Darwins Theory of Evolution

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• Darwins Theory of Evolution

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THE PUZZLE OF LIFES DIVERSITY

• Evolution change overtime and the process by
  which modern organisms have descended from
  ancient organisms.

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Charles Darwin (born 1809 published Origin of
Species in 1859) worked as a naturist on the HMS
Beagle (1831) made many observations and proposed
what is now the theory of Evolution.

•   Lots of diversity in animals and plants.
• Fossils Why had so many species disappeared?
  How were ancient animals related to living
  animals.
•   Animals and plants varied from island to island
• 4.   Tortoise shells and the beaks of finches
  varied from island to island

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IDEAS THAT SHAPED DARWINS THINKING-

• in Darwins Day, most people believed that the
  Earth was only a few thousand years old and they
  believed in the idea of original creation where
  neither, plant, animal or microbes had changed
  since their original creation.

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• Fossil evidence was challenging original
  creation. Maybe there were several periods of
  creation, which were ended by catastrophe such as
  Noahs ark.
• James Hutton (1795) Layers of rocks form slowly
  and wind, rain, heat and cold and erosion and
  forces beneath the Earths surface operate slowly
  and the Earth must be millions of years old.
• Charles Lyell (Principles of Geology Darwin read
  on the Beagle) Natural processes shaped the
  Earth over millions of year. Even Darwin found
  seashells on mountaintops in the Andes and an
  earthquake lifted a shoreline 3 meters above its
  original position.
• Darwins question If the Earth can change, can
  life also slowly change over time as well?

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• Lamarks Theory of Evolution first published
  theory of evolution
• Use-disuse theory to propose how living things
  changed over time (1809). Snake stopped using
  its legs there for it lost them.
• Inheritance of acquired traits Pass on acquired
  traits. If you lift weight and get big muscles
  and you pass that on to your child. Pierce your
  ears and your child is born with pierced ears.
  NO! WRONG.
• Tendency towards perfection. Birds felt an
  innate urge to fly and used its limbs until they
  turned into wings and flight was possible

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• Malthus (1798) If human population continued to
  grow unchecked, sooner or later there would not
  be enough food to feed everyone. The forces that
  limit human population were war, famine and
  disease.
• Darwin applied Malthuss reasoning to plants and
  animals. If all offspring survived, they would
  overrun the Earth.

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DARWIN PRESENTS HIS CASE

• 1859, 25 years after the voyage of the Beagle,
  Darwin published the On the Origin of Species.

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• Evolution by Natural selection
• The struggle for existence in the competition
  for food, living spacefaster predators survive
  and better camouflaged survives.  
• Survival of the fittest Ability to survive and
  reproduce. Organisms with a low level of fitness
  either die of have few offspring. Organisms with
  high levels of fitness survive and reproduce
  successfully. So, over time, natural selection
  results in changes in then inherited
  characteristics of a population. This is only
  seen in populations.
• Descent with modification over very long
  periods, natural selection produces organisms
  that have different structures, establish
  different niches or occupy different habitats.
• Common Descent All living organisms are related
  to one another.
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Evidence for Evolution

• Fossil Record Countless species of many appeared
  forms appeared on Earth and then vanished.
  Island species developed modifications and
  distinctions from mainland species.

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Homologous structures body parts that look
different in its mature form but arise out of the
same embryological tissue.

• Limbs have different functions but the same basic
  plan.
• Adapt to survive in different environments.
• Ex. Bird winds are similar to reptile or
  dinosaur limbs where bat wings are more similar
  to mammal limbs

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Vestigial Organs

• Remnants of limbs or organs from ancestral forms.
  Ex mini legs or tails or the human appendix.

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Embryology

• Embryos look similar during early stages of
  development. Embryonic cells develop in the same
  order and similar patterns to produce the tissues
  and organs of all vertebrates

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Biogeography

• Distribution of animals in geographic regions
  show relationships to each other.
• Island species tend to be similar to mainland
  species

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Evolution Today- what we have learned since
Darwin

• Micro and Macro evolution- microevolution shows
  evolution within a species, ex. Moths in
  industrial evolution. Macroevolution shows the
  appearance of a new species
• The fossil record-
• Relative dating- position within strata.
• Radioactive dating-using the half life of C-14
  (5700 Years) and K-40 (1.3 billion years).
• Using both- in rock more than 50,000 years old
  estimations of isotopes are in volcanic ash. To
  date these scientists look for where volcanic
  rock has intruded into sedimentary rock.
• Paleomagnetism- looking at the magnetic poles.
  The magnetic poles of the earth have occasionally
  reversed. The direction of polarity is preserved
  in the rock.

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• Changes in the earth-
• Contintintal drift- the movement of continents do
  to movement of plates. This has caused climate,
  sea levels and distribution of organisms.
• Volcanic activity- altered climate
• External events- meteorites that were larger than
  any we have seen have caused changes in climate
  by igniting fires and causing tidal waves.

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• Evolutionary rates have varied over time. Some
  organisms have gone through long periods of
  stasis (unchanging). These have often been
  disrupted by massive global change leading to
  extinctions. 99 of organisms have become
  extinct. These mass extinctions have changed
  flora and fauna allowing for the evolution of the
  organisms left.

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• Size and complexity of organisms have increased.
  The size of organisms is however, limited by the
  fact on average larger organisms liver shorter
  lives, but larger organisms tend to dominate
  smaller organisms.
• Human factor- humans are the most powerful agent
  of evolution today. The effects we are having
  are as yet unknown.