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Transcript of Evolution
Darwin’s hypothesis became known as the theory of evolution by natural selection—organisms
with traits best suited to their environment will more likely survive and reproduce.
How fast does it happen?
1. Gradualism—describes evolution as a slow, ongoing process
2. The punctuated equilibrium model says gene mutation can result in a new species in a
relatively short time.
Darwin hypothesized that plants and animals on islands off the coast of South America originally came from Central and South America. (example: species of island finches looked similar to a mainland finch species)
Darwin reasoned that members of a population best able to survive and reproduce will pass their traits to the next generation; over time, differences can result in separate species.
Remains, imprint, or trace of organisms
Quick burial of the original specimen gives best results
Relative dating - older items are found lower in the strata
Radiometric Data - compare the amount of radioactive element to nonradioactive element in specimen
Types of Evidence
An inherited trait that makes an individual organism different from others in the species
Many environmental factors can cause changes in the sources of genes.
Geographic isolation can make two populations so different they become different species.
Evolution explains changes in inherited characteristics of a species over time.
Species are organisms that share similar characteristics and can reproduce among themselves.
Tigers reproduce with tigers.
Ligers and tigons also can reproduce - does this change the definition of species?
Lamarck's Theory of Acquired Characteristics
Not supported by the evidence
The changes have to occur in the hereditary information, not in the things that have happened "externally."
A variation that makes the organism better suited to survive in its environment
Embryology - similarities in the early growth and development process
Homologous structures - similar shape and function
Vestigial structures -structures that don't seem to have a function
DNA - number and type of chromosomes show similarities between species
phylogenetic tree - shows relationships between common ancestors and modern species