Biology SAC 3
“The Transport systems play an essential role in the survival of flowering plants and mammals”
It is imperative that the organism’s cells have an ideal supply of the necessary materials to ensure its survival. At the same time, waste material must be removed to make room for the new material coming in and to avoid infection. Necessary substances and waste material merely move in and out of unicellular organisms by diffusion, osmosis or active transport due to direct contact with their surroundings. However, not all the cells in multi-cellular organisms are in contact with the external environment for rapid exchange of substances between the internal and external environment. Thus, specialized transport systems are utilized. The substances travel along vessels to where they are needed. However, osmosis, diffusion and active transport remain the key procedures employed by transport systems.
The cardiovascular system, a transport system in mammals, composes of the blood, heart, and blood vessels. Blood vessels consist primarily of arteries, veins and capillaries. Blood traveling in them comprise of water, mineral ions and proteins, white blood cells, platelets and red blood cells. Red blood cells carry oxygen and waste material (carbon dioxide) around the organism. Oxygen is bound loosely to haemoglobin, an iron-containing protein in the blood cell. In this form, it’s called oxy-haemoglobin. Oxygenated blood is mostly found in arteries. The blood in veins is usually deoxygenated and waste-material. Blood in capillaries gather food from the small intestine by diffusion as it passes. The food molecules mainly consist of glycerol and fatty acids, glucose, and amino acids. The capillaries also carry oxygenated blood before oxygen is delivered and deoxygenated blood after it is.
Lymphatic vessels, part of a transport system called the lymphatic system, acquire lymph from leftover tissue fluid from capillaries. Lymph is not present in the cardiovascular system, though comprised of the components of fluids leaked from capillaries.
Flowering plants’ transport system encompasses vascular tissue, consisting of xylem and phloem. Xylem transports water molecules and dissolved minerals, while phloem transports sucrose, a form of food for plants. Phloem also conducts water, minerals, hormones and amino acids. They make up the substance sap. The cardiovascular system, in comparison, has no designated vessels for separate food and water transport, just vessels that transport blood containing these materials. The food transported in mammals is in digested forms of food, while the sucrose in plants is a simple sugar manufactured by the plant. However, both transport systems carry food and water.
Xylem and phloem have many significant differences. Xylem tissue is dead when mature; therefore movement of substances through it is passive. It encompasses tubular vessels with thick, strong walls made of packing cells and supporting fibre cells. The conducting cells are vessel elements and tracheid. The secondary walls of vessel elements contain lignin, which increase strength. The end walls are perforated so that water can flow more easily. Tracheid is pitted and bordered to allow water exchange between cells. Xylem vessels have spiral thickening on its walls to provide extra strength and rigidity. They are present in the roots stems and leaves, where they transport water and minerals from the roots. Besides the roots, xylem also uses water lost from phloem activities.
Phloem, on the other hand, is alive when mature. Therefore transport mostly requires energy, although diffusion suffices sometimes. The tissue also comprises of packing cells and supporting fibre cells, but contains sieve tubes and companion cells, which are unique to it. Although tubular like the xylem, its walls are soft celled. Phloem is also found in leaves, roots and stems.
The blood vascular system (cardiovascular) requires a...