Observation of Diffusion Rate in Relation to Cell Size As you have observed, cells are small. Consider your little toe: it is made of about 2-3 billion
cells! A newly-made cell will grow, but once it reaches a certain size it will divide to form two
new cells rather than growing bigger. Why is this? Why aren't you made of a few dozen, or a
few hundred cells, instead of trillions? Why don't single-celled organisms like amoebas and paramecia grow
as big as a human? In this lab, we will investigate this question using model cells.

Explanation:

new cells rather than growing bigger. Why is this ?

There are two main reasons why cells divide rather than continuing to grow larger and larger: ... If the cell grows too large, it will have trouble moving enough nutrients and wastes across the cell membrane. Cell Division. Cell division is the process by which cellular material is divided between two new daughter cells.

Why aren't you made of a few dozen, or a

few hundred cells, instead of trillions?

if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume. When this happens, the cell must divide into smaller cells with favorable surface area/volume ratios, or cease to function. That is why cells are so small.

Why don't single-celled organisms like amoebas and paramecia grow

as big as a human?     again The important point is that the surface area to the volume ratio gets smaller as the cell gets larger. Thus, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume.

i belive this is just the introduction to the project but here

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.