Answer:
The animals present body structure is due to evolution. It is seen in each part including the structure of the heart. The vertebrate heart becomes complex from a simpler form.
Invertebrates, the heart of fishes is two-chambered having one auricle and one ventricle. The deoxygenated blood gets purified in the gills. They are aquatic and no lungs for breathing. The hearts pump a mixture of oxygenated and deoxygenated blood to the body.
The amphibians and reptiles have 3 chambered heart as they lead terrestrial mode of life. The gills modified into the lungs. The left auricle receives pure blood and the right auricle receives deoxygenated blood. The blood purified in the lungs and in the ventricle, both types of blood get a mix. The ventricle pumps the mixed-blood throughout the body.
In the case of birds and mammal, the heart is 4 chambered and the oxygenated and deoxygenated blood are separated. These two are higher vertebrates. No mix of pure and impure blood, the body receives only the oxygenated blood.
This shows to construct the phylogenetic tree of vertebrates - the fishes should be in the bottom, and above it amphibians, reptiles, then, mammals and birds on the top branch of the tree. As the chambers and structure of the hearts modified one after another.
Pericardium in the Medical report from Ms. K means fibrous tissue surrounding the heart. The pericardium is the membrane that is enclosing the heart, consisting of an outer fibrous layer and an inner double layer of serous membrane. It is a membrane that surrounds and protects the human heart. It is also a double-walled sac containing the heart and the roots of the vessels. The Pericardial sac has a serious layer and a fibrous layer, total of two layers. This pericardial sac encloses the pericardial cavity which contains pericardial fluid. Pericardium also has a disorders namely Pericarditis, Pericardial effusion, and Cardiac Tamponade.
Adaptations can give an organism a competitive edge but adaptations are not always used for completion against other species
3) a glacier because a river would be a V shape, mud flow would cause the valley to have flat bottom
