Homework Help: Biology

Posted by mysterychicken on Saturday, February 13, 2010 at 7:28pm.

38. Mitosis and meiosis are the two different ways cells divide. They both share common characteristics and processes, but differ in some very important ways.

I answered part A and B of this, but I need help with C:
c. Why is it important for chromosomal exchange to occur during meiosis and not mitosis?

Also:

2. Which statement best explains the effect of resources on population size?
a. The exponential growth curve models the effect of limiting resources on population size.
b. Limited resources decrease the growth rate of population size
c. Density-dependent factors invariably lead to a positive DN
d. all of the above
Need help with this as well.

Thanks!
-MC

Biology - bobpursley, Saturday, February 13, 2010 at 7:41pm
The purpose of meiosis is to form gametes, and ultimately offspring; therefore, "crossing over" is advantageous because it increases genetic variation. Mitosis, however, is necessary to grow bigger and repair damaged tissues. If you had chromosomal exchange during mitosis, then the daughter cell would not be the same as the parent cell.

The effect of limited resources is to decrease the growth rate. No food, no offspring.
Biology - mysterychicken, Saturday, February 13, 2010 at 7:45pm
Thanks so much!
-MC
Biology - Priscilla, Saturday, February 13, 2010 at 7:51pm
Ok your first question,

In mitosis you end up with two cells, each of which has exactly the same chromosomes as the original cell. In meiosis, you end up with 4 cells, each of which has half as many chromosomes as the original cell. In many organisms, the for cells formed by meiosis are the gametes that are used in sexual reproduction.

In meiosis, there are basically 2 consecutive rounds of division. The details of the chromosome separation are different for the first and second division of meiosis.

Chromosome exchange (recombination) happens in meiosis, but not in mitosis.

Chromosomal exchange insures that every gamete that is formed has a different combination of genes. That makes every offspring from matings of two individuals be genetically unique. In mitosis, you want to make sure that every cell formed is genetically identical to every other cell.

The second question has to be Dbecause I know a and b are right and im pretty sure c is right as well.
Biology - Anonymous, Thursday, August 9, 2012 at 3:12pm
describe the ecosystem's population growth and regulation through community interaction

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