection between the right and left sides. What can be a reasonable conclusion supported by these observations?

Answer 1

The heart obtained is fossilized from an extinct animal.

The organism had a large heart and was well-formed. Hence, it definitely belongs to a chordate who has a well-developed heart. Additionally, it is mentioned that the evidence suggests that the heart had four chambers. Now the chordates have 6 classes. These are:

1. Cyclostomata: However, these are cold-blooded and do not have a well-developed heart.

2. Pisces: These are bony and cartilaginous fishes and are characterized by a two-chambered heart with a significant mixing of the oxygenated and deoxygenated blood.

3. Amphibia: They have a three-chambered heart. The heart is characterized by two atria and one ventricle and therefore, there is a mixing of oxygenated and deoxygenated blood.

4. Reptilia: These also have a three-chambered heart consisting of two atria and one ventricle and hence have the mixing of oxygenated and deoxygenated blood. An exception to this are crocodiles who have a four-chambered heart.

5. Mammalia: These are characterized by a four-chambered heart consisting of two atria and two ventricles and there is a clear separation between the right and left compartment. The left receives oxygenated blood from the lungs while the right receives deoxygenated blood from the body. Therefore, there is no mixing of oxygenated and deoxygenated blood in mammals.

Since the evidence suggests that the fossilized animal had a four-chambered heart with well-separated right and left chambers, it most likely belongs to a Mammal.