Ecosystems & Conservation Decisions — Chapter Practice, Grade 10

Analyze populations, food webs, cycles, disturbance, and evidence for conservation designs.

Problem 1

All the members of a single species living and interbreeding in the same area make up a
  1. community
  2. biome
  3. trophic level
  4. population
Answer and explanation

population

A population is one species in one area; a community is all the different populations together.

Problem 2

A bacterial colony starts with 200 cells and doubles every hour. Growing exponentially, how many cells are there after 4 hours?
Answer and explanation

3200 cells

N = 200 × 2⁴ = 200 × 16 = 3,200 cells.

Problem 3

On a logistic (S-shaped) growth curve, the population finally levels off at
  1. the carrying capacity
  2. twice the carrying capacity
  3. an ever-increasing value
  4. zero
Answer and explanation

the carrying capacity

Logistic growth flattens out at the carrying capacity (K), where birth and death rates roughly balance.

Problem 4

A tapeworm lives inside a dog's intestine, absorbing nutrients from the dog's food and gradually weakening the dog. This symbiotic relationship is an example of
  1. commensalism
  2. parasitism
  3. competition
  4. mutualism
Answer and explanation

parasitism

In parasitism one species benefits (the tapeworm) at the direct expense of the other (the dog).

Problem 5

Explain the difference between a density-dependent and a density-independent limiting factor, and give one example of each.
Answer and explanation

A density-dependent limiting factor grows stronger as a population becomes more crowded — for example, competition for food, disease, or predation. A density-independent limiting factor affects a population regardless of its density — for example, a hard freeze, a flood, or a wildfire. Density-dependent factors tend to pull a population back toward its carrying capacity, while density-independent factors can strike no matter how sparse or crowded the population is.

Problem 6

A population starts at 200, gains 30 births and 10 immigrants, and loses 20 deaths and 5 emigrants. Find the new size. Explain the reasoning in your own words.
Answer and explanation

215 individuals under the stated accounting.

Net change=30+10−20−5=15.

New size=200+15=215.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

A population gains 40 births and loses 55 deaths with no migration. What is net change? Show the reasoning, not just the conclusion.
Hints

Include both migration flows, not just births and deaths.

Answer and explanation

−15 individuals.

Problem 8

Why can density-dependent disease regulate growth differently from a sudden storm?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Transmission may increase with crowding, while a storm can affect populations regardless of density, depending on the event.

Problem 9

A loss can reduce abundance without regulating it in the same wayA loss can reduce abundance without regulating it in the same wayPer-individual loss rate (model units)02460204060Population density (model units)Density-dependent exampleDensity-independent example
Original selected loss-rate/density models, not universal storm or infection behavior.
Interpret the supplied visual. Why is a larger total number lost not alone evidence of density dependence?
Answer and explanation

More individuals can experience the same per-individual risk; density dependence concerns how that risk or effect changes with density.

A density-dependent effect changes per-individual impact with density, as selected competition or infection processes can. A density-independent event can affect abundance without that same dependence, though its final consequences still interact with conditions. A storm killing organisms does not automatically create feedback that restores a fixed population. Define the per-individual effect and compare densities under matched conditions. Changes in total losses can occur simply because more individuals are exposed even when the per-individual rate is unchanged.

More individuals can experience the same per-individual risk; density dependence concerns how that risk or effect changes with density.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 10

A population starts at 80, with 20 births, 12 deaths, 9 immigrants and 5 emigrants. Find final count, change and percentage change.
Answer and explanation

Final count is 80+20−12+9−5 = 92. Change is +12, or 12/80×100 = 15%, under the stated boundary and interval.

Final count is 80+20−12+9−5 = 92. Change is +12, or 12/80×100 = 15%, under the stated boundary and interval.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 11

OpenSciEd graph titled observed Masai giraffe numbers, 1977–2015 in Kenya, with a high early peak, lower later counts and sharp fluctuations; its displayed data credit names IUCN and Muller et al. (2018).
Historical observed Masai giraffe numbers in Kenya, OpenSciEd 7.5; retain the graph’s displayed IUCN/Muller et al. (2018) annotation. Historical Masai giraffe observations in Kenya · OpenSciEd · 7.5 Ecosystem Dynamics, Lesson 10 graph; data source retained in image, source, CC BY 4.0. Figure excerpt rendered from the PDF and resized for the web.
Compare the high early peak with the generally lower later counts, and identify one subinterval with an increase. Does every pair of endpoints show a decline? Explain why neither an increase nor a decline alone identifies a unique cause. State two details about survey methods/context that would help interpret the counts.
Answer and explanation

The high early peak exceeds 1,000 observed giraffes, while most later plotted counts are much lower. The record is not monotonic: a valid rise occurs just after the very low count near 2000. Trend descriptions depend on the chosen endpoints, so the early peak-to-later decline is not a claim that every possible interval declines. Neither a rise nor a decline isolates causality. Comparable survey area/effort, detection methods, dates/season and habitat or population movement information help interpret the counts.

Read the named organism, region, years and count axis.

Compare both a long interval and a specific rising segment rather than choose one convenient section.

Request sampling/detection and biological context before assigning a cause.

Response criteria

  • Compare the high early peak with later values, identify a rising segment and explain why endpoint choice matters.
  • Retain the organism/region/interval and observed-count meaning.
  • State two relevant monitoring details and a causal limitation.

Problem 12

An organism that makes its own food from sunlight, carbon dioxide, and water is best described as a(n)
  1. primary consumer
  2. decomposer
  3. autotroph
  4. heterotroph
Answer and explanation

autotroph

Autotrophs (producers) build their own food, usually through photosynthesis; heterotrophs must consume other organisms.

Problem 13

Producers in a pond store 60,000 kcal of energy. Using the 10% rule, how many kcal are available to the primary consumers?
Answer and explanation

6000 kcal

60,000 × 0.10 = 6,000 kcal.

Problem 14

If secondary consumers have 600 kcal of energy available, about how many kcal reach the tertiary consumers above them?
Answer and explanation

60 kcal

600 × 0.10 = 60 kcal.

Problem 15

Which trophic level in an energy pyramid has the LEAST usable energy available?
  1. Producers
  2. Primary consumers
  3. Secondary consumers
  4. Top predators
Answer and explanation

Top predators

Energy is lost at every step, so the top predators at the peak have the least energy available.

Problem 16

Use the 10% rule to explain why a given field of farmland can feed more people if it grows grain for humans than if it grows grain to raise cattle for beef.
Answer and explanation

When cattle eat grain, about 90% of the grain's energy is used for the cattle's own life processes or lost as heat, so only about 10% is stored as beef for people to eat. Eating the grain directly skips that lossy step, so far more of the field's captured energy actually reaches people — meaning the same land can feed many more of them.

Problem 17

A level contains 8000 kJ of production; supplied transfer efficiency to the next is 15%. Find the next level's production. Explain the reasoning in your own words.
Answer and explanation

1200 kJ under the supplied efficiency; remaining energy is not all converted into one identical output.

Convert 15% to 0.15.

8000×0.15=1200 kJ.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 18

A level produces 2000 kJ and transfer efficiency is 8%. Find next-level production. Show the reasoning, not just the conclusion.
Hints

Production transferred is only part of the total consumed-energy account.

Answer and explanation

2000×0.08=160 kJ.

Problem 19

Why do food-web arrows typically point from food to consumer?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

They represent transfer of matter and energy to the consumer; check the diagram's stated convention.

Problem 20

A small standing biomass can support a larger stock through rapid turnoverA small standing biomass can support a larger stock through rapid turnoverSupplied standing mass at one instantProducer standingbiomass20Consumer standingbiomass100Rapid producer turnover can replenish a small standing stock.Energy-flow rate and standing biomass are different quantities.
Original snapshot biomass example, not a measured aquatic ecosystem or a matched energy-flow pyramid.
Interpret the supplied visual. Does greater consumer standing mass imply energy was created between trophic levels?
Answer and explanation

No. Standing stock differs from production/transfer rate; rapid producer turnover and the stated time boundary matter.

Standing biomass is material present at one time; production is new material per time. A producer community can turn over rapidly, sustaining consumers while its instantaneous mass remains relatively small, as some aquatic comparisons show. Pyramids of numbers can also invert when many consumers depend on a few large producers. A conventional energy-transfer pyramid uses matched rates and boundaries, not the same snapshot quantity. Distinguish stocks, rates and organism counts before declaring a diagram impossible or generalizing to every system.

No. Standing stock differs from production/transfer rate; rapid producer turnover and the stated time boundary matter.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 21

A supplied chain transfers 15% of 8,000 kJ to its primary consumer level, then 8% of that to a secondary level. Calculate both outputs and explain why 10% should not replace the supplied values.
Answer and explanation

The outputs are 1,200 kJ and 96 kJ. The stated transfer fractions define this comparison; ten percent is an approximation, not a compulsory constant.

The outputs are 1,200 kJ and 96 kJ. The stated transfer fractions define this comparison; ten percent is an approximation, not a compulsory constant.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 22

Which process removes carbon dioxide from the atmosphere and stores its carbon in sugars?
  1. Photosynthesis
  2. Nitrogen fixation
  3. Combustion
  4. Cellular respiration
Answer and explanation

Photosynthesis

Photosynthesis absorbs carbon dioxide and builds it into sugars inside producers.

Problem 23

Nitrogen fixation is important because it
  1. breaks nitrates down into nitrogen gas
  2. converts nitrogen gas into a form plants can absorb
  3. releases carbon dioxide into the atmosphere
  4. turns liquid water into vapor
Answer and explanation

converts nitrogen gas into a form plants can absorb

Nitrogen fixation, done mainly by bacteria, converts unusable N₂ gas into ammonia and nitrates that plants can take up.

Problem 24

Air is about 78% nitrogen gas by volume. In a 500 mL sample of air, about how many milliliters are nitrogen gas?
Answer and explanation

390 mL

500 × 0.78 = 390 mL of nitrogen gas.

Problem 25

In the water cycle, water vapor released into the air from the leaves of plants is called
  1. condensation
  2. precipitation
  3. transpiration
  4. runoff
Answer and explanation

transpiration

Transpiration is water evaporating from plant leaves; it is a major source of atmospheric water vapor.

Problem 26

Explain how fertilizer washing off farm fields into a lake can end up killing the fish there.
Answer and explanation

The fertilizer adds extra nitrogen and phosphorus to the lake, which fuels an explosive bloom of algae. When the algae die, decomposer bacteria break them down and use up much of the dissolved oxygen in the water. With the oxygen depleted, fish and other aquatic animals suffocate. This process is called eutrophication.

Problem 27

Explain how excess nutrients can lead to low dissolved oxygen in a water body. Explain the reasoning in your own words.
Answer and explanation

Nutrient enrichment can promote blooms followed by oxygen depletion, depending on conditions.

Added nutrients can stimulate producer growth under limiting conditions.

Decomposition of added organic matter consumes oxygen faster than it is replenished.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 28

Distinguish a carbon reservoir of 1000 units from an input of 20 units/year. Show the reasoning, not just the conclusion.
Hints

Nutrients do not directly become oxygen depletion without a mechanism.

Answer and explanation

The reservoir is a stored amount; the input is a rate. They cannot be compared as the same quantity.

Problem 29

Why can matter cycle while energy needs ongoing input?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Atoms are reused among stores, while usable energy disperses and must be replenished.

Problem 30

Abundant atmospheric nitrogen needs suitable transformationsAbundant atmospheric nitrogen needs suitable transformationsAir N₂Usable compoundsBiomassMicrobial pathways: fixation, nitrification and denitrification differ.
Original selected nitrogen-route model, omitting several compounds and microbial pathways; it is not a full balanced nitrogen-cycle chemistry chart.
Interpret the supplied visual. Why does 78% nitrogen in air not mean a plant can directly build proteins from that N₂?
Answer and explanation

The appropriate chemical transformation and uptake pathway are needed; atmospheric abundance and usable form differ.

Nitrogen fixation converts atmospheric N₂ into forms that can enter biological nitrogen use. Nitrification and denitrification are different microbial transformations; denitrification can return nitrogen to gaseous forms under suitable conditions. Many plants take up nitrogen compounds rather than directly using N₂, with some relying on microbial associations. Availability depends on pathways, soil/water conditions and transport, not only the total nitrogen nearby. A diagram should trace compound forms and mechanisms rather than assign every microbial process the word fixation.

The appropriate chemical transformation and uptake pathway are needed; atmospheric abundance and usable form differ.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 31

A nitrogen store begins at 50 units and receives 12 while losing 9 each year for four years. Find its final amount and distinguish that result from the annual input.
Answer and explanation

The final store is 50+4×(12−9)=62 units. Twelve units/year is an input flux, not the stock or net annual gain; the net gain is three units/year.

The final store is 50+4×(12−9)=62 units. Twelve units/year is an input flux, not the stock or net annual gain; the net gain is three units/year.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 32

Worldwide, what is the single leading cause of species extinction and biodiversity loss?
  1. Collecting animals for zoos
  2. Too many decomposers
  3. Volcanic eruptions
  4. Habitat loss and fragmentation
Answer and explanation

Habitat loss and fragmentation

Destroying and fragmenting habitat removes the places species need to live and is the biggest driver of biodiversity loss.

Problem 33

Greenhouse gases such as carbon dioxide warm the planet because they
  1. absorb and re-radiate heat that would otherwise escape to space
  2. block sunlight from ever reaching Earth's surface
  3. cool the atmosphere by releasing oxygen
  4. destroy the ozone layer directly
Answer and explanation

absorb and re-radiate heat that would otherwise escape to space

Greenhouse gases let sunlight in but trap outgoing heat (infrared), re-radiating some of it back toward the surface and warming it.

Problem 34

A toxin is present at 0.02 ppm in algae and biomagnifies about 10 times at each trophic level. What is its concentration, in ppm, in a fish two trophic levels above the algae?
Answer and explanation

2 ppm

0.02 × 10 × 10 = 2 ppm.

Problem 35

Why do invasive species often grow out of control in a new ecosystem?
  1. Native species immediately go extinct on their own
  2. They arrive without the predators, diseases, and competitors that limited them back home
  3. They can survive without any energy source
  4. New ecosystems always have unlimited resources
Answer and explanation

They arrive without the predators, diseases, and competitors that limited them back home

Without their usual limiting factors, invasive populations can grow explosively and outcompete native species.

Problem 36

Describe two different actions — one personal and one societal — that promote sustainability, and explain how each reduces human impact on ecosystems.
Answer and explanation

A personal action is reducing, reusing, and recycling, which cuts the demand for raw materials and energy and lessens pollution and habitat destruction from extracting new resources. A societal action is shifting from fossil fuels to renewable energy like solar and wind, which lowers greenhouse gas emissions and slows climate change. Both meet human needs while using resources at a rate ecosystems can sustain, protecting biodiversity for the future. (Other valid answers include protecting habitat, sustainable farming or fishing, and using less water or energy.)

Problem 37

A wildlife corridor increases sightings but population size is unknown. What can be concluded? Explain the reasoning in your own words.
Answer and explanation

Use is plausible; population recovery is not established by sightings alone.

Sightings suggest corridor use, but detectability and sampling effort matter.

Population growth needs independent abundance or reproduction evidence.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 38

Why match runoff controls to water-quality threats instead of assuming a corridor solves them? Show the reasoning, not just the conclusion.
Hints

The success measure must match the conservation goal.

Answer and explanation

Different interventions address different mechanisms; connectivity does not necessarily reduce pollutant inputs.

Problem 39

What should a monitoring plan specify?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Baseline, indicators, comparable methods, timing, uncertainty and criteria for revising the intervention.

Problem 40

A larger count can reflect improved detection rather than recoveryA larger count can reflect improved detection rather than recoveryObserved individuals010203040500123Monitoring intervalChanged survey effortComparable reference
Original hypothetical monitoring-confound record, not actual conservation outcome data.
Interpret the supplied visual. Why is attributing the whole jump to protection uncertain when survey effort increased?
Answer and explanation

Detection changed with the intervention period and can increase counts; comparable sampling or modeled correction is needed.

Detection probability is the chance of observing a present organism under a sampling method. A count can rise when effort, access, season or tools change even without equal population growth. An intervention evaluation needs baseline and follow-up measurements with suitable comparison sites and comparable methods. Before–after evidence establishes temporal order but does not alone isolate cause. Several indicators can reveal tradeoffs that one abundance measure hides, including condition, reproduction, habitat quality and unintended effects.

Detection changed with the intervention period and can increase counts; comparable sampling or modeled correction is needed.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 41

After restoration, observed animals rise from 40 to 60, but survey effort doubles. Explain why a 50% recovery claim is not established and suggest a better evaluation.
Answer and explanation

The raw count rises 50%, but changed detection can contribute. Use comparable effort/methods, suitable reference sites and repeated population/condition indicators; estimate detection where appropriate before attributing recovery.

The raw count rises 50%, but changed detection can contribute. Use comparable effort/methods, suitable reference sites and repeated population/condition indicators; estimate detection where appropriate before attributing recovery.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 42

OpenSciEd historical American tree sparrow abundance-indicator graph with year-to-year changes and an overall decline, credited to Zeller et al. (2019) and Mass.gov; vertical units are not specified as a census count.
Historical abundance indicator from the OpenSciEd case; the vertical scale is not labeled as a population census or percentage. Historical American tree sparrow abundance indicator · OpenSciEd · 7.5 Ecosystem Dynamics, Lesson 10 graph; data source retained in image, source, CC BY 4.0. Figure excerpt rendered from the PDF and resized for the web.
Compare the source corn/soybean acreage graph in the lesson with this tree-sparrow indicator. Name their different variables, time coverage and vertical-unit limits. Explain why their broad patterns alone do not prove that planted acreage caused the entire bird trend, and propose a stronger comparison.
Answer and explanation

Acreage measures US land planted in millions of acres over 1997–2017; the bird indicator covers a longer selected historical period through 2019 and has no stated census/percentage unit. Their regions, methods and other conditions require clarification. Broad opposing patterns can motivate a habitat hypothesis, but matched local habitat/bird monitoring with comparable effort, relevant controls and alternative pressures would test causality more directly.

Keep land area separate from an abundance indicator.

Check years, area and method; do not convert the bird axis into percent without definition.

Propose comparable local surveys and control for detection/other pressures.

Response criteria

  • Identify the different variables and periods.
  • Do not invent a bird census or percentage unit.
  • Explain causal limits and propose appropriate matched evidence.

Problem 43

Cover falls from 60% to 30%. What is the decrease in percentage points?
Answer and explanation

30 percentage points

60 − 30 = 30; this differs from percent reduction.

Problem 44

Which evidence best tests a recovery claim?
  1. A time series and suitable comparison sites
  2. Only one decorative photo
  3. The species name alone
  4. A guaranteed endpoint
Answer and explanation

A time series and suitable comparison sites

Repeated and comparison evidence helps separate recovery from other changes.

Problem 45

Why might removing a predator affect plants?
Answer and explanation

Changes in herbivores can alter grazing, but other interactions may modify the response.

Problem 46

After a flood, species richness returns but nutrient retention remains low. Has every function recovered? Explain the reasoning in your own words.
Answer and explanation

No; different indicators reveal different aspects of recovery.

Richness is one structural indicator.

Nutrient retention measures a different function and remains altered.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 47

A predator decline precedes heavier grazing. What causal evidence would strengthen a food-web explanation? Show the reasoning, not just the conclusion.
Hints

Define recovery operationally instead of assuming one universal measure.

Answer and explanation

Repeated abundance and feeding data, comparisons and mechanisms that rule out alternative resource or climate changes.

Problem 48

Why can two disturbances close together impede recovery more than one?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

The second may arrive before populations, soils or resources recover, altering thresholds and trajectories.

Problem 49

Resistance and recovery describe different parts of a responseResistance and recovery describe different parts of a responseSelected system output index025507510001234Years around disturbanceA: large change / fast recoveryB: small change / slow recovery
Original resistance/recovery comparison with arbitrary output indices, not complete ecosystem restoration evidence.
Interpret the supplied visual. Which supplied model has lower resistance but faster recovery?
Answer and explanation

A changes from 100 to 20, then returns to 100 by year four; B changes less but has not returned in that interval.

Resistance describes how little a system changes during a specified disturbance. Recovery describes return of selected properties afterward. Resilience is used in several related ways, so define the sense and measured variable before comparing systems. A system can change strongly yet recover rapidly, while another changes little but recovers slowly. Returning one output to baseline does not guarantee identical species composition or restored every function. Compare reference variability and the time interval rather than rank ecosystems by one undefined resilience label.

A changes from 100 to 20, then returns to 100 by year four; B changes less but has not returned in that interval.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 50

A supplied system loses 80% of its output during disturbance and returns to its initial output after three years. Describe resistance and recovery and explain one limit of that evidence.
Answer and explanation

It has low resistance for this disturbance/output but relatively rapid recovery over the stated interval. Output recovery alone does not establish restored species composition or every ecological function.

It has low resistance for this disturbance/output but relatively rapid recovery over the stated interval. Output recovery alone does not establish restored species composition or every ecological function.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 51

A sample records counts 8, 4, 2, and 0 for four named species. How many were observed?
Answer and explanation

3 species

Only three have nonzero observed counts.

Problem 52

Which strengthens a before/after project evaluation?
  1. Comparable untreated sites and consistent sampling
  2. Changing methods every visit
  3. Only an expected result
  4. Removing all uncertainty statements
Answer and explanation

Comparable untreated sites and consistent sampling

Comparison sites help account for other changes.

Problem 53

Why might a cheaper conservation design not be the best choice?
Answer and explanation

It may fail important outcomes or impose other costs; compare criteria and constraints.

Problem 54

Site A yields 12 species in 1 h; B yields 18 in 4 h. Can you confidently rank their richness? Explain the reasoning in your own words.
Answer and explanation

No confident ranking follows from these counts alone.

Sampling effort differs and rare species need time to detect.

Use comparable effort or a method that accounts for detection before ranking.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 55

Why repeat surveys at comparable seasons and effort? Show the reasoning, not just the conclusion.
Hints

Observed count is not automatically total species present.

Answer and explanation

It improves comparability and helps distinguish real change from detection or timing effects.

Problem 56

A corridor is proposed for a pollution-driven decline. What must be checked?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Whether isolation is actually a limiting mechanism; the design must address the documented cause and measure relevant outcomes.

Problem 57

Monitoring criteria should be defined before results are inspectedMonitoring criteria should be defined before results are inspectedComparable habitat-use index0102030400123YearsIntervention siteReference site
Original matched-monitoring illustration, not an estimate of a real restoration effect.
Interpret the supplied visual. Why should failure/revision criteria be written before the outcome is known?
Answer and explanation

This limits selecting only favorable measures afterward and makes the evaluation transparent and testable.

A monitoring criterion states what result would support progress, reveal failure or trigger revision. Reference sites help distinguish intervention effects from broader changes, though they need comparable conditions and sampling. A before–after difference can be misleading when weather, detection or other pressures also change. Record methods, repeated observations and uncertainty before selecting favorable outcomes. A project’s activity count, such as materials installed, is not automatically evidence that the desired ecological mechanism occurred.

This limits selecting only favorable measures afterward and makes the evaluation transparent and testable.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 58

Two equal-area reserves have dimensions 100×100 m and 200×50 m. Find their perimeters and explain why shape alone cannot select the best design.
Answer and explanation

Their areas are 10,000 m² and perimeters 400 versus 500 m. Boundary exposure and width differ, but species, habitat quality, connectivity, disturbance, costs and goals determine the useful comparison.

Their areas are 10,000 m² and perimeters 400 versus 500 m. Boundary exposure and width differ, but species, habitat quality, connectivity, disturbance, costs and goals determine the useful comparison.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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