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

52. Ecosystems

Introduction to Ecosystems

General Biology

52. Ecosystems

Introduction to Ecosystems

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2: minutes

Problem 8

Textbook Question

Explain why it is more energy efficient (in terms of the amount of total NPP required) to eat a pound of tofu (bean curd) than a pound of hamburger.

Verified step by step guidance

Step 1: Understand the concept of Net Primary Productivity (NPP). NPP is the amount of energy that plants, or primary producers, store as biomass after accounting for the energy they use during respiration. This energy is available to the next trophic level in the food chain, which are the herbivores or primary consumers.

Step 2: Recognize that energy transfer between trophic levels is inefficient. Only about 10% of the energy stored as biomass in one trophic level is transferred to the next. This is known as the 10% rule in ecology.

Step 3: Understand that tofu is made from soybeans, which are primary producers. When we consume tofu, we are consuming energy directly from the first trophic level.

Step 4: Understand that a hamburger is made from beef, which comes from cows. Cows are primary consumers, as they eat grass, a primary producer. When we consume a hamburger, we are consuming energy from the second trophic level.

Step 5: Conclude that eating a pound of tofu requires less total NPP than eating a pound of hamburger because energy transfer between trophic levels is inefficient. By eating tofu, we are consuming energy directly from the first trophic level, whereas eating a hamburger involves an additional step of energy transfer, resulting in more energy loss.

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Key Concepts

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

Net Primary Productivity (NPP)

Net Primary Productivity (NPP) refers to the amount of organic matter or biomass produced by plants through photosynthesis, minus the energy used in respiration. It is a crucial measure of ecosystem productivity, indicating how much energy is available to support herbivores and higher trophic levels. Higher NPP means more energy is available for consumption, making plant-based foods like tofu generally more energy-efficient than animal-based foods.

Trophic Levels

Trophic levels represent the hierarchical positions in a food chain, where energy is transferred from producers to consumers. In a typical food chain, energy decreases as it moves up trophic levels due to energy loss at each stage, primarily through metabolic processes. Since tofu is derived from plants (producers), it requires less energy input compared to hamburger, which comes from animals (higher trophic levels) that consume multiple levels of plants.

Energy Transfer Efficiency

Energy transfer efficiency refers to the percentage of energy that is passed from one trophic level to the next. This efficiency is typically low, averaging around 10%, meaning that only a small fraction of energy is available to the next level. Consequently, consuming plant-based foods like tofu is more energy-efficient than consuming animal products like hamburger, as less total NPP is required to produce the same amount of food.

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Related Practice

Textbook Question

The web of life refers to the

a. Evolutionary relationships among living organisms

b. Connections between species in an ecosystem

c. Complicated nature of genetic variability

d. Flow of information from parent to child

e. Predatory effect of humans on the rest of the natural world

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Textbook Question

Which of the following would be considered an example of bioremediation?

a. Adding nitrogen-fixing microorganisms to a degraded ecosystem to increase nitrogen availability

b. Using a bulldozer to regrade a strip mine

c. Reconfiguring the channel of a river

d. Adding seeds of a chromium-accumulating plant to soil contaminated by chromium

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Textbook Question

Why are the open oceans nutrient poor? Why are coastal areas and intertidal habitats relatively nutrient rich?

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Textbook Question

If you applied a fungicide to a cornfield, what would you expect to happen to the rate of decomposition and net ecosystem production (NEP)?

a. Both decomposition rate and NEP would decrease.

b. Neither would change.

c. Decomposition rate would increase and NEP would decrease.

d. Decomposition rate would decrease and NEP would increase.

For which chemicals are biogeochemical cycles global? Explain.

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Textbook Question

Most of the nutrients available for plant growth in an ecosystem are

a. Deposited in rain

b. Made available through the recycling of decomposers

c. Maintained within that ecosystem over time

d. B and C are correct

e. A, B, and C are correct

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Textbook Question

What roles do bacteria play in the nitrogen cycle?

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Textbook Question

Use Figures 34.5C and 34.18 to predict how global warming (rapid increase in Earth's average temperature; see Module 7.14) might affect the water cycle.

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