Study Guide Answers: Animal Fertilization & Development
1. B,C,D 2. E 3. A 4. F 5. G
6. At the 2nd cleavage stage, the single cell zygote mitotically divides to the 2 cell stage but should stay together as a whole cluster of cells throughout future cleavages. When the single cell zygote divides into two cells, sometimes there is complete cleavage into 2 separate, single cells. These 2 cells then continue the cleavage process and fully develop into 2 identical embryos. A conjoined (Siamese) twin would have nearly full cleavage, but there is not complete separation so that there will be sharing of organs, etc. FYI: dizygotic (fraternal) twins result from 2 separate eggs being released from follicles with 2 separate sperm fertilizing the eggs.
7. ENDODERM: inner lining and organs of the digestive system, respiratory organs, glands such as liver and pancreas
MESODERM: notochord, muscles, excretory system, gonads, bones and cartilage, circulatory system
ECTODERM: skin, brain and nervous system
8. fertilization, zygote, cleavage, morula, blastula/differentiation, morphogenesis, gastrula, neurulation
9. Notochord à arises from mesoderm and will become the spinal column (the backbone)
Neural tube à arises from the ectoderm and will become the spinal cord (the nerves)
10. Egg activation à cell respiration increases and synthesis of new proteins; barrier formed by egg so that no new sperm can penetrate to add extra genetic material; zygote cytoplasm is rearranged
11. This pic is only 1 to 2 cells, but the point behind this question is for you to understand that there are individual proteins floating around in the cytoplasm. Depending on their location, they are “unfairly shared” during mitosis/cleavage. These proteins and chemicals can act as signals throughout the cell’s metabolism so that eventually, different cells will contain different signals and therefore different capabilities.
12. The uterus is the reproductive organ of the mother where the baby will develop
All other terms arise from the fertilized egg
The blastocyst contains the inner cell mass that will develop into the
Embryo, giving rise to the organism. The outer cells of the blastocyst
will implant into the uterine wall and are known as the chorion. These cells
will give rise to the placenta which will allow diffusion of nutrients and
waste into the uterine blood vessels of the mother.
The amnion and yolk are organized areas within the blastocyst that will
support the growing embryo. The yolk is an energy rich collection of lipids
and proteins in the cytoplasm of the egg. This structure is very early in the
development of humans and is diminished because of the formation of the
placenta. However, this structure remains in egg developing animals.
The amnion surrounds the embryo, cushioning the organism, and also
surrounds the umbilical arteries and veins
13. gamete, zygote, blastocyst, embryo, fetus, baby
GnRH – hypothalamus ; pituitary
FSH – pituitary; ovary
LH – pituitary; ovary
Estrogen – ovary or placenta; uterus
Progesterone – ovary or placenta; uterus
HCG – placenta; ovary
Oxytocin – pituitary; uterus
14. External refers to outside the body (remember, fertilization is a separate event from development). Both types of fertilization require moisture for success because sperm swim; both types involve a large number of sperm. However, the number of eggs needed for successful fertilization will vary. External fert. requires many eggs just like it requires many sperm. Internal fert. can rely on less eggs of high quality because predation and environmental factors are not a threat.
15. Mammals have hair and produce milk. They also have internal fertilization but not always internal development. These are the major characteristics in this unit. Other distinguishing characteristics: 4 chambered heart, endothermy, well-developed internal respiratory system and nervous system.
16/17 Female:
1. Ovary – produces eggs
2. Oviduct – connects ovary to uterus. Where fertilization takes place
3. Uterus – where fetus will develop
4. Bladder – unrelated to the reproductive system, but located nearby
5. Urethra – in females, unrelated to the internal reproductive system, separate opening
6. Vagina – opening to the uterus; where baby will exit during birth
Male
1. Penis – delivery mechanism of sperm that allows for internal fertilization
2. Testis – hormone and gamete production organ; semineferous tubules make-up the testes
3. Vas deferens – delivers sperm from testes, past prostate and seminal vesicles which will add semen liquid
4. Scrotum – skin that holds testes
5. Urethra – common duct of urinary and reproductive systems to exit male body
6. Bladder – excretory organ that serves to hold urine. Not involved in reproductive system, except for the proximity it has to other structures.
18. The picture should be labeled from 1 to 28 in clockwise fashion, where event A represents ovulation and should occur at day 14. Early structures near the top of the figure are the follicle; ovulation is event A, the corpus luteum is the structure following event A. LH and FSH are high to stimulate the follicle formation. Estrogen is also higher at the this point than at other places in the cycle
19. 3/4 represents day 1 of a cycle since this was the first day of menses. Ovulation would occur 14 days later (3/17). However, if you consider that a sperm could stay alive for 3 days, the range would be 3/15 – 3/20. It would be reasonable to extend this range a few days towards 3/22, remembering that the sperm fertilizes the egg within the oviduct. Since the egg will be in the oviduct for a few days, then the sperm has a better chance of interacting with the egg. Also, remember that every woman is different and that a perfectly regular 28 day schedule is seldom the case.
20. 3/4 plus 28 days would be 3/31
21. HCG hormone which indicates that a placenta is forming and implantation of a fertilized egg
22. progesterone, LH, estrogen