Law of Evolution
The change in the genetic allele frequency of a population over time resulting in a change in phenotypic characteristics
Allele Frequency
The incidence of gene variance
5 Mechanisms of Evolution
Natural selection, mutation, gene flow, sexual selection, and genetic drift
what is natural selection
happens at a INDIVIDUAL LEVEL
the adaptive trait (trait that promotes survival) persists
4 conditions for natural selection (VOIDs)
Varience: differences due to random fertilization, crossing over, and independent assortment
Overpopulation: more of one species means some will have to die and the adaptive trait will become more prominent
Inheritance: parents pass on genes
Differential Survival: the struggle for existence means advantageous characteristics survivethe struggle for existence means advantageous characteristics survive
Fitness
reproductive success
Selection Pressure
Force that causes a population to evolve. The stronger it is the more change there is
Mutation
a random change in DNA
Gene Flow
The transfer of genes between different populations e.g. migration
Sexual selection
The selection of a mate based on phenotypic characteristics
e.g. peacock feathers
Genetic Drift
Chance event that causes change in SMALL POPULATIONS
2 types:
Bottleneck effect
Sudden disaster that happens to pick survivors with different alleles
Founder effect
A few individuals from one population start a new population and therefore change the allele frequencyA few individuals from one population start a new population and therefore change the allele frequency
Evidence of Evolution
fossil record analysis
molecular evidence
experiments
observation
comparative anatomy (homologous vs analogous)
artificial selection (breeding)
comparative embryology
biogeography
types of population selection
Directional, stabilizing, and disruptive
Species
A group of living organisms consisting of similar individuals capable of interbreeding and producing fertile offspring
Hardy-Weinberg meaning and equation
Genetic variation will stay consistent across generations in the absence of disturbances
p = dominant
q = recessive
phenotypic frequency:
p² + 2pq + q² = 1
Allele Frequency:
p + q = 1
speciation
The formation of a new and distinct species in the course of evolution
2 Types of speciation
Allopatric and sympatric
Allopatric Speciaiton
One species is separated by geographic environments they undergo allopatric speciation. If they were to meet again in the future they would not interbreed
e.g. california salamanders
Sympatric Speciation
Even though both populations inhabit the same area, a new species evolves through pre-zygotic isolation
Types of pre-zygotic isolation
Gamete Isolation
gametes cant fuse/fertilize
Behavioral Isolation
courtship displays and different
Mechanical Isolation
Incompatible sex organs
Temporal Isolation
mating timing becomes different (nocturnal vs diurnal)
Habitat Isolation
different habitats in the same location
post-Zygotic isolation
prevents the creation of a fertile offspring
Advantages of hybridization
favorable traits, survival of endangered species
Disadvantages of hybridizaiton
low zygotic viability (severe abnormalities, fails to mature), infertility, low adult viability (low survival rate because traits arent suited for any environment)
Micro evolution vs Macro evolution
micro: evolution in a short period of time (couple of generations)
macro: evolution over a long period of time
Phylogeny
The history of the evolution of a species in reference to a line of ancestry
evidence used in phylogeny (strongest to weakest)
DNA
Comparative anatomy
Developmental biology
Behavior
cladogram
phylogenic tree
shared trait
a trait shared between 2+ lineages
conserved gene
a gene remained generally unchanged throughout most of the lineage