S3: W12 (Prof. Kelsey) Flashcards
(71 cards)
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).
