CourseCourseConceptConcept

IB ESS SL 3.1 Biodiversity and Evolution Questions

Practise IB ESS SL 3.1 by comparing richness and evenness, interpreting diversity data and explaining selection and speciation from evidence.

Syllabus
First assessment 2026
Course
ESS SL
Level
SL

Exam points

  • Distinguish habitat, species and genetic diversity and compare richness and evenness from abundance data.
  • Explain natural selection through heritable variation, selection pressure and differential reproduction.
  • Explain speciation through isolation, divergent selection and loss of fertile reproduction.
  • Calculate Simpson’s reciprocal index and interpret higher values as greater diversity.

Covered syllabus points

3.1.1—Biodiversity levels3.1.2—Diversity and resilience3.1.3—Biodiversity from evolution3.1.4—Natural selection3.1.5—Natural selection process3.1.6—Speciation3.1.7—Species diversity components3.1.8—Simpson's reciprocal index3.1.9—Biodiversity knowledge for conservation

Question 1

[Maximum number: 1]
Figure 1(a): Extinction risk levels of species in global biodiversity by category

Figure:Extinction risk levels of species in global biodiversity by category

Figure 1(b): Changing species extinction risk by category 1980–2015

Figure:Changing species extinction risk by category 1980–2015

Figures 1(a) and 1(b) are based on records for species diversity. Identify one other factor that may be measured to assess the diversity of life on Earth.

Question 2

[Maximum number: 11]

Question (a)

(a)

Outline the mechanisms by which a terrestrial species may have evolved from an aquatic ancestor.

[ 4 ]

Question (b)

(b)

Explain the ways in which species diversity and an abundance of plant and herbivore species will increase the resilience of an ecosystem.

[ 7 ]

Question 3

[Maximum number: 7]

Explain one natural and one human-caused factor that influences changes in biodiversity.

Question 4

[Maximum number: 7]

Explain the ways in which species diversity and an abundance of plant and herbivore species will increase the resilience of an ecosystem.

Question 5

[Maximum number: 2]
Continents and species diversity over time

Figure:Continents and species diversity over time

Outline the role of natural selection in increasing the diversity of species.

Question 6

[Maximum number: 2]
Fact file on Mindo cloud forest

Figure:Fact file on Mindo cloud forest

Fact file on Mindo harlequin toad

Figure:Fact file on Mindo harlequin toad

There is no cure and those infected experience 85–100% mortality.

Explain how the disease in the Mindo harlequin toad could contribute to the evolution of resistance to this disease in the species for future generations.

Question 7

[Maximum number: 7]

Explain how natural processes may lead to the formation of new species.

Question 8

[Maximum number: 2]
Figure: Four species of the family Leporidae

Figure:Four species of the family Leporidae

Figure: A dichotomous key for species A to D

Figure:A dichotomous key for species A to D

Figure: Sagebrush ecosystem without invasive cheatgrass

Figure:Sagebrush ecosystem without invasive cheatgrass

Figure: Sagebrush ecosystem with invasive cheatgrass

Figure:Sagebrush ecosystem with invasive cheatgrass

The family Leporidae includes hares and rabbits. The figures show four species that can be found in western North America.

Distinguish between the biodiversity of the sagebrush ecosystems in Figures 1(c) and 1(d).

Question 9

[Maximum number: 2]
Eight freshwater organisms

Figure:Eight freshwater organisms

Figure 2 shows eight freshwater organisms.

Organisms sampled in streams A and B

Table:Organisms sampled in streams A and B

The table shows data from sampling two streams: A and B. Calculate the Simpson’s Diversity Index for Stream B.
D=N(N−1)∑n(n−1)D=\frac{N(N-1)}{\sum n(n-1)}
You must show your working.

Question 10

[Maximum number: 1]
Figure 2(c): Conservation status of indigenous species groups in New Zealand

Figure:Conservation status of indigenous species groups in New Zealand

Suggest one reason why there is insufficient data available to categorise the conservation status of a large proportion of marine mammals, as shown in Figure 2(c).

All question bank results loaded