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Author Question: The morula is a: a. Fertilized ovum before mitosis begins. b. Flattened disk-shaped layer of ... (Read 94 times)

danielfitts88

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on: Jun 27, 2018
The morula is a:
 
  a. Fertilized ovum before mitosis begins.
  b. Flattened disk-shaped layer of cells within a fluid-filled sphere.
  c. Double layer of cells that becomes the placenta.
  d. Solid ball composed of the first cells formed after fertilization.

Question 2

The purpose of the ovum's zona pellucida is to:
 
  a. Make a pathway for more than one sperm to reach the ovum.
  b. Allow the 46 chromosomes from each gamete to merge.
  c. Prevent multiple sperm from fertilizing the ovum.
  d. Stimulate the ovum to begin mitotic cell division.


jaykayy05

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Reply #1 on: Jun 27, 2018
Answer to Question 1

D
The morula is so named because it resembles a mulberry. It is a solid ball of 12 to 16 cells that develops after fertilization.
The fertilized ovum is called the zygote.
This is the embryonic disk; it will develop into the body.
The placenta is formed from two layers of cells; the trophoblast, which is the other portion of the fertilized ovum, and the decidua, which is the portion of the uterus where implantation occurs.

Answer to Question 2

C
Fertilization causes the zona pellucida to change its chemical composition so multiple sperm cannot fertilize the ovum.
Once sperm has entered the ovum, the zona pellucida changes on order to prevent other sperm from entering.
Each gamete (sperm and ovum) has only 23 chromosomes; there will be 46 chromosomes when they merge.
Miotic cell division begins when the nuclei of the sperm and ovum unite.


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