1. THE NEED FOR A CIRCULATORY SYSTEM

2. 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

3. 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

4. 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

5. 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

6. «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

7. BONUS!