(14) Evo-Devo Flashcards
(17 cards)
What does development refer to?
The process through which an embryo becomes an adult organism and eventually dies.
(T/F) Ancestral characters are often, but not always, preserved in an organism’s development.
True!
E.g., both chick and human embryos go through a stage where they have slits and arches in their necks like the gill slits and gill arches of fish
Does Ontogeny Recapitulate Phylogeny?
No. Although some scientists felt that ontogeny could not only reveal something about evolutionary history, but also preserved a step-by-step record of that history, this is clearly not the case.
What has major effects on the morphology of an adult organism?
Changes in the genes controlling development
What is likely to have helped bring about large-scale evolutionary transformations?
Changes in developmental genes
Define the term “module” and provide an example
A unit that can be duplicated and further adapted.
E.g., arthropods have various numbers of body segments. Segment duplication and loss is a developmental change that probably occurred many times in the evolution of clades
What is individualization?
The modification of a particular module, usually when there is selection for a specialized function
E.g., One set of scorpions’ appendages has evolved into pincers whereas the same appendage in many spiders has evolved into colourful pompoms used in mating rituals
What is heterotopy?
Change in the physical position of a trait during development, relative to an ancestor.
E.g., feathers from one part of a bird’s body may become expressed on another part
What is heterochrony?
A change in the rate or timing of development, relative to an ancestor
E.g., Paedomorphosis (Heterochronic retention of juvenile structures in adulthood. A change in timing might slow down the development of the body, but not alter the maturation of the reproductive system, yielding an adult organism with a form similar to the ancestral juvenile form.
Provide an example of heterochrony in humans
Paedomorphosis observed in human skull development.
The chimp skull develops a reduced brain case and extended jaws into adulthood while the human skull retains the juvenile features of the young chimp skull
What is allometric growth?
The relative growth rates of different body parts within a species during development
E.g., Bat wings are basically paws with really long fingers and skin stretched between them. In order for these wings to evolve, the rate of growth of finger bones must have increased relative to the growth of the rest of the bat’s body - or perhaps the rate of growth of the rest of the body decreased relative to the fingers. Either way, it is allometry.
E.g., Allometric growth in horned scarab beetles; certain clusters of cells grow faster than others
What is the function of regulatory genes?
They control when are where other genes get turned on.
How much can a single regulatory gene control?
Since they can start “chain reactions” of effects, they can control the construction of a body parts as complex as a leg or eye
How did biologists discover genes that determine animal body plan?
By studying rare mutations that caused changes in fruit fly development.
These mutations caused structures present on one body segment to be replaced by structures found on another segment.
What is the term for mutations that cause structures present on one body segment to be replaced by structures found on another segment?
Homoeotic mutations
Where was the gene logic that is used in regulatory gene “switches” discovered previously?
Bacteria (The lac operon in E. coli)
What is the gene logic used by regulatory gene “switches”?
Gene expression controlled by DNA-binding proteins (i.e., TFs)
DNA-binding proteins recognize specific DNA sequences near a gene
