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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:
Adaptations• A favorable trait that makes an organism more
likely or “fit” to survive.– **Traits are controlled by genes.
Adaptations1. 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.
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
• Embryological evidence: Comparing the embryos of different species can give clues to evolutionary relationships.
Mechanisms of Evolution:• Evolution occurs when the genes in a
population change.*Populations evolve, individuals don’t!
• Basic mechanisms of evolutionary change.1. Natural Selection2. Mutations3. Genetic Drift4. 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 Evolution2. 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 Evolution3. 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.
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.
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