Transcript Ch 022evolution[1]

Ch. 22
Descent with Modification:
A Darwinian View
of Life
View of life
• Before Darwin:
• Plato:
» Two worlds, real (ideal/eternal) and
illusory (imperfect)
» Evolution counterproductive
• Aristole: scala naturae
» No evolution, permanent.
• Natural Theology:
» Nonevolving, Creator’s plan, creator’s
purpose/design
• Carolus Linaeus: Taxonomy, no
evolutionary kinship
Fossils, Paleontology
•Sedimentary Rocks/fossils, strata, erosion,
organism succession
• Georges Cuvier: catastrophism (Paleontology)
•James Hutton: gradualism/mechanisms, current
•Charles Lyell: uniformarianism geological
processes
Lamarck
Two Concepts used:
•Use/Disuse
•Inheritance of acquired
characteristics
•Adaptation to the Environment: Primary
product of evolution
•Sentiments interieurs or “felt needs”
Darwinian Revolution
(1809-1882)
•University of Edinburgh (medicine)
•Christ College at Cambridge (clergyman)
•Natural theology
•22 yrs. Old sailed on HMS Beagle
•Chart South American coastline
•Studied plants and animals
•Galapagos
•Returned 1836
•Used Lyell and Lamarck studies
Figure 22.5 The Voyage of HMS Beagle
What was his reasoning?
• The voyage of the Beagle
• Galapagos islands
• Darwin focused on adaptation
– descent with modification
– observations
What’s the reason for diversity and
numerous similarities among species?
• On the Origin of Species by Means of
Natural Selection. 1859. Charles Darwin.
• In his book, Charles Darwin made 2 major
points:
– 1. Species evolve from ancestral species and
were not specially created.
– 2. Natural selection is the mechanism that
could result in this evolutionary change.
•Branching history
•Most branches extinct (99%)
Figure 22.7 Descent with modification
Observation #1
• All species have such great potential
fertility that their population size
would increase exponentially if all
individuals that were born
reproduced successfully.
Observation #2
• Populations tend to remain stable in size,
except for seasonal fluctuations.
Observation #3
• Environmental
resources are limited.
• Inference #1
– Production of more
individuals that the
environment can support
leads to a struggle for
existence, with only a
fraction of offspring
surviving.
Observation #4
• Individuals of a population vary extensively
in their characteristics/ no two individuals
are exactly alike.
Observation #5
• Much of this variation is heritable.
Inference #2
– Survival is not random, but depends in part on the
hereditary constitution of the surviving individuals.
Those individuals whose inherited characteristics fit
them best to their environment are likely to leave more
offspring than less fit individuals.
Inference #3
– This unequal ability to survive and reproduce will lead
to a gradual change in a population.
Summary of Darwin’s Ideas
• Natural selection: differential success in
reproduction.
• Natural selection occurs from the interaction
between the environment and the inherent
variability in a population.
• Variations in a population arise by chance, but
natural selection is not a chance phenomenon.
• Artificial Selection: breeding of plants and
animals.
Example of Natural Selection
• Ground Finches
– avg. beak depth (inherited trait) oscillates
with rainfall.
• Wet years - feed on small seeds - avg. beak depth
decreases.
• Dry years - small seeds less plentiful, survival
depends on the finches being able to crack the less
preferred larger seeds. Avg. beak depth increases.
• What does this study indicate?
What does this study indicate?
• Natural selection is situational. What works
in one environment may not work in
another.
• The environment did not create beaks
specialized for large or small seeds, but only
acted on inherited variations already present
in the population.
Current evidence of Natural Selection
Figure 22.12 Evolution of insecticide resistance in insect populations
Figure 22.13 Evolution of drug resistance in HIV
Evidence for Evolution
• Homology
• Anatomical
• Vestigial
• Embryonic
• Molecular
• Biogeography
• endemic
• Fossil record
• Drosophila fossils in Hawaii
Theoretical about Evolution???
Theories are attempts to explain facts and
integrate them with overreaching concepts.
Natural Selection is the proposed
mechanism of Darwin’s Theory of Evolution
Theories are more than a simple
hypothesis.
Predictions stand up with continuous
testing by experiments and observations
“There is grandeur in this view of life”