Chapter 10 Darwin’s
Theory of Evolution
Life’s Diversity
• What scientific explanation can account for
the diversity of life?
• Evolution is the change over time in a
population where modern organisms have
descended from an ancient organism
Charles Darwin
Summary of Darwin’s Theory:
• Individual organisms differ, and some
variation is heritable
• Organisms produce more offspring than
can survive, and many that survive may not
reproduce
• Organisms compete for limited resources
• Each organism has different advantages
and disadvantages in the struggle for
existence, those that are better suited for
environment will survive and reproduce
those that aren’t will die off
• Species today descended with modification
from ancestral species
HMS Beagle
How did Darwin’s views take shape?
• In 1831, Darwin began his journey on the HMS Beagle
- Primary purpose of the mission was to map and explore
little known territories along South American coastline
- His travel around the world led to many observations and
collected evidence that would become the theory of
evolution
- Most influential stop was the Galapagos Islands in
which organisms existed no where else like the ones on the
various islands
*differences even existed between animals on
each of these close islands
Darwin’s Views
• Darwin’s views are thought to be revolutionary
because…
• At that time scientists thought the Earth was only
a few thousand years old.
• Also, plants and living species were fixed and
unchanging.
• Catastrophic events were believed to be the only
cause of change of existence of species
• Beginning in the Eighteenth and Nineteenth
century scientific thought changed it’s views
Influences of Evolution
• James Hutton proposed that the Earth was shaped by
geological forces that had occurred over millions of years
• Thomas Malthus predicted human population would grow
faster and exceed the space and food needed to sustain life
* applied to mass reproduction in plants and some
animals explained the competition for limited
resources
• Jean Baptiste Lamarck – proposed use and disuse of body
parts, tendency toward perfection, and inherited acquired
traits
*Most of theories were found to be incorrect, but incorporated
early mechanisms of evolution
• Charles Lyell – proposed that processes of the Earth
presently shaping it were the same processes that have
always taken place
Origin of Species
• In 1859 Darwin published his work
in a book titled “Origin of Species.”
- proposed the mechanism of
evolution as natural selection
of species
- almost had ideas presented
before publishing the book by
Alfred Wallace
- changed the face of biology
and other scientific disciplines
Contents of His Book
• Artificial variation – farmers and ranchers have
selective breed desired characteristics for
livestock in a short time
• Created variation of modern species much
different in genotype and phenotype from
ancestors
• If it could be done artificially in little time
could it happen naturally over a long period of
time?
Natural Selection
• Struggle for existence – created from limited
resources causing organisms to regularly compete
for food, living space, and necessities of life
• Survival of the Fittest – organism’s ability to
survive and reproduce are a result of adaptations
it has made to fit an environment
*Successful adaptations means organism are
better suited for the environment and will
continue to be successful as they pass those
traits to offspring
Natural Selection
• In natural selection only certain individuals
produce offspring
• Over time, natural selection results in changes in
the inherited characteristics of a population
• Those changes increase a species’ fitness in the
environment
• Can not be directly seen, but can be observed by
changes in a population over successive
generations
Descent with Modification
• Descent with modification means that
organisms have descended, with changes,
from other species over time
- different structures, different niches,
different habitats
- different appearance from distant
ancestor
Evidence of Evolution
• How could Darwin prove his theory about the
Earth being millions of years old?
Evidence existed in:
1. Fossil record
2. Geographic distribution of species
3. Homologous structures
4. Embryology
Evidence
• Different organisms in similar
environments have features of
anatomy and behavior in common
• Homologous structures –
structures that are different in
mature form but come from the
same type of cells and embryonic
tissues
- common purpose of the
structures
- different organisms with
similar structure and
function of these vestiges
- Vestigial organs –
resemble miniature
structures like arms, legs, or
tails that have no real
function or use.