Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 40m
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 12m
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

11. Cell Division

Introduction to Cell Division

General Biology

11. Cell Division

Introduction to Cell Division

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Multiple Choice

Normally, menstruation occurs when which of the following events takes place?

The fertilized egg implants successfully in the uterine lining

The levels of estrogen and progesterone decrease due to the degeneration of the corpus luteum

Ovulation is triggered by a surge in luteinizing hormone (LH)

The endometrial lining thickens in preparation for implantation

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Verified step by step guidance

Understand the menstrual cycle: The menstrual cycle is divided into phases, including the follicular phase, ovulation, luteal phase, and menstruation. Menstruation occurs when the uterine lining (endometrium) is shed due to hormonal changes.

Identify the role of the corpus luteum: After ovulation, the corpus luteum forms from the ruptured follicle and secretes estrogen and progesterone. These hormones maintain the thickened endometrial lining in preparation for a potential pregnancy.

Recognize the trigger for menstruation: If fertilization does not occur, the corpus luteum degenerates, leading to a significant drop in estrogen and progesterone levels. This hormonal decrease causes the endometrial lining to break down and shed, resulting in menstruation.

Eliminate incorrect options: Implantation of a fertilized egg in the uterine lining prevents menstruation by maintaining high levels of progesterone. Similarly, ovulation and endometrial thickening are preparatory steps in the cycle, not triggers for menstruation.

Conclude the correct answer: Menstruation occurs when the levels of estrogen and progesterone decrease due to the degeneration of the corpus luteum, as this hormonal drop initiates the shedding of the uterine lining.