Answer:
see below :)
Explanation:
Infectious are more easily spread nowadays becuse of an increased population. The more the population increases, the bigger the advantage an infectious disease has. As of right now, because everyone is wearing masks, their immune systems are being weakened. Another reason for this is because of the increase in chemicals in our foods, which are now being transferred to our bodies. All of the medications people are taking also have an affect on the spread of disease; it gives diseases a chance to mutate.
<span>Covered by the two cerebral hemispheres, the diencephalon is
the structure of the central nervous system that surrounds the third ventricle.
It is composed of several other structures. The most important of them are the
Thalamus, which plays a very important role in movements and emotions; and the
Hypothalamus, which provides functions including thermoregulation, appetite and
regulation of the sleep-wake cycle.</span>
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.
1. electrical signals travel toward the heart. 2. signal received by the atrioventricular node. 3.signal by the nodes in the atrium. 4.the atria contracts. 5. signal transferred to the ventricles. 6. the ventricles contract.
