EVOLUTION (BIOL 318) BIOLOGY EXAM
3 (Turbeville) STUDY NOTES (I studied
before my exam) COMPETE AND
ACCURATE LATEST GUIDE VIRGINIA
COMMONWEALTH UNIVERSITY
, Exam 3 Study Guide Evolutionary
Developmental Biology
• Evolutionary Developmental Biology (Evo-Devo): Study of developmental characters in an evolutionary
context
o A fusion of developmental biology and evolutionary biology
• Ontogeny: Development of an individual
o When looking at development of individuals, the same basic pattern emerges
▪ Zygotes start as simple forms and then develop into more complex forms
▪ Zygote: Single cell that results when the sperm fuses with the egg
• After zygote forms, embryonic development commences
• Complexity arises from cell divisions and rearrangements (gastrulation)
o Differential gene expression results in differentiation of cells
• The beginnings of evo-devo can be traced to Greek philosophers
o When comparing embryos within a taxon, common general features appeared first compared to
more complex features
▪ Lineage specific traits arrive later
▪ So most embryos look the same or similar in earlier stages than later
o Early embryologists recognized evolutionary links among taxa through comparisons and
development of the embryos
▪ Comparative observations of embryonic development in vertebrates revealed
homologous features (shared ancestral)
• Ex: Pharyngeal gills developed into gills in fish and salamanders; contribute to
tonsils, parathyroid gland, etc in humans
• Ex: Tail – gone in humans, but coccyx bone is retained for muscle attachments
o Ontogeny capitulates phylogeny – means the development of the individual repeats the
phylogeny
▪ Comparative analysis reveal homologous features that wouldn’t be detected across all
vertebrates if only comparing adults
• Timing of development can be divided into 2 steps
o Development of reproductive traits
o Development of non-reproductive traits (somatic)
• Heterochrony: Changes to the rate and/or timing of development with reference to an ancestor
o Recapitulation: Appearance of adult somatic traits prior to reproductive maturity, a form of
heterchrony
▪ Acceleration: Somatic traits appear early in development
▪ Hypermorphosis: Reproductive traits appear later
o Paedomorphosis: Juvenile traits appear in the adult stage
▪ Neoteny: Appearance of somatic traits is delayed
• Ex: Neoteny evolved in a lineage of Ambystoma (axolotl)
o Reproductive maturity occurs in individuals with juvenile characteristics
▪ Axolotl vs Tiger salamander
• Tiger salamander developed all somatic traits; axolotl
retained juvenile traits in adulthood
• Ancestral condition = lack of neoteny
▪ Supports hypothesis that neoteny rose in this lineage
• Derived condition, lack = ancestral condition
• Probably evolved recently
o Addition of thyroid hormone to cultures salamander larvae develops
somatic traits (the traits the axolotl lacks under normal conditions)
▪ Genetic studies reveal that neotenous condition is due to the
downregulation of mRNA for thyroid hormone
o Predation pressure may have selected for this
▪ Like maybe is was higher in terrestrial environments
o Some salamanders are facultatively neotenous
▪ More common when predation rates are lower in water than land
▪ Progenesis: Reproductive traits appear early
• Evo-devo = change in timing
o There’s evolutionary change
• There’s an underlying genetic component
o Research shifted to genetics in late 20th century
3 (Turbeville) STUDY NOTES (I studied
before my exam) COMPETE AND
ACCURATE LATEST GUIDE VIRGINIA
COMMONWEALTH UNIVERSITY
, Exam 3 Study Guide Evolutionary
Developmental Biology
• Evolutionary Developmental Biology (Evo-Devo): Study of developmental characters in an evolutionary
context
o A fusion of developmental biology and evolutionary biology
• Ontogeny: Development of an individual
o When looking at development of individuals, the same basic pattern emerges
▪ Zygotes start as simple forms and then develop into more complex forms
▪ Zygote: Single cell that results when the sperm fuses with the egg
• After zygote forms, embryonic development commences
• Complexity arises from cell divisions and rearrangements (gastrulation)
o Differential gene expression results in differentiation of cells
• The beginnings of evo-devo can be traced to Greek philosophers
o When comparing embryos within a taxon, common general features appeared first compared to
more complex features
▪ Lineage specific traits arrive later
▪ So most embryos look the same or similar in earlier stages than later
o Early embryologists recognized evolutionary links among taxa through comparisons and
development of the embryos
▪ Comparative observations of embryonic development in vertebrates revealed
homologous features (shared ancestral)
• Ex: Pharyngeal gills developed into gills in fish and salamanders; contribute to
tonsils, parathyroid gland, etc in humans
• Ex: Tail – gone in humans, but coccyx bone is retained for muscle attachments
o Ontogeny capitulates phylogeny – means the development of the individual repeats the
phylogeny
▪ Comparative analysis reveal homologous features that wouldn’t be detected across all
vertebrates if only comparing adults
• Timing of development can be divided into 2 steps
o Development of reproductive traits
o Development of non-reproductive traits (somatic)
• Heterochrony: Changes to the rate and/or timing of development with reference to an ancestor
o Recapitulation: Appearance of adult somatic traits prior to reproductive maturity, a form of
heterchrony
▪ Acceleration: Somatic traits appear early in development
▪ Hypermorphosis: Reproductive traits appear later
o Paedomorphosis: Juvenile traits appear in the adult stage
▪ Neoteny: Appearance of somatic traits is delayed
• Ex: Neoteny evolved in a lineage of Ambystoma (axolotl)
o Reproductive maturity occurs in individuals with juvenile characteristics
▪ Axolotl vs Tiger salamander
• Tiger salamander developed all somatic traits; axolotl
retained juvenile traits in adulthood
• Ancestral condition = lack of neoteny
▪ Supports hypothesis that neoteny rose in this lineage
• Derived condition, lack = ancestral condition
• Probably evolved recently
o Addition of thyroid hormone to cultures salamander larvae develops
somatic traits (the traits the axolotl lacks under normal conditions)
▪ Genetic studies reveal that neotenous condition is due to the
downregulation of mRNA for thyroid hormone
o Predation pressure may have selected for this
▪ Like maybe is was higher in terrestrial environments
o Some salamanders are facultatively neotenous
▪ More common when predation rates are lower in water than land
▪ Progenesis: Reproductive traits appear early
• Evo-devo = change in timing
o There’s evolutionary change
• There’s an underlying genetic component
o Research shifted to genetics in late 20th century
