THE NEED FOR A CIRCULATORY SYSTEM

What do all living things require to live? Unicellular organisms perform all processes using only one cell Multicellular organisms require organ systems to function properly Circulatory System: responsible for transporting (circulating) nutrients, dissolved gases, waters, and chemicals to and from individual cells in an organism What do all living things require to live? Unicellular organisms perform all processes using only one cell Multicellular organisms require systems to function properly Recall the order from least complex to most complex on the quiz, cells, tissues, organs, organ systems, organism Circulatory system: responsible for transporting (circulating) nutrients (what are some possible nutrients?), dissolved gases (what are some gases found in our body that we are transporting?), waters, and chemicals (what chemicals could we be transporting?) to and from individual cells in an organism

Unicellular organisms are in direct contact with their environment Gases diffuse across a cell membrane Nutrients are engulfed or absorbed through the membrane Unicellular organisms are in direct contact with their environment Think of that cell of being the “flesh” of its own self, the outside environment is shared with the cell, whereas, our organs and cells live almost in their own warm and moist environment which is the inside of our body, beneath our skin In unicellular organisms, gases diffuse across a cell membrane And nutrients are engulfed (what does engulfed mean again?) or absorbed through the membrane

Simple Circulation Some simple multicellular organisms do NOT need a circulatory system Sponges Has two layers O2 is absorbed through the cell Nutrients are trapped CO2 and wastes are pushed out through the top Central cavity is flushed every 4.3 seconds Can move up to 20,000x is body volume in water/ day Some simple multicellular organisms do NOT need a circulatory system Sponges Has two layers The outside layer, as seen in the diagram, is the epithelium (so the outer skin, just like we have), then the second layer is the collar cell The inner part of the collar cell has a flagellum (tail) that will be able to beat water around the inside of the sponge Oxygen is absorbed into the cell, nutrients are trapped, carbon dioxide and wastes are eliminated by a big push and are released from the top of the sponge The central cavity (point out) is flushed every 4.3 seconds, and the sponge can move up to 20,000x its body volume in water in a single day

Circulatory Evolution The need for a circulatory system arose with increase in body size Circulatory systems must bring O2 and nutrients from the external environment in AND the waste from the internal environment back to the external environment The need for a circulatory system arose with an increase in body size With more complex organisms, that are also larger, their insides, are not exposed to the outside environment that could be air or water Circulatory systems must bring oxygen and nutrients from the external environment in, and the waste from the internal environment back to the external environment

«OPEN» «CLOSED» Types of Circulatory Systems There are two types of circulatory systems Open and closed Does anyone know what defines each one? No matter whether it is open or closed, all circulatory systems have three fundamental features 1) A fluid that circulates materials through the body A network of tubes in which the fluid circulates A pump that pushes the fluid through the tubes A fluid that circulates materials through the body A network of tubes in which the fluid circulates A pump that pushes the fluid through the tubes

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