About Lesson
The Circulatory System
A circulatory system in animals is important for the transportation of:
- Oxygen and nutrients for tissue
- Carbon (IV) oxide and other waste products from tissues to excretory sites.
- Hormones, salts and some enzymes to different parts of the body.
Unicellular (single-celled) organisms have a large surface area to volume ratio. They depend on simple diffusion for the movement of materials into and out of their bodies across their cell membrane.
As organisms increase in size and complexity, the quantity of materials moving into and out of their bodies increase and so does the distance over which the materials moves.
Types of Circulatory System
There are two types of circulatory system in animals;
- Open circulatory system
Closed circulatory system
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