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Evolution = change over
time
Evolution
• Individuals do NOT evolve! Populations
evolve.
• Evolution occurs at conception, when new
combinations of DNA are made.
– The only role you have left in evolution will be
when you have children!
Jean-Baptiste Lamarck (1744-1829)
3 ideas of Lamarck:
1. Organisms desired to change and better
themselves.
2. The law of use and disuse.
3. The inheritance of acquired traits.
Darwin and Wallace: Similar ideas,
different places & times
• Both founders of the theory of evolution
Alfred Russell Wallace
• Was also voyaging and observing
similar things that Darwin was
seeing.
• He sent an essay to Darwin, and
Darwin published their ideas in a
paper on the theory of
evolution.
Darwin’s Ideas
•
Darwin proposed evolution occurred through the
process of Natural Selection.
•
“Survival of the Fittest” means the organism that has
traits that are more suitable to the environment will
survive and reproduce.
•
The principles of Natural Selection are:
• 1. Organisms have more offspring than is
needed to replace themselves.
• 2. There is a variation of traits amongst the
offspring.
• 3. Some of these traits are better suited to the
environment than others.
• 4. The offspring that possess these favorable
traits will survive and reproduce.
• 5. These favorable traits will be passed on to
future generations.
Adaptations
• A favorable trait that makes an organism more
likely or “fit” to survive.
– **Traits are controlled by genes.
Adaptations
1. Mimicry – An individual gains an advantage by
looking like the individuals of a different species.
"Red touch yellow, kills a fellow. Red touch black,
venom they lack.“
Scarlet king snake and coral snake.
Evidence for Evolution
1.
2.
3.
4.
5.
Fossil record
Anatomical
Embryological
DNA
Artificial Selection
Evidence for Evolution
• Fossil record: Fossils
show change over time.
Anatomical Evidence
• Homologous
structures:
– A common limb
that has evolved to
perform a different
function.
– Ex: Bird wing,
human arm,
elephant leg all
have the same
bones
Analogous structure:
• Different structures
that perform the
same function
• Ex: Bird wing,
grasshopper wing
• Vestigial structures: A structure that is
reduced in function. (snake hips)
• Embryological evidence: Comparing the
embryos of different species can give clues to
evolutionary relationships.
• DNA Evidence:
Comparing DNA of
organisms can show
hidden relationships.
(scrub jays)
Mechanisms of Evolution:
• Evolution occurs when the genes in a
population change.
*Populations evolve, individuals don’t!
• Basic mechanisms of evolutionary change.
1.
2.
3.
4.
Natural Selection
Mutations
Genetic Drift
Migration
Mechanisms of Evolution:
1. Mutations: Changes in DNA sequences that
result from environmental factors (ex:
radiation or chemicals) or just by chance.
Mechanisms of Evolution
2. Genetic Drift: A random change in allele
frequencies that cause changes in populations.
–
By chance, some individuals leave behind more offspring than others.
The genes of the next generation are the genes of the "lucky" ones, not
necessarily the healthier or "better" individuals.
Mechanisms of Evolution
3. Migration or Gene Flow: When new
individuals enter or leave a population. As a
result the allele frequencies change.
Speciation: a new species is created.
• Species- A group of organisms that breed with
one another and produce fertile offspring.
How do new species form?
1. Geographic isolation: occurs when a natural physical
barrier separates a population and they evolve separate
from each other.
– Ex: Body of water, landslides, mountains, deserts
How do new species form?
2. Reproductive Isolation occurs when formerly
interbreeding population can no longer breed and
produce fertile offspring.
– Geographic isolation can lead to reproductive
isolation.
1. Mechanical- Failure due to physical interference
2. Behavioral- Sexual selection differences
3. Biological- Failure to create fertile offspring
4. Time- Two or more species reproduce at different
times
Patterns of Evolution
• Divergent Evolution: When animals evolve
away from their common ancestors to become
more successful in their niches.
– Ex. Galapagos Finches, and Hawaiian
Honeycreepers
• Convergent Evolution: When two or more
distantly related organisms evolve similar
characteristics because they occupy the same
niches.
Convergent Evolution
• The “Fish” body form has evolved several
times in very different organisms.
Convergent Evolution
• Placental vs. Marsupial
mammals. In Australia,
marsupials evolved in
isolation. Their body
forms match their
placental counterparts.