Summary
a level biology animal transport summary
- Institution
- OCR
summary of animal transport topic in module 3
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ANIMAL TRANSPORTCIRCULATORY SYSTEM
● Liquid transport medium (blood) -is transported to carry molecules
● Vessels - to carry the transport medium
● Pump (heart) - to create pressure that pushes the fluid around the body .
OPEN
● Few blood vessels don’t always contain the transport medium
● Blood + fluid (haemolymph) circulates through the body cavity
● Tissues + cells are bathed directly in blood for exchange (glucose into cells / waste
products out of cells )
● Transport medium returns to heart through an open ended vessel
E.g. invertebrates - insects + molluscs
- Flowing of haemolymph (blood) can’t be varied to meet changing demands or
directed to particular tissues , so it depends only on body movement
- Low blood pressure = slow blood flow + no steep concentration gradient
CLOSED
● Transport medium enclosed in vessels all the time
● Cells + tissues bathed in tissue fluid, so exchange occurs through walls of vessels
● Volume of blood flow can be adjusted by narrowing/ widening of vessels and
directed to specific tissues
+ Higher pressure = rapid blood flow + steep concentration gradient
SINGLE
1
, ● Blood flows through the heart once for each complete circuit by flowing through 2
sets of capillaries
1. In gills for exchange of gases
2. To body for exchange of substances
- Low blood pressure = blood returns slowly to the heart , limiting efficiency of system
and activity levels
FISH still active :
- Countercurrent gas exchange : absorb more oxygen from water
- Body weight supported by water
- No thermoregulation as same water and temperature
= reducing metabolic demands on their bodies
DOUBLE
● Blood flows through heart twice for each complete circuit (to lungs, then to rest of
body)
+ High blood pressure as it passes through 1 set of capillaries = fast blood flow
2
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