43. Organisms that reproduce sexually display a high frequency of genetic variation. Which two
meiotic processes provide most of the genetic diversity of a species?
A. synapsis and separation
C. polar migration and cytokinesis
B. replication and condensation
D. independent assortment and crossing over

D. independent assortment and crossing over.

Explanation: Genetic diversity of a species occurs when crossing over of the chromosomes is done in the process of meiosis. In crossing over, the parts of chromosomes are exchanged between two different chromatids for the production of gametes due to which variation occurs in the organisms. So crossing over is very important for producing genetic variation among species.

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."

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