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

51. Community Ecology

Introduction to Community Interactions

General Biology

51. Community Ecology

Introduction to Community Interactions

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2:11 minutes

Problem 4

Textbook Question

To ensure adequate nitrogen for a crop, a farmer would want to decrease _________ by soil bacteria.
a. Nitrification
b. Denitrification
c. Nitrogen fixation
d. a and c

Verified step by step guidance

Understand the nitrogen cycle: Nitrogen is an essential nutrient for plants, and its availability in the soil is influenced by processes carried out by soil bacteria, including nitrification, denitrification, and nitrogen fixation.

Define the processes: Nitrification is the conversion of ammonium (NH₄⁺) into nitrate (NO₃⁻) by bacteria, making nitrogen available to plants. Denitrification is the conversion of nitrate (NO₃⁻) into nitrogen gas (N₂), which removes nitrogen from the soil. Nitrogen fixation is the conversion of atmospheric nitrogen (N₂) into ammonium (NH₄⁺), making it usable by plants.

Analyze the question: The farmer wants to ensure adequate nitrogen for the crop. This means the farmer would want to prevent processes that reduce the availability of nitrogen in the soil.

Identify the relevant processes: Denitrification decreases nitrogen availability by converting nitrate into nitrogen gas, which escapes into the atmosphere. Nitrogen fixation, on the other hand, increases nitrogen availability, so decreasing it would not be beneficial for the crop.

Conclude the correct answer: The farmer would want to decrease denitrification (option b) to ensure adequate nitrogen for the crop. Option d (a and c) is incorrect because decreasing nitrogen fixation would reduce nitrogen availability, which is counterproductive.

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Key Concepts

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

Nitrification

Nitrification is the biological process by which ammonia is converted into nitrites and then into nitrates by soil bacteria. This process is crucial for the nitrogen cycle, as it transforms nitrogen into forms that plants can readily absorb. In the context of the question, decreasing nitrification would mean reducing the conversion of ammonia to nitrates, which could limit nitrogen availability for crops.

Denitrification

Denitrification is the process by which nitrates are reduced to nitrogen gas (N2) or, to a lesser extent, nitrous oxide (N2O) by soil bacteria. This process returns nitrogen to the atmosphere and decreases the amount of nitrogen available in the soil for plant uptake. In the context of the question, a farmer may want to decrease denitrification to retain more nitrogen in the soil for crop use.

Nitrogen Fixation

Nitrogen fixation is the process through which atmospheric nitrogen (N2) is converted into ammonia (NH3) by certain bacteria, making nitrogen available to plants. This process is essential for replenishing soil nitrogen levels, especially in agricultural systems. In the question, decreasing nitrogen fixation would also limit nitrogen availability, which is why it is included as a potential answer.