Transcript Darwin`s Voyage

Natural Selection
Darwin’s Voyages
Chapter 5
Section 1
A Darwin Voyage
• Evolution
– A change over a
period of time
• Charles Darwin; 22
– Voyage on the Beagle
• 1831
– 5-year trip around the
world
– Started in England
Living Diversity
• Diversity
– The variety of living
things on earth
• Scientists estimate…
– Between 5-50 million
living species on earth
right now
• Quite a guess!!!
Fossil Diversity
• Fossils give us a
glimpse into the past
• Extinction
– 99.9% of all species
that have ever lived
are now extinct
Adaptations
• Physical and
behavioral traits
– Enable organisms to
survive
• Catch food
• Withstand conditions
• Reproduce
Fitness
• The ability of an
individual to survive &
reproduce
• To successfully pass
on its genes to its
offspring
The Galapagos Islands
• 1000 kilometers west
of S. America
– 600 miles
• Small & short islands
– Dry & hot
• Larger & taller islands
– More lush
Darwin’s Finches
• 1 species of finch
evolved into many
different “specialized”
species
Giant Tortoise Shells
• Tortoises from
different islands had
different shells
• Ah, hah!!!!
– Natural Selection
• Survival of the fittest
– Evolution!!!
Vestigial Organs
• Wings on flightless birds
• Tailbones on primates
Homologous Structures
• Develop from similar
tissues in the early
development stages
of the organism
Arguments for an Ancient Earth
• River Valleys
– Carved by glaciers over 100,000’s years
• Shells found in high elevation mountains
– Plate tectonics!!!
Problems with Reproduction
• Extinction
– Birth Rate < Death Rate
• Over Population
– Birth Rate > Death Rate
• Disease
• Famine
• War
Peppered Moths
• Before the industrial
revolution, England
– Trees were light in
color from lichen
growing on them
• After the pollution
from Ind. Rev.
– Lichen died, leaving
just the dark bark
Helpful Mutations
• Increases fitness
– more offspring than others in population
• Becomes more common in the population
Evolution
• Any change to the
relative frequencies of
alleles in the gene
pool of a species
Species
• A group of similar-looking organisms that
can breed with one another and produce
fertile offspring
– Bobcat & Lynx
Natural Selection
• The struggle for existence selects only the
fittest individuals to survive in nature
– Generation after generation
Struggle for Existence
• Only the fastest rabbits
will escape the lynx
• Only the fastest lynx
will catch the rabbits