IB Biology Quiz: Apply Transfer Of Energy And Matter
19 questions · exam conditions
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Apply Transfer Of Energy And MatterQuestion 1 of 19

[HL] A herbivorous insect consumes 2500 J of plant material. 1200 J of this material is egested as faeces. The insect uses 1000 J for its own cellular respiration.

What is the Net Secondary Production (NSP) for this insect?

300 J
1000 J
1300 J
1500 J
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IB Biology Quiz

IB Biology Quiz: Apply Transfer Of Energy And Matter

Practice Apply Transfer Of Energy And Matter in IB Biology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

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This quiz focuses on Apply Transfer Of Energy And Matter, giving you a quick way to practice the rules, question types, and explanations that matter most for IB Biology.

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Question 1

[HL] A herbivorous insect consumes 2500 J of plant material. 1200 J of this material is egested as faeces. The insect uses 1000 J for its own cellular respiration.

What is the Net Secondary Production (NSP) for this insect?

  1. 300 J (correct answer)
  2. 1000 J
  3. 1300 J
  4. 1500 J
Explanation: First, calculate the assimilated energy, or Gross Secondary Production (GSP). GSP = Energy Consumed - Energy Egested = 2500 J - 1200 J = 1300 J. Next, calculate the Net Secondary Production (NSP), which is the energy converted to new biomass. NSP = GSP - Respiration = 1300 J - 1000 J = 300 J.

Question 2

An ecosystem's producers have a Gross Primary Production (GPP) of 20,000 kJ m⁻² yr⁻¹ and lose 12,000 kJ m⁻² yr⁻¹ through cellular respiration. Primary consumers in this ecosystem assimilate 800 kJ m⁻² yr⁻¹ from consuming the producers. What is the approximate trophic efficiency of energy transfer from the producers to the primary consumers?

  1. 4%
  2. 10% (correct answer)
  3. 40%
  4. 60%
Explanation: Trophic efficiency is the percentage of energy from one trophic level that is incorporated into the biomass of the next. First, calculate the Net Primary Production (NPP), which is the energy available to primary consumers: NPP = GPP - Respiration = 20,000 - 12,000 = 8,000 kJ m⁻² yr⁻¹. Then, calculate the efficiency: (Energy assimilated by primary consumers / NPP) * 100 = (800 / 8,000) * 100 = 10%.

Question 3

A farmer observes that corn plants are showing signs of chlorosis (yellowing leaves) despite the application of a fertilizer rich in ammonium (NH₄⁺). The field is heavily compacted and waterlogged. Which process in the nitrogen cycle is most likely inhibited, directly causing these symptoms?

  1. Nitrogen fixation
  2. Nitrification (correct answer)
  3. Denitrification
  4. Ammonification
Explanation: Nitrification is the aerobic process where bacteria convert ammonium (NH₄⁺) into nitrates (NO₃⁻), the form of nitrogen most readily absorbed by corn plants. In waterlogged, anaerobic soil, the bacteria responsible for nitrification cannot function effectively. Although ammonium was added, it is not being converted to the usable nitrate form, leading to nitrogen deficiency and chlorosis.

Question 4

[HL] A tropical rainforest has a Gross Primary Production (GPP) of 2,200 g C m⁻² yr⁻¹ and a Net Primary Production (NPP) of 1,000 g C m⁻² yr⁻¹. A temperate grassland has a GPP of 600 g C m⁻² yr⁻¹ and an NPP of 300 g C m⁻² yr⁻¹.

Based on the data provided, what can be deduced about the energy allocation in these two ecosystems?

  1. The temperate grassland is more efficient at converting solar energy into total biomass.
  2. The rainforest allocates a greater proportion of its gross production to respiration. (correct answer)
  3. The rate of decomposition must be higher in the temperate grassland than in the rainforest.
  4. The standing crop of producer biomass is greater in the grassland than in the rainforest.
Explanation: Respiration (R) can be calculated as GPP - NPP. For the rainforest, R = 2200 - 1000 = 1200. The proportion of GPP used for respiration is 1200/2200 ≈ 54.5%. For the grassland, R = 600 - 300 = 300. The proportion is 300/600 = 50%. Therefore, the rainforest allocates a greater proportion of its GPP to respiration.

Question 5

In a marine food web, sea otters prey on sea urchins, which in turn graze on large kelp forests. If a disease epidemic causes a drastic decline in the sea otter population, what is the most probable indirect effect on the transfer of energy within this ecosystem?

  1. Energy transfer to all other primary consumers that feed on kelp will be reduced. (correct answer)
  2. Energy transfer from producers to decomposers will decrease significantly.
  3. Energy transfer to the secondary consumer level will increase due to higher sea urchin biomass.
  4. Energy that was assimilated by sea otters will be immediately available to primary producers.
Explanation: This describes a trophic cascade. The decline in sea otters (the keystone predator) will lead to a rapid increase in the sea urchin population. The large number of sea urchins will overgraze the kelp forests, drastically reducing the total producer biomass. This loss of kelp means there is less energy available for all primary consumers that rely on it, not just the urchins.

Question 6

In an aquatic food chain, the concentration of a persistent toxin is 0.04 ppm in phytoplankton. Zooplankton that feed on phytoplankton have a concentration of 0.60 ppm. Small fish that feed on zooplankton have a concentration of 7.2 ppm. What is the biomagnification factor from the zooplankton to the small fish?

  1. 12 (correct answer)
  2. 15
  3. 120
  4. 180
Explanation: The question asks for the biomagnification factor specifically between zooplankton and small fish. This is calculated by dividing the concentration in the higher trophic level (small fish) by the concentration in the lower trophic level (zooplankton). Calculation: 7.2 ppm / 0.60 ppm = 12.

Question 7

An ecologist observes an open ocean ecosystem where the standing crop of phytoplankton (producers) is consistently lower than the standing crop of zooplankton (primary consumers), resulting in an inverted pyramid of biomass. What is the best explanation for this observation?

  1. The zooplankton have a much higher rate of respiration than the phytoplankton.
  2. The phytoplankton have an extremely high rate of reproduction and are consumed rapidly. (correct answer)
  3. Energy is transferred from zooplankton to phytoplankton in this specific ecosystem.
  4. The zooplankton supplement their diet through chemosynthesis, reducing reliance on producers.
Explanation: An inverted pyramid of biomass is possible when the producers have a very short lifespan and high reproductive rate (high turnover). Even though the phytoplankton biomass at any single moment is low, they reproduce so quickly that they can support a larger standing crop of longer-lived primary consumers. The pyramid of energy for this ecosystem would still be upright.

Question 8

Which statement best distinguishes the movement of energy from the movement of matter in ecosystems?

  1. Matter flows in a single direction from producers to consumers, while energy is recycled by decomposers.
  2. Energy is cycled between trophic levels, whereas matter is lost from the ecosystem primarily as heat.
  3. Both energy and matter are cycled, but energy cycles much faster than matter due to high metabolic rates.
  4. Energy flows unidirectionally and is dissipated as heat, whereas matter is cycled between biotic and abiotic pools. (correct answer)
Explanation: The fundamental difference is that energy flows through an ecosystem, typically entering as light and exiting as heat at each trophic level transfer, following the laws of thermodynamics. It does not cycle. In contrast, chemical elements (matter) like carbon, nitrogen, and phosphorus are finite and are continuously recycled between living organisms (biotic) and the non-living environment (abiotic).

Question 9

A forest ecosystem has the following annual carbon fluxes: absorption by photosynthesis is 15 GtC, release by plant respiration is 8 GtC, and release by soil and decomposer respiration is 6 GtC. Assuming no other major fluxes such as fire, what is the net ecosystem production (NEP) for this forest?

  1. A net source of 1 GtC per year
  2. A net sink of 1 GtC per year (correct answer)
  3. A net sink of 7 GtC per year
  4. The ecosystem is in carbon equilibrium
Explanation: Net ecosystem production (NEP) is the total carbon influx minus the total carbon outflux. Influx = Photosynthesis = 15 GtC. Outflux = Plant Respiration + Decomposer Respiration = 8 GtC + 6 GtC = 14 GtC. Therefore, NEP = 15 GtC - 14 GtC = +1 GtC. A positive value indicates that the ecosystem is accumulating carbon, acting as a net sink.

Question 10

The conversion of atmospheric nitrogen gas (N₂) into ammonia (NH₃) or ammonium (NH₄⁺) is an essential step in the nitrogen cycle. What is this process called, and why is it a limiting factor in many ecosystems?

  1. Denitrification; it is a slow process that permanently removes nitrogen from the ecosystem.
  2. Nitrification; it requires specific acidic soil conditions that are not widely found.
  3. Nitrogen fixation; it is an energetically expensive process carried out by only a few types of microorganisms. (correct answer)
  4. Ammonification; it relies on the decomposition of organic matter which varies greatly between ecosystems.
Explanation: The process of converting N₂ gas into ammonia/ammonium is called nitrogen fixation. The triple bond in N₂ is extremely strong, and breaking it requires a large amount of energy. Only a limited number of specialized prokaryotes (e.g., Rhizobium, cyanobacteria) can perform this conversion, making the availability of fixed nitrogen a major limiting factor for plant growth in many environments.

Question 11

Scientists measure the concentration of a pollutant in four species from a food web: Species A (0.05 ppm), Species B (1.5 ppm), Species C (25.0 ppm), and Species D (1.7 ppm). Given that species C preys on both B and D, and that both B and D prey on A, which species occupies the highest trophic level?

  1. Species A
  2. Species B
  3. Species C (correct answer)
  4. Species D
Explanation: Persistent pollutants biomagnify, meaning their concentration increases at successively higher trophic levels. Species A has the lowest concentration, suggesting it is the producer. Species B and D feed on A, making them primary consumers. Species C feeds on B and D, making it a secondary consumer. Consistent with this, Species C has the highest concentration of the pollutant, indicating it is at the highest trophic level in this food web.

Question 12

In aquatic ecosystems, carbon dioxide dissolves in water to form carbonic acid (H₂CO₃), which can then dissociate into hydrogen carbonate ions (HCO₃⁻). What is the primary significance of this chemical equilibrium for aquatic food webs?

  1. It ensures that the pH of the water remains stable, protecting organisms from acid stress.
  2. It provides an alternative source of inorganic carbon that aquatic producers can use for photosynthesis. (correct answer)
  3. It reduces the total amount of carbon available for producers, as most is sequestered as carbonic acid.
  4. It provides the energy required for chemosynthetic organisms to act as primary producers.
Explanation: Many aquatic producers, including algae and submerged plants, have adaptations (like the enzyme carbonic anhydrase) that allow them to utilize hydrogen carbonate ions (HCO₃⁻) as a source of carbon for photosynthesis, in addition to dissolved CO₂. This equilibrium makes a larger pool of inorganic carbon available for fixation into organic matter at the base of the aquatic food web.

Question 13

The Haber-Bosch process, used for industrial fertilizer production, converts atmospheric N₂ to ammonia (NH₃). What is the most direct and significant impact of the widespread use of these fertilizers on the global nitrogen cycle?

  1. It has caused a significant decrease in the atmospheric reservoir of N₂ gas, altering global climate patterns.
  2. It has increased the rate of denitrification in agricultural soils, leading to a net loss of nitrogen from the biosphere to the atmosphere.
  3. It has reduced the importance of decomposers in the nitrogen cycle, as plants no longer rely on ammonification for their nitrogen supply.
  4. It has dramatically increased the rate of nitrogen fixation, adding a massive new input of reactive nitrogen into terrestrial and aquatic ecosystems. (correct answer)
Explanation: The Haber-Bosch process is an artificial method of nitrogen fixation. Its industrial scale is so vast that it is estimated to have doubled the rate at which nitrogen is removed from the atmosphere and converted into reactive forms available to organisms. This massive influx of new nitrogen into the biosphere, far exceeding natural fixation rates, has profound effects on ecosystems, including eutrophication.

Question 14

[HL] Consider a caterpillar (an ectotherm) and a shrew (an endotherm) of similar body mass. Both animals assimilate 100 kJ of energy from their food.

Which is the most likely outcome regarding their net secondary production (NSP)?

  1. The shrew will have a higher NSP because endothermy allows for more efficient conversion of energy to biomass.
  2. The caterpillar will have a higher NSP because it allocates less assimilated energy to maintaining body temperature. (correct answer)
  3. Their NSPs will be nearly identical because they assimilated the same amount of energy from their food source.
  4. The shrew will have a higher NSP because its higher metabolic rate leads to faster growth and biomass accumulation.
Explanation: Net secondary production (NSP) is the assimilated energy minus the energy lost to respiration. Endotherms like shrews have high metabolic rates and expend a large proportion of their assimilated energy on respiration to maintain a constant internal body temperature. Ectotherms like caterpillars do not, so a much smaller proportion of their assimilated energy is lost to respiration. Consequently, the caterpillar will have more energy left over to allocate to growth and reproduction (NSP).

Question 15

In an effort to sequester atmospheric carbon, a large-scale reforestation project is undertaken on land previously used for grazing. Assuming other factors remain constant, which change in carbon fluxes is most likely to occur in this area during the first few decades of forest growth?

  1. The flux of carbon from the atmosphere to biomass will increase significantly. (correct answer)
  2. The flux of carbon from soil organic matter to the atmosphere will decrease to near zero.
  3. The flux of carbon from biomass to the atmosphere via combustion will show a net increase.
  4. The flux of carbon from the atmosphere into aquatic sinks in the region will increase.
Explanation: Reforestation involves planting trees, which have a high rate of photosynthesis. This process fixes atmospheric carbon dioxide (CO₂) into organic compounds (biomass). Therefore, the most significant and direct change will be an increased flux of carbon from the atmosphere into the growing plant biomass.

Question 16

A secondary consumer eats a primary consumer. The primary consumer's body contained 1000 kJ of energy. Due to metabolic inefficiencies, the secondary consumer only manages to convert 120 kJ of that energy into its own new biomass. What happened to the remaining 880 kJ of energy?

  1. It was returned to the primary producer level through nutrient cycling processes.
  2. It was egested as faeces and became available to decomposers in the ecosystem.
  3. It was stored as chemical energy in non-growing tissues like fat reserves for later use.
  4. It was converted into a larger amount of lower-quality energy (heat) and lost to the environment. (correct answer)
Explanation: The question specifies that the 1000 kJ was in the primary consumer's body, meaning it was already assimilated. The 120 kJ converted to new biomass is the net secondary production. The vast majority of the difference (assimilated energy minus production) is lost as heat during cellular respiration, a consequence of the second law of thermodynamics. While some energy might be egested if the 1000kJ was consumed not assimilated, the most significant loss from assimilated energy is respiratory heat.

Question 17

Peat bogs are characterized by acidic, waterlogged, and anaerobic conditions that inhibit the activity of decomposers. How does the formation of peat affect the global carbon cycle?

  1. It functions as a net carbon sink by significantly slowing the flux of carbon from dead biomass to the atmosphere. (correct answer)
  2. It functions as a net carbon source by increasing the rate of methanogenesis, releasing methane to the atmosphere.
  3. It has a neutral effect, as the reduced rate of photosynthesis in acidic conditions balances the reduced rate of decomposition.
  4. It increases the flux of carbon into aquatic systems as organic acids leach from the bog into surrounding waterways.
Explanation: The primary effect of peat bog conditions is the incomplete decomposition of organic matter. Plant biomass, which contains fixed carbon, accumulates over thousands of years instead of being respired by decomposers. This traps carbon that would otherwise be released as CO₂, making peat bogs a significant long-term carbon sink.

Question 18

Which statement provides the most fundamental, universal reason for the progressive loss of energy at each successive trophic level in an ecosystem?

  1. A significant portion of biomass at each level is not consumed and instead becomes detritus.
  2. Not all consumed biomass can be assimilated and is egested as waste.
  3. Energy is converted into heat during metabolic activities in accordance with the second law of thermodynamics. (correct answer)
  4. Predators must expend energy to hunt and capture their prey, which reduces net energy gain.
Explanation: While choices A, B, and D describe valid ways in which energy is lost from a trophic pathway, the most fundamental reason is rooted in physics. The second law of thermodynamics states that in any energy conversion, some energy is lost as unusable heat. Cellular respiration, the process by which all organisms release energy from food, is an energy conversion that releases a significant amount of heat. This is a universal and unavoidable loss at every trophic level.

Question 19

Food chains are generally limited to four or five trophic levels. Which hypothetical change to an ecosystem would most likely allow for the support of a viable population at a sixth trophic level?

  1. An increase in the average metabolic rate of consumers at each trophic level.
  2. An increase in the average body size of organisms at all trophic levels.
  3. A decrease in the total biomass of decomposers in the ecosystem.
  4. A significant increase in the net primary production of the ecosystem. (correct answer)
Explanation: The length of a food chain is limited by the amount of energy available at its base. Due to the ~90% energy loss at each trophic transfer, there is insufficient energy to support a viable population at higher levels. If the net primary production (the energy captured by producers) were to increase significantly, there would be more energy available at the base of the food web, which could potentially be enough to be transferred up through the trophic levels to support a sixth level.