transport in animals snap revise Flashcards
why is there a need for transport systems in animals
all living cells need a constant supply of oxygen and nutrients- respiration occurs to produce ATP
-nutrients need to be moved around
what’s an exchange surface in humans
the lungs
factors requiring an organism to have a transport system
- size- big= large diffusion distance
- surface area to vol ratio- big= small sa:vol
- level of metabolic activity
features of a good transport system and what they might have
- a fluid medium running through them
- a pump to create the pressure for circulation
-exchange surfaces for substances to enter and exit
might have:
-vessels or tubes
-two circuits
what are open circulatory systems
ones in which blood is not always held in vessels
what has open circulatory systems
insects
two disadvantages of open circulatory systems
- blood pressure remains low= slow flow of blood
- circulation is affected by body movements
what are closed circulatory systems
are ones which the blood is held in vessels
what separate fluid does organisms with closed circulatory systems have
tissue fluid
two key advantages of closed circulatory systems
+ blood pressure in vessels can be high and circulation is rapid
+ circulation is not affected by any body movements.
what are single circulatory systems
ones which the blood flows through the heart once for each circuit of the body
compare the pressure of single circulatory systems and double circulatory systems
double has a higher pressure
why do fish have single circulatory systems
- counter current flow maintains a large diffusion gradient for exchange in the gills
- most fish are exothermic and the water is thermally insulating
whats a double circulatory systems
ones which the blood flows twice for every circuit of the body
talk about the pressure in double circulatory systems
- pressure to the lungs is low (pulmonary circuit)
- pressure to the body is high (systemic)
whats tissue fluid
extracellular fluid which bathes the cells of most tissues
state the circulatory system that a fish has
closed single
explain why larger organisms need transport systems rather than relying on diffusion
- large organisms ahve a small surface area to vol ratio. This means some tissues are too far for molecules to be exchanged fast enough. Transport systems ensure that even tissues far away from the organisms surface can exchange molecules rapidly