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Evolution Tutorial


Common vocabulary:(and others listed below)

  • Evolution = the theory that organisms change over time
  • natural selection = the idea that organisms with the best traits will live to reproduce and pass on their genetic information
  • Charles Darwin = the scientist who first came up with the theory of natural selection
  • Galapagos Islands = the islands where Darwin observed many organisms
  • adaptive radiation = occurs when an organism inhabits an area and many species develop from this one organism due to competition
  • gene pool = the sum of all genes in a population
  • geographic isolation = occurs when a species becomes geographically isolated from one another and they develop into new species and are no longer able to reproduce
  • adaptation = a trait that enables an organism to survive in the wild

 

The following help to support the theory of evolution and are explained further in this site:
    • DNA similarities
    • analyzing and dating fossils
    • homologous structures
    • embryonic similarities
    • vestigial structures

 

 

DNA similarities

According to the theory of evolution, organisms that are closely related share similar DNA and therefore shared a common ancestor at one time.

  • For example, humans and chimps share approximately 98.2% of the same DNA. Humans and orangutans share approximately 94% of the same DNA. Most scientists believe this indicates that humans and other primates share a common ancestral primate.
  • Organisms are often categorized into taxonomic groups based on similarities in DNA.

 

Fossil Evidence

Scientists view the age of fossils and can see how a particular plant or animal has physically changed over time.

  • Scientists use carbon-14 dating and other methods to date fossils and can use this to determine when certain organisms dominated.
  • According to the law of superposition, younger rock units are deposited on top of older rock units.

 

 

 

Homologous Structures

Homologous structures are structures from different organisms that look similar because the organisms descended from common ancestors (according to evolution).

  • Ex. all organisms on right contain the same limb bones- humerus, radius, ulna, etc, but they evolved to look different over time in length.

 

 

 

Embryonic Structures

Scientists look at embryos of different organisms and find that many embryos resemble one another.

  • ex. see right picture - The embryos of the tortoise, chick, rabbit, and human resemble one another due to the distinguishing tail, gill slits, and overall shape during early development.

 

 

Vestigial Structures

A structure found in an organism that is no longer in use but may have been useful at some point in the organism's life. Provides evidence for evolution.

  • ex. Whales possess a femur and pelvis, but these bones are no longer useful to the mammals.
  • The appendix is thought to be a vestigial structure, because scientists are unsure of the function.