Expectations:
- Explain the functions of a transport system in multicellular organisms
- Identify the main types of transport system found in animals
- Distinguish between an open and closed transport system
- Explain how adaptations such as double circulation alter the efficiency of the transport system
-The transport system delivers nutrients and oxygen to cells and carries away the wastes of cellular processes and acts as a pathway for disease fighting agents, hormones, and other chemical messengers
-In warm-blooded animals the transport system also helps control temperature
-Almost all multicellular organisms have a vascular system a system of fluid that plays a role in transporting nutrients and other materials to cells
-Most animals have a circulatory system which is a vascular system that uses muscle movementss to control the flow of fluid to follow a specific pattern
-A cardiovascular system is a circulatory system found in higher animals that uses a heart to pump the vascular fluid around the body
Simple Internal Transport[]
-Respiratory gases and nutrients enter the cell throught diffusion or active transport across the cell membrane which are distributed by the streaming of the cytoplasm
-Wastes are diffused or carried back across the cell membrane
-Some multicellular animals also lack an organized transport system instead taking fluid through the mouth into a body cavity that extends through most of the organism and materials can be exchanged between the fluid and cells
-Planaria have a branching digestive cavity and separate excretory cavity which functions in a similar way
-This fluid may be assisted by contraction of cells and muscle fibres as the animal moves
Open Transport System[]
-Fluid bathes cells directly
-A transport system in which the blood does not always stay contained in blood vessels
-Fluid can slosh back and forth and circulates relatively slowly
-This system cannot provide rapid transport of materials and is best suited to insects and other arthropods that have relatively small body cavities
-Insects also have separate respiratory and circulatory systems so an efficient circulatory system is not needed to meet its respiratory needs
Closed Transport System[]
-Animals that rely on the circulatory system to carry respiratory gases need a faster blood flow than an open transport system can provide
-Blood does not bathe cells directly but is pumped through the body within a network of vessels
-This network include larger vessels that collect blood for pumping, smaller vessels that distribute blood around the body, and tiny capillaries that provide a surface for exchange of materials between cells
-Blood circulates in only one direction, passing through the gas exchange system in its cycle
-Factors that affect the efficiency of a circulatory system include the composition of blood, the path of circulation, and the speed of bloodflow (usually measured in terms of blood pressure)
Circulation in Annelids[]
-Consists of two main blood vessels connected by a series of five pairs of heart-like pumps called aortic arches -Blood enters the aortic arches from the dorsal (top) vessel, which (like the arches) contracts to pump blood forward -Blood is then pumped into the ventral (bottom) vessel located under the intestinal tract -The blood flows through a branching series of smaller and smaller vessels to the internal organs where the exchange of materials occurs across the thin walls of the capillaries -Some vessels also lead to the animal's body walls where gas exchange occurs between the capillaries and the outside environment -The capillaries lead to larger vessels which direct the blood back to the dorsal vessel
-Dissolved in the blood of the earthworm is a respiratory pigment, a molecule that binds to oxygen -The presence of this pigment allows the blood to pick up and transport more oxygen than would otherwise be possible -The respiratory pigment found in earthworms is the same on found in the blood of vertebrates
-The earthworm uses its entire skin surface to exchange gases, which means the blood is being oxygenated as it circulates around the animal