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Flashcards · IB Diploma Programme Environmental Systems and Societies · Topic 3

Biodiversity and conservation flashcards

17 cards on Topic 3, subtopics 3.1 to 3.3. Pick a subtopic or study them all.

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3.1 Biodiversity and evolution

What are the three levels of biodiversity?
Genetic diversity: the range of genes and alleles within a species or population. Species diversity: the number of species and their relative abundance. Habitat diversity: the range of habitats or ecosystems in an area.
Species richness versus species evenness
Richness: the number of species present. Evenness: how similar the population sizes of the species are. "Biodiversity = number of species" describes richness only.
How do you calculate Simpson's reciprocal index?
D = N(N − 1) ÷ Σn(n − 1), where N is the total number of individuals and n the number of each species. A species with n = 1 contributes 0. Higher D = more diverse; minimum 1. Example: counts 5, 5, 5, 5 → 380 ÷ 80 = 4.75.
How does speciation happen?
Variation exists; a geographical barrier or a difference in behaviour or timing stops gene flow; different selection pressures act on each population; allele frequencies change separately over many generations; the populations can no longer interbreed to give fertile offspring.
How does plate tectonics affect biodiversity?
Splitting land masses isolates populations (speciation); collisions build mountains and new habitats; land bridges allow species to spread and compete.
Mass extinction versus background extinction rate
Mass extinction: loss of a large share of species over a geologically short time; five are recorded in the fossil record (the end-Cretaceous, about 66 million years ago, followed an asteroid impact). Background rate: the normal, slow rate of extinction between them.

3.2 Human impact on biodiversity

Name five main human causes of biodiversity loss
Habitat loss and fragmentation; overexploitation (harvest exceeds replacement); invasive species; pollution; climate change (conditions shift faster than species can move or adapt).
What is an edge effect?
Changed conditions near a habitat's boundary: more light, wind and drying, and more predators and invasive species. Fragmentation increases the amount of edge.
Which features make a species vulnerable to extinction?
Small population, small range, low reproductive rate, specialised niche, high trophic level or large body, low genetic diversity, and value to people (hunting or trade).
Why are tropical rainforests especially vulnerable?
They have very high diversity, most nutrients are held in the biomass rather than the soil, and they recover slowly once cleared.
What is the IUCN Red List?
A classification of extinction risk: Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild, Extinct (plus Data Deficient). Criteria include population size, rate of decline, range size and fragmentation.

3.3 Conservation and regeneration

Keystone, flagship and umbrella species: what is the difference?
Keystone: has a large effect on the ecosystem relative to its numbers (defined by effect, not trophic level). Flagship: has public appeal that attracts support. Umbrella: needs a large area, so protecting it protects many others.
Captive breeding and reintroduction: one strength and two limitations
Strength: can save species close to extinction and educates the public. Limitations: expensive; small gene pool; the habitat may still be damaged.
What does the SLOSS debate compare?
Single large or several small reserves. One large reserve usually gives more core area (less edge); several small ones can spread risk from fire or disease and cover more habitat types.
How do you calculate the core area of a square reserve?
(side − 2 × edge depth)², because the edge depth comes off both sides. Core share = core area ÷ total area × 100. Example: a 10 km square with a 1 km edge → (10 − 2)² = 64 km², 64% of the reserve.
What is the role of corridors and buffer zones in reserve design?
Corridors link habitat fragments so organisms can move between them. Buffer zones surround the core and protect it from outside disturbance. Compact shapes have less edge per unit area than long, thin ones.
Regeneration versus rewilding
Regeneration: active restoration of a degraded site. Rewilding: restoring natural processes so the ecosystem regulates itself with minimal ongoing management, often with reintroductions.

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