Transcript Biological Science 2/e

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.
Organisms living in similar habitats,
but geographically separated,
are often very dissimilar.
Western gray kangaroo, Australia
Photo by Mary Beth Ofstedal
Organisms living
in different
habitats,but
geographically
close,are often
very similar.
Bromeliad on cactus in Mexico
Bromeliads in tropical forests
Bromeliad (Puya) above treeline in Ecuador
Islands have odd biota
Tenrecs - Madagascar
Archaic and endemic
30 species, ecologically
diverse
Lemurs
Endemic to Madagascar
30 species
Island gigantism and dwarfism
500-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 head
in a limestone house,
kicking food into its mouth.’
Louis Agassiz
photo
© S. A. Belorustseva
Rock Pigeon
Tumbler
Owl Pigeon
Fantails
Jacobin
Malthus:
Struggle for existence
* Artist: Christian Krohg (1852–1925, Norway).
* Title: Kampen for tilværelsen.
* Year: 1889.
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 polymerase
BUT
Prevent rifampin from binding to it.
Bacterium is resistant to antibiotic.
Does evolution of antibiotic resistence fulfill the postulates
of natural selection?
1. Was there variation in the population?
2. Was this variation heritable?
3. Did individuals in the population differ in their rates of
survival/reproduction?
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?
2. Was this variation (at least partly) heritable?
3. Did individuals of different heights in the population
differ in their rates of survival/reproduction?
4. Did evolution occur; that is, did the frequency of genes
responsible for tallness change across generations?