Quick questions on Biodiversity patterns and hotspots: HSC Geography 2022 Focus Area

Biodiversity is measured at three levels:

The continents and oceans are divided into broad biogeographic realms with distinct evolutionary histories: Nearctic (North America), Neotropical (South America), Palaearctic (Eurasia and North Africa), Afrotropical (sub-Saharan Africa), Indomalayan (South and South-East Asia), Australasian, Oceanian and Antarctic. Australia and New Zealand together form an Australasian realm with deep evolutionary isolation since the breakup of Gondwana; this is why Australia has a fauna dominated by marsupials and monotremes found almost nowhere else.

The biodiversity hotspots framework was developed by Norman Myers in the late 1980s and is now maintained by Conservation International. A region qualifies as a hotspot if it meets two criteria:

A centre of endemism is a region with an unusually high number of species found nowhere else. Endemism arises through long isolation, climatic stability, or unique substrates. Important examples for HSC reference:

MacArthur and Wilson's theory of island biogeography (1967) is the canonical framework for understanding why isolated systems matter. Two principles drive the number of species an island supports:

The number and relative abundance of different species in a defined area. Often the headline figure, but only one of three layers.

Variation within species (different populations, different alleles). Important because genetic variation provides the raw material for adaptation to environmental change. A population reduced to low numbers loses genetic diversity even if it recovers in count.

The variety of ecosystem types within a region. A landscape with rainforest, savanna, wetlands and reef has more ecosystem diversity than one of uniform plantation.

Define the three levels of biodiversity and give one example of each. [3 marks]

Explain Conservation International's biodiversity hotspots framework and identify two hotspots, one outside Australia and one within. [6 marks]

Analyse the principles of island biogeography and apply them to a fragmented landscape of your choice. [8 marks]