S3: W12 (Prof. Kelsey) Flashcards
Biogeographic components of Southern Africa attributes? (3)
• 2 components in the pre-Gondwana habitat.
• Present South African biota has had input from the north.
• Also appears to be an “Arid” biogeographic entity for some groups.
2 components in the pre-Gondwana habitat?
• Tropical.
• Temperate.
Tropical attributes? (4)
• Warm.
• Moist.
• High rainfall.
• High temperatures.
Temperate?
Pre-Gondwana temperate component is more than that of tropical.
Attributes on the components of the pre-Gondwana habitat? (2)
• Involve elevation & latitude.
• High elevation, high latitude, increased temperature conditions.
Explain what you mean that present South African biota has had input from the north? (2)
● Species in Europe & South Africa are related.
● Afro-eurasian groups that have come into existence since the time Gondwana was intact.
Egs of where present South African biota has had input from the north? (2)
• Helichrysum found in Cape Floristic region & Mediterranean.
• Many vertebrates & invertebrates.
Palaeoclimate kinds that we talk about? (2)
• Glacial periods.
• Interglacial periods.
Palaeoclimate attributes? (10)
● Before rifting, Gondwana was a stable, very ancient series of plains ringed by mountains.
● Vast regions were deserts/semi-desert, as would be expected in the interior of a super-continent.
● After rifting, Africa became more moist, i.e., from dry to moist (was ~15°S of its previous position).
● Drying commenced as Africa formed connections with the northern landmasses, which affected ocean currents & air circulation.
● This, combined with global cooling, cycles of uplifting & warping in the African continent, brought about complex environmental changes (in turn affects species diversity & distribution).
● Cooling started again ~40mya as the Earth went into glacial cycles.
● Fluctuations became more extreme during the Pleristocene (~1.8mya).
● Last glacial maximum was ~20 000 years ago.
● Last inter-glacial climaxed 800 years ago.
● These extremes have left a huge impression on the present biogeographical features of southern Africa.
Glacial?
= cooling.
Inter-glacial?
= warming.
Glacial period attributes? (5)
• Summer rainfall area became cooler, smaller & received less rainfall than current.
• Winter rainfall area expanded & received more rain, extended over the Free State plateau.
• Involves cooling, ice sheets & less water.
• Change in summer & winter rainfall had a significant impact on plants.
• More water was locked in the ice sheets (=drop in sea level).
Why were the vast regions of Africa desert/semi-desert in the interior of the super-continent?
It’s because of the mountains surrounding the super-continent, which experience conventional rain (explain).
How did the drying that came about when Africa commenced with the northern landmasses affect ocean currents & air circulation?
It changed how moist or dry an area of the continent was.
Explain the drop in sea level through ice sheets? (2)
● In the last glacial period the sea level dropped to about 130m below present.
● This resulted in an increase of land along the Agulhas bank.
Egs of Glacial periods? (2)
• Podocarpus forest spread in the SW Cape.
• Southern Cape coastland became grassveld.
Inter-glacial period attributes? (5)
• The area of summer rainfall expanded & received more rainfall.
• Winter rainfall became restricted to the SW Cape & rainfall reduced.
• Involves climate tracking.
• Generally wetter in the summer rainfall areas.
• Fits world trend: maximum glaciation results in the desert belt north & south of the tropics getting more rainfall, while the tropics received reduced rain.
Eg of Inter-glacial period?
Drier in the Karoo & Free State.
Thing to think about when talking about Glacial & Inter-glacial periods?
Think about how parts of Africa change during the Glacial & Inter-glacial periods.
Climate tracking?
= when a species moves from one habitat to the other to keep staying in good environmental conditions.
Climate tracking attributes? (2)
• Move according to the environment.
• Can happen vertically (N<=>S) & horizontally (E<=>W).
Climate tracking attributes? (2)
• Move according to the environment.
• Can happen vertically (N<=>S) & horizontally (E<=>W).
Climate tracking attributes? (2)
• Move according to the environment.
• Can happen vertically (N<=>S) & horizontally (E<=>W).
Current biogeographic patterns in South Africa/Current patterns of distribution attributes? (6)
• South Africa has 3 main biogeographic units with centers that are not all in southern Africa.
• Geographic centre is not equal to biogeographic centre.
• RTZ is found between the margins of all units.
• Map of biogeographic units could be a consequence of refugia.
• Transitional species.
• Time frames have an impact on the biogeographic unit size (via rainfall & temperature).
List of the biogeographic units found in South Africa? (3)
• Tropical.
• Temperate.
• Arid.
Biogeographic centre found in the temperate biogeographic unit?
In the SW Cape (for nearly every major tax on group).
Biogeographic centre found in the tropical biogeographic unit?
In East Africa with ranges extending into southern Africa.
Biogeographic centre found in the arid biogeographic unit?
In the Arid west of southern Africa.
