Question 1
Biodiversity exists at several connected levels.
State the three levels of biodiversity.
[3]
Question 2
Figure 1 shows the abundance of four species in each of two communities. Each community contains 100 individuals.
Identify which community has the greater species evenness.
[1]
Outline why the two communities have equal species richness but different species diversity.
[2]
Question 3
A woodland contains several tree species that perform similar ecological roles. Following a disease outbreak, one tree species declines substantially.
Explain how species diversity may increase the resilience of this woodland.
[3]
Question 4
Mutation and sexual reproduction are both sources of genetic diversity.
Distinguish between how mutation and sexual reproduction increase genetic diversity.
[3]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 5
A population of insects contains heritable variation in resistance to an insecticide. The insecticide kills most susceptible insects, but some resistant insects survive.
Define an adaptation.
[1]
Explain how natural selection could increase insecticide resistance in this population.
[3]
Question 6
A new river divides a population of small mammals. The environments on opposite sides of the river have different climates and food resources.
Explain how the divided population could eventually form two species.
[4]
Question 7
The fossil record indicates that mass extinctions have sometimes been followed by relatively rapid diversification of surviving groups.
Explain why a mass extinction may be followed by a rapid rate of speciation.
[3]
Question 8
A crop variety has been bred repeatedly from a small number of parent plants selected for uniform ripening and high yield.
State why this is an example of artificial selection.
[1]
Explain how this breeding programme could reduce the resilience of the crop variety.
[3]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 9
The Vardal floodplain reserve was restored after decades of drainage and grazing. Drainage channels were blocked in 2015, native vegetation was planted and livestock were excluded. The maps are schematic representations of selected land cover and are not a complete inventory of the habitat types recorded by the survey; use the table for the numerical biodiversity indicators.
Calculate the percentage increase in wetland habitat area between 2015 and 2024.
[2]
Describe two changes in biodiversity shown by the data.
[2]
Explain how the changes in biodiversity may increase the ecological resilience of the reserve.
[3]
Evaluate the evidence that restoration has increased the biodiversity and resilience of the reserve.
[4]
Question 10
The mottled ground beetle has heritable light and dark body-colour forms. In 2018, dark furnace material was deposited on the ground surrounding an industrial site. A rural control site retained pale sandy soil. Beetles were surveyed for six generations.
Describe the change in the frequency of the dark form at the two sites.
[2]
Calculate the difference between the percentage-point changes in dark-form frequency at the two sites.
[1]
Explain how natural selection could have produced the change at the industrial site.
[4]
Discuss whether the data provide sufficient evidence that natural selection caused the observed change.
[3]
Question 11
Ecologists used equal-sized quadrats and equal sampling effort to record four plant species at two grassland sites.
Plant abundance recorded at two grassland sites.
| Site | Species P | Species Q | Species R | Species S | Total abundance |
|---|---|---|---|---|---|
| Site A | 20 | 20 | 20 | 20 | 80 |
| Site B | 65 | 5 | 5 | 5 | 80 |
| Simpson's reciprocal index | |||||
| Definitions | : total individuals | : individuals of one species |
State the species richness of each site.
[1]
Calculate Simpson's reciprocal index, , for Site A. Show your working.
[2]
Calculate Simpson's reciprocal index, , for Site B. Show your working.
[2]
Compare the species diversity of the two sites using the data.
[2]
Question 12
Two coastal ecosystems were monitored for four years after the same cyclone. Ecosystem function is expressed as a percentage of its pre-cyclone value.
Coastal ecosystem function and biodiversity measures at two sites monitored after a cyclone.
| Measure | High-diversity site | Low-diversity site |
|---|---|---|
| Ecosystem function before cyclone / % | 100 | 100 |
| Ecosystem function immediately after cyclone / % | 45 | 45 |
| Ecosystem function after 1 year / % | 68 | 52 |
| Ecosystem function after 2 years / % | 86 | 58 |
| Ecosystem function after 3 years / % | 96 | 61 |
| Ecosystem function after 4 years / % | 99 | 63 |
| Number of habitat types | 6 | 2 |
| Number of common species | 18 | 9 |
| Mean genetic heterozygosity | 0.72 | 0.31 |
| Monitoring effort | Equal | Equal |
Calculate the difference in ecosystem function between the two sites two years after the cyclone.
[1]
Describe the recovery of the two sites after the cyclone.
[2]
Using the data, explain how the three components of biodiversity may have contributed to the different recovery rates.
[3]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 13
A lizard population contains heritable dark and pale skin-colour variants. A wildfire darkened the ground in one part of its habitat. Birds prey on lizards in both the burned and unburned areas.
Skin colour is inherited; immigration between the burned and unburned areas is negligible.
| Area | Measure | Generation 0 | Generation 1 | Generation 2 | Generation 3 | Generation 4 |
|---|---|---|---|---|---|---|
| Burned | Dark lizards / % of population | 20 | 32 | 47 | 61 | 72 |
| Unburned | Dark lizards / % of population | 20 | 21 | 19 | 22 | 20 |
| Burned | Dark lizards / mean surviving offspring per adult | Not measured | 4.8 | Not measured | Not measured | Not measured |
| Burned | Pale lizards / mean surviving offspring per adult | Not measured | 2.1 | Not measured | Not measured | Not measured |
| Unburned | Dark lizards / mean surviving offspring per adult | Not measured | 2.3 | Not measured | Not measured | Not measured |
| Unburned | Pale lizards / mean surviving offspring per adult | Not measured | 4.6 | Not measured | Not measured | Not measured |
Calculate the percentage-point increase in dark-coloured lizards in the burned area from generation 0 to generation 4.
[1]
Describe the change in the frequency of dark-coloured lizards in the two areas.
[2]
Explain how natural selection produced the observed change in the burned area.
[4]
Question 14
A conservation agency combined citizen-science records and professional surveys to monitor a threatened wetland frog in four sectors of a protected landscape.
Citizen-science observations and the proportion verified as correct in each reserve sector.
| Reserve sector | Citizen-science observations / count | Verified correct / % |
|---|---|---|
| North | 480 | 62 |
| East | 220 | 78 |
| South | 75 | 91 |
| West | 310 | 84 |
Identify the sector with the greatest number of citizen-science observations.
[1]
Estimate the number of verified citizen-science observations from the north sector.
[2]
Using both figures, explain two limitations of relying only on the citizen-science observations.
[2]
Suggest two ways the agency could use or improve the biodiversity information for conservation management.
[2]
Question 15
A student recorded the abundance of four plant species in a grassland sample. The results are shown in Table 1.
Table 1: Abundance of plant species in a grassland sample.
| Plant species | Number of individuals, | |
|---|---|---|
| P | 12 | |
| Q | 8 | |
| R | 5 | |
| S | 5 |
Simpson's reciprocal index is calculated using:
Calculate Simpson's reciprocal index, , for the grassland sample. Show your working.
[3]
State one sampling condition that should be kept constant when comparing this value with another grassland.
[1]
Question 16
A remote volcanic archipelago contains many species that are endemic to individual islands.
Explain why isolated islands may develop high rates of endemism.
[4]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 17
In a harvested fish population, large adults are consistently removed before they reproduce. Fish that mature earlier are more likely to reproduce before reaching the size at which they are harvested, whereas fish that mature later are more likely to be removed before reproducing. Age at maturity and adult body size both contain heritable variation.
Explain how this harvesting practice could cause evolutionary change in the fish population.
[4]
Question 18
The Anthropocene has been proposed as a geological epoch separate from the Holocene.
State one characteristic required of a suitable golden spike marking the beginning of a geological epoch.
[1]
Outline three human-generated signals that may be detectable in the future geological record.
[3]
Question 19
Three populations of the silver-stream minnow occupy tributaries of the River Nera. A waterfall formed about 12 000 years ago and isolated the upper tributary. Scientists investigated whether the upper population is becoming a separate species.
Breeding outcomes and genetic differences among silver-stream minnow populations.
| Cross / comparison | Viable offspring / % | Fertile adults / % | Mean genetic difference / % |
|---|---|---|---|
| 88 | 81 | — | |
| 90 | 84 | — | |
| 87 | 80 | — | |
| 75 | 69 | 2 | |
| 19 | 6 | 15 | |
| 14 | 2 | 17 |
Identify the factor that initially isolated population U.
[1]
Outline two pieces of evidence that population U is reproductively isolated from the other populations.
[2]
Explain how isolation could lead to the speciation of population U.
[4]
Evaluate the claim that population U is already a separate species.
[3]
Question 20
Ground-dwelling invertebrates were sampled in two areas of the same woodland. Simpson’s reciprocal index was calculated using:
Ground-dwelling invertebrates sampled with equal effort at two woodland sites.
| Species | Site A count | Site B count |
|---|---|---|
| Beetles | 12 | 36 |
| Woodlice | 12 | 4 |
| Millipedes | 12 | 4 |
| Snails | 12 | 4 |
| Total individuals | 48 | 48 |
Calculate Simpson’s reciprocal index for each site.
[4]
Compare the species diversity of the two samples.
[2]
Outline two changes that would improve the sampling design.
[2]
Evaluate the conclusion that site A has greater invertebrate diversity than site B.
[4]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 21
Isla Verdan is a remote tropical island with a central mountain range. A conservation agency must decide where to establish a new protected area.
Biodiversity indicators for the three proposed reserves on Isla Verdan.
| Reserve | Habitat types | Native vertebrate species | Endemic vertebrate species | Threatened vertebrate species |
|---|---|---|---|---|
| P | 3 | 86 | 12 | 19 |
| Q | 7 | 143 | 51 | 46 |
| R | 4 | 74 | 39 | 21 |
Distinguish between mutation and sexual reproduction as sources of genetic diversity.
[2]
Analyse the relationship between habitat diversity, species richness and endemism in the proposed reserves.
[3]
Explain why isolated tropical islands may have high rates of endemism.
[2]
Evaluate which proposed reserve should receive priority for protection.
[4]
Question 22
An insect population contains a pesticide-resistance allele, R. A pesticide was applied in one field, while a second field was left unsprayed.
Results from sprayed and unsprayed insect fields; migration between fields was prevented.
| Generation | frequency, sprayed field | frequency, unsprayed field | Sprayed field, resistant: surviving offspring per adult | Sprayed field, non-resistant: surviving offspring per adult |
|---|---|---|---|---|
| 0 | 0.08 | 0.08 | — | — |
| 2 | — | — | 6.2 | 1.4 |
| 5 | 0.54 | 0.09 | — | — |
| 10 | 0.86 | 0.10 | — | — |
Identify the process that is the ultimate source of the new allele R.
[1]
Calculate the increase in the frequency of allele R in the sprayed field between generations 0 and 10.
[1]
Distinguish the contributions of mutation and sexual reproduction to genetic diversity in this population.
[2]
Explain how pesticide application acted as a selective force in the sprayed field.
[3]
Question 23
Two populations of the same ancestral fruit-eating bird occur on a mainland and a nearby island. Researchers investigated possible reproductive isolation.
Identify two mechanisms that may be reproductively isolating the populations.
[2]
Calculate the percentage reduction in successful fertile pairings for crosses between populations compared with the mean success of pairings within populations.
[2]
Explain how the evidence indicates that speciation may be occurring.
[3]
Question 24
Fossils from several correlated rock sequences were used to reconstruct biological change around a past mass-extinction event. Time zero represents the extinction boundary.
Extinction intensity and marine fossil-family diversity relative to an extinction boundary.
| Time relative to boundary / Ma | Extinction intensity / % | Marine fossil families |
|---|---|---|
| 5 | — | |
| 9 | — | |
| (immediately before) | — | 240 |
| (extinction boundary) | 72 | — |
| (immediately after) | — | 68 |
| 18 | — | |
| 7 | 95 | |
| — | 160 | |
| — | 225 |
Identify the time at which extinction intensity was greatest.
[1]
Calculate the percentage decrease in the number of marine fossil families from immediately before to immediately after the event.
[2]
Describe the pattern of biological recovery after the extinction event.
[2]
Explain why mass extinctions may be followed by relatively rapid speciation.
[2]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 25
The bluefin snapper is harvested commercially. A hatchery also selectively breeds snapper for rapid growth and releases juveniles to supplement the wild population.
Comparison of wild no-take and eighth-generation hatchery bluefin snapper.
| Measure | Wild no-take fish | Eighth-generation hatchery fish |
|---|---|---|
| Mean alleles per surveyed locus | 18 | 7 |
| Survival after fungal disease exposure / % | 74 | 31 |
| Mean mass at age two / kg | 1.8 | 2.7 |
Calculate the percentage decrease in mean length at sexual maturity in the heavily fished zone.
[2]
Explain how fishing may have caused evolutionary change in the wild population.
[3]
Distinguish between the selective processes affecting the wild and hatchery populations.
[2]
Evaluate the use of selectively bred hatchery fish to increase the commercial snapper population.
[5]
Question 26
Palaeontologists examined sedimentary rocks from the Karu Basin to investigate changes in marine biodiversity across a past mass-extinction event.
State the hierarchy of the four named divisions of geological time from largest to smallest.
[1]
Outline two pieces of evidence that boundary X represents a mass-extinction event.
[2]
Explain why rates of speciation may increase after a mass extinction.
[3]
Evaluate the fossil evidence for extinction followed by rapid speciation in the Karu Basin.
[5]
Question 27
Scientists compared three proposed markers for the lower boundary of the Anthropocene. They also examined other human-generated signals in recent sediments.
Comparison of proposed lower-boundary markers for the Anthropocene.
| Proposed marker | Date | Cores detected (out of 8) | Dating uncertainty | Abruptness | Likely preservation |
|---|---|---|---|---|---|
| Atmospheric dip | 1610 | 3 | years | Gradual signal | Mainly in ice and peat |
| First widespread spherical fly-ash particles | 1950 | 7 | years | Abrupt first appearance | Durable particles in lake and marine sediment |
| Carbon-14 fallout peak | 1964 | 8 | year | Sharp peak | Globally distributed radioactive signature; declines through radioactive decay |
Identify the proposed boundary marker detected in the greatest number of sediment cores.
[1]
Calculate the percentage of studied cores containing the 1950 fly-ash marker.
[2]
Compare the suitability of the 1950 and 1964 markers as golden spikes.
[2]
Using both figures, evaluate whether the geological evidence supports recognizing the Anthropocene as an epoch separate from the Holocene.
[3]
Question 28
Distinguish between habitat diversity, species diversity and genetic diversity.
[4]
Explain how each level of biodiversity may contribute to the resilience of an ecological system following disturbance.
[7]
Using named examples, evaluate the importance of different sources of biodiversity knowledge in developing effective conservation management strategies.
[9]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 29
Outline the process of evolution by natural selection.
[4]
Explain how isolation and natural selection may result in the formation of a new species.
[7]
Using named examples, to what extent is maintaining connections between habitats the most effective way to conserve biodiversity and evolutionary potential?
[9]
Question 30
Explain how species richness and evenness determine species diversity in a community.
[4]
Explain how Simpson’s reciprocal index could be used to compare plant diversity at two sites in the same grassland ecosystem.
[7]
Using named examples, evaluate the value of quantitative diversity indices in making conservation-management decisions.
[9]
Question 31
Scientists compared possible geological markers for the lower boundary of a proposed Anthropocene epoch. Sediment cores were analysed from five widely separated regions.
Geological-marker observations from five sediment cores.
| Core region | 1610 carbon-isotope signal | First fly-ash signal / year | Carbon-14 peak / year |
|---|---|---|---|
| Northern lake | Clear | 1950 | 1963 |
| Tropical peatland | Weak | 1954 | 1964 |
| Temperate estuary | Clear | 1950 | 1964 |
| Southern ice margin | Weak | 1950 | 1965 |
| Deep-ocean basin | Absent | 1957 | 1964 |
Identify the proposed marker that is most globally synchronous in the cores and support the answer with data.
[2]
Explain how three human signals shown in the resources could be preserved in the geological record.
[3]
Compare the suitability of the 1610, 1950 and 1964 signals as a golden spike.
[3]
Justify whether the evidence supports recognizing the Anthropocene as an epoch separate from the Holocene.
[4]
Question 32
Distinguish between mutation and sexual reproduction as sources of genetic diversity.
[4]
Explain why tropical islands and tropical mountain regions often contain high species richness and endemism.
[7]
Using named examples, evaluate the use of biodiversity hotspots as a basis for allocating global conservation resources.
[9]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 33
Distinguish between natural selection and artificial selection.
[4]
Explain the environmental and economic importance of maintaining genetic diversity in crop and livestock populations.
[7]
Using named examples, to what extent can artificial selection contribute to environmentally and economically sustainable food production?
[9]
Question 34
Outline how fossils and the geological timescale provide evidence for the evolution of life on Earth.
[4]
Explain why a mass extinction may be followed by a relatively rapid rate of speciation.
[7]
Evaluate the argument that the Anthropocene should be formally recognized as an epoch separate from the Holocene.
[9]
The Ultimate All-in-One
IB Platform
All content on this website has been developed independently from and is not endorsed by the International Baccalaureate Organization. International Baccalaureate and IB are registered trademarks owned by the International Baccalaureate Organization.