Why do Multicellualar organisms need specialised exchange surfaces and Single cell...

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liverpool_x
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Celled organisms do not?

This is my answer...

Single celled organisms can exchange gases, nutrients and wastes across their surfaces; they have a larger surface area to volume ratio, once and organism becomes larger its surface are to volume ration becomes smaller. Osmosis/diffusion across theirs surfaces is not very efficient, most internal cells would die due to the lack of substances, large organisms have internal transport systems to supply the gases and nutrients to the cells
Anything else I can write?

Thanks x
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thegodofgod
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(Original post by liverpool_x)
Celled organisms do not?

This is my answer...

Single celled organisms can exchange gases, nutrients and wastes across their surfaces; they have a larger surface area to volume ratio, once and organism becomes larger its surface are to volume ration becomes smaller. Osmosis/diffusion across theirs surfaces is not very efficient, most internal cells would die due to the lack of substances, large organisms have internal transport systems to supply the gases and nutrients to the cells
Anything else I can write?

Thanks x
Yup, and also that larger organisms tend to have higher metabolic rates, so would need diffusion (of O2 / CO2) to be more efficient
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liverpool_x
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(Original post by thegodofgod)
Yup, and also that larger organisms tend to have higher metabolic rates, so would need diffusion (of O2 / CO2) to be more efficient
My paragraph + higher metabolic rate?

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thegodofgod
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(Original post by liverpool_x)
My paragraph + higher metabolic rate?

Thank you x
Yup
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liverpool_x
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(Original post by thegodofgod)
Yup
I think that (now) is a perfect exam answer
Thank you once again x
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Maker
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I disagree. What is meant by specialised? A lot of single cell organisms are very large like amoebas and they don't have specialised exchange surfaces like multicellular organisms.

I suggest the real reason is inter cellular communications via signalling chemicals that cells excrete and passed between each other.
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Eloades11
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(Original post by liverpool_x)
Single celled organisms can exchange gases, nutrients and wastes across their surfaces
So multicellular organisms can't? I think you should re-word this

(Original post by thegodofgod)
larger organisms tend to have higher metabolic rates
I'm not entirely sure this is true...
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thegodofgod
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(Original post by Eloades11)
So multicellular organisms can't? I think you should re-word this


I'm not entirely sure this is true...
Woops - meant higher demand for oxygen
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liverpool_x
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(Original post by Eloades11)
So multicellular organisms can't? I think you should re-word this


I'm not entirely sure this is true...
Multi Cellular organisms can aswell, I can eat 2 grapes at a time... It's irrelevant
Why do large organisms need transport systems? Because simple osmosis/diffusion on its own is not enough..

An aoemeba will just "float about" so the organism won't be using as much of the gases, nutrients etc compared to a human excercising..or a human in general
x
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liverpool_x
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(Original post by Maker)
I disagree. What is meant by specialised? A lot of single cell organisms are very large like amoebas and they don't have specialised exchange surfaces like multicellular organisms.

I suggest the real reason is inter cellular communications via signalling chemicals that cells excrete and passed between each other.
tis at AS Level :L
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Maker
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(Original post by liverpool_x)
tis at AS Level :L
So, it doesn't mean you should be deliberately wrong.
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liverpool_x
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(Original post by Maker)
So, it doesn't mean you should be deliberately wrong.
What I've it written is right... You mentioned inter cellular communication which we haven't covered
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Maker
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(Original post by liverpool_x)
What I've it written is right... You mentioned inter cellular communication which we haven't covered
I also thought of multicellular organisms have to stick together to form structures like skin so the individual cells would need to stick to their neighbours, something unicellular organisms don't do.
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grgrg
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hi
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grgrg
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Eloades11
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Thread closed for being 5 years old (and making me feel old!)
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