Download Theory of Evolution

Theory of Evolution
Chapter 15: pgs 368 – 391
What is Evolution?
• Evolution
– Change over time
– Process by which modern organisms have
descended from ancient organisms
– Considered a theory
• Is a well-supported testable explanation of
phenomena that have occurred in the natural world
Charles Darwin
• Contributed the most to
our current
understanding of
evolution
• Joined the crew of the
H.M.S. Beagle
– Sailed around the world
– Darwin's major focus
was the Galapagos
Islands
Darwin’s Observations
• Noticed that there were
NUMEROUS variations
of similar species
• Why do some species
inhabit some countries,
but not others? For
Example: Rabbits &
Kangaroos
– Fossils needed to be
considered
• Preserved remains of
ancient organisms
Galapagos Islands
• One of the many spots the
H.M.S. Beagle visited
– Darwin’s Favorite & Most
Influential
• Small group of islands off of
South America
– Islands close in location,
but different climates!
– Vegetation sparse on
some & others abundant
• Animals of interest
– Tortoise’s: Originally did
not notice shell difference
– Birds: beaks were shaped
differently (journey home)
• Especially island to island
Jean-Baptiste Lamarck
• Published hypotheses in
1809 (Year Darwin was
born!)
• Proposed: that by
selective use or disuse of
organs, organisms
acquired or lost certain
traits during their lifetime.
These traits could then be
passed on to their
offspring. Over time,
process led to change in
species
Darwin Presents His Case
• Continuously studied specimens from the
islands
– Determined that birds were actually related &
NOT found anywhere else on Earth
• Published “The Origin of Species” (Book)
• Challenged fundamental scientific beliefs &
religion
– At first, most people did not support his findings
– Others considered him to be brilliant
• Proposed a mechanism called “Natural
Selection”
Inherited Variation &
Artificial Selection
• Inherited Variation
– Exists in Nature & on Farms
• Some plants (same species) produce larger fruit
• Some animals (Cows) produce more milk than others
– Caused by variation in genes
• Heredity was unknown during Darwin’s era
• Artificial Selection
– Nature causes/allows the variation
– Humans then select favorable traits
Natural Selection
• All species struggle for existence
– Example: Competition for food, shelter,
mates, etc.
– Certain traits allow similar species to survive
• Survival of the Fittest
– How well suited an organism is to its
environment
– Fitness- the ability of an individual to survive
and reproduce in its specific environment
– Adaptation - Any inherited characteristic that
increases an organisms chance of survival
• Examples: Porcupine’s Quills or Cheetah’s speed
Evidence of Evolution
• Fossil Record
– Helped Darwin to argue how animals could change
over time
• Geographic Distribution of Living Species
• Homologous Body Structures
– Body structure, like a fin, leg, or wing
– Allows researchers to compare similarities and
differences
• Vestigial organ
– Structure that remains, but no longer has a function;
like legs on a snake
• Similarities in Embryology
– Appearance of developing embryos