The principle of circulation Flashcards
Transport system in small organisms
- Very small diffusion distance
- Large surface area to volume ratios
- Low metabolic demands
Surface area to volume ratio
As organisms get bigger their surface area to volume ration gets smaller. So, as organisms become bigger it is more difficult for them to exchange materials with their surroundings
Calculating surface area to volume ratios - cube: surface area
6s^2
Calculating surface area to volume ratios - cube:
S^3
Calculating surface area to volume ratios- sphere:
4
Calculating surface area to volume ratios- sphere :
Need for circulatory system in animals
Within a large multicellular organism many chemical reactions takes place inside every microscopic cell
Multicellular organisms have internal transport systems that carry substances to every cell in the body
Transport system in humans (not done)
Heart
Blood vessels
Blood
Features of a mass transport system
Exchange surfaces to get materials into & out of the transport system
A system of vessels that carry substances
A way of making sure substances are moved in one direction
A way of moving materials fast enough to supply the needs of the organism
A suitable transport medium
Closed circulation system
Blood is moved through blood vessels by the hearts action. It does not come in direct contact with body organs
Single circulation
Blood passes once through the heart in each complete cycle
Double circulation
Blood passes twice through the heart in each complete cycle
Importance of double circulation
Double circulation prevents mixing of oxygenated blood with deoxygenated blood
It also helps to carry more oxygen to the cells
It helps to pump blood at high pressure through systemic circulation & at low pressure through the pulmonary circulation
