What is the reason why unicellular organism are usunlly small?

Answer 1

because there is a limit to how big a single cell can be due to the reducing ratio volume/surface area. when the ratio is below a certain limit the diffusion of chemicels in or out of the cell gets too slow

Answer 2

Just a couple of thoughts. As cells get bigger, the components (used to be called organelles but I guess that's changed) get further from the cell walls or membranes. Given the limitations of transport mechanisms within cells, their ability to interact with the cell exterior would eventually be limited to such an extent that the cell would no longer be viable (volume:area). This logic would suggest that cells that do not require much interaction could be comparatively big e.g. some plant and animal structural cells or human eggs (not sure where ostrich eggs fit - are they uni or multi cellular structures?). But, this logic is based on a vision of a cell as a sphere and, by elongating, flattening or other deviation from the sphere, cells can grow larger whilst maintaining effective interaction with the cell exterior e.g. nerve and skin cells.

Answer 3

It has to do with surface to volume ratio. Cells must exchange gas through the membrane, and it must exchange enough gas to service the entire cell. Imagine how the volume and surface area change when you blow up a balloon. As the balloon expands, there is less surface area to compensate for the increase in volume.

Answer 4

"because they only have on one cell, and to grow larger they need to add more cells to their body, which they cant do" - this is what another dude said but I'm not sure it's accurate. I mean if you're in AP Bio, then it's a totally different answer.

Single cell organisms can't be any larger than they already are because they need to be able to transfer energy as fast as possible. But if the single celled organism is the size of a person then that cell will die because of the energy takes time to go through the cell. And it needs to be fast enough to feed the cell.
diffusion of nutrients into the cell's interior would be too slow

Answer 5

Unicellular organisms are usually small because their single cell must perform all the functions necessary for survival, limiting their size. Smaller size allows for easier diffusion of nutrients and gases into and out of the cell, supporting efficient metabolism. Additionally, larger organisms may struggle to maintain a high surface area to volume ratio necessary for sufficient nutrient exchange.

Answer 6

they don't have the organelles like we do. we are multicellular organisms

Answer 7

i dont kjnwo

Answer 8

pp