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Darwin’s Theory of
Evolution
The History of Evolution
• Evolution is defined as change over time
• The theory that all organisms on Earth are
related by common ancestry and that they
have changed over time (adapted) mostly
because of natural selection.
• Charles Darwin is one of the most famous
scientists associated with the theory of
evolution
Darwin’s voyage
Darwin’s interest
• Darwin’s observations and research played
an important role in the development of the
theory of evolution that is still widely
accepted today
• During his voyage on the U.S.S. Beagle, he
would collect specimens from the different
areas he visited
• He was fascinated to see the variety in the
different plants and animals that he studied
He did notice one
similarity:
All of the organisms he observed
were well suited (well matched) to
their environment
Beaks of finches
• The finches beaks have adapted and naturally
selected for over time based on what they eat
Adaptation
• An adaptation is any inherited characteristic
that increases an organisms chance for
survival
• Adaptations can be physical or behavioral and
can be passed from generation to generation
• The process of becoming better suited to the
environment
Different types of adaptations:
• Genetic adaptation – always genetically
controlled (ex: 5 fingers, giraffe’s neck)
Different types of adaptations:
• Physiological adaptation – change in the
reactions; can be genetic or not (ex:
acclimation to altitude or climate, coat
color change during seasons)
Different types of adaptations:
• Behavioral adaptation – change in
behavior; can be genetic or not (ex:
chimps using sticks to catch termites,
bears eating garbage)
Survival of the fittest
• The ability of an individual to survive and
reproduce is called fitness
• Adaptations that help an animal become
more fit to survive and reproduce more
successfully are commonly selected
• This is known as survival of the fittest
Survival of the fittest is
also known as natural
selection
Over time, natural selection
will change the
characteristics of a
population,
increasing the fitness of
that population
Proof? You want proof?
• Evidence of evolution through adaptation
and natural selection can be found in:
– the fossil record
– Geographical distribution (different animals evolve
similarly because of the same environmental factors)
– Homologous structures
– Similarities in early development of embryos
Fossil Record
Fossil
Record
Geographical Distribution
Geographical Distribution
Homologous structures
Homologous structures
Development of embryos
Development of embryos
TODAY…
• Evolution is widely accepted by the scientific
community
• Theories are constantly changing based on new
evidence (mitochondrial DNA/rapid evolution…)
• Evolution is still occurring
• Many species are becoming extinct because they
cannot evolve as fast as humans are changing
the environment.
• Humans are “meddling” with evolution through
artificial selection (fruit, dogs…)