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samenvatting van tentamen 1 EVO DEVO
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Tentamen 1 EVO-DEVO01. Introduction
History of the field of evolutionary biology:
Evolutionary biology is to interpret and understand organismal adaptation to environmental conditions.
Charles Darwin (1859): evolution is change in the heritable characteristics of biological populations over
successive generations. Natural selections occurs when:
1. Variation in reproductive success
2. Variation in the trait of interest
3. Correlation between the trait and the reproductive success.
4. The trait is heritable
“survival of the fittest”. The way of thinking about evolution changed after Darwin. There was a big
success when DNA sequencing came across, and we did learn a lot of new things. Since a few years, the
range of evolution in medicine is growing.
Ways of thinking: Typological, population, tree:
Typological: The normal of average condition is the most important aspect to consider. In biology
this way is not that common.
Population: Understanding the variation in a population. Show a pattern in space and time. This
way you can see evolution in ‘action’. This is used by the covid-19.
There are heritable traits that allow genetic variation to occur, and therefore selection in humans.
Take for example: behaviour (intelligence), physiology (lactase persistence), morphology (waist-
to-hip ratio) and life cycle traits (lifespan)
When is something adaptative? > not everything is adaptive! To say something is adapting, we
need examination, which can be difficult in humans. Examination is done in 3 ways:
1. Observing natural selection: experiment in microorganism with a short life span and
many offspring.
2. Perturbing the trait: move trait away from its optimum and see what happens. Done by
birds and their eggs.
3. Trait is productive only when it serves a function: spine develop Daphnia when predators
are present.
Most of these are not possible on humans, so we need model organism and association
studies of phylogenetic analyses.
Tree thinking: Understanding the position of a species or trait in a phylogenetic tree. This
expresses the relationships among organism and their evolutionary history.
02. The story of our ancestors
Biological classification of Homo Sapiens:
Homo Sapiens means knowledgeable man. They are from the Homininea family,
but they are the only one still alive. They are different in their brain size, and the
family structure and sexuality.
Phylogeny of the primates:
Primates are our extended family. Homininea specific characteristics are that they
have no tail, remarkably long periods of nursing and adolescence, and have sexual
dimorphism. An apomorphic trait is a trait that is characteristic for a defined
specie. Pleiomorphic is a trait that an ancestral character state.
Characteristics of hominin evolution:
Homininea are our closest relatives. They have many split and dead ends, called cladogenesis. They
evolved gradual, called anagenesis. The precise phylogeny is still debated. All old fossils of hominis are
found in Afrika. Via ecological niche they adapted because they did not live in trees anymore, walked up
straight after some time. There are 3 important hominin we need to know: Australopithecus africanus
(ancestor all hominin), Homo erectus (the African H. erectus is ancestor of H. sapiens) and the Homo
Neanderthalensis (similar to the homo sapiens).
, Australopithecus afarensis:
This first hominin was the road to bipedalism (walking on two feet). They
were bipedal but have very primitive traits. The foot had a large hallux
abduction. The walking on two feet needed a reorganization of the entire
skeleton. This was the basis of human adaption.
Lucy was an almost complete fossil found of this hominin. It shows
characteristics of bipedalism and a small brain.
Mosaic evolution: not all human traits evolved at the same time.
Apomorphic = derived and plesiomorphic = ancestral. In this evolution
the skull shape and brain volume changed plesiomorphic. The teeth
changed from a U and big form, to smaller and more parabolic. And there
was a reduction in canine teeth. BUT! there was still strong sexual dimorphism (gradually disappeared).
Sexual dimorphism: Harem groups are very dimorph.
Genus Homo: evolution of brain volume takes off! Use and manufacturing stone tools. This compromised
3 things: understanding mechanism, sensor control and understand where to strike. Homo rudolfenesis is
an alternative for the first homo, because it made tools.
Homo erectus:
Clearly more human like features. Less body hair, and more brain volume. They were associated with the
hunting of animals, and the use of fire. The Homo erectus moved out of Afrika. Therefore, the morphology
became very diverse. Like the H. ergaster in Asia.
There comes the problem with splitting versus lumping. When do you call variation a different specie?
Therefore, we need to know what a specie is:
Group of organisms that can produce fertile offspring (cannot exanimated in fossils)
DNA sequence similarity (also problem in old fossils)
Behaviour
Ecological niche
Morphology, variation within and between species
Speciation in the hominins:
Reproductive isolation followed by local adaption or genetic drift.
1. Sympatric speciation: side-by-side evolution is rare. They occurred in East Africa after each other
2. Allopatric speciation: a group separates and starts a new group. Evolution of Homo erectus
subspecies after migration to Asia
3. Parapatric speciation: new species due to local adaption. Evolution of neanderthalensis in Europe
and Asia from the H. Heidelberg’s during the ice age.
03. Migration and Hybridizations
Evolution of the Neanderthals, phylogeny and species characteristics:
The ancestor of the H. sapiens and the neanderthal is the homo
heidelbergensis. The Neanderthals fossil was found in Germany. They have
distributed across Europe and Asia. Their skull looks different, and they
don’t have s chin. The body was stocky, they got short legs, and a barrel
shaped chest. This shorter body was probably due to the cold, because
there is a correlation is shortness and colder
regions. Their brains were even big, but the
anatomy was different. They have structures to
speak and used tools and fire. They also had cultural traditions.
Theories of the origin of Homo sapiens:
There are 2 theories: ‘out of Africa’ > all from afrika and replaced all homo
species. All humans descend from an African ancestor. And the multiregional
evolution > evolved locally, Asians form erectus, and European from ergaster.
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