Unicellular organisms and some multicellular organisms lack circulatory systems and instead rely on
Passive diffusion to transport molecules from place to place
Nematodes move fluid through their body cavities by
Contracting muscles in their body walls and relying on passive diffusion
List the Solutions to Problem of Slow Diffusion in Large Animals:
- Specialized cells to transport fluid
- Circulatory Systems
Sponges lack a circulatory system but move fluid around through
Bodies via specialized cells called choanocytes that have a flagella
Circulatory Systems are found in
Large animals
Animal Circulatory Systems have three main components:
- Pump
- Fluid
- System
Fairy shrimp hearts have
Ostia
Describe Ostia:
- Open when the heart is not contracted, allowing hemolymph to flow from a sinus back into the heart
- Opened with the help of suspensory ligaments that pull ostia open when the heart relaxes
- Close during contraction so hemolymph is sent through the vessels
Closed Circulatory Systems have which 2 advantages?
- High Pressure + Flow Rates
- Ability to Control and Direct Blood Flow to Specific Locations
Annelids have closed circulatory systems because they
Offer an advantage for organisms living in low oxygen environments
Describe the Bony Fish Circulatory System:
- Bony fish hearts have four chambers arranged in a series
- Pumped blood flows to the gills and the rest of the body in a single loop / single circuit
All the other vertebrate groups besides fish have two circuits:
- Pulmonary
- Systemic
