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ETD 49 A. What is natural selection? B. What are the 4 Types of evidence supporting the theory of evolution?
February 26, 2014 at 11:31am


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Sophie Wulfing
March 02, 2014 at 10:11pm

Darwin's two big ideas were 1) Natural Selection - nature selects which traits are better for their environment   2) Differential reproductive success - positive traits are more successful in reproducing

1) Direct observation - can be seen in HIV and TB resistance, 2) Fossil records - show intermediate forms, 3) Homology - structure, 3 types, morphology, embriology, biomolecular data,  4) Bio geography - Pangea "and stuff"


I had to review all the evidence for evolution. Also, the two big ideas of evolution can be interpreted similarly. The difference between them is that #1 sort of causes #2, as organisms that have less of a chance of survival are less likely to reproduce

Madison Boggan
February 01, 2015 at 1:23pm

Parent: Darwin had two big ideas which were that individuals with traits that are better in the environment survive and reproduce more and the traits are seen more in the population because of this (natural selection). He also saw differential reproductive success.

The evidence that is used to back up evolution is fossils, direct observation, biogeography and homology. 

Student: What I thought was interesting about going over this ETD with my mom was which type of evidence for the theory of evolution she found most fascinating: fossils. Similar concept to direct observation, a person can clearly and distinctly see change over time through fossils. 

Amber Neathery
February 22, 2016 at 7:27pm

Student: My dad is familiar with the concept of evolution, so I shared that its “official” definition is a change in gene frequency in a population over generations. I used the example of finches in the galapagos to demonstrate this: different variations of finches have different types of beaks according to their environment. For example, the large ground finch has a large beak for consuming seeds, while the cactus ground finch has a long and sharp beak to tear cactus leaves. Explaining to my dad the concept of evolution more in depth made me recall the definition myself. Darwin’s four main observations were that: 1) Individuals have variation, 2) Traits are inheritable, 3) Organisms practice surplus reproduction, and 4) Competition and scarcity lead to limited resources and more competition.


Parent: I thought it was interesting that evolution is gene frequency. It makes sense that different birds have different beaks depending where they are.

Maddy Magana
February 08, 2018 at 5:45pm


Student: I talked to my dad about evidence that supports the theory of evolution. I gave him examples of each evidence. After I explained direct observation of evolving diseases such as HIV, homology between species, fossilized organisms that show the changes of species types throughout time, and the careful distribution of species throughout the world, my dad went through the evidence I provided and argued the error of each point. He argued that the changes of the HIV virus only proves adaptation, not evolution. He claimed that similarity between organisms as embryo's are irrelevant in equating an organism to another. He also argued that fossils only proved adaptation of a species depending on their environment and not evolution into higher beings. I was surprised that he had done research prior to our discussion and already had firm counter-arguments against the theory of evolution.

Parent: Discussed 5 areas where evidence of evolution occurs

  1. Embryonic evidence – many mammals look similar at an embryonic stage
  2. Anatomy of animals are similar to one another.  Progression of evolution between species can be connected visually between species
  3. Vestigial organs reflect similar anatomy that may explain how evolution transpired into different species
  4. Striation or layers of sedimentary rock uncovers a geographic timeline where fossils and remains of organisms point to gradual changes through millions of years
  5. Continental land separations mimic evolution between similar species
  6. Molecular or DNA changes also can explain how evolution may have occurred from a common ancestry


Jacob Michaels
March 08, 2018 at 7:16pm

Parent- Natural selection is the environment positively selecting favorable traits and killing lesser traits.  Individuals with better traits for their environment survive.

1.  Direct observation of evolution (guppies and HIV resistance)

2.  Fossils intermediate plus archetype plus extinction (horses and trilobytes)

3.  Homology similar features in separate species morphology is looking at the shape (arms, wings and flippers)

4.  Biogeography the distribution of species (there are marsupials in both South America and Australia)

Student- I taught my dad about the definition of natural selection about how it positively selects favorable traits and negatively selects unfavorable ones. I also told him four pieces of evidence for evolution, explained each piece of evidence and gave an example for each so I know all four for the AP Bio Exam.

Zach Holtz
February 09, 2020 at 11:06pm

Student:   It was a nice review to go over Darwin's two biggest ideas.  The first is natural selection, the environment "picking" what traits will continue and which ones will not.  The second is differential reproduction with success.  It was also nice to look at the 4 types of evidence.  Direct observation, fossil records, homology, and biogeography.

Parent:   A nice summary of Natural Selection is: 1) individuals that have certain characteristics that are inherited survive and reproduce at a higher rate than others.  2) over time, the match between organisms and their environment can increase 3) if the environment changes or individuals move, adaptation to these new conditions sometimes increases genetic diversity

Alaina Brady
February 11, 2020 at 11:44pm

Parent: Darwin's two big ideas are Natural Section - nature positively or negatively selects trains in a population and Differential Reproductive Success - individuals with traits positively suited the environment reproduce at greater rates than those with traits negatively suited to the environment.

Evidence of evolution: 1.  Direct observation - watching a population change to survive, like fish becoming more colorful to escape being eaten   2.  Fossil Record - shows the changes with various stages of change in evolving species  3.  Homologous structures - different species have very similar structure 4. Biogeography - A similar species evolving differently on different continents, the possum in US giving live birth and similar animal in Australia having a pouch.

Student: I explained to my mom that natural selection is the process by which nature positively selects for traits best suited to the environment and selects against traits less suited to the environment. I then explained the 4 main sources of evidence for evolution, direct observation, fossil record, homologous structures, and biogeography. Direct observation is exactly what it implies, watching a population change over time. The fossil record shows intermediate structures as populations change over time. Homologous structures shared by different species indicate a relationship and a shared common ancestor. Biogeography shows distribution of similar species

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