Evolution concepts

Phyletic evolution (anagenesis): Yes, but not this example!

Implications

Contrast of two ideas about the fundamental basis of change

Lamark: principles of 1) use and disuse 2) inheritance of acquired characteristics

Darwin: principle ofevolution by natural selection

Variation presentbefore it would beof value.

Transformationalevolution

Lamarck

Variationalevolution

Darwin

1798

Example of an adaptation.

Giraffe neck size

Why do giraffes haveLong necks?

Set up an hypothesis.

Evidence

• Why do giraffes have long necks?• There was (is) a difference in neck size among bulls.• Competition for females during a brief reproduction

season. Males engage in combat; necks are used. • Neck length accompanied by a gain in mass• Sexual selection: males with stronger necks have greater

mating success….win more contests.• Alleles resulting in stronger necks tend to be passed on to

progeny and increase in the population.• The population changes over time.

Biological diversity: created or product of evolution

• A random survey of 2,000 adults• 42% believed that biological diversity has not

increased since the beginning of time.• Special creation• 48% believed that biological evolution has

taken place.• Descent with modification

Special creationThe intelligent design argument

• 1. Fixity of species• 2. Each species was independently created

– No relationships among species• 3. Biblical evidence: origins are recent• Movement called creation science attempts to legitimize

special creation.• Creation “science” is not a science.• Argument is based on idea of Intelligent Design supported by

the idea of irreducible complexity.

Bacterial flagellum: irreducible complexity?

E. coli Mobility

YersiniaType III Export System

30 protein components20 proteins involved in assembly

Eyes of mollusks: snails, clams, squid & octopi

Convergent evolution