Natural Selection Essay

Submitted By shahmoonkle
Words: 3510
Pages: 15

MEchanis:
Monitor hormone levels at time of dispersal no change

Ontogeny:
Triggered externally (social/environmental cues) or internally (body changes)?
Tigger= aggression towards males? No difference between males and females
Trigger= avoiding litter-mates? No influence of litter size
Trigger= body weight, need to have enough resources to make journey: yes around 125 g

Fitness value
Dispersal allows avoidance of:
-shortage of food/burrows. Dispersion is happening in order to go to new place w/ more abundant resources: nope
-parasites? Maybe males are targeted by parasites rather than females so they need to leave: nope, males and females had the same parasite load
-competition for mates, males take off: nope, competition the same
-avoiding inbreeding, if males stay at native burrow, more chance of inbreeding because females are staying put: males that moved farther and farther away had more mates, which indicates that they were looking for more suitable mates, which was why they kept moving away to avoid their relatives

Phylogenetic History:
Is male dispersal a behavior inherited from a common ancestor or is it newly evolved in this species?
Study many different species that are closely related.

Evolution of Behavior:
Wolves are more closely related to dogs (1.8% sequence divergence) than to coyotes (4%).

Evolution: a change in the frequencies of different alleles in a population or species over the course of generations

4 forces cause evolution: mutation: a change in the dna sequence;affects protein structure and function gene flow: when animals move from one population to another genetic drift: variation in allele frequencies through random fluctuations; important in small populations (freak accidents) bottleneck affect. Sudden drastic reduction in population, surviving population has a different allele frequency, though nothing to do with actual traits, just random founder effect: populations breaks apart so two separate populations exist, can have different allele frequencies than original population selection: disproportionate and reproductive success of organism that possess certain alleles, as a result of the influence of those alleles.
Natural selection: alleles make it easier to survive in environment
Sexual selection: alleles increase sexual attractiveness and therefore you get more mates
Artificial selection: humans select what traits make it into next generation
Kin selection: animals share genes because they are related to each other, behaviors to protect your relatives

How can we determine the relationship between genes and behavior?

Mendelian Crosses:
-dominant (B) and recessive (b) alleles
-homozygous: BB, bb
-heterozygous: Bb, bB

Genetic Differences cause behavioral differences in drosophila
Sitter larvae vs rover larvae

Crossing homozygous paresnts= 100% dominant phenotype
Heterozygous parents= 75% dominant, 25% recessive

Gene knockouts:
Targeting and disrupting specific gene
Create (through breeding) strain of animals homozygous for knockout to inactivate gene
Determine behavioral change resulting from inactivated gene

Pleiotropy: a single gene having multiple phenotypic effects

Epistasis: multiple genes at different loci interact to produce the phenotype

Cross-fostering experiments:
Compare genetically similar animals in different rearing environments
(two similar species genotypically that have different behavior.)
Is different behavior caused by genetics or parenting?
Asses effects of genotype vs parental care
If both groups show original behavior? –genetics
If two groups swap behavior?- parenting/environment

Twin and Adoption Studies r= coefficient of relatedness

Measuring heritability:
Selection differential= u-u1 difference between average of parental population and offspring
R= respose to selection: u1-u0

S=16-10 = 6
R=14-10= 4

Heritability= R/S= 4/6= .666666

Measuring fitness:
Not measuring lifetime reproductive success bc hard
Proxy: look at traits that hint at what overall…