Unleash Your Potential - Namagunga Girls Coding Club
biogeography+and+adaptation
1. 7 billion people
Assoc Prof. Rebecca Ackermann
Department of Archaeology
Beattie Bldg, Rm 3.19
becky.ackermann@uct.ac.za
Archaeology
Biogeography & Adaptation
Overview of Humans/Primates
Vision
Linguistics Anthropology Socio Cultural
Socio-Cultural Bipedalism
Bi d li
Brains
Skin
Agriculture
Biology Domestication
World Population Growth
All readings are on Vula Remain at the ENGEO Building venue for the
first practical
Practicals and supplemental materials for the
practicals are also on Vula Practical 1 will run Th/F (May 3 & 4) in first
/
week and M/Tu (May 7 & 8) in second week
Bring a calculator
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2. Practical 2 will run Th/F of the second week (May 10 & 11) Introduction
and M/Tu of the third week (May 14 & 15)
Adaptation through natural selection
Meet at the Pick-up / drop off area at the end of University
Avenue South What is a species?
p
13h00 – 18h00
How does one species split into two?
Extinction
Wear good shoes!!! Bring appropriate clothes (e.g. rain
gear)!!!
Bring something (e.g. clipboard) to write on
Be sure to read background material AHEAD of time
Biogeography = the study of the pattern of distribution of (mutation, selection, gene flow, genetic drift)
organisms (individuals, species, ecosystems) across space and
through geological time
Patterns of distribution of organisms across geographical areas
can usually be explained through historical factors (e.g.
speciation; extinction; continental drift; glaciation, variations in
i i i i i l d if l i i i i i
sea level, river routes, habitat) in combination with geographic
constraints (landmass areas and isolation) and the available
energy supplies in the ecosystem
Evolution (adaptation through natural selection) provides the
key explanation for the pattern of distribution of organisms
(i.e. the link between organismal variation and the
climate/environment)
Evolution = descent with modification (i.e. change through
time) fast slow
Adaptation of plants and animals to their environment
occurs through the process of natural selection Ship Naturalist
Adaptation = a change of structure, form, or habits to fit
different conditions, which increases fitness 1831 1836:
1831-1836: Voyage of the
Adaptive traits = a trait with a current functional role in Beagle
the life history of an organism that is maintained and
evolved by means of natural selection
1859: On the Origin of
Natural selection = preservation of favorable individual Species by Means of Natural
differences and variations and the destruction of those
that are injurious Selection
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4. Parallel between species morphology, behaviour,
geography and adaptation (‘fit’) to environments
(the foundation of biogeography!!)
Demonstrated FACT of evolution (and defined Malay Archipelago:
it as descent with modification) 1848-1862
1857: “On the
Offered explanatory mechanism (i.e. natural
Tendency of Variation
selection… survival and mortality KEY to this
to Depart Indefinitely
definition)
from the Original Type”
Heredity of most features The peppered moth, Biston
Heritable variation in the population betularia, occurs in two varieties,
melanic and non-melanic
Variation leads to differential rates in survival &
Non-melanic form is virtually
reproductive success among variations invisible against pale-coloured
pale coloured
Differential survival and reproduction leads to change backgrounds, vice versa for melanic
in frequency of characters (e.g. populations will diverge form.
from one another) Differential survival rates under
If process goes on long enough, parent & daughter environments of different colour.
Prior to industrial revolution,
species can no longer interbreed (e.g. they have become
lighter form dominant - a survival
too different) advantage against lichen-covered
trees.
ENVIRONMENTAL CONTEXT IS ESSENTIAL!!!
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5. After the industrial revolution,
more offspring of melanic form
survive to reproduce.
Relative frequency shift: before
melanic = 5% after = 98%
l i 5%, f 98%.
Process occurred in just 40
generations.
Note that in this case natural
selection does not create the forms,
but rather edits the populations.
Natural selection is ‘fine-tuning’
populations to their physical
environments.
Daubentonia
madagascariensis
Xanthopan morganii praedicta Angraecum sesquipedale
Bergmann’s Rule Allen’s Rule
Correlates between latitude (climate) and body mass / limb length
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6. Natural selection can act to create (or delete) Species are uniform ‘types’ of organisms:
forms (species) when viewed over deep biogeographers classify organisms as belonging to one
(geological/evolutionary) time or other species.
There are many different ways of defining species
Other evolutionary forces (mutation, drift, gene
In practice, species are generally recognised not solely
flow) also play a role in creating new forms (or even necessarily) by reproductive isolation, but by
some combination of factors such as morphology,
genetics, geographic proximity, and ecology, that
together make a species distinct even in the face of
gene flow.
Western Meadowlark Eastern Meadowlark
Modes of species change
anagenesis
cladogenesis
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7. Tempo (pace/rate) Tempo + Mode
time
gradual gradual punctuated punctuated stasis
Phyletic gradualism Punctuated equilibrium anagenesis cladogenesis anagenesis cladogenesis
phenotype
Speciation – e.g. diversification of lineages (lineage
splitting)
Most important type of speciation is allopatric speciation
(although you may also encounter the terms sympatric
and parapatric speciation).
Adaptive radiation
Time 4
Differentiation (speciation)
Species becomes geographically divided by a barrier (continental
drift, rifting, change in course of river, fire etc).
Time 3
Separate populations are reproductively isolated from each other. Reproductive isolation
Natural selection operates independently in each population and the
N l l i i d d tl i h l i d h
populations gradually become adapted to their own unique
Time 2
environments (divergence also occurs through genetic drift).
Physical barrier
Reproductive isolation is initially imposed by the geographical
constraints, but eventually populations diverge too much resulting
in permanent barrier (different genomes, behaviours, etc). Time 1
Original population
Speciation is complete; one species has become two (or more).
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8. If speciation occurs all the time, there should be more
species today than 10,000 years ago, and more then than
there were 10 million years ago, right?
No, because extinction is ubiquitous.
No ubiquitous
99% or all species that have ever existed on Earth have
gone extinct.
Some geological periods are characterised, or dominated,
by extinction (e.g. end-Permian, end-Cretaceous).
These are so-called mass extinction events
Causes varied and sometimes controversial
End-Permian event resulted in loss of 90% of all marine
species - global warming may have been the culprit (a
lesson?).
End-Cretaceous (K-T) likely caused by asteroid impact.
Loss of large proportion of reptiles (especially the Chicxulub crater
dinosaurs).
Causal factors may have been climate change induced by
impact: global cooling.
Sudden disappearance ~50Ka Climate?
Human-induced environmental 14 genera disappear
change caused by burning before the first
p
practices
Clovis point is
Drought-adapted flora with
palatable nutritious grasslands found
became fire-adapted desert
scrub with low-nutrition
grasses
Stress and extinction of
megafauna
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9. Climate change (severe
droughts).
Arrival of humans
(including overhunting,
introduction of alien
species, the use of
agricultural fires).
In the American South-West the dates for Clovis sites (~13Ka) coincide Hypervirulent/hyperlethal
closely with the dates for the last appearance of the Shasta Ground Sloth. disease
Human-induced climate change, habitat change,
and hunting are continuing to threaten megafauna
worldwide
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