Because they change over time
Answer:
1) Recursive definition: 
2) At the beginning of the 4th interval
Explanation:
1)
The initial population of the bacteria at time zero is

Here we are told that the reading is taken every two hours; we call this time interval "n", so

And also, after every time interval n, the number of bacteria has tripled.
This means that when n = 1,

And when n=2,

Applied recursively, we get

And substituting p0,
(1)
2)
Here we want to find at the beginning of which interval there are

bacteria.
This means that we can rewrite eq.(1) as

By simplifying,

Which means that

However, this means that the number of bacteria is 1,350,000 after 3 time intervals; therefore, at the beginning of the 4th interval.
<span>A scenario where a cell may be needed to perform a form of endocytosis is when transporting large molecules.
A scenario where a cell may be needed to perform a form of exocytosis is when releasing the large molecule from the cell. The movement of macromolecules of polysaccharides or proteins out of or into the cell is known as Bulk transport.
Bulk transport is of two types which include endocytosis and exocytosis whereby both require an expenditure of energy. Exocytosis materials are being exported out of the cell via secretory vesicles.
Golgi complex they do package macromolecules into transport vesicles which travel to and spill its content out of cells. Exocytosis is very much important in the expulsion of waste materials out of the cell and also in products secretion. Endocytosis is the process where materials move into the cell.
Endocytosis is divided into the three types which include pinocytosis, phagocytosis, and receptor-mediated endocytosis.</span>
The answer is "c. Some alleles are dominant and other are recessive"