CH 17 -- Processes of Evolution
Genetic Equilibrium
allele frequencies remain constant in a population at genetic equilibrium
Genetic Equilibrium
if the allele frequencies change from one generation to the next, the population is evolving
Evolving Populations
Natural selection determines the alleles that are most fit.
Two examples of selection the peppered moth warfarin resistant rats
Natural Selection in Action
Peppered Moth wide range of speckle patterns
spend daytime at rest on tree trunks and branches
prey for birds
Natural Selection in Action
What factor or factors in the environment “selected” for the darker moths?
Natural Selection in Action
warfarin blocks a protein needed for blood clotting Rat Poison
one allele of the gene coding for this protein makes a mutant protein that is not as good for clotting, but is insensitive to warfarin.
Natural Selection in Action
Allopatric Speciation
Macro Evolution
Over LONG time spans -- species diverge enough to form separate species, separate lineages.
Many processes may be involved --
mutations and changes in allele frequenceis
mass extinctions
adaptive radiations
and others
Evolutionary Relationships
human
earthworm
tuna
lizard
mouse
multicellular
multicellular with a backbone
multicellular with a backbone and legs
multicellular with a backbone, legs, and hair
Hypothesis: All life on Earth is Descended from One Common Ancestor.
CH 18 -- Early Evolution
How did life on earth evolve?
boiling water
gases
spark discharge
electrodes
water droplets
water containing organic compounds
CH4 NH3 H2O H2
ancestral prokaryote
infoldings of the plasma membrane
infoldings evolve into the nuclear envelope and endomembrane system
Eukaryotic cells: animals, fungi, some protists
Eukaryotic cells: plants, some protists
engulfed photosynthetic bacteria evolve into chloroplasts
photosynthetic bacteria
aerobic bacteria evolve into mitochondria
aerobic bacteria are engulfed or infect the cell
DNA Endosymbiont Theory
Endosymbiont Theory
Evidence -- some features of mitochondria and chloroplasts are more similar to prokaryotes than to eukaryotes.
1) they have their own circular DNA
2) reproduce by binary fission
3) ribosomes are similar to prokaryotic
4) codon usage similar to prokaryotes
5) inner membrane similar to prokaryote plasma membrane
Evolutionary Relationships
BACTERIA ARCHAEA EUKARYA
common ancestor
Evolutionary Relationships
Learning Outcomes
Describe genetic equilibrium. Explain directional selection and how changes in peppered moths and warfarin resistant rats provide evidence of this process. Describe how speciation can occur using allopatric speciation as an example. Explain ideas about formation of organic molecules in earth’s early atmosphere. Explain the endosymbiont theory and evidence supporting it.