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39 Cards in this Set
- Front
- Back
Fact
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The nucleus of the sperm fuses with the nucleus of the egg, making the new, fused nucleus diploid
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Fact
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The product of fertilization = a zygote (one cell stage)It contains all the necessary DNA for a new organism
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Why is the zygote surrounded by a fertilization membrane immediately after the sperm penetrates the plasma membrane of the ovum?
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so that no more sperm can get in
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Through the process of _____ the zygote is changed into a mulitcellular embryo.
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cleavage
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Fact
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Cleavage is a special form of rapid cell division with no cell growth between the divisions.
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Fact
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This results in an increased cell number, but decreased individual cell size, the overall embryo size changes very little
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Morula
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stems cells, many cells solid ball cluster
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blastula
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more division and getting smaller in denssity but now is hollow and has cavity
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Gastrula
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cells migrate inward until against top row of cells beginning of gastrointestinal tract
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neurula
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forming the nervous system
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At which stage is a human embryo when it implants in the thickened uterine lining?
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zygote?
morula |
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What happens if fertilization occurs too late in the cycle?
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wont develop fully
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What happens if fertilization occurs too early?
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get stuck in the follopian tube
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At which stage do you first have two tissue layers?
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gastrula
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Endoderm develops into ______
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intestinal tract
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ectoderm develops into ______
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skin, nervous system, nails, hair, teeth
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mesoderm develops into ______
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muscles and skeleton, circulatory system
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When the embryo is developing in an aquatic environment, it has several advantages, what are they
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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 |
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What is the major disadvantage to embryonic development in an aquatic environment?
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predation
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Terrestrial organisms that evolved needed to stimulate the advangageous conditions.
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The amniote egg simulates an aquatic environ by surrounding the embryo with a series of extra-embryonic membranes
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The four extra-embryonic membranes are not actually part of the embryo, but develop from it.
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Each membrane is formed from 2 of the 3 tissue layers from the embryo (endo, meso, and ectoderm)
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Function of the yolk sac in an amniote egg
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surrounds yolk, digest the yolk, transport it to the embryo formed of meso, blood vessels and ectoderm
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Function of the amnion in an amniote egg
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surrounds embryo filled with water, provides an aquatic environment
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Function of the chorion in an amniote egg
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membrane just inside the shell develops next to the shell, facilitate gas exchange
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Function of the allantois in an amniote egg
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forms a pouch garbage can gets rid of waste
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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
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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 |
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Function of the yolk sac in a mammalian embryo
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develops 1st, no yolk, forms empty cavity, produces the 1st blood cells, germ cells are set aside here
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Function of the amnion in a mammalian embryo
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surrounds the embryo and the yolk sac provides aquatic environment (ectoderm)
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Function of the chorion in a mammalian embryo
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encircles the developing embryo finger-like vili grow outward, branch, and penetrate the endometrium, then blood vessels form the placenta
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Function of the allantois in a mammalian embryo
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develops but its very small and largely vestigal mainly helps to form the umbilical cord (endoderm)
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At what age is the embryo so human-like in appearance that it is then referred to as a fetus?
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9 weeks
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What are trimesters?
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stages of pregnancy (3 months)
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What are monozygotic twins?
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1 fertilized egg that splits (identical)
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What are dizygotic twins?
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2 eggs were fertilized (fraternal)
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Which type shares the same placenta?
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monozygotic
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Which type is more common?
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fraternal
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Which type is identical to the mother?
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neither
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Which type can develop into conjoined twins?
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monozygotic
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What is a teratogen?
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anything that effects the fetus
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