Relationships & Biomes
A tapeworm obtains nutrients inside a mammal, reducing the nutrients available to its host. Identify the relationship.
Parasitism, the tapeworm benefits and the host is harmed.
Which microscopic ocean producers release dissolved oxygen through photosynthesis?
Phytoplankton
Name the process that releases water vapor from plant leaves into the atmosphere.
Transpiration
What measures all chemical energy captured by producers through photosynthesis?
Gross primary productivity (GPP)
In grass → cricket → frog → snake, identify the herbivore and its trophic role.
Cricket; primary consumer
Root-associated fungi receive sugars from a plant and help the plant absorb minerals. Identify the relationship and explain your choice.
Mutualism: both organisms benefit.
A submarine moves from the sunlit surface ocean to water 4,500 meters deep. Describe the changes in light and pressure.
Light decreases; pressure increases.
What process takes in atmospheric carbon dioxide into glucose, and what process releases carbon dioxide as organisms break down glucose for energy?
Photosynthesis takes in carbon; cellular respiration releases it.
What must be subtracted from GPP to calculate NPP?
Respiration (R)
Why are decomposers essential to ecosystems, even though they do not return usable energy to producers?
They recycle nutrients from dead material and waste. Energy flows through ecosystems and eventually dissipates as heat.
Two bird species use the same limited supply of tree cavities for nesting. Identify their interaction and predict what happens if suitable cavities become more scarce.
Competition; it increases as nesting sites become scarcer.
Why does atmospheric carbon dioxide enter the ocean directly through surface water rather than through deep water?
Surface water contacts the atmosphere, allowing carbon dioxide to dissolve across the air–water boundary.
Why can forests and oceans function as carbon sinks? Give one way each takes up carbon.
They can take up more carbon than they release.
Forests incorporate carbon through photosynthesis; oceans take up dissolved carbon dioxide and support photosynthetic producers.
Producers capture 21,000 kJ/m²/year and use 8,000 kJ/m²/year for respiration. Calculate NPP.
13,000 kJ/m²/year
Producers contain 60,000 kg of biomass. Assuming a 10% transfer between trophic levels, estimate the biomass of secondary consumers.
600 kg = 60,000 × 0.10 × 0.10.
A forest in Russia is dominated by evergreen conifers. A forest in the Appalachian Mountains is dominated by broadleaf trees that lose their leaves seasonally. Identify both biomes.
Russia: boreal forest/taiga
Appalachians: temperate deciduous forest
Why can shallow coastal waters support greater biodiversity than nearby deep-ocean waters? Give two reasons.
Any two: sunlight, nutrient inputs, greater primary productivity, or varied habitats.
Bacteria convert soil nitrate into nitrogen gas. Name the process and explain its effect on nitrate available to plants.
Denitrification; it decreases plant-available nitrate by transferring nitrogen into the atmosphere.
Habitat A has an NPP of 4,500 kcal/m²/year. Habitat B has an NPP of 6,000 kcal/m²/year. Both have a GPP of 10,000 kcal/m²/year. Which uses more energy for producer respiration, and by how much?
Habitat A, by 1,500 kcal/m²/year.
A’s respiration is 5,500; B’s is 4,000.
Only a fraction of the energy a rabbit consumes becomes new rabbit biomass. Explain why this is consistent with the second law of thermodynamics.
Energy transformations release heat, reducing usable energy. Energy also supports metabolism or remains in waste and uneaten material.
A fungus absorbs nutrients from a living tree and reduces its growth. Another fungus exchanges soil minerals for sugars from tree roots, improving the growth of both organisms. Identify each relationship and predict how removing each fungus would affect its tree.
The first relationship is parasitism; removing that fungus should improve tree growth.
The second is mutualism; removing that fungus could reduce mineral uptake and tree growth.
A student claims that ocean photosynthesis occurs equally at all depths and that zooplankton produce most of the ocean’s biological oxygen. Correct both claims.
1. Photosynthesis requires light and occurs mainly in the photic zone.
2. Phytoplankton produce much of the ocean’s biological oxygen; zooplankton consume oxygen through respiration.
Unlike carbon and nitrogen, phosphorus has no significant gaseous phase in its cycle. How does phosphorus typically enter an ecosystem, and why can its supply limit plant growth?
Phosphorus enters through the weathering of rocks, which releases phosphate. This process is slow, so available phosphate may not meet plants’ needs, limiting growth.
The open ocean has low net primary productivity per square meter but contributes greatly to Earth’s total primary production. Explain how both statements can be true.
The open ocean covers an enormous area, so low productivity per square meter adds up to a large amount of total production.
1. Approximately what percentage of incoming sunlight is typically converted into chemical energy by photosynthesis: 1%, 30%, or 95%?
2. Using that approximation, calculate the chemical energy captured from 700,000 kJ of sunlight.
3. Estimate the energy reaching secondary consumers using the 10% rule.
1. 1%
2. Producers capture 7,000 kJ
3. Secondary consumers receive approximately 70 kJ = 7,000 × 0.10 × 0.10.