Assemblage of brachiopod Archaeorthis from the Lower Ordovician of Waratah Bay, South Gippsland.Source: Museum Victoria.

photograph by Rachel Ratcliff, Kruger National Park, South Africa.

Western gray kangaroo, AustraliaPhoto by Mary Beth Ofstedal

Organisms living in similar habitats,but geographically separated,are often very dissimilar.

Bromeliad on cactus in Mexico

Bromeliad (Puya) above treeline in Ecuador

Bromeliads in tropical forests

Organisms living in different habitats,but geographically close,are often very similar.

Islands have odd biota

Tenrecs - MadagascarArchaic and endemic

30 species, ecologicallydiverse

Lemurs

Endemic to Madagascar30 species

Island gigantism and dwarfism500-pound Komodo Dragon ate pygmy elephants

and tortoise

Homology in forelimbs of tetrapods

Homology in development of vertebrates

Homology in proteins

But isn’t homology (as evidence for evolution)

circular reasoning?

How do we know for sure that traits are homologous?

Plato: ideal of stable, permanent, and unchanging objects.

Variation reflects imperfection from ideal.

VARIATION

Barnacle

a ‘shrimp-like animal standing on its headin a limestone house, kicking food into its mouth.’Louis Agassiz

photo© S. A. Belorustseva

Rock Pigeon

Tumbler Fantails

Owl PigeonJacobin

* Artist: Christian Krohg (1852–1925, Norway). * Title: Kampen for tilværelsen. * Year: 1889.

Malthus:Struggle for existence

Individuals within populations possess heritable variation.

Rifampin binds to

RNA polymerase of

Mycobacterium tuberculosis.

Bacterium can’t make mRNA….dies.

Mutations reduce effectiveness of RNA polymeraseBUT

Prevent rifampin from binding to it.

Bacterium is resistant to antibiotic.

Does evolution of antibiotic resistence fulfill the postulatesof natural selection?

1. Was there variation in the population for the trait?

2. Was this variation heritable?

3. Did individuals in the population differ in their rates of survival/reproduction with respect to the trait?

4. Did evolution occur; that is, did the frequency of resistance change across generations?

Does the increase in human height in Europe over the past centuries fulfill the postulates of natural selection?

1. Was there variation in the population for the trait?

2. Was this variation (at least partly) heritable?

3. Did individuals of different heights in the population differ in their rates of survival/reproduction with respect to the trait?

4. Did evolution occur; that is, did the frequency of genes responsible for tallness change across generations?