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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1:55 minutes

Problem 2

Textbook Question

In sperm competition, what is 'second-male advantage'?
a. The observation that when females mate with two males, each male fertilizes the same number of eggs
b. The observation that when females mate with two males, the second male fertilizes most of the eggs
c. The observation that females routinely mate with at least two males before laying eggs or becoming pregnant
d. The observation that accessory fluids prevent matings by second males—for example, by forming copulatory plugs

Verified step by step guidance

Understand the concept of sperm competition: Sperm competition occurs when the sperm of two or more males compete to fertilize the eggs of a female. This is common in species where females mate with multiple males.

Identify the term 'second-male advantage': This refers to a phenomenon observed in sperm competition where the second male to mate with a female has a higher chance of fertilizing the majority of the eggs.

Analyze the options given: We need to find the option that best describes the 'second-male advantage'.

Evaluate option b: 'the observation that when females mate with two males, the second male fertilizes most of the eggs'. This directly describes the second-male advantage, where the second male's sperm is more successful in fertilizing eggs.

Conclude that option b is the correct description of the 'second-male advantage', as it aligns with the definition of the term in the context of sperm competition.

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Key Concepts

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

Sperm Competition

Sperm competition refers to the biological phenomenon where the sperm of different males compete to fertilize the eggs of a female. This occurs when a female mates with multiple males, leading to a competitive environment for the sperm to achieve fertilization. It is a significant factor in sexual selection and can influence male reproductive strategies.

Second-Male Advantage

Second-male advantage is the observation that when a female mates with two males, the sperm of the second male often has a higher chance of fertilizing the eggs compared to the first male. This advantage can arise due to various factors, such as the timing of mating, sperm displacement, or physiological mechanisms that favor the second male's sperm.

Copulatory Plugs

Copulatory plugs are gelatinous secretions produced by males during mating that can block the female's reproductive tract, preventing subsequent matings by other males. This mechanism is a form of post-copulatory sexual selection, aimed at ensuring the first male's sperm has a better chance of fertilizing the eggs by physically obstructing other males' sperm.