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
Practise IB ESS SL 3.1 by comparing richness and evenness, interpreting diversity data and explaining selection and speciation from evidence.
Figure:Location of Yasuni National Park in Ecuador
Table:Species richness of Yasuni National Park
Table:Ocelot phototrap survey data from Yasuni National Park
Define biodiversity.
biodiversity is a broad concept encompassing the total diversity of living systems / biodiversity includes the species, habitat and genetic diversity within an area / the amount of biological diversity per unit area;
OWTTE;
Award [1 max] for a correct definition.
Outline the mechanisms by which a terrestrial species may have evolved from an aquatic ancestor.
there was genetic variety in aquatic species/mutations accumulated over years;
b. certain features may have adaptation/advantage for terrestrial existence;
c. individuals with these features could colonize terrestrial habitat;
d. they would be more likely to survive/survival of the fittest/experience less competition (natural selection);
e. they produce offspring like themselves/feature will become more abundant;
f. individuals with feature may be unable to breed with others without feature /speciation occurs / reproductive/geographical barrier will give rise to new terrestrial species;
Explain the ways in which species diversity and an abundance of plant and herbivore species will increase the resilience of an ecosystem.
Diversity:
a. a greater diversity of plant and herbivore species would mean there are more species to take over the role of any that would be lost/creates a more complex food web;
b. a wider variety/diversity set of plant species will support a wider range of herbivores/increase habitat diversity;
c. a wider variety/diversity of plant species will be able to exploit a wider range of abiotic conditions;
d. more plant species/greater plant diversity will be more likely to include species that will survive a change in conditions;
e. a wider variety/diversity plant species will increase interspecific competition resulting in evolution of more species;
f. a wider variety/diversity of herbivorous species will support a wider range of predators;
g. a wider variety/diversity of herbivore species will occupy a wider range of niches adding to the complexity of the system;
Abundance:
h. a greater abundance/larger populations of plant species means greater primary productivity which supports a greater abundance/larger populations of herbivores;
i. a greater abundance/larger populations of plant species is less likely to become extinct from the ecosystem;
j. a greater abundance/larger populations of herbivores will support a greater abundance/larger populations of predators;
k. a greater abundance/larger populations of herbivores will be less likely to become extinct in the ecosystem;
Explain one natural and one human-caused factor that influences changes in biodiversity.
Natural factor [4 max]:
(Extinction)
a. mass extinctions of the past/local extinctions caused by various natural factors, have (temporarily) reduced biodiversity;
b. e.g. tectonic plate activity / super-volcanic eruption;
c. e.g. climatic changes (including drought and ice ages);
d. e.g. meteorite impacts;
(Evolution)
e. Evolution is a natural factor that has led to increased biodiversity;
f. Mutation leads to increases in genetic diversity;
g. Natural selection may lead to some reduction in genetic diversity;
h. Speciation has led to increased species diversity;
i. Adaptive radiation has led to increased speciation/genetic diversity;
Human caused factor [4 max]:
(Extinction)
j. human activity is considered to be causing a sixth mass extinction;
k. e.g. habitat destruction/deforestation/urbanisation;
I. e.g. pollution of freshwater water bodies/oceans/soils/atmosphere/leading to climate change/associated environmental hazards;
m. e.g. over-exploitation of resources/overfishing/hunting/intensive agriculture;
(Conservation)
n. conservation/restoration of ecosystems has led to increased biodiversity;
o. e.g. establishment of national parks/nature reserves etc.;
p. e.g. ex situ conservation/zoos/plantations/seed banks reduce loss of biodiversity;
q. e.g. legislation/trade agreements protecting species e.g. CITES/fishing quotas/endangered species act;