What risk is there for a species that only reproduces by cloning?
Everyone would have the same genes and DNA and a disease would wipe out an entire population - we would all have the same immune system
How does DNA of sexually produced offspring compare to the DNA of the parents?
It has 23 chromosomes from each parent, so its different from either one
What happens to the genes when two chromosomes "embrace" (crossing over)
Big chunks carrying bunches of DNA is shared; cells duplicate and divide (meiosis)
What is the advantage of diversity within a species?
The better the odds are that someone will survive to produce a new generation
When does the human female produce her eggs?
When she is a fetus in the mother's womb
When does the human male produce his sperm?
Starts at puberty and continues throughout life
What danger confronts sperm in the vagina?
It's acidic. That's why pre-ejaculation is necessary. Many sperm die. The sperm make it through and are pushed through very quickly because it is a "danger zone"; escape or die
What risk does the blastocyst face after it attaches to the uterus?
The immune system attacking it.
Egg is fertilized in the....
Does the blood of the mother and baby ever mix?
No - the placenta keeps it from mixing
to get bigger
usually results in a miscarriage
could kill the mother if fetus isn't removed
When is a C-section necessary?
When baby isn't head first
When cervix is not fully dialated
What is DNA "very good" at?
making copies of itself
(genetics) cell division that produces reproductive cells in sexually reproducing organisms
How many chromosomes come from each parent?
23 each for a total of 46
How many sperm are produced by the average human male?
2 trillion over one lifetime; 1000 new sperm every second
What are some of the changes that happen in the body when "love is in the air"?
Chemistry between the man and woman, drugs in the brain and glucose is stimulated, sexual excitement, blood in the penis; vital signs elevated
What are some ways the women's body helps control the success of the sperm?
the egg itself will help, cervix is locked shut. Mucus becomes watery and cervix unlocks, the uterine muscle propels sperm into the tube
What percentage of fertilized eggs fail to develop?
more than 50% fail to develop
What happens if the cell cluster splits into two groups?
creates identical twins, 2 embryos
After fertilization, how long does it take for the cell cluster (blastocyst) to arrive in the uterus?
5 days, beginning on the 6th day, enzyme to leave for uterus (to leave the fallopian tubes)
How could you tell the sex of a 7 week old embryo?
see the chromosomes, SRY Gonad
Glands related to sexual characteristics and the processes involved in reproduction
the sex determining region of the Y chromosome in males. Encodes the testis-determining factor, which turns the primordial gonads into the testes
When is an embryo called a fetus
after 8 weeks of fertilization
Where specifically does the fetus gets its nutrients?
dwarfed embryo forms the placenta and the fetus gets nutrients and oxygen from the mother's blood
A structure in the pregnant uterus for nourishing a viviparous fetus with the mother's blood supply; formed from the uterine lining and embryonic membranes; dwarfed embryo
How does the fetus get its nutrients?
via the umbilical cord from the placenta
What is the main job of the fetus during the last trimester?
to grow and provide fat to the brain
What is happening to the female body during pregnancy to aid in delivery?
the baby's need for fat becomes great, somehow it has to get out. Oxytocin hormone is triggered to start uterine contractions and the cervix opens
wraps around cells enhancing brain development
A thick, transpartent coating rich in glycoproteins that surrounds the egg; the sperm must break through when the egg draws the contents of the sperm inside this coating
the slower sperm get caught in the cilia of the tubes and soon will be drawn to the Zona
All sperm is locked out
of the Zona once one meets the egg
(1) A fingerlike projection of the inner surface of the small intestine. (2) A fingerlike projection of the chorion of the mammalian placenta. Large numbers of villi increase the surface areas of these organs.
Villi grab nutrients and oxygen
through the umbilical cord to take to the fetus