Circulatory system
Almost all ectotherms have either a three or two-chambered heart because they do not require as high amounts of oxygen and nutrient transportation as endotherms. This is due to the fact that ectotherms do not generate their own heat, but are rather dependent on external heat sources. Consequently they have a lower metabolic rate and therefore require less oxygen and nutrient transportation, so a less advanced and efficient heart would still work for them.
All endotherms have a four-chambered heart. A four-chambered heart allows for faster transportation of blood through higher pressure, by having a two-loop system and four chambers, to meet the high metabolic rate that is required since they are capable/dependent on their own generation of heat.
The circulatory system of vertebrates has also adapted to life on land, as the least advanced heart is found in animals that live in the water due to the low pressure in water and less gravity force acting on them, which means that they require less energy to move the same distance as an animal on land. As animals adapted to life on land they started evolving three and later on four-chambered hearts with two loop systems as on land gravity force is much stronger, therefore they need to use more energy to do the same movements as in the water, which required the blood flow to be faster (by having higher pressure in the circulatory system) to transport nutrients and oxygen.
A four-chambered heart is much more efficient because it keeps deoxygenated and oxygenated blood separate, thereby effectively transporting and utilizing blood because if they mix then it would mean that some deoxygenated blood gets sent to the body’s cells and some oxygenated blood gets sent back to the lungs. This would result in a very inefficient flow and supply of oxygen and nutrients to the cells.
All endotherms have a four-chambered heart. A four-chambered heart allows for faster transportation of blood through higher pressure, by having a two-loop system and four chambers, to meet the high metabolic rate that is required since they are capable/dependent on their own generation of heat.
The circulatory system of vertebrates has also adapted to life on land, as the least advanced heart is found in animals that live in the water due to the low pressure in water and less gravity force acting on them, which means that they require less energy to move the same distance as an animal on land. As animals adapted to life on land they started evolving three and later on four-chambered hearts with two loop systems as on land gravity force is much stronger, therefore they need to use more energy to do the same movements as in the water, which required the blood flow to be faster (by having higher pressure in the circulatory system) to transport nutrients and oxygen.
A four-chambered heart is much more efficient because it keeps deoxygenated and oxygenated blood separate, thereby effectively transporting and utilizing blood because if they mix then it would mean that some deoxygenated blood gets sent to the body’s cells and some oxygenated blood gets sent back to the lungs. This would result in a very inefficient flow and supply of oxygen and nutrients to the cells.
In order of development and complexity:
1. Fish have a two-chambered heart, are ectotherms, and only live in the water. They only have single circulation of blood and definitely possess the lowest pressure and least advanced heart. 2. Amphibians have a three-chambered heart, are ectotherms, but live both on land and in the water. They were the first animals with double circulation: pulmonary and systemic circulation, as they required higher pressure for faster flow of blood due to the sudden higher metabolism by living on land. 3. Most Reptiles have a three-chambered heart, are ectotherms and occupy both terrestrial and aquatic environments. 3a. Crocodilia have a four-chambered heart, are ectotherms, and are reptiles. A reason, why they have a four-chambered heart even though are reptiles, is that they require a great control over their blood flow as they spend a long time under water, and on average can spend one to two hours underwater without breathing. Therefore their body requires that blood is diverted from the lungs and to crucial parts of the body during that time, and a four-chambered heart allows for the most control of blood flow. 4. Birds have a four-chambered heart, are endotherms, and live on land (flying requires a lot of energy). This allows them to maintain high pressure in their circulation of blood and maintain their heat level. 5. Mammals have a four-chambered heart, are endotherms and are terrestrial. This allows them to maintain heat levels and a high pressure in the circulation of their blood. |