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The Fact of Evolution: Observable Evidence

Lines of Evidence: Biogeography

Biologists who study the distribution and diversity of living things over time and space are engaging in the study of biogeography.

As the ancient, single land mass known as Pangaea split apart and gave rise to the continents we know today, living things rode those pieces of land as they drifted apart.

The results of the long, slow allopatry-generating event known as continental drift can be seen in the fossil record.

The continents are dancing.

The evolution of related lineages can be traced by comparing the descendants' current geographic distributions with their genetic makeup.

Lines of Evidence: Microevolution Observed

There are thousands of scientifically documented cases of microevolution. Here are just a few.


2. Antibiotic-resistant Mycobacterium tuberculosis

Was this an example of natural selection? Let's put Darwin to the (post hoc) test.

1. Did variation exist in the bacterial population?

2. Was the variation heritable?

3. Did differential reproduction among variable bacteria occur?

4. Did a non-random subset of the original population remain after selection?
3. North American House Sparrow body mass and wing surface area

5. Citrate-feeding E. coli

In Michigan State University's Escherichia coli Evolution Lab run by Dr. Richard Lenski, observations of evolution in action are ongoing.
In 2004:

6. Evolution as Compromise: Corolla shape in flowering plants.

The whorl of petals surrounding the reproductive parts of a flower (the male stamens and the female stigma(s) are collectively termed the corolla.

Conventional Wisdom: Selection by pollinators has resulted in the shapes and colors of flowers.

New Theory: Flower morphology may be shaped by multiple factors, and may reflect a compromise reached by the plant to both

In 2001, Candace Galen, et al. discovered such a balance in the Alpine Skypilot Polemonium viscosum.
  • Skypilots are pollinated primarily by bumblebees, which prefer a wide, tubular corolla for easy access to nectar at the base of the flower.

    Same species.
    Different genes.

  • You can read about more examples HERE. (Which might help you when it comes to extra credit questions on the exam. Just maybe.)

    Lines of Evidence: Macroevolution Observed

    Over time, microevolutionary changes can, under certain circumstances, result in reproductive isolation (<-- required link), which defines a biological species.

    Macroevolution includes the generation of new species from previously existing species.

    Some who do not wish to accept the observable, verifiable process of evolution are sometimes heard to say

    "Well, yes, we can see microevolution happening. But no one has ever observed speciation."

    This is incorrect.

  • All the lines of evidence we have examined so far (fossils, homology, biogeography) provide strong evidence for past macroevolutionary events.

  • There are examples of speciation (<-- required link) having happened in the observable present.