Human Life Cycle 16.1 p. 320 INSERTING FIGURES IS ALWAYS A GOOD THING.
(1) How many chromosomes does a mother contribute to a new individual? A father?
mother: 23
father:23
(2) Where does meiosis occur in males? in females?
Meiosis occurs in the testes of males during the production of sperm and occurs in the ovaries of females during production of the eggs.

(3) Compare and egg cell to a sperm cell.
Sperm carries the chromosomes to the the egg. The egg receives the sperms chromosomes.

(4) What is the difference between meiosis and mitosis.
Mitosis is the duplication of division and meiosis is the reduction of division.
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Development Chapter 17
17.1
(5) Describe in detail how fertilization occurs
1. The sperm makes its way through the corona radiata. Only one sperm can enter the egg.
2. Acrossomes allow the sperm to penetrate the zona pellucia.
3. The sperm binds to and fuses with the egg plasma membrane. The sperms head, middle and tail usually all go into the egg.
4. The sperm nucleus enters cytoplasm of egg.
5. Cortical granules release enzymes and zona pellucida becomes fertilization membrane.
6. The sperm and egg pronuclei are enclosed in a nuclear envelope.

(6) What is polyspermy and how is prevented during fertilization?
Polyspermy is when more than one sperm enters the egg.
This is prevented during fertilization because the egg plasma membrane and the zona pellucida change. As soon as the sperm touches the egg, the egs plasma membrane depolarizes and prevents binding of other sperm. Vesicles called cortical granules release enzymes that cause zona pellucida to becomes an impenetrable fertilization membrane, which allows sperm not to combined with zona pellucida.

17.2
(7) Describe the processes involved in development.
First there is Cleavage which follows right after fertilization. The zygote begins to divide so there is 2 cells then 4 cells then 8 cells and all th way up till there is 32 cells. Cell division during cleavage is mitotic meaning each cell receives full complement of chromosomes and genes.
Then there is Growth which is during embryonic development. The cells grow in the size of daughter cells
Next there is Morphogeneis which is the shaping of the embryo and is when we see cells start to move or migrate to other cells.
Finally there is Differentiation which is when cells have a specific structure and function. The 1st systems to become visibly differentiated is the nervous system.

(8) What are the extraembryonic membranes and what is their role?
Extraembryonic membranes are located on the outside of the embryo. They have four different roles. The Chorion, which develops in the fetal half of the placenta. The next role is allanttois, which is like a yoke sac and extends away from the embryo. It collects the small amount of urine produced by the ffetal kidneys and gives it to the urinary bladder. Then there is the yoke sac, which is the first embryonic membrane to appear. The yoke sac is taken over by the placenta and contains little yoke. This is the first site of blood cell formation. The last role is amnion, which gets bigger as the embryo and the fetus get bigger.

(9) What happens during pre-embryonic development?
Follows right after fertilization.
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(10) What happens during embryonic development?
It begins with the second week and last until the end of the second month of development.
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(11) What are the primary germ layers and what body structures come from each layer?
The primary germ layers are the ectoderm, which is the outer layer consisting of, skin, oral cavity, rectum and nervous system. Then the mesoderm, which is the middle layer,consisting of the skeleton, muscular system, dermis of skin, cardiovascular system, urinary system, reproductive system, outer layers of the respiratory system and the ddigestive system. Finally there is the endoderm, which is the inner layer,consisting of the lining of the digestive tract and the lining of the urinary bladder.
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