March 18th 2020
BIO220 LEC0101
BIO220 Lecture 21: Extend Phenotypes
Phenotype:
- An observable trait or features of an organism
- Morphology, physiology, behavior
Z = G + E
- Phenotype (z) involves both genetic and environment influence
Extended notion of Phenotypes:
- Things that are produced by the organism
Beavers:
- E.g. beaver build dams → the size of the damp can affect the fitness of beaver → could
have natural selection on the genes of dam building behavior
A gene for behavior or gene for the dam?
- The bigger dam the beaver builds, the higher their fitness (bigger lake, hide from
predator, etc…)
- Thus: Z = dam, G = genes for building the dam
- Gene ‘A’ = smaller sized dam, Gene ‘B’ = larger sized dam
- Thus, Gene B has a higher fitness
- Note: Evolution by N.S require → 1) variation in traits, 2) variation in fitness for the trait,
3) genetic basis for the trait
Bower birds:
- E.g. bower building by organisms
- Influence fitness with bower building → behavior is associated with genetic variation
- Bower that looked good led to a higher fitness
Extended phenotype:
- For example, if a parasite that infect you influence your phenotype in a positive way →
this is called an extended phenotype. → N.S can act on it
- Fitness for parasite:
- R0 = The number of infections by a single infected individual (the number of infection =
their fitness
- Depend on growth and replication, opportunity of transmission.
Broad categories of extended phenotypes:
1) Behavior changes in host
2) Morphological changes in host
3) Molecular changes in host
*influence fitness of the parasite even though it may seem to benefit the host