Chapter 37 Animal development
Terms
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- Fact
- This results in an increased cell number, but decreased individual cell size, the overall embryo size changes very little
- 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
- Morula
- stems cells, many cells solid ball cluster
- blastula
- more division and getting smaller in denssity but now is hollow and has cavity
- Gastrula
- cells migrate inward until against top row of cells beginning of gastrointestinal tract
- neurula
- forming the nervous system
- At which stage is a human embryo when it implants in the thickened uterine lining?
-
zygote?
morula - 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?
- gastrula
- 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?
- predation
- 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?
- monozygotic
- Which type is more common?
- fraternal
- Which type is identical to the mother?
- neither
- Which type can develop into conjoined twins?
- monozygotic
- What is a teratogen?
- anything that effects the fetus