Transcript Notes on Evolution, Natural Selection, and the Evolution of Primates

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Acclimatization effects on final rectal temperature, heart rate, and sweat rate,
for a group of men exposed daily to 2 hr of hard work in a hot environment.
(after Leithead CS, Lind AR. Heat Stress and Heat Disorders. 1964. Philadelphia, Pa.: FA Davis Co, 304.
acclimitization
EMILI GARCÍA-BERTHOU
Ontogenetic Diet Shifts and Interrupted Piscivory
in Introduced Largemouth Bass (Micropterus salmoides)
Internat. Rev. Hydrobiol. 87 2002 4 353–363
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acclimitization
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Life Table
Fall 05 Start
Notes on Evolution,
Natural Selection, and
Speciation
One picture of evolution
What is going on before a split?
How did the splits occur?
What is speciation?
Types of evolution
migration
• Macro
• Micro
– Gene flow (E and I)
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In isolated populations
Migrating indivs. start breeding
Immigrants can add new alleles
Not necessarily random
– Genetic Drift
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Mainland
↑NA
Random mating in small populations
Causes relative success of only a fraction of individuals
Population bottlenecks (large population)
Founder effects (small population)
↓NA
– Natural Selection
• Differential contribution of offspring to next
generation by individuals in a population
• Not Random
Recall:
Normal curve of phenotypic variation
Height of students in class
Another way to look at it…
Fitness
• Directional Selection
Trait
Positive Directional Selection
Trait
Negative Directional Selection
Peppered Moth – Biston betularia
Fitness
• Stabilizing selection
average trait value
Egg laying wasp
that eventually kills
the cactus
Malaria and Sickle Cell Anemia
SSA caused by mutation in the past…
Fitness
• Disruptive Selection
average trait value
Black-bellied seed cracker
(Pyrenestes ostrinus)
• Smith, T. B. 1990. Evolution. 44(4):832
• Black-bellied seed crackers (Pyrenestes) in Cameroon
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Same birds different
study
Open portion of bar –
Number hatched
Black portion of bar –
Number survived
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Two more types of selection
• Correlational – working on combinations of
traits at once.
(body size)
(Wing length)
• Frequency Dependent Selection – Level of
selection dependent upon most common
phenotype (at the time)
Genyochromis
Scale eater
Scalebiters – frequency dependent
selection
Right “mouthedness”
Left “mouthedness”
Frequency of left
“mouthedness”
Frequency of right
“mouthedness”
Time
• Selection can lead to speciation
• Speciation:
– Splitting of one species into two or more species
(cladistic or punctuated).
– Transformation of one species into a new species
over time (gradual or anagenic).
Anagenetic (gradual) versus
Cladistic (punctuated) Speciation
B
A
TIME
TIME
B
A
A
PHENOTYPIC
VARIATION
PHENOTYPIC
VARIATION
Species
• Many, many definitions
• Biological species definition: A group of actually
or potentially breeding individuals which are
reproductively isolated from all other groups.
• Doesn’t work in all situations
– Fossils
– Asexual organisms
Isolating mechanisms
• Prezygotic –
• Postzygotic -
Prezygotic I.M.s
• Habitat isolation
– Dendroica warblers in Eastern US
Modes of speciation
• Allopatric – allo = different, patri = fatherland
• Sympatric – sym = together
• Has to do with location or habitat
Allopatric Speciation
Speciation occurs with reproductive isolation
Grand Canyon
Kaibab Squirrel
Abert’s Squirrel
Sympatric speciation
• Rare
• Polyploidy in plants
• Hybrids
Evolution &
Speciation of Primates
including Homo
Divisions of Primates
• Prosimians (“before ape”)
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Lemurs
Tarsiers
Lorises
Galagos
• Lemurs
sifaka
• Tarsier
• Lorises and Galagos
Slow-loris
galago
• New
World
Monkeys
• Old World Monkeys
– Baboons
– Macaques
Asian apes
• Gibbons
African Apes
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Chimps
Gorillas
Hominids
etc…
bonobo
Hominids
• Several genera
• Homo
4w human embryo
• Most
Homonid
adaptation
related to
bipedialism
• Sahelanthropus tchadensis
– “Toumai child”
– 6-7 MYA
– Chad
• Ardepithecus ramidus
– 5.8 – 4.4 MYA
– Ethiopia
Australopithecines
• Genus Australopithecus
– Slender (“gracile”) forms
• A. africanus, A. afarensis
– Robust forms
• A. robustus, A. boisei, A. aethopicus
• A. africanus
– South Africa
– 3 – 2 mya
– “slender” type
• A. afarensis
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Slender form
“lucy”
East Africa
~3mya
Dr. Corbin
• A. robustus
– Robust form
– Olduvai gorge
– 1.8 mya
Genus Homo
• Homo habilis
– 2.0 – 1.9 mya
– Brain size 775 cc
• Speech centers
– Omnivore
– Olduvai gorge
• H. habilis (cont.)
• H. erectus
– Java
– 1.9-0.3 mya
– Brain 800-1000cc
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H. erectus (cont)
Extensive tool use
Fire
Dispersed into Europe and Asia
• H. neanderthalensis
– 200k bp
– Neander valley
– 1450 cc
• H. sapiens
– Cromagnon man
• 100-150k bp
• ~1360 cc
• Culture
• Timeline of Homonid evolution
Out-of-Africa Hypothesis
Thousands of years before present
Note on human variability
• Ethnic - of or relating to large groups of
people classed according to common racial,
national, tribal, religious, linguistic, or
cultural origin or background.
Lewontin – 17 genes, 7 ethnic groups
Morphological differences
not adaptive
Genetic
variation
a
b
a
b
c
d
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