Transcript The Theory of Evolution

The Theory (?) of Evolution
What is evolution?
Evolution - the change in the inherited traits (genes/alleles,
geno/phenotypes) of a species over time
• Evolution is the process that best explains why life exists the
way it does on Earth
Who came up with evolution theory?
• The most famous explanation of evolution was
made by Charles Darwin
• Theory 1st published in ‘On
the Origin of Species by
Means of Natural Selection,
or the Preservation of
Favoured Races in the
Struggle for Life’
Others helped…
• Georges-Louis Leclerc, Comte de Buffon
(1707 – 1788)
• Noticed that some species look similar
and may have a common ancestor
• Postulated that the Earth was
>6000 years old
Others helped…
• George Cuvier (1769 – 1832)
• Father of modern paleontology
• Noticed that deeper rock strata contained
more dissimilar species
• Species appear/disappear over time
Others helped…
• George Cuvier (1769 – 1832)
• Proposed that Earth has experienced mass
extinctions (“catastrophism”)
• These events (floods, eruptions,
meteorites, etc.) are visible in rock strata
• Correspond to new species appearance
Others helped…
• Jean-Baptiste Lamarck (1744 – 1829)
• 65 when Darwin was born
• Compared current species with fossils
• Observed that fossil series led to modern
species
• Postulated ‘theory of acquired
characteristics’
• Species increase in complexity over time until
achieving perfection
Others helped…
• Jean-Baptiste Lamarck (1744 – 1829)
• Hypothesized that organisms would
become better suited to their environment
over time
• Body parts that were used to cope with
environmental conditions would get better
(larger, stronger, etc.)
eg. Lamarck’s giraffe
• Giraffes stretched their necks to reach the
foliage from tall trees
• Over time this stretched neck condition is
passed down to offspring
• This theory was critical because it highlighted the idea that
physical traits could be passed to offspring
Darwin (1809 - 1882)
• 1831
• 5 year voyage to South America on HMS Beagle
• Darwin’s job was to collect/record data on rocks, plants
and animals
Darwin’s observations
1. The flora/fauna found on the journey were similar
but distinct from those found elsewhere
• Concept of biogeography ( the study of the geographic
distribution of species & ecosystems over geological time)
Darwin’s observations
2. Fossils of extinct animals are structurally similar and
share a distribution pattern with modern animal
versions
Sloth
Megatherium
Armadillo
Glyptodont
Darwin’s observations
3. Galapagos species varied slightly between islands
• eg. Finches throughout the Galapagos islands had beaks
adapted to eating different types of food
Darwin’s observations
4. Sexual reproduction results in variation within a
species
• Gregor Mendel’s genetics work wasn’t accepted until 1900
• Many people at the time, thanks for dog/plant breeding,
knew that traits were somehow passed from parent to
offspring
Finalizing the theory
• Darwin used these observations theorize how/why species
change over time
• Darwin and Alfred Wallace both popularized the idea that
species change over time but could not explain how
• Thomas Malthus had previously suggested
that populations produce far more offspring
than the environment can support
• Darwin used this idea to postulate natural
selection (survival of the fittest)
Natural selection
• Individuals with traits that help
them survive (better fitness) in
their environment are more likely
to survive
• Individuals who survive longer are
more likely to reproduce and pass
on their traits
• Subsequent generations will
exhibit the surviving trait more
frequently
Natural selection
• FYI: Darwin used the word
evolution once in Origin of Species
(he called it descent with
modification)
• Natural selection does not always
demonstrate progress (devolution
is possible)
Activity
• Sample study: Lamarck vs Darwin