Name: ____________Answer Key____________________

Name: ____________Answer Key____________________ Section: ___________________
PBS Nova: Life’s Greatest Miracle Movie Worksheet
Please answer the following questions as you watch. This sheet will be collected at the end of of the
movie for a class grade.
What is DNA “very good” at? making copies of itself
What risk is there for a species that only reproduces by cloning? everyone would have the exact same
immune system, and one successful parasite could wipe us all out.
How many sperm are produced by the average human male? a thousand new sperm every second.
That's about a hundred million new sperm every day and more than two trillion over a lifetime.
How many chromosomes come from each parent? Exactly half of those, 23, came from your mom,
and 23 came from your dad
What happens to the genes when two chromosomes “embrace”? They cling so closely, big chunks
carrying whole bunches of genes get exchanged between the partners
What is the advantage of diversity within a species? Higher chances of survival of a new generation.
When does a human female produce her eggs? in the fetus
What do the support cells do with the egg? tend to the egg, feeding it until it grows fat. Oozes out of
the ovary with egg
Inside the fallopian tube, how long does the egg have to get fertilized? What happens if it doesn’t?
With a few hours it will die
What are some changes that happen in the body when “love is in the air”? body temp rises, skin
sweats, heartbeat and breathing get faster, hormones cue blood vessels to relax in man allowing penis
to fill with blood
What is the immediate danger which confronts sperm in the vagina? Acidity
What are some ways the women’s body helps control the success of the sperm? in the cervix, the
mucous becomes watery and forms tiny channels that guide the sperm, uterine muscle contractions
propel the sperm into fallopian tube, cilia in fallopian tubes release chemical that alter the sperm’s
outer coating.
What does the sperm need in order to be allows through the egg’s zona? Proteins protruding from
sperm’s head must hook up precisely with a set of proteins on the egg’s surface
What percent of fertilized eggs fail to develop? 50%
What is happening as the fertilized egg moves down the fallopian tube toward the uterus? Every few
hours it divides
What happens if the cell cluster splits into two groups? Identical twins
After fertilization, how long does it take for the cell cluster (blastocyst) to arrive in the uterus? 5 days
What risk does the blastocyst face after it attaches to the uterus? It could be attacked by the woman’s
immune system
Gastrulation, when the cells organize themselves into an embryo occurs 2 weeks after conception.
What do the 3 layers of cells go on to form?
Lower - lungs, liver, lining of digestive tract
Middle - heart, muscles, bones, blood
Top - nervous system, skin, hair
How could you tell the sex of a seven-week-old embryo? Look at the chromosomes - XX usually
becomes a girl, XY is most likely a boy
When is an embryo called a fetus? How big is a fetus? How much bigger will the fetus grow by the
time of birth? two months, an inch long, ⅓ an ounce, 400X
Where specifically does the fetus get its nutrients? How does it get its nutrients? Mother’s blood,
placenta - villi grab oxygen and nutrients and flows through umbilical cord
What is the main job of the fetus during the last trimester? What does myelin help? to grow, enhance
brain power
During the course of a pregnancy, by how much has the mother’s blood supply increased? 50%
What is happening in the female body during pregnancy to aid in delivery? uterus contracts and
cervix opens to about 4 inches