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39 Cards in this Set

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  • Back
The nucleus of the sperm fuses with the nucleus of the egg, making the new, fused nucleus diploid
The product of fertilization = a zygote (one cell stage)It contains all the necessary DNA for a new organism
Why is the zygote surrounded by a fertilization membrane immediately after the sperm penetrates the plasma membrane of the ovum?
so that no more sperm can get in
Through the process of _____ the zygote is changed into a mulitcellular embryo.
Cleavage is a special form of rapid cell division with no cell growth between the divisions.
This results in an increased cell number, but decreased individual cell size, the overall embryo size changes very little
stems cells, many cells solid ball cluster
more division and getting smaller in denssity but now is hollow and has cavity
cells migrate inward until against top row of cells beginning of gastrointestinal tract
forming the nervous system
At which stage is a human embryo when it implants in the thickened uterine lining?
What happens if fertilization occurs too late in the cycle?
wont develop fully
What happens if fertilization occurs too early?
get stuck in the follopian tube
At which stage do you first have two tissue layers?
Endoderm develops into ______
intestinal tract
ectoderm develops into ______
skin, nervous system, nails, hair, teeth
mesoderm develops into ______
muscles and skeleton, circulatory system
When the embryo is developing in an aquatic environment, it has several advantages, what are they
1) no sudden changes in temp (enzymes and cells are touchy)
2) replenishes nutrients and oxy removes wastes
3) provides bouyancy (less pressure)
4) acts as a shock absorber
What is the major disadvantage to embryonic development in an aquatic environment?
Terrestrial organisms that evolved needed to stimulate the advangageous conditions.
The amniote egg simulates an aquatic environ by surrounding the embryo with a series of extra-embryonic membranes
The four extra-embryonic membranes are not actually part of the embryo, but develop from it.
Each membrane is formed from 2 of the 3 tissue layers from the embryo (endo, meso, and ectoderm)
Function of the yolk sac in an amniote egg
surrounds yolk, digest the yolk, transport it to the embryo formed of meso, blood vessels and ectoderm
Function of the amnion in an amniote egg
surrounds embryo filled with water, provides an aquatic environment
Function of the chorion in an amniote egg
membrane just inside the shell develops next to the shell, facilitate gas exchange
Function of the allantois in an amniote egg
forms a pouch garbage can gets rid of waste
In the placental mammals (all mammals except the marsupials and the monotremes), the developing embryo is still surrounded by membranes to provide the ideal environment
1)relatively unlimited nutrient & 0xy supply
2)waste and C02 removal
3)surrounded by its own aquatic environment
4) internal protection during the most vunerable period of life
Function of the yolk sac in a mammalian embryo
develops 1st, no yolk, forms empty cavity, produces the 1st blood cells, germ cells are set aside here
Function of the amnion in a mammalian embryo
surrounds the embryo and the yolk sac provides aquatic environment (ectoderm)
Function of the chorion in a mammalian embryo
encircles the developing embryo finger-like vili grow outward, branch, and penetrate the endometrium, then blood vessels form the placenta
Function of the allantois in a mammalian embryo
develops but its very small and largely vestigal mainly helps to form the umbilical cord (endoderm)
At what age is the embryo so human-like in appearance that it is then referred to as a fetus?
9 weeks
What are trimesters?
stages of pregnancy (3 months)
What are monozygotic twins?
1 fertilized egg that splits (identical)
What are dizygotic twins?
2 eggs were fertilized (fraternal)
Which type shares the same placenta?
Which type is more common?
Which type is identical to the mother?
Which type can develop into conjoined twins?
What is a teratogen?
anything that effects the fetus