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

48. Ecology

Introduction to Ecology

General Biology

48. Ecology

Ecology

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Multiple Choice

After nutrient enrichment from sewage contamination, a lake often becomes inhospitable to fish. Why?

Nutrient input to a lake causes the explosive growth of algal and cyanobacterial populations. This reduces the penetration of light into the lake, the water temperature falls, and eventually the fish population dies.

Nutrient input to a lake poisons the fish.

Nutrient input to a lake poisons the organisms that fish eat.

Nutrient input causes the death of algae and cyanobacteria and, thus, the ultimate sources of organic compounds in a lake ecosystem. Eventually, this reduces the availability of food for fish within the lake, leading to their death.

Nutrient input to a lake causes the explosive growth of algal and cyanobacterial populations. Decomposition of dead algae and cyanobacteria by bacteria results in the depletion of oxygen in the water, which leads to the death of fish.

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Verified step by step guidance

Understand the concept of nutrient enrichment: Nutrient enrichment, often from sources like sewage, introduces excess nutrients such as nitrogen and phosphorus into aquatic ecosystems.

Recognize the effect of nutrient enrichment on algae and cyanobacteria: These nutrients promote the rapid growth of algae and cyanobacteria, a phenomenon known as algal bloom.

Consider the impact of algal blooms on the ecosystem: The dense growth of algae and cyanobacteria can block sunlight from penetrating the water, affecting photosynthesis in aquatic plants.

Analyze the role of decomposition: When algae and cyanobacteria die, they are decomposed by bacteria. This process consumes a significant amount of dissolved oxygen in the water.

Connect oxygen depletion to fish mortality: The depletion of oxygen, known as hypoxia, creates an inhospitable environment for fish and other aerobic organisms, leading to their death.