Week 1.1 – introduction:
Every start, of the first practical session that week, you have a theme test which counts for 10%
of your final grade, 3/4 tests need to be made, average taken.
Exam only closed questions.
Week 1.2 – study skills:
Functions, places, names
Week 1.3 – lz2 phenotype:
Gradualism
Darwin’s theory of gradualism opposes arguments for the sudden origin of species
- A simple statement of Darwin’s theory of gradualism is that accumulation of quantitative
changes leads to qualitative change.
Hereditary vs. adaptation
Evolution is the result of random mutations, that turn out to be beneficial
- Mutations: adaptation in genotype
• Population gradualism: new traits become established in a population by increasing their
frequency initially from a small fraction of the population to a majority of the population.
Populational gradualism is not controversial. Due to genotypic changes.
• Phenotypic gradualism: new characteristic is consequence of beneficial changes over
many generations.
- Sports: some mutations that appear during artificial breeding change the
phenotype substantially in a single mutational step.
➔ Darwin and others state that sporting mutations always have negative side-effects
that would cause selection to eliminate them from natural populations.
Phenotypic plasticity
Range of phenotypes within genotypic limits, so changes in organism without changes in its
DNA.
Genotype and environment influence phenotype.
- Homeostasis: internal environment needs to remain constant; set point.
- Phenotype: characteristic is optimized within the limits of genetic properties;
optimum.
Phenotype determines how well homeostasis can be maintained.
- Capacity to change within a given genotype.
, 1. Developmental plasticity
Environmental factors during ontogeny determine: size, form and behaviour of the adult
organism.
Epigenetics: study of phenotypical changes for which NO change in DNA sequence is required.
Phenotype (gene activity) influenced by:
- DNA methylation
- Histone modification (acetylation)
2. Polyphenetic properties – polyphenism
Subcategory of developmental plasticity
Discrete Alternative phenotypes
Environmental factor → certain hormone/ endogenous pathway → epigenetic mechanism
changed → different gene expression
• Polyphenism: Same genetic background, but discrete alternative phenotypes (no gradual
changes)
➔ Changing from 1 type to another type.
➔ Like male of female.
Depending on the environmental factors, with the same genotype, you can get a completely
different phenotype.
,Regulation vs. conformation
• Conformers: internal environment follow the external environment, no adaptation
• Regulators: internal environment is kept constant independent of external environment,
adapt to situation.
Homeostasis
Phenotype determines homeostasis.
Environment determines homeostasis → Outside temperature during development determines
adaptation potential when grown up.
• Osmoregulation: the regulation of amount of salts in your body/ blood.
- Have conformers and regulators
Migratory fish, 2 patterns, can completely adapt to changing environments
1. anadromous: egg in fresh water, adult in salt water
2. catadromous: egg in salt water, adult in fresh water
water adaptations:
fresh water: vs. salt water:
- influx water - influx ions
- loss of ions - loss of
water
this adaptation in physiology is caused by: salinity change, which induces hyperosmotic
response:
- Hypertrophy ionocytes
- Proliferation ionocytes
Week 1.3 – lz3 embryonic development:
Evo Devo (evolution – development) buildplan:
Stages of development
Key stages ontogeny vertebrates:
1. Fertilization (fusion egg & sperm → zygote)
2. Cleavage (cell divisions → blastocoel)
3. Gastrulation (formation 3 germ layers → archenteron)
- Ectoderm
- Mesoderm
- Endoderm
4. Organogenesis, neurulation (folding and formation
organs)
5. Growth (adult form)
, 1. Fertilization: formation of zygote (sperm + egg cell)
2. Cleavage: the embryo divides repeatedly
- Before cleavage an animal-vegetal axis is visible on the embryo, the axis exist
because yolk, nutrition for developing only occurs at the end. Yolk is at the
vegetal pole and the animal pole is mostly cytoplasm.
- Formation blastomeres: a single cell converting into smaller ones, daughter
cells
- No growth occurs, only subdivision of mass until normal somatic cell size is
reached.
- At the end of cleavage → blastula stage in which a blastocoel is formed, a
central fluid-filled cavity with blastula cells that form a layer around.
Radial cleavage → 1st cleavage right trough the animal-vegetal pole. The 2nd cleavage through
both blastomeres parallel to the animal-vegetal pole. Cleavage furrows next form
simultaneously in the four daughter blastomeres, perpendicular to the animal- vegetal pole.
Subsequent cleavages yield an embryo composed of several tiers of cells.
• Deuterostome: embryo develops through the blastula and gastrula stages, and forms a
complete gut. The blastopore becomes the anus, and a second, opening becomes the
mouth.
Sorts of cleavage:
4 terms for the amount of yolk:
1. Isolecithal: eggs with very little yolk evenly
distributed
2. Mesolecithal: eggs have a moderate amount of yolk
concentrated at the vegetal pole
3. Telolecithal: eggs contain an abundance of yolk
densely concentrated at the vegetal pole of the egg
4. Centrolecithal: eggs have a large, centrally located
mass of yolk
Why does the amount of yolk matter? Cytoplasm is dense,
and is a mixture of proteins that provides nutrients for
developing embryo. The furrow has difficulty forming when
the cytoplasm is dense with yolk → Cleavage proceeds
more slowly in the presence of yolk.
- Meroblastic: when much yolk present, the
cleavage furrow does not completely
divide the cytoplasm of the egg at each
cell division. Meroblastic cleavage is
incomplete because cleavage furrows
cannot cut through the heavy
concentration of yolk.
- Holoblastic: when little yolk present
Every start, of the first practical session that week, you have a theme test which counts for 10%
of your final grade, 3/4 tests need to be made, average taken.
Exam only closed questions.
Week 1.2 – study skills:
Functions, places, names
Week 1.3 – lz2 phenotype:
Gradualism
Darwin’s theory of gradualism opposes arguments for the sudden origin of species
- A simple statement of Darwin’s theory of gradualism is that accumulation of quantitative
changes leads to qualitative change.
Hereditary vs. adaptation
Evolution is the result of random mutations, that turn out to be beneficial
- Mutations: adaptation in genotype
• Population gradualism: new traits become established in a population by increasing their
frequency initially from a small fraction of the population to a majority of the population.
Populational gradualism is not controversial. Due to genotypic changes.
• Phenotypic gradualism: new characteristic is consequence of beneficial changes over
many generations.
- Sports: some mutations that appear during artificial breeding change the
phenotype substantially in a single mutational step.
➔ Darwin and others state that sporting mutations always have negative side-effects
that would cause selection to eliminate them from natural populations.
Phenotypic plasticity
Range of phenotypes within genotypic limits, so changes in organism without changes in its
DNA.
Genotype and environment influence phenotype.
- Homeostasis: internal environment needs to remain constant; set point.
- Phenotype: characteristic is optimized within the limits of genetic properties;
optimum.
Phenotype determines how well homeostasis can be maintained.
- Capacity to change within a given genotype.
, 1. Developmental plasticity
Environmental factors during ontogeny determine: size, form and behaviour of the adult
organism.
Epigenetics: study of phenotypical changes for which NO change in DNA sequence is required.
Phenotype (gene activity) influenced by:
- DNA methylation
- Histone modification (acetylation)
2. Polyphenetic properties – polyphenism
Subcategory of developmental plasticity
Discrete Alternative phenotypes
Environmental factor → certain hormone/ endogenous pathway → epigenetic mechanism
changed → different gene expression
• Polyphenism: Same genetic background, but discrete alternative phenotypes (no gradual
changes)
➔ Changing from 1 type to another type.
➔ Like male of female.
Depending on the environmental factors, with the same genotype, you can get a completely
different phenotype.
,Regulation vs. conformation
• Conformers: internal environment follow the external environment, no adaptation
• Regulators: internal environment is kept constant independent of external environment,
adapt to situation.
Homeostasis
Phenotype determines homeostasis.
Environment determines homeostasis → Outside temperature during development determines
adaptation potential when grown up.
• Osmoregulation: the regulation of amount of salts in your body/ blood.
- Have conformers and regulators
Migratory fish, 2 patterns, can completely adapt to changing environments
1. anadromous: egg in fresh water, adult in salt water
2. catadromous: egg in salt water, adult in fresh water
water adaptations:
fresh water: vs. salt water:
- influx water - influx ions
- loss of ions - loss of
water
this adaptation in physiology is caused by: salinity change, which induces hyperosmotic
response:
- Hypertrophy ionocytes
- Proliferation ionocytes
Week 1.3 – lz3 embryonic development:
Evo Devo (evolution – development) buildplan:
Stages of development
Key stages ontogeny vertebrates:
1. Fertilization (fusion egg & sperm → zygote)
2. Cleavage (cell divisions → blastocoel)
3. Gastrulation (formation 3 germ layers → archenteron)
- Ectoderm
- Mesoderm
- Endoderm
4. Organogenesis, neurulation (folding and formation
organs)
5. Growth (adult form)
, 1. Fertilization: formation of zygote (sperm + egg cell)
2. Cleavage: the embryo divides repeatedly
- Before cleavage an animal-vegetal axis is visible on the embryo, the axis exist
because yolk, nutrition for developing only occurs at the end. Yolk is at the
vegetal pole and the animal pole is mostly cytoplasm.
- Formation blastomeres: a single cell converting into smaller ones, daughter
cells
- No growth occurs, only subdivision of mass until normal somatic cell size is
reached.
- At the end of cleavage → blastula stage in which a blastocoel is formed, a
central fluid-filled cavity with blastula cells that form a layer around.
Radial cleavage → 1st cleavage right trough the animal-vegetal pole. The 2nd cleavage through
both blastomeres parallel to the animal-vegetal pole. Cleavage furrows next form
simultaneously in the four daughter blastomeres, perpendicular to the animal- vegetal pole.
Subsequent cleavages yield an embryo composed of several tiers of cells.
• Deuterostome: embryo develops through the blastula and gastrula stages, and forms a
complete gut. The blastopore becomes the anus, and a second, opening becomes the
mouth.
Sorts of cleavage:
4 terms for the amount of yolk:
1. Isolecithal: eggs with very little yolk evenly
distributed
2. Mesolecithal: eggs have a moderate amount of yolk
concentrated at the vegetal pole
3. Telolecithal: eggs contain an abundance of yolk
densely concentrated at the vegetal pole of the egg
4. Centrolecithal: eggs have a large, centrally located
mass of yolk
Why does the amount of yolk matter? Cytoplasm is dense,
and is a mixture of proteins that provides nutrients for
developing embryo. The furrow has difficulty forming when
the cytoplasm is dense with yolk → Cleavage proceeds
more slowly in the presence of yolk.
- Meroblastic: when much yolk present, the
cleavage furrow does not completely
divide the cytoplasm of the egg at each
cell division. Meroblastic cleavage is
incomplete because cleavage furrows
cannot cut through the heavy
concentration of yolk.
- Holoblastic: when little yolk present
