Development 4: Evolution & development Flashcards
What are the similarities between organisms a result of?
A common ancestor
What are the differences between organisms a result of?
Natural selection
Why are genetic relationships between organisms determined (partly) through comparison of embryos?
Because changes in developmental processes will modify the form of an adult organism over evolutionary time
= Darwin recognised that organisms embryos can be similar while adult phenotypes often differ
Many genes that regulate development are ______ _______
highly conserved
Why does developmental genes being highly conserved show that they alone do not determine morphology?
Huge variety of animals are produced by a common set of instructions
= Differences in form mean that the genes alone can’t determine an organism’s morphology
What are changes to morphology a result of?
- Mutations in genes that regulate development
- Changes in the spatial expression of development genes
- Changes in the temporal expression of development genes
Give an example of how mutations can modify morphology
- Insect Ultrabithorax (Ubx) gene has a mutation
- Mutated gene is expressed in the abdomen → represses the dII gene
- Distal-less (dII) gene is essential for leg formation in arthropods
= Insects don’t form legs on their abdomens
Give an example of how changes in spatial expression can modify morphology
- In most birds, gene encoding BMP4 is expressed between developing toes (webbed) and instructs cells to undergo apoptosis
- Ducks have BMP inhibitor ‘gremlin’ = inhibits apoptosis around toes = webbed feet
Give an example of how changes in temporal expression can modify morphology
- Webs of most salamanders disappear as the animals mature
- If expression of genes that dissolves the webs is delayed, the digits don’t grow and ‘juvenile’ webbed feet result
What is heterochrony?
Modularity allows the timing of developmental processes to shift independently (compared to ancestor)
Give an example of an environmental cue causing normal development
In mosquitoes the blood meal stimulates the brain to stimulate the body to produce vitellogenin (critical for egg production)
What kind of response do animals have to environ cues for normal dev?
They have a fixed adaptive response
Describe the response of animals to environ signals closely correlated with future conditions.
Organisms are likely to respond differently to different cues
Give an example of an environmental cue being closely correlated with future conditions.
- ‘The Squinting Bush Brown butterfly’ has a dry-season form and a wet-season form with different wing coloration
- Temp during pupation determines adult form
= Polyphenism