Active Transport & Passive Transport |
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Relating Diffusion & Active Transport To The Transportation Of Nutrients In A Living System. First off, diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Active transport is the opposite: the movement of molecules from an area of low concentration to high concentration, and it must have ATP. The nutrients in a living system are glucose, which is our blood sugar, and oxygen. Our digestive system does its job of breaking down carbohydrates. Glucose is then moved from our intestines into our bloodstream through the process of diffusion and active transport. Fresh oxygen in the air is breathed into our lungs where it then diffuses across specialized cells called aveoli. However, not all animals have blood, veins, or hearts. An example of this would be the flatworm. The diagram below shows how oxygen goes into the flatworm, and how carbon dioxide comes out.  Open Circulatory System vs Closed Circulatory System The whole purpose of a circulatory system is to move blood to one or more sites where it can be oxygenated and where wastes can be disposed. With this said, many invertebrate's don't even have a circulatory system, because their cells are close enough to their environment that oxygen, gases, nutrients, and waste products can diffuse in and out of their cells. Animals with multiple layers of cells can't do this, because their cells are too protected from the external environment. Open circulatory systems are very inefficient. It can be described as a "bleeding" Halloween costume, where you have a pump that pushes the blood out or up, and then it eventually gets back to the pump. Anthropods and mollusks have open circulatory systems. They have no "true heart" or capillaries. Instead, they have blood vessels that act as pumps to force the blood along. These blood vessels directly join with the open sinuses. The blood is forced from the vessels ti the large sinuses where it baths the internal organs. Other vessels take the blood from the sinuses and get it back to the pumping vessels. Insects can use this system because they also have "spiracles", which are openings in their body, to allow the blood to get air. In the closed circulatory system, blood is pumped through a closed system of arteries, veins, and capillaries, which surround the organs and make sure that all cels have an equal opportunity for nourishment and removal of their waste products. There are different types of closed circulatory systems. The simplest type is the one chambered heart. It is found in earthworms. It has two main blood vessels: the dorsal and ventral vessel, which carry out blood towards the head or tail. The blood is moved along the dorsal vessel by waves of contraction called "peristalis". In the front of the worm, there are 5 pairs of vessels that connect the dorsal and ventral vessels. These connecting vessels act as basic hearts, and force the blood into the ventral vessel. This system still isn't very efficient since blood could flow backwards, but the earthworm's skin is thin and constantly moist, so there is still an opportunity for exchanges of gases, making this system work for the earthworm. Below is a diagram of an earthworm's circulatory system.  One, Two, Three, & Four Chambered Heart Systems The one chambered heart system was discussed in the above section. The two chambered heart system is found in fish. It has one atrium and one ventricle. It has muscular walls and a valve between its chambers. Blood is pumped from the heart to the gills, where it receives oxygen and gets rid of carbon dioxide, then it moves on to the organs of the body where nutrients, gases, and wastes are exchanged. There is no division of circulation between the respiratory organs and the rest of the body. Blood travels in a circuit that takes the blood from the heart to the gills, to the organs, and then back to the heart. The three chambered heart is found in frogs and other amphibians. It has two atria and one ventricle. Blood leaving the ventricle comes to a forked aorta; blood can either go through a circuit of vessels leading to the lungs, or through a circuit leading to other organs. The blood returning to the heart from the lungs goes through one atrium, while blood returning from the rest of the body passes into the other, and both of the atria empty into the one ventricle. This mixes up oxygenated blood and deoxygenated blood so some orangs don't get blood saturated in oxygen. This only works with cold blooded creatures. The four chambered heart is found in humans, mammals, and birds. It is the most efficient of the four, and it is the most powerful. It has two atria and two ventricles. There is one ventricle for deoxygenated blood, and one ventricle for oxygenated blood. This is so that the blood wont mix. The four chambers ensure efficient and fast movement of highly oxygenated blood to the organs of the body. The four chambered heart allows blood leaving the heart to have more oxygen, which is good for enhancing the fast paced lifestyle of birds and mammals.  |
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