Exam 1 Flashcards
What are the three factors of Natural Selection?
- variation in a trait
- heritable trait
- differences in fitness
What are the two theories of evolution?
macroevolution and microevolution
Macroevolution
evolution as a pattern
-fossile record
- think of evolution as descent with modification
ex. pattern of bones
microevolution
evolution as a process
- changes is allele frequencies
-proportions of a population
What are the three factors that are used as evidence of evolution?
- Direct evolutions
- Homology
- Fossil record
Direct evolutions
example the soapberry bug: difference of beak length in different locations
homology
evolution as a process of decent of modification and ancestral traits are altered by natural selection over time (bones in the bat, whale, and human)
Fossil record
documents gradual change through time
what are the forces of evolution?
- mutation
- natural selection
- genetic drift
- gene flow
Mutation
-random changes in DNA; can be beneficial, neutral, or harmful
-ultimate source of variation
Natural selection
only force that leads to adaptations
Genetic Drift
ALWAYS OCCURRING
-random changes in the frequency in the trait over time (can greatly impact small populations)
-force of genetic drift; fixation=allele frequency becomes 100%
Gene flow
-migration that is purposeful
- An individual that changes allele frequencies
- can lead to patterns that differ than we expect by natural selection
Fixation
allele frequency becomes 100% due to genetic drift
speciation
process of species splits into two
what is the link between microevolution and macroevolution?
speciation
What are the Pre-zygotic barriers
geographical isolation
behavioral isolation
temporal isolation
pre-zygotic
mechanisms prevent fertilization
Post-zygotic
prevent a hybrid
Geographical isolation
a geographic feature separating species
Behavioral isolation
behaviors that prevent reproduction of different species
Temporal Isolation
species can’t reproduce together b/c they reproduce at different times
Post-zygotic barriers
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
What are the ecological contexts of speciation?
Allopatric and sympatric speciation
Allopatric speciation
gene flow is restricted when a population is divided into 2 and geographically isolated
Sympatric speciation
occurs in populations that live in the same geographical location; gene flow must be restricted by another mechanism
Is speciation instantaneous?
no it takes billons
stabilizing selection
form of selection in which individual with average (intermediate phenotypes are more fit)
Directional selection
form of natural selection on which an extreme phenotype is favored
Diversifying selection
form of natural selection which favors extreme values for a trait over intermediate values
What is used as evidence for phylogenic trees?
molecular and morphigical
molecular evidence
comparing nucleotide frequencies to view changes; assumptions is fewer difference the more closely related
morphological evidence
powerful independent source pf evidence for testing
what is the only evolutionary force that can be used to explain the match between traits and the environment?
natural selection
root
represents ancestor that all lineages share
tips
represent organisms; each tip a major group of organisms
how does evolutionary flow on a phylogenic tree?
from root to tips
node
the most common ancestor that all lineages on the tree have in common
out-group
distantly related group of organisms; serves as a refrence
sister taxa
share an immediate common ancestor
