IB Diploma Environmental Systems & Societies HL Β· Biodiversity and Conservation
Mini-Lesson
Biodiversity and Conservation
This mini-lesson explores the variety of life and how we protect it: the three kinds of biodiversity, how it originates (evolution, speciation and mass extinctions), the human threats driving todayβs extinction crisis, how biodiversity is measured (diversity indices, the IUCN Red List, hotspots), and the conservation strategies β in-situ, ex-situ and international agreements β used to defend it.
Perspectives lens: people value biodiversity for different reasons β intrinsic worth, ecosystem services, economic use and aesthetic or cultural meaning. These values shape conservation choices.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you're ready.
Biodiversity Β· what it means
The three kinds of biodiversity
Species diversity β the variety and relative abundance of species in a community (captured by indices such as Simpsonβs D).
Genetic diversity β the range of genetic material (alleles) within a species; low genetic diversity makes a population vulnerable to disease and change.
Habitat diversity β the range of different habitats in an area; more habitats generally support more species.
Why it matters: diverse systems are more resilient β they can absorb disturbance and still recover, protecting the ecosystem services humans depend on.
Quick check
Which kind of diversity?
?Cheetahs passed through a population bottleneck and now have very few different alleles, making the whole species vulnerable to a single disease. This describes low...
Biodiversity Β· where it comes from
Evolution, speciation and extinction
Biodiversity is the product of evolution by natural selection: individuals vary; those with advantageous heritable traits survive and reproduce more, so those alleles become more common over generations.
Speciation β new species form when populations become isolated (e.g. by geographical barriers or plate movements) and diverge until they can no longer interbreed.
Mass extinctions β five past events wiped out most species; many scientists argue a sixth, human-driven extinction is now underway, at 100β1000Γ the natural background rate.
Quick check
How evolution works
?Which statement best describes natural selection?
Biodiversity Β· pressures
Threats to biodiversity
The main human drivers of biodiversity loss are often remembered as HIPPO:
Habitat loss and fragmentation β the single biggest threat (deforestation, urbanisation, agriculture).
Invasive species β non-natives that out-compete or prey on natives.
Pollution β including nutrient run-off and plastics.
Population (human) growth and overexploitation.
Overharvesting β hunting and fishing beyond replacement rates.
Add climate change, which shifts habitats faster than many species can track. Small, isolated, specialist or slow-breeding species are most at risk.
Quick check
Naming the threat
?Cane toads, introduced to Australia, spread rapidly and poison native predators that try to eat them. This is an example of which threat?
Calculate
Your turn β comparing diversity
1A restored meadow contains four species with counts of 5, 5, 5 and 5 (N = 20). Using Simpsonβs index D = N(Nβ1) Γ· Ξ£ n(nβ1), calculate D for this site.
Ecologists quantify biodiversity so change can be tracked and priorities set:
Diversity indices (e.g. Simpsonβs D) combine richness and evenness into one comparable number.
Biodiversity hotspots β regions with exceptional numbers of endemic species under serious threat; conserving them protects many species efficiently.
IUCN Red List β ranks species from Least Concern to Critically Endangered and Extinct, using population size, rate of decline, range and fragmentation.
Calculate
Your turn β proportion threatened
2Of 150 000 species assessed by the IUCN, 42 000 are classed as threatened with extinction. Calculate the percentage of assessed species that are threatened.
%
Hint: (42 000 Γ· 150 000) Γ 100.
Quick check
Judging extinction risk
?Which factor does the IUCN Red List use to classify how threatened a species is?
Conservation Β· protecting species
In-situ and ex-situ conservation
In-situ β conserving species in their natural habitat: national parks, nature reserves, marine protected areas and rewilding. Maintains ecological interactions and evolution, but needs enforcement.
Ex-situ β conserving species outside their habitat: zoos, captive-breeding programmes, botanic gardens and seed banks. Useful as a last resort or backup, but expensive and limited in genetic diversity.
Species-based approaches target one organism (e.g. CITES trade bans, flagship species). Habitat-based approaches protect whole ecosystems and everything in them.
Sort it
Sort the conservation methods
Tap a method, then tap the category it belongs to.
ποΈ In-situ
ποΈ Ex-situ
π Global agreement
Conservation Β· designing reserves
Reserve design and global agreements
Good protected-area design improves success:
Bigger reserves support larger, more viable populations.
A more compact (rounded) shape reduces damaging edge effects.
Corridors linking reserves let species move, feed and breed.
International agreements coordinate action: CITES regulates trade in endangered species; the Convention on Biological Diversity (CBD) from the Rio Earth Summit commits nations to conserve biodiversity and share its benefits fairly.
Calculate
Your turn β deforestation rate
3A tropical forest covered 80 000 ha. After ten years only 68 000 ha remain. Calculate the percentage of the original forest that has been lost.