Download evolution notes

Mechanisms of Evolution
Natural Selection
 
Populations evolve, NOT individuals
 
Gene pool - all alleles in a population s genes
together (remember: alleles: alternative forms of
a gene)
Allelic frequency - % of any specific allele (p.
405 snapdragons)
Genetic equilibrium - frequency of alleles
remains same over generations = no evolution
 
 
evolution.berkeley.edu/evosite/misconceps
How does evolution happen? disrupting genetic equilibrium
 
 
 
 
Mutations - caused by radiation or chemicals
Genetic drift - alteration of allelic frequencies by
chance events (random, affects small
populations greater)
Gene flow - Migration & Emigration
Natural selection - allelic frequencies change
due to nature selecting for advantageous
variations
 
____________ selection - favors
average phenotypes
Spiders- larger spiders
eaten by predators
-Smaller spiders can t
catch enough food
-Favors _______ size
Stabilizing, directional, and disruptive
1
BoardJennifer
Wednesday, April 25, 2012 6:09:52 PM ET
__________ selection - favors ONE
extreme (on graph, selects to ____or ____)
Woodpeckerslonger beaks
eat more insects
buried deep in bark
(have more fitness)
Long beaks favored
  Can lead to
rapid evolution
 
How do changes in gene pool
lead to evolution?
 
 
_____________ - when members of similar
populations no longer interbreed to produce fertile
offspring within natural environment
_____________ isolation -physical barrier divides
a population
 
 
In an environment,
medium-sized seeds
become less common
-Birds with smaller or
larger beaks have easier
time finding food
= higher fitness
 
Speciation rates - 2 hypotheses,
both supported by fossil record
 
 
____________ - species originate through
gradual change of adaptations; slow &
steady
___________________- species originate
quickly, in rapid bursts
_____________ isolation - populations no longer
mate and produce fertile offspring
 
 
 
BoardJennifer
Lava from volcanic eruptions, sea-level changes,
rivers, mountains
_________ selection - eliminates
intermediate phenotypes
Behavorial - different mating calls or seasons
Different genetic material = fertilization won’t happen
Polyploidy - having multiple chromosome sets
Wednesday, April 25, 2012 6:09:52 PM ET
2
Patterns of evolution
 
____________ evolution - occurs when
populations change as they adapt to different
environmental conditions
 
___________________- ancestral species evolves
into many new species to fit various niches
 
 
 
Structural adaptations
 
Body parts of an organism that help it survive
 
Mimicry – more subtle
 
 
Hawaiiian honeycreepers; Darwin’s finches
____________ evolution - unrelated species
evolve similar traits because of similar
environmental pressures
 
*Adaptations: Evidence for Evolution
Different cactus species around the world
Ex. Teeth, claws, keen eyes, thorns,
One harmless species looks a dangerous one
 
 
Two or more harmful species look alike
 
 
Harmless fly looks like a wasp; scarlet kingsnake looks like
coral snake
Yellow jackets, honeybees, many wasps use same coloring to
say “Hey, stay away, I’ll hurt you!”
_______________– enables species to blend in
*_______________ adaptations
 
 
 
Can happen very quickly
Changes in an organism s metabolic
processes
Antibiotic-resistance bacteria (________)
 
 
BoardJennifer
Penicillin not as effective now
Insects & weeds resistant to pesticides
Wednesday, April 25, 2012 6:09:52 PM ET
3
*Evidence for evolution
Fossils are aged by  
 
___________ dating: using location of
fossils in different layers of rock/soil to
determine their age compared to where
other fossils are located (___________
fossils in deepest layer)
___________ dating: measuring ½ life of
radioactive isotopes of the element carbon
(also called ________________ dating)
  _________
______________ structures
 
 
_______________ structures
  Structural
*Indirect Evidence for Evolution
 
 
Bird wing, butterfly wing
Body part in present-day organism that no longer
serves its original purpose (but was useful at some
time)
Our wisdom teeth, appendix, blind cave fish with
eyes
Embryology
 
 
Embryo – earliest stage of growth & development of
plants & animals
Page 402 fig. 15.9: You had a tail and gills??
_______________ evidence
 
Biochemical molecules: RNA, DNA, ATP, and many
enzymes
Compare amino acid sequences among organisms to see
common ancestry
  Enzyme - cytochrome c - involved in cellular respiration
 
 
BoardJennifer
features (bones) indicate common
ancestry
http://evolution.berkeley.edu/evolibrary/article//evo_31
Vestigial structures
 
Anatomy (p. 401 fig. 15.6)
 
Body parts have similar function but NOT
common ancestry
 
 
 
accurate than relative dating
*Anatomy cont.
 
*Indirect evidence for evolution
Wednesday, April 25, 2012 6:09:52 PM ET
P.403
4