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.