Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

44. Animal Reproduction

Animal Reproduction

General Biology

44. Animal Reproduction

Animal Reproduction

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3:21 minutes

Problem 15

Textbook Question

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?
Use Table 47.2 to compare and contrast the mechanisms of action of emergency contraception and mifepristone to that of the pill. Which methods act as contraception and which act to terminate a pregnancy? Explain.

Verified step by step guidance

The mechanism of action of 'the pill' involves the use of synthetic hormones similar to progesterone and estradiol to prevent ovulation. The pill works by maintaining consistent hormone levels that inhibit the release of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH), which are necessary for ovulation.

Analyze the provided image: The graph shows hormone concentrations before and while using the pill. FSH and LH levels are significantly lower while using the pill, indicating suppression of ovulation. Estradiol and progesterone levels are also reduced, supporting the prevention of the natural menstrual cycle and ovulation.

Emergency contraception typically uses higher doses of hormones to prevent ovulation or fertilization after unprotected intercourse. It acts as contraception by preventing pregnancy before it occurs.

Mifepristone, on the other hand, is used to terminate an existing pregnancy. It works by blocking the action of progesterone, a hormone crucial for maintaining pregnancy, leading to the breakdown of the uterine lining and termination of the pregnancy.

In summary, 'the pill' and emergency contraception act as contraceptive methods by preventing ovulation and fertilization, while mifepristone acts to terminate a pregnancy by disrupting the hormonal environment necessary for its continuation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mechanism of Action of Oral Contraceptives

Oral contraceptives, commonly known as 'the pill', primarily work by delivering synthetic hormones that inhibit ovulation. These hormones, typically a combination of estrogen and progestin, prevent the release of eggs from the ovaries. Additionally, they thicken cervical mucus to block sperm entry and alter the uterine lining to prevent implantation, thus effectively preventing pregnancy.

Emergency Contraception

Emergency contraception (EC) methods, such as levonorgestrel or ulipristal acetate, are designed to prevent pregnancy after unprotected intercourse. They primarily work by delaying or inhibiting ovulation, ensuring that no egg is released for fertilization. Unlike the regular contraceptive pill, EC is used post-coitus and is not intended for regular use, making it a critical option for preventing unintended pregnancies.

Mifepristone and Pregnancy Termination

Mifepristone, often used in combination with misoprostol, is a medication that terminates an early pregnancy. It works by blocking the hormone progesterone, which is essential for maintaining the uterine lining during pregnancy. By disrupting this hormonal support, mifepristone leads to the detachment of the embryo and subsequent expulsion from the uterus, distinguishing it from contraceptive methods that prevent pregnancy rather than terminate it.

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Textbook Question

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?

Scientists confirmed the pill's mechanism of action by measuring plasma hormone levels in women before and after they went on the pill (* means P<0.05, ** means P<0.01, and *** means P<0.001). Do the data shown here support the hypothesis that the pill affects hormonal signaling?

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Textbook Question

The embryos of reptiles (including birds) and mammals have systems of extraembryonic membranes. What are the functions of these membranes, and how do fish and frog embryos survive without them?

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Textbook Question

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Use the information in the graph to explain how the pill affects each of the following: (a) maturation of a follicle, (b) thickening of the uterine lining during the follicular phase, (c) probability of ovulation, and (d) volume of menstrual fluid.

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Textbook Question

Compare sperm formation with egg formation. In what ways are the processes similar? In what ways are they different?

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Textbook Question

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Imagine that four different contraceptives are under development. One blocks ovulation, one blocks fertilization, one blocks cleavage, and one blocks implantation. In the United States, which contraceptive is likely to be the least controversial to bring to market? Why?

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Multiple Choice

Which form of reproduction can result from damage to the original animal?

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Multiple Choice

Which term refers to the production of offspring in animals?

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Multiple Choice

The female reproductive and endocrine systems work interactively for which main purpose?

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