This discussion is now closed.

Check out other Related discussions

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

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 :smile:

x

(edited 12 years ago)

Reply 1

thegodofgod

19

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 :smile:

x

Yup, and also that larger organisms tend to have higher metabolic rates, so would need diffusion (of O₂ / CO₂) to be more efficient :smile:

Reply 2

liverpool_x

OP

8

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 :smile:

My paragraph + higher metabolic rate?

Thank you :smile:

x

Reply 3

thegodofgod

19

Original post by liverpool_x

My paragraph + higher metabolic rate?

Thank you :smile:

x

Yup

Reply 4

liverpool_x

OP

8

Original post by thegodofgod

Yup

I think that (now) is a perfect exam answer
Thank you once again :smile:

x

Reply 5

Maker

20

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.

Reply 6

Eloades11

17

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 :smile:

Original post by thegodofgod

larger organisms tend to have higher metabolic rates

I'm not entirely sure this is true...

(edited 12 years ago)

Reply 7

thegodofgod

19

Original post by Eloades11

So multicellular organisms can't? I think you should re-word this :smile:

I'm not entirely sure this is true...

Woops - meant higher demand for oxygen :colondollar:

Reply 8

liverpool_x

OP

8

Original post by Eloades11

So multicellular organisms can't? I think you should re-word this :smile:

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
:smile:

x

Reply 9

liverpool_x

OP

8

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

Reply 10

Maker

20

Original post by liverpool_x

tis at AS Level :L

So, it doesn't mean you should be deliberately wrong.

Reply 11

liverpool_x

OP

8

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

Reply 12

Maker

20

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.