Lecture 30: Evolution of Development & Size & Shape Flashcards
What is evolution?
- descent with modification
- Modification must include a change in the developmental program
- Evolutionary change must involve changes in the genetic basis of development
What is Ernst Haeckel’s biogenetic law?
ontogeny recapitulates phylogeny
- During development, descendants pass through developmental stages resembling the adult forms of their ancestors
What is Von Baer’s thought?
embryos diverge during ontogeny
- embryos of descendants only resemble embryos of ancestors
Define “phylotypic” stage.
the stage at which the embryo takes on the form that is distinctive for its phylogenetic lineage
What where D’Arcy Thompson’s thoughts on growth and form?
- Geometric transformation to “warp” one species form into another
- Good descriptor of pattern, but doesn’t get at underlying mechanism
Define allometry.
differential rates of growth (or evolution) of two different traits, not a 1:1 ratio
Y = b•Xa
- Logarithmic increase in Y as a function of X
- Linear relationship between Y and X
(log(Y) = log(b) + a•log(X))
positive allometry
Y grows faster than X
- Slope of line is still positive, but compare to slope of a = 1.0
negative allometry
Y grows slower than X
- Slope of line is still positive, but compare to slope of a = 1.0
Relationship between slopes/intercepts and allometry.
- Different slopes: Allometric relationship is different -Same slopes, Different intercepts: Allometric relationship is different
Define interspecific allometry
- Comparison across species
- Use a fixed age
Define intraspecific allometry
- Static allometry (same age) Ontogenetic allometry (across ages)
Define heterochrony
different timing of developmental events in evolution
Define neoteny
Retention of juvenile
forms in the adult stage
Define copes rule
Increase in body size in a lineage
- think of odd structures
