Surface Area To Volume Ratio Flashcards
What does the easiness for an organism to exchange substances with its environment depend on?
It’s surface area to volume ratio.
How can simple multicellular and unicellular organisms exchange sufficient substances?
By diffusion through their outer surface.
Why can simple multicellular and unicellular do this?
-have a high SA:vol ratio.
-Diffusion pathway is small, so diffusion rate is quick.
-Have a low metabolic rate so don’t need to exchange many substances.
What can’t large multicellular organisms do that small multicellular and unicellular organisms can?
Can’t exchange sufficient substances by diffusion through their outer surface.
Why can’t large multicellular organisms do this?
-have a small SA:vol ratio so diffusion through outer surface wouldn’t be sufficient to supply their large volume of cells
-diffusion pathway is to big
-have higher metabolic rate than smaller organisms so need to exchange substances more rapidly
What do large organisms need in order to exchange a sufficient amount of substances?
-Specialised exchange surfaces
-A transport system
What do all exchange systems have and what does this do?
Have similar adaptations to increase their efficiency.
What is the first thing exchange surfaces have? And why?
Large surface area so more space for exchange
What is the second thing exchange surfaces have? And why?
Thin epithelium to reduce the diffusion distance.
What is the third thing exchange surfaces have? And why?
Good blood supply maintaining the concentration gradient as substances are quickly carried to/from exchange surfaces.
What is the fourth thing exchange surfaces have? And why?
Gas exchange surfaces are well ventilated which also helps to maintain concentration gradient.
What is the fifth thing exchange surfaces have? And why?
Mammalian gas exchange surfaces are warm which speeds up diffusion as molecules have more KE.
What is Fick’s Law?
Rate of Diffusion ∝ conc gradient x SA
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diffusion distance
