Natural Selection: Fact, Theory or Hypothesis?

Are they the same thing?Why is natural selection classified as a theory?

Photo courtesy of http://www.darwin.ie/wordpress/wp-content/uploads/2008/02/darwin.jpg

Scientific Fact

• Webster’s online dictionary defines a fact as “a piece of information presented as having objective reality”– It is true universally– It does NOT try to give an explanation of an

observation, but is the objective observation of a phenomenon

Examples of scientific facts

• Air pressure at sea level 14.7 psi

• The moon orbits the earth

• Plants create food by the process of photosynthesis

www.costaricatravelguide.com/sugar_beach/ www.aerospaceweb.org/.../moon/orbit.jpgwww.2desktop.com/Beautiful_Green_Leaf_Plants_...

Hypothesis

• Webster’s online dictionary states a hypothesis is “a tentative assumption made in order to draw out and test its logical or empirical consequences”– A hypothesis attempts to explain a

phenomenon, but still needs to be tested

Example of hypothesis

• Observation: ground water is contaminated

• Hypothesis: There is a leak in an underwater container holding gasoline.– This possible explanation can be tested

• Examine the container to see if there is a leak• Examine the water to see if it contains the same

type of gasoline held in the container• If the evidence supports the hypothesis, it is on its

way to becoming a theory.

Scientific Theories

• According to Webster’s online dictionary a theory is “a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena”– It is a hypothesis that has been tested,

reviewed, and supported by many scientists under different circumstances

– It tries to explain or interpret an observation– It is NOT proven, but supported

Examples of scientific theories

• Gravitation Theory– All objects with mass attract each other

• Einstein’s General Theory of Relativity would view gravity as the geometry of space and time, showing that neither theory can be considered fact as there are two very reasonable explanations for why objects behave the way they do when they fall

• Germ Theory– Microorganisms cause disease

• There are exceptions to this idea, but for the most part evidence supports this idea, making it theory

Humming Birds: A Beauty of Natural Selection

http://en.wikipedia.org/wiki/Image:Archilochus-alexandri-002-edit.jpg

Profile• Order: Apodiformes • Family: Trochilidae

• Location: North & South America

• Feeding: insects and nector

• Characteristics: fast hovering type flight, bifurcated tongue, pollination

• Species Range widely in shape of color, bill and wings, and feeding areas

http://en.wikipedia.org/wiki/Image:Colibri-thalassinus-001-edit.jpg

Fossil Record

• Very rare due to bone structure• Discovered in Germany by

Gerald Mayr• Species: Eurotrochilus

inexpectatus • 30 million years old (Early

Oligocene)• First Species might have split

from extinct family, the Jungorithidae

• Radiation in South America must have taken place 12-13 mya

http://www.cbc.ca/gfx/photos/hummingbird_cp_5795177.jpghttp://www.cbc.ca/gfx/photos/hummingbird_cp_5795177.jpg

Ecuador Humming Birds

• Most diversity is found in Andes Mountain in Ecuador

• Studies by Tom Smith & Chris Schneider

• Found two distinct populations each in a different ecosystem:– Shortbilled vs. Longbilled– Open forest vs. closed rainforest

Ecuador Humming Birds

http://www.pbs.org/wgbh/evolution/library/05/2/quicktime/l_052_04.htmlhttp://www.pbs.org/wgbh/evolution/library/05/2/quicktime/l_052_04.html

Natural selection in this case did not involve Natural selection in this case did not involve geographic isolationgeographic isolation

In areas of longer flowers, there was an In areas of longer flowers, there was an abundance of long-billed hummingbirds abundance of long-billed hummingbirds because that characteristic was more efficient because that characteristic was more efficient so more reproduction of long-billed birds so more reproduction of long-billed birds occuredoccured

Hummingbird Conclusions

• Humming Birds have evolved significantly into many species by the process of natural selection as shown from previous studies on the regional survival statuses between long billed and short billed types.

• It is natural selection that determines which hummingbirds are fit to survival in which type of geographic area depending on the bill shape and depending on the flower types as well.

• Over time, when enough reproduction occurred to display a distinct characteristic within that population a distinct species has been created as proven by DNA comparisons

Natural Selection is…

• Natural Selection is NOT a fact because it is an explanation/interpretation of observations, not the actual universal reality

• Natural Selection is NOT a HYPOTHESIS because it has been overwhelmingly tested and supported, making it a THEORY.

http://www.wsu.edu/~rquinlan/basics_files/image002.jpg

Conclusion

• Facts, theories, and hypothesis are NOT the same thing• Natural Selection is a scientific theory, since it has been

tested, reviewed and supported by an abundance of evidence compiled from many scientists in many fields.

• Examination of hummingbirds is just one example of evidence supporting natural selection

http://www.crimescene.com/store/images/large/evidence-stamp_LRG.jpg