Genes & Evolu,on
Lecture 1: Evolu.onary Biology, 14-10-2024
Chapter 2 & 3
Theore'cal and conceptual basis for a good understanding of evolu'onary and popula'on
gene'cal processes at different levels of organiza'on: gene → individual → popula'on →
species → phylogeny
DNA describes the gene'c proper'es of the organisms, gene'c/DNA varia'on codes for the
differences
DNA code inside every cell of your body that affects how you look, feel, learn, interact, etc.
this includes how long you may live and the diseases you may have. Decoding the DNA helps
us understand ourselves, pets, parasites, evolu'on.
Evolu'on of diversity in traits and species fascina'ng, but prone to story-telling
What is evolu.on: descent with modifica'on (Darwin), changes in allele frequencies over
'me (Dobzhansky, all changes that have transformed life on earth from its origins up to the
current (bio)diversity, phylogenesis: transforma'on within an evolu'onary lineage with
specia'on
Crea.onism/special crea.on theory: species are created separately, genealogically
unrelated → “One species never springs from the seed of another”, unchanged since their
origin, varia'on among individuals limited
Pre-Darwin, Scien.fic revolu.on: the world and its diversity are not the perfect end-product
created by God. Not designed for a purpose by an intelligent designer / omnipotent Creator.
Start of concept of evolu'on: Life is not forever unchanged and may diversify.
- Geologists: earth profoundly changed through 'me
- Astronomers: universe is not perfectly shaped around Earth
- Naturalist: life is not sta'c, but it changes
Lamarckian evolu.on: organisms altered their behavior in response to environmental
change. Their changed behavior, in turn, modified their organs, and their offspring inherited
those "improved" structures.
,Darwinian evolu.on: the idea that species change over 'me, give rise to new species, and
share a common ancestor, ‘descent with modifica'on’. Evolu'onary change based on the
existence of heritable differences between individuals
Natural selec.on: struggle for existence (intra- and interspecific compe''on, environmental
stress), survival of the fiUest (the individual with the most offspring), fitness differences are
heritable → change in gene'c composi'on of popula'ons and improved adapta'on
The mere recogni'on of a paUern does not cons'tute a scien'fic study → if we are to claim
we understand the evolu'on of a trait or of the diversity of species, we must not only explain
what happened but also the mechanisms that are responsible. Studying the mechanisms of
evolu'onary change requires the inclusion of gene.cs and heredity
Blending inheritance: mixing of characters of both parents
Par.culate inheritance: characters inherit as discrete en''es (GENES)
Gregor Mendel → father of modern gene'cs.
Galton studies con.nuous (quan'ta've) traits, whereas Mendel studied discrete (qualita've)
traits
The modern synthesis: interac'on between many different genes and environmental factors.
Ac'on of numerous gene'c and environmental factors gives con'nuous distribu'on. Natural
selec'on can lead to changes in allelic frequencies
One of the major accomplishments of the founders of the Modern Synthesis → providing a
solid gene'c mechanism for Darwinian selec'on
Theory of adap.ve evolu.on: alleles associated with higher fitness increase in frequency
over genera'ons
New coronaviruses emerge by muta'on and recombina'on. Some acquired the ability to
infect and replicate in, and transmit between, humans. Muta'ons con'nue to arise and are
passed on. Some virus variants are more successful. The variants that are most successful are
not a random subset, but those with highest fitness (R0).
Fundamental principles of evolu.onary change
- Individuals differ from one another
- Gene'c varia'on arises by random muta'on and recombina'on
- The propor'ons of alleles and genotypes within a popula'on change over 'me
- Such changes in the propor'ons of genotypes may occur either by nonrandom,
consistent differences among genotypes in survival or reproduc'on rates (natural
selec'on) or by random fluctua'ons (gene'c dri\)
- As a result of different histories of gene'c dri\, gene flow and natural selec'on,
popula'ons of a species may diverge
- New taxa arise from prolonged, gradual evolu'on & all species form a great tree of
life (phylogeny)
- The molecular basis of traits and adapta'on affect their evolu'on (mul'ple loci,
genomes)
,The Chilean blob could be iden'fied as a whale due to DNA sequencing. It is difficult to study
whales, because of their global distribu'on. DNA can be collected from small skin samples;
those are largely the same but have small individual differences. From the DNA we can tell in
which region it was born and how popula'ons changed over 'me (e.g., size, effects of
hun'ng/climate change). Whales have mammalian blood, bones, organs that are adapted to
life at sea
- Pres.n gene: molecular motor aUached to 'ny mobile hairs in mammalian ear. This is
needed for echo-loca'on (similar with bats)
The informa'on that we can extract from DNA lets us connect changes in individual genomes
to popula'on level processes to the genera'on of biodiversity. It allows us to reach back in
'me to test hypotheses on individuals, traits, popula'ons, species! DNA sequences are
widely used in ecology and evolu'on to iden'fy species, families (paternity), popula'ons,
diets, to track organisms through 'me & space (birthplace, migra'on) and to reconstruct
evolu'on of adapta'ons, ancestors, phylogenies, species origins and ex'nc'ons, body plans
DNA is discovered in 1860 and was recognized as
the carrier of gene'c informa'on in 1950.
Central dogma of molecular biology: from DNA to
RNA to protein. Only changes to the DNA (in the
germline) are passed on to offspring.
Muta'ons are essen'al for evolu'on, but not all
muta'ons are good or bad
Muta'on creates differences among individuals.
Muta'on creates variants of the DNA sequence,
where the nucleo'de sequence differs between
some members of a popula'on. From point-
muta'ons (SNPs) to larger DNA sequence changes. Muta'ons can be lost, or they are
inherited by offspring.
DNA is being copied from genera'on to genera'on. Sequence
varia'ons are passed on to offspring from genera'on to
genera'on. In sexually reproducing organisms, parents each
pass on a half of their hereditary informa'on to their offspring.
This is simply a re-distribu'on & re-shuffling of the gene'c
varia'on to the next genera'on (reproduc'on, not evolu'on!)
Muta'ons arise con'nuously, but DNA repair is devasta'ngly
good at its job, 'ny chance per nucleo'de for new muta'ons to
establish. Genomes are huge & muta'ons accumulate over long
'me.
Human (haploid) genome size: 3 billion
How many differences in DNA between any 2 humans? 4 million
, DNA sequence varia.ons (‘SNPs’) can be used by evolu'onary biologists to study traits,
individuals & popula'ons
Natural selec'on acts on individual varia'on, but evolu'onary consequences occur in
popula.ons
Individuals:
- Individuals differ (both in phenotype & genotype)
- Natural selec'on acts on the individual phenotype
- Individuals do not evolve → any changes to their phenotype are NOT passed on to
their offspring
Popula.ons:
- Popula'ons can differ (in gene'c composi'on)
- Popula'ons are not the target of natural selec'on
- Evolu'on operates at the level of popula'ons → it is a change in allele frequency
over 'me
The frequency of DNA sequence variants may change through 'me: Evolu'on!
- Through natural selec.on when a DNA sequence variant is either beneficial or
deleterious
- Through random processes, such as chance events (dri\), or the immigra'on or
muta'on of a new allele
Evolu'on by natural selec'on is a non-random process. Popula'ons become beUer adapted
to their environment. Random and other processes may also lead to changes in allele
frequencies (= evolu'on) → muta'on, chance events (gene'c dri\) – migra'on – non-
random ma'ng. Different processes operate simultaneously, but they may differ in strength
and importance
Genealogy reflects popula'on history. Different evolu'onary and demographic processes
lead to different paUerns of change in allele frequency.
Gene.c varia.on is the raw material for evolu'on. It can be quan'fied and studied to
iden'fy evolu'onary paUerns and to test hypotheses on evolu'on and evolu'onary
processes
Evolu.on is the changes in allele frequencies over 'me. By natural selec'on: individuals
carrying par'cular alleles do beUer. Random and other processes may also lead to evolu'on.
Darwin’s evolu'onary theory a\er Modern Synthesis. Individuals vary as a result of
muta'ons. Individuals pass on their alleles to their offspring. In every genera'on, some
individuals are more successful at surviving and reproducing than others. The most
successful individuals are those with alleles that best adapt them to their environment.
Lecture 1: Evolu.onary Biology, 14-10-2024
Chapter 2 & 3
Theore'cal and conceptual basis for a good understanding of evolu'onary and popula'on
gene'cal processes at different levels of organiza'on: gene → individual → popula'on →
species → phylogeny
DNA describes the gene'c proper'es of the organisms, gene'c/DNA varia'on codes for the
differences
DNA code inside every cell of your body that affects how you look, feel, learn, interact, etc.
this includes how long you may live and the diseases you may have. Decoding the DNA helps
us understand ourselves, pets, parasites, evolu'on.
Evolu'on of diversity in traits and species fascina'ng, but prone to story-telling
What is evolu.on: descent with modifica'on (Darwin), changes in allele frequencies over
'me (Dobzhansky, all changes that have transformed life on earth from its origins up to the
current (bio)diversity, phylogenesis: transforma'on within an evolu'onary lineage with
specia'on
Crea.onism/special crea.on theory: species are created separately, genealogically
unrelated → “One species never springs from the seed of another”, unchanged since their
origin, varia'on among individuals limited
Pre-Darwin, Scien.fic revolu.on: the world and its diversity are not the perfect end-product
created by God. Not designed for a purpose by an intelligent designer / omnipotent Creator.
Start of concept of evolu'on: Life is not forever unchanged and may diversify.
- Geologists: earth profoundly changed through 'me
- Astronomers: universe is not perfectly shaped around Earth
- Naturalist: life is not sta'c, but it changes
Lamarckian evolu.on: organisms altered their behavior in response to environmental
change. Their changed behavior, in turn, modified their organs, and their offspring inherited
those "improved" structures.
,Darwinian evolu.on: the idea that species change over 'me, give rise to new species, and
share a common ancestor, ‘descent with modifica'on’. Evolu'onary change based on the
existence of heritable differences between individuals
Natural selec.on: struggle for existence (intra- and interspecific compe''on, environmental
stress), survival of the fiUest (the individual with the most offspring), fitness differences are
heritable → change in gene'c composi'on of popula'ons and improved adapta'on
The mere recogni'on of a paUern does not cons'tute a scien'fic study → if we are to claim
we understand the evolu'on of a trait or of the diversity of species, we must not only explain
what happened but also the mechanisms that are responsible. Studying the mechanisms of
evolu'onary change requires the inclusion of gene.cs and heredity
Blending inheritance: mixing of characters of both parents
Par.culate inheritance: characters inherit as discrete en''es (GENES)
Gregor Mendel → father of modern gene'cs.
Galton studies con.nuous (quan'ta've) traits, whereas Mendel studied discrete (qualita've)
traits
The modern synthesis: interac'on between many different genes and environmental factors.
Ac'on of numerous gene'c and environmental factors gives con'nuous distribu'on. Natural
selec'on can lead to changes in allelic frequencies
One of the major accomplishments of the founders of the Modern Synthesis → providing a
solid gene'c mechanism for Darwinian selec'on
Theory of adap.ve evolu.on: alleles associated with higher fitness increase in frequency
over genera'ons
New coronaviruses emerge by muta'on and recombina'on. Some acquired the ability to
infect and replicate in, and transmit between, humans. Muta'ons con'nue to arise and are
passed on. Some virus variants are more successful. The variants that are most successful are
not a random subset, but those with highest fitness (R0).
Fundamental principles of evolu.onary change
- Individuals differ from one another
- Gene'c varia'on arises by random muta'on and recombina'on
- The propor'ons of alleles and genotypes within a popula'on change over 'me
- Such changes in the propor'ons of genotypes may occur either by nonrandom,
consistent differences among genotypes in survival or reproduc'on rates (natural
selec'on) or by random fluctua'ons (gene'c dri\)
- As a result of different histories of gene'c dri\, gene flow and natural selec'on,
popula'ons of a species may diverge
- New taxa arise from prolonged, gradual evolu'on & all species form a great tree of
life (phylogeny)
- The molecular basis of traits and adapta'on affect their evolu'on (mul'ple loci,
genomes)
,The Chilean blob could be iden'fied as a whale due to DNA sequencing. It is difficult to study
whales, because of their global distribu'on. DNA can be collected from small skin samples;
those are largely the same but have small individual differences. From the DNA we can tell in
which region it was born and how popula'ons changed over 'me (e.g., size, effects of
hun'ng/climate change). Whales have mammalian blood, bones, organs that are adapted to
life at sea
- Pres.n gene: molecular motor aUached to 'ny mobile hairs in mammalian ear. This is
needed for echo-loca'on (similar with bats)
The informa'on that we can extract from DNA lets us connect changes in individual genomes
to popula'on level processes to the genera'on of biodiversity. It allows us to reach back in
'me to test hypotheses on individuals, traits, popula'ons, species! DNA sequences are
widely used in ecology and evolu'on to iden'fy species, families (paternity), popula'ons,
diets, to track organisms through 'me & space (birthplace, migra'on) and to reconstruct
evolu'on of adapta'ons, ancestors, phylogenies, species origins and ex'nc'ons, body plans
DNA is discovered in 1860 and was recognized as
the carrier of gene'c informa'on in 1950.
Central dogma of molecular biology: from DNA to
RNA to protein. Only changes to the DNA (in the
germline) are passed on to offspring.
Muta'ons are essen'al for evolu'on, but not all
muta'ons are good or bad
Muta'on creates differences among individuals.
Muta'on creates variants of the DNA sequence,
where the nucleo'de sequence differs between
some members of a popula'on. From point-
muta'ons (SNPs) to larger DNA sequence changes. Muta'ons can be lost, or they are
inherited by offspring.
DNA is being copied from genera'on to genera'on. Sequence
varia'ons are passed on to offspring from genera'on to
genera'on. In sexually reproducing organisms, parents each
pass on a half of their hereditary informa'on to their offspring.
This is simply a re-distribu'on & re-shuffling of the gene'c
varia'on to the next genera'on (reproduc'on, not evolu'on!)
Muta'ons arise con'nuously, but DNA repair is devasta'ngly
good at its job, 'ny chance per nucleo'de for new muta'ons to
establish. Genomes are huge & muta'ons accumulate over long
'me.
Human (haploid) genome size: 3 billion
How many differences in DNA between any 2 humans? 4 million
, DNA sequence varia.ons (‘SNPs’) can be used by evolu'onary biologists to study traits,
individuals & popula'ons
Natural selec'on acts on individual varia'on, but evolu'onary consequences occur in
popula.ons
Individuals:
- Individuals differ (both in phenotype & genotype)
- Natural selec'on acts on the individual phenotype
- Individuals do not evolve → any changes to their phenotype are NOT passed on to
their offspring
Popula.ons:
- Popula'ons can differ (in gene'c composi'on)
- Popula'ons are not the target of natural selec'on
- Evolu'on operates at the level of popula'ons → it is a change in allele frequency
over 'me
The frequency of DNA sequence variants may change through 'me: Evolu'on!
- Through natural selec.on when a DNA sequence variant is either beneficial or
deleterious
- Through random processes, such as chance events (dri\), or the immigra'on or
muta'on of a new allele
Evolu'on by natural selec'on is a non-random process. Popula'ons become beUer adapted
to their environment. Random and other processes may also lead to changes in allele
frequencies (= evolu'on) → muta'on, chance events (gene'c dri\) – migra'on – non-
random ma'ng. Different processes operate simultaneously, but they may differ in strength
and importance
Genealogy reflects popula'on history. Different evolu'onary and demographic processes
lead to different paUerns of change in allele frequency.
Gene.c varia.on is the raw material for evolu'on. It can be quan'fied and studied to
iden'fy evolu'onary paUerns and to test hypotheses on evolu'on and evolu'onary
processes
Evolu.on is the changes in allele frequencies over 'me. By natural selec'on: individuals
carrying par'cular alleles do beUer. Random and other processes may also lead to evolu'on.
Darwin’s evolu'onary theory a\er Modern Synthesis. Individuals vary as a result of
muta'ons. Individuals pass on their alleles to their offspring. In every genera'on, some
individuals are more successful at surviving and reproducing than others. The most
successful individuals are those with alleles that best adapt them to their environment.
