why are multicelled organisms made from lots of small cells rather than a few large ones?

Answer 1

The underlining evolutionary principle behind multicellularity is cellular spcialisation. If an organism has many cells, certain tasks can be assigned to specific cell types and the different kinds of cells can do different work. This means that, in comparison to the organisms with few larger cells, much more cellular work can be accomplished and the quality of life, from the biological perspective, is much better. Cellular specialisation is therefore the reason why multicellular organisms have many smaller cells that few large cells.

Answer 2

Because cells must take in all their nutrients, water and oxygen, and release all their waste products through the cell membrane, their maximum size is sharply limited by the ratio of cell volume to membrane surface area. The larger a cell becomes, the larger this ratio becomes. In other words, the larger a cell is, the smaller the amount of surface area that is available per unit of cell volume. A very large cell would not have sufficient surface area to serve its large inner volume.

For example, a 1-inch cube has a surface area of 6 square inches, and a volume of 1 cubic inch, therefore a volume/surface ratio of 1:6.

A 2-inch cube has a surface area of 24 and a volume of 8, so a volume/surface ratio of 1:3.

A 3-inch cube has a surface area of 54 and a volume of 27, so a volume/surface area of 1:2.

As you can see, with each increase in size the cell effectively loses surface area, until finally there just isn't enough to take care of the cell's physiological needs.

Answer 3

there are lots of reasons for that
1. small cells can have everything that a large cell has. It is just that small cells have more surface area (more folded membranes)
2. having a lot of small cells give the organism the oportunity to have more than one kind of tissue (imagine having just a few large cells for skin..). If you had just one big cell for for liver, or for your heart: once that cell is dead..you are dead. Also, regeneration of cells would take a long time with large cells.
3. Well..everything is about surface area: the small size of cell and all the surface area they have, make the functions of the organism better: you don't waste a lot of energy.
4. and most important: a single large cell cannot have/do everything that a tissue can do. Imagine having one large cell for your biceps..

Answer 4

It all boils down to efficiency. I Remember back in the day when a super-computer was made with tons of hoses, vacuums, ect. and took up a whole entire room! Nowadays, our home PC's are 100-fold more powerful than the massive computers in the 70's, and take up less space. They are, ultimately, more efficient.

The same holds true in the world of molecular biology. It's extremely inefficient for a creature to use larger cells rather than smaller ones. You can fit 'more' into less space by optimizing cell structure and size. That large cell does the same thing as the small cell, but takes up more than twice its space, thanks to the cell evolving (as our computers did). Imagine trying to piece together a human being using those large cells. It would be extremely inefficient. We'd weigh more; our bone structure would have to componsate for the extra weight, causing even more inefficiency. Our 'precision' would lessen; try picking up a grain of sand--it's hard enough as is--with fingers twice the normal size!...

Bottom line- efficiency.

Answer 5

A multicelled organism has a lot of functions and needs specialized cells for those functions.

Answer 6

SENIOR BIOLOGY LINKS.

On-Line Biology Book

http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookTOC.html

http://www.clickandlearn.org/Bio/bio_links.htm

Excellent Biology Links:

http://www.wiley.com/legacy/college/boyer/0470003790/animations/animations.htm

http://science.nhmccd.edu/biol/index.html

http://www.sumanasinc.com/webcontent/animation.html

Bio 275
molecular animations

http://www.soest.hawaii.edu/~ffd/bio275/

Good luck.

Kevin, Liverpool, England.