Lecture 8: Development and evolution Flashcards
what is an example of how development is not determined solely by genes active in early life
fish that change sex
the phenotype of an adult organism results from an
an interaction of genes, gene products, and the environment.
similarities among organisms are due to them having a
common ancestor
differences among organisms result from
natural selection, which has adapted them to different environments
Darwin recognised that relationships among organisms could be deduced from
similarities among their embryos
- Changes in developmental processes will modify the form of an adult organism over evolutionary time
Genetics + Embryology =
Evo Deov (evolutionary developmental biology)
what is evolutionary developmental biology all about
- How changes in the genes that regulate development affect the adult forms of organisms
- How those genes have changed during the course of evolution
- How these changes have influenced evolution
many developmental genes are highly ____ + e.g.
conserved.
e. g. same gens drive the development of the fruit fly’s compound eye and the house mouse’s camera-like eye
what will develop in place of a fruit flys leg when a mouse Pax6 gene is expressed in it?
AN EYE
the same set of how genes provide anterior-posterior information in both
mammal & insect embryos.
a ___ variety of animals are produced by a common set of instructions
HIGHLY.
The differences in form mean that the instructions alone can’t determine an organism’s morphology
morphological changes can result from:
a) Mutations in genes that regulate development
b) Changes in the spatial expression of developmental genes
c) Changes in the temporal expression of developmental genes
-Modularity makes all of these pathways of evolution easier
Mutations: The insect Ultrabithorax (Ubx) gene
- The insect Ultrabithorax (Ubx) gene has a mutation. This mutated gene is expressed in the abdomen where it represses the dll gene
- The distal-less (dll) gene is essential for leg formation in arthropods.
- So insects don’t form legs on their abdomens
changes in spatial expression: In most birds what instructs the cells to undergo apoptosis, which destroys the webs between their toes
-the gene encoding bone morphogenetic protein 4 (BMP4) is expressed between the developing toes
ACCEPTION:
Ducks have a BMP inhibitor protein called Gremlin in their webs.
This stops BMP4 from signaling cell death, leaving a web.
Changes in Temporal Expression:
- Modularity allows the timing of developmental processes to shift independently (heterochrony).
- The webs of most salamanders disappear as the animals mature.
- If expression of genes that dissolve the webs is delayed, the digits don’t grow, and “juvenile” webbed feet result.
environmental effects on developmental patterns: Development is sensitive to _________
ENVIRONMENTAL CONDITIONS
A single genotype may encode a range of phenotypes under different environmental conditions
types of cues that determine development:
1) Cues necessary for normal development
- -Organisms have a fixed adaptive response.
2) Signals closely correlated with future conditions
- -Organisms are likely to respond differently to different cues.
Cues that determine NORMAL development: In Aedes aegypti
a blood meal stimulates production of vitellogenin, unnecessary component of eggs
Cues that determine NORMAL development: In Euscelis leafhoppers
gut bacteria are necessary for normal abdomen development
Cues that predict FUTURE conditions: West African butterfly
- The West African butterfly Bicyclus anynana has a dry-season and a wet-season form with different wing colouration.
- Temperature during pupation determines adult form.
Cues that predict FUTURE conditions: spring larvae of Nemoria arizonaria
- The spring larvae of Nemoria arizonaria feed on and resemble oak flowers, the summer larvae feed on oak leaves and resemble oak leaf stems.
- Spring caterpillars can be experimentally converted to summer caterpillars by feeding them oak leaves.
Developmental Response to Predators in Daphnia
- Daphnia increase the size of their “helmets” when they encounter Chaoborus.
- Helmet induction occurs if they are exposed to water in which the larvae have been swimming.
- Offspring developing inside mothers with large helmets are born with large helmets.
Developmental response to the environment in Spadefoot Toads. If their pond begins to dry up, the tadpoles…
1) Develop a wider mouth, powerful jaw muscles & a modified intestine.
2) Speed up development by eating other tadpoles.
Can organisms evolve to responses they have yet to encounter?
NO
-This is important because humans have changed the environment so much (e.g. by the release of chemicals).
EvoDevo Evolutionary developmental biology is generating ….
new insights which help us to understand the evolution of life and how to protect it
