Lecture 13.1/13.2 Intro to Evolutionary Mechanisms Flashcards
Evolution?
- Change over time
- refer to a change in allele frequencies
Evidence of Evolutonary Change?
- Geology
- Historical Biogeography
- Comparative Embryology
- Comparative Morphology
- Comparative Genetics
Geology
- Fossil records documents continuity
- Darwin’s theory proposes all species that have ever lived are related
Historical Biogeography
in relation to landforms (earthquakes creating barriers that makes animals evolve differently)
Comparative Embryology
Early embryos of related species are similar
Comparative Morphology
reflects common ancestry (may have different functions human forearm and bat wings)
note: homologous structures
Comparative Genetics
Homologies (similarities in DNA) can also be present at the molecular level
- a wooly mammoth and our current elephants
- humans to mouse
Fact about Wooly Mammoth?
In molecular homologies they are related to the Asian Elephant
Microevolution?
Describes small-scale genetic changes in population
Macroevolution?
- Describes large scale evolutionary chages
- results from microevolution over millions of years
Genotype
genetic make-up of an organism
Phenotype
observable or expressed traits of an indiviual
(size, height, hair color)
ex: a flower may have the same genotype but the phenotype is different based on enviornment. Like a flower that has different colors.
What are the two types of genetic variation
- new alleles via mutation
- rearrangment of exsiting alleles into new combination via sexual reproduction
Why do mutation happen?
Are they good or bad?
Mutations arise randomly with respect to “needs”
- Can be deleterious - harmful
- Advantageous - benefit
- Neutral mutations- no benefit but also not harmful
Sexual Reproducation?
- is another source of variation
- does not generate new alleles but it generates new combinations of alleles
Quantitive variation?
- broad curves indicates lots of vartiations
- narrow curves indicate little variation
ex: height
Qualitative variation?
traits that are discrete and do not vary continuously
- discrete phenotypes
- Ex: albanism, tounge rolling, widows peak
Hardy & Weinberg principle?
it specifies the condition in which evolution would not occur
- alleles frequencies will not change
Genetic equilibrium is possible only if?
- no mutation occurs
- population is closed to migration-no new individuals
- population is infinite in size
- all genotype survive and reproduce equally well
- mate randomly with respect to genotype
this will never happen!
Relative Fitness?
Number of surviving offspring that an individual produces compared with others in the population
- Being able to reproduce and survive
Example of evolution by Natural Selection?
Pesticide resistance
Ex: roaches at first they die off because they are not resistant to RAID, the ones that are resistant reproduce offspring that are resistant to RAID.
Coat Coloring
Ex: mice coat color darker mice didnt survive in the beach but lighter coated mice did because they blended in better
Adaptation
increase survival and reproduction in a given enviornment
Product- increases the relative fitness of an organism in its enviornment
Process- accumulation of adaptive traits over time
Two forms of adaptation?
Physical- camouflage, hair, large ears, flashy plumage
Behavior- group living, migration, hibernation, defensive postures
Directional Selection?
shifting from an existing mean to a more favored mean
Ex: small horses —-> larger horses
Natrual Selection?
- Differential survival and reproduction of individuals in a population based on heritable variation in their phenotype
Does natural selection produce perfect organisms?
No, there has to be a trade off
Disruptive selection?
favors extreme phenotypes over intermediate phenotype
Ex: larger beaks or smaller beaks in order to open there food. Medium beaks wouldnt be able to open anything
Stabilizing Selection?
when intermediate phenotypes are favored
Ex: small infants and to large infants are not likely to survive, favoring the mean or medium infants.
Do individuals evolve?
No, individuals DO NOT evolve, populations do!
