EVOLUTIEBIOLOGIE 1
LECTURE 1 | HISTORY | 5 MAART ’25
Niko Tinbergen: Dutch ethologist, set up 4 questions to understand behavior and phenotypes.
- Proximate Causation (regarding individual organisms)(what?):
− Ontogeny: What is the development of the behavior? How is it learned or shaped over the
life of the individual? (How did it develop during the lifetime of the individual?)
− Mechanism: What is the biology of the behavior? What are the morphological structures
or biochemical responses that give rise to the behavior? (How does it work?)
- Ultimate Causation (regarding species level traits)(why?):
− Phylogeny: What is the evolution of the behavior? Is the behavior derived (new to this
species) or ancestral (present in immediate, phylogenetic ancestors)? (How did it evolve over
the history of the species?)
− Adaptive Value: What is the survival function of the behavior? What is it about the
behavior that confers a reproductive advantage over others? (What is it for?)
Primary goals of evolutionary biology are: Pattern (what do we see?), Process (why/how’d it happens?) and
Utility (what can we do with it?).
What is evolution? It’s a descent with modification. Changes in the properties of populations that
transcend the lifetime of a single individual. And changes in allele frequencies over time.
Hereditary similarity: offspring resemble parents.
-> If the offspring resembles their parents, the trait has a high chance of being heritable.
Lamarck: chain of ladder. organisms arise by spontaneous generation. There is an innate drive towards
complexity. Adaptation through use. But there is no evidence for it all.
Thomas Malthus and Alfred Russel Wallace came up with the idea of natural selection and survival of the
fittest.
DARWIN’S 4 INSIGHTS OF EVOLUTION
1. Evolution has occurred (pattern)
2. Primary cause of evolutionary change is natural selection (process)
3. Splitting of single species into two or more species had occurred (conclusion: we all have a
common ancestor)
4. Evolutionary change is gradual (maybe not so true)
NECESSARY CONDITIONS FOR EVOLUTION BY NATURAL SELECTION ! TEST QUESTION !
- Variation in the phenotype
- Heritability of traits affecting survival and reproduction
- Differential reproductive success: A situation in which some individuals leave more offspring in
the next generation than do others, often due to traits that confer advantages in survival and/or
reproduction.
This process is repeated generation after generation over long or short times of periods.
,LECTURE 2 | NATURAL SELECTION | 6 MAART ’25
Fittest individuals that have traits that lead them to be most fit in the environment they live in, are predicted
to increase in frequency in the population.
Fitness: how well a species is able to reproduce in its environment.
How to increase fitness?
- Be more aggressive.
- Be larger.
- Be choosy, mate with only the best.
- Have more offspring.
- Have offspring of a higher quality
Fitness takes into account both survival and reproductive success. Fitness changes for an individual based
on where (and when) it’s found.
HERITABILITY
‘Environment runs in families too’, effects outcome of similarity test between parent and child.
Graph c): evidence the variation among individuals is due to genes.
Graph a): evidence the variation among individuals is due to environmental factors.
To make sure that the environment is not causing some of the variation you could use a common garden
or foster families when testing. If the relationship persists, then it has the do with the home environment.
SELECTION DIFFERENTIAL
= the difference between the mean of the selected group (those that reproduce) and the mean of the
population. S = mean selected – mean trait.
Selection differential x heritability = evolutionary response. S x h2 = R ! TEST QUESTION !
, Directional selection: the mean (of phenotype) is changing in one
direction. Typically, the variance will shift as well. It will get thinner. (not
always)
Stabilizing selection: selection acts against extreme phenotypes. Too
small or too big has high mortality. Variance changes. Mean stays in the
exact same place.
Disruptive selection: selection against the middel of a trait. Selects for
extremes. Doesn’t change the mean. Increases variance.
LECTURE 3 | ADAPTATION | 6 MAART ‘25
Not all features of a population are adaptive or adaptations and not all adaptations are perfect.
Ways to identify an adaptation.
- Complexity: complex structures are usually adaptive. Wouldn’t expect it to appear by chance.
- Engineering: mostly the adaptive features fit their purpose.
- Convergence: convergent evolution.
The study of adaptation proceeds in three conceptual stages:
1. Identify the phenotypic variation associated with a trait, does it vary, and can it respond to
selection?
2. Develop a hypothesis of the trait’s function.
3. Test the hypothesis predictions.
A good hypothesis will predict the features of the trait exactly, and the predictions will be testable.
Four main methods are available to test an adaptive hypothesis:
1. Observational studies: examine if traits are associated with a given postulated
function/advantage (such as reduced predation). often correlative and lack clear links with
causality.
2. Conduct experiment: especially if trait can be manipulated experimentally. For example, paint
out the wing stripes of a butterfly species. If the butterflies with their stripes painted out survived
equally well as control butterflies, the wing-stripes are therefore probably not adaptations to
increase survival.
3. Experimental evolution: conduct laboratory studies of selection. Allows examination of
evolutionary processes underdefined and reproducible conditions over many generations.
Artificial selection.
4. Comparative method: examining similar traits in related/unrelated species. Look for parallelism/convergence in character states.
Adaptive traits can evolve from preexisting feature: exaptation: a character evolved for a different purpose
for that which it is currently used. It gets a new use.
Key variables:
- Population size
- Mutation rate
- Recombination
- Parasites?
- Constant of fluctuating environment
LECTURE 1 | HISTORY | 5 MAART ’25
Niko Tinbergen: Dutch ethologist, set up 4 questions to understand behavior and phenotypes.
- Proximate Causation (regarding individual organisms)(what?):
− Ontogeny: What is the development of the behavior? How is it learned or shaped over the
life of the individual? (How did it develop during the lifetime of the individual?)
− Mechanism: What is the biology of the behavior? What are the morphological structures
or biochemical responses that give rise to the behavior? (How does it work?)
- Ultimate Causation (regarding species level traits)(why?):
− Phylogeny: What is the evolution of the behavior? Is the behavior derived (new to this
species) or ancestral (present in immediate, phylogenetic ancestors)? (How did it evolve over
the history of the species?)
− Adaptive Value: What is the survival function of the behavior? What is it about the
behavior that confers a reproductive advantage over others? (What is it for?)
Primary goals of evolutionary biology are: Pattern (what do we see?), Process (why/how’d it happens?) and
Utility (what can we do with it?).
What is evolution? It’s a descent with modification. Changes in the properties of populations that
transcend the lifetime of a single individual. And changes in allele frequencies over time.
Hereditary similarity: offspring resemble parents.
-> If the offspring resembles their parents, the trait has a high chance of being heritable.
Lamarck: chain of ladder. organisms arise by spontaneous generation. There is an innate drive towards
complexity. Adaptation through use. But there is no evidence for it all.
Thomas Malthus and Alfred Russel Wallace came up with the idea of natural selection and survival of the
fittest.
DARWIN’S 4 INSIGHTS OF EVOLUTION
1. Evolution has occurred (pattern)
2. Primary cause of evolutionary change is natural selection (process)
3. Splitting of single species into two or more species had occurred (conclusion: we all have a
common ancestor)
4. Evolutionary change is gradual (maybe not so true)
NECESSARY CONDITIONS FOR EVOLUTION BY NATURAL SELECTION ! TEST QUESTION !
- Variation in the phenotype
- Heritability of traits affecting survival and reproduction
- Differential reproductive success: A situation in which some individuals leave more offspring in
the next generation than do others, often due to traits that confer advantages in survival and/or
reproduction.
This process is repeated generation after generation over long or short times of periods.
,LECTURE 2 | NATURAL SELECTION | 6 MAART ’25
Fittest individuals that have traits that lead them to be most fit in the environment they live in, are predicted
to increase in frequency in the population.
Fitness: how well a species is able to reproduce in its environment.
How to increase fitness?
- Be more aggressive.
- Be larger.
- Be choosy, mate with only the best.
- Have more offspring.
- Have offspring of a higher quality
Fitness takes into account both survival and reproductive success. Fitness changes for an individual based
on where (and when) it’s found.
HERITABILITY
‘Environment runs in families too’, effects outcome of similarity test between parent and child.
Graph c): evidence the variation among individuals is due to genes.
Graph a): evidence the variation among individuals is due to environmental factors.
To make sure that the environment is not causing some of the variation you could use a common garden
or foster families when testing. If the relationship persists, then it has the do with the home environment.
SELECTION DIFFERENTIAL
= the difference between the mean of the selected group (those that reproduce) and the mean of the
population. S = mean selected – mean trait.
Selection differential x heritability = evolutionary response. S x h2 = R ! TEST QUESTION !
, Directional selection: the mean (of phenotype) is changing in one
direction. Typically, the variance will shift as well. It will get thinner. (not
always)
Stabilizing selection: selection acts against extreme phenotypes. Too
small or too big has high mortality. Variance changes. Mean stays in the
exact same place.
Disruptive selection: selection against the middel of a trait. Selects for
extremes. Doesn’t change the mean. Increases variance.
LECTURE 3 | ADAPTATION | 6 MAART ‘25
Not all features of a population are adaptive or adaptations and not all adaptations are perfect.
Ways to identify an adaptation.
- Complexity: complex structures are usually adaptive. Wouldn’t expect it to appear by chance.
- Engineering: mostly the adaptive features fit their purpose.
- Convergence: convergent evolution.
The study of adaptation proceeds in three conceptual stages:
1. Identify the phenotypic variation associated with a trait, does it vary, and can it respond to
selection?
2. Develop a hypothesis of the trait’s function.
3. Test the hypothesis predictions.
A good hypothesis will predict the features of the trait exactly, and the predictions will be testable.
Four main methods are available to test an adaptive hypothesis:
1. Observational studies: examine if traits are associated with a given postulated
function/advantage (such as reduced predation). often correlative and lack clear links with
causality.
2. Conduct experiment: especially if trait can be manipulated experimentally. For example, paint
out the wing stripes of a butterfly species. If the butterflies with their stripes painted out survived
equally well as control butterflies, the wing-stripes are therefore probably not adaptations to
increase survival.
3. Experimental evolution: conduct laboratory studies of selection. Allows examination of
evolutionary processes underdefined and reproducible conditions over many generations.
Artificial selection.
4. Comparative method: examining similar traits in related/unrelated species. Look for parallelism/convergence in character states.
Adaptive traits can evolve from preexisting feature: exaptation: a character evolved for a different purpose
for that which it is currently used. It gets a new use.
Key variables:
- Population size
- Mutation rate
- Recombination
- Parasites?
- Constant of fluctuating environment
