Evolutionary Morphology Flashcards
Series of developmental stages
Ontogeny
New stages yielding derived adult morphologies are added onto the end of ancestral ontogeny.
Terminal addition
Idea that development accelerates in descendants
Condensation
Idea that descendant ontogenies represent ancestral adult forms
Palingenesis; DISCARDED THEORY
Change that doesn’t fit recapitulation
Cenogenesis
Repetition of an evolutionary process during growth
Recapitulation
Idea that descendant ontogenies tend to recapitulate ancestral ones.
Paleogenesis
Example of paleogenesis
Notochord doesn’t persist into adult; extra stage where they disappear exists as compared to ancestor.
Mechanism for adaptation
Natural selection
Genetic modifications that cause phylogenetic change
Changes in protein structure and changes in regulatory mechanisms during development
List modes of evolutionary change
- Cell division and allometry
- Cellular differentiation
- Apoptosis
- Embryonic tissue interactions
- Heterochrony
- Pattern formation
- Reduction and loss
When different parts of the body grow at different rates during development.
Allometric growth
Evolutionary change in rates of cell growth that give rise to descendants with different proportions.
Evolutionary allometry
When cell populations differentiate differently in descendant lineages
Change in cellular differentiation
Example of cellular differentiation
Cartilaginous skeleton in Chondrichthyes
When a descendant retains a fetal stage of the ancestor into adulthood
Paedomorphosis
Programmed cell death
Apoptosis
Example of apoptosis in evolution
In ducks, webbing between feet fails to die during development resulting in webbed feet
Example of embryonic tissue interactions affecting evolution
Bird mesenchyme has lost the ability to respond to induction and will not form tooth germ.
Process of normal tooth development
Oral epithelium induces neural crest mesenchyme to form tooth germ, which induces the oral epithelium to form the enamel organ.
Evolutionary change in the timing of developmental events.
Heterochrony
Example of heterochrony
Cessation of brain growth occurs later in humans than in other great apes.
Developmental establishment of precise spacial relationships between parts.
Pattern formation
Example of pattern formation affecting evolution
Modern birds proximal tarsals fuse to form tibiotarsus and distal and metatarsals fuse to form tarsometatarsus
