Miracle of Life
1. DNA is very good at making copies of itself.
2. Why is sexual reproduction more advantageous than cloning?
With sexual reproduction two individuals provide some DNA. So, the variety is produced.
3. How many new sperm are created every day?
1000 new sperm are created every second. About 100 million new sperm every day.
4. During meiosis, what happens to the matching X-shaped chromosomes?
Chromosomes partners get together and four will embrace, they cling so closely, carrying
whole bunches of genes and get exchanged between partners.
5. How is the egg pushed along within the Fallopian tube?
The tentacle of the fallopian tube catches the egg and pulls it inside. The egg gets swept
along the tube and tiny cilia into the fallopian tube.
6. To fertilize the egg, sperm encounter several obstacles, what is the last one they encounter
before they penetrate the egg?
The last obstacle that the sperm encounters before it penetrates the egg is "the zona '' a
thick protein shell covering the egg. To fertilize the egg, the sperm must break through the
zona.
7. The blastocyst must do two things to survive, it must break out of the zone and what else?
The second one, that must be done by blastocyst to survive is finding a source of
nourishment
8. Two weeks after conception, the cells organize themselves into an embryo, a process called
gastrulation.
9. The three layers of cells created during gastrulation are destined for three different functions.
Describe what each will become:
Bottom layer form lung, liver and layers of the digestive tract
Middle Layer form muscles, heart, bones and blood
Top Layer forms the nervous system and the outer layer of skin.
10. Genes turn on and off to make proteins. Collagen is a protein that makes tendons and bones,
keratin makes hair. Hemoglobin in the blood has what job?
It carries oxygen from the lungs to the rest of the body.
11.An embryo with two X chromosomes will become a girl. An embryo with the XY
combination will become a boy.
12. Two months after fertilization, the embryo is called a fetus.
13. What structure is used to gather blood and nutrients from the mother's blood and pass it to the
umbilical cord? Placenta (villi)
14. At the end of pregnancy, the baby is growing myelin around its neurons. This growth
increases its need for what nutrients? Fat
15. Why is it harder for human babies to be delivered than other animals?
The human brain is three to four times bigger than an ape's brain. And the pelvis is
narrower to allow us to walk upright. A human baby must go through considerable
contortions to make it through the narrow opening.