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ETD 48: A. What is evolution? B. What were Darwin's 4 main observatoins that led him to the law of natural selection?
February 26, 2014 at 11:29am


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Sophie Wulfing
March 02, 2014 at 10:03pm

'Descent with modification" - Species change over time. A change in gene frequency in a population over generations.  Darwin didn't discover evolution, just described a mechanism for it.  


1)  Individual variation, 2) Traits are inheritable, 3) competition for limited resources, 4) surplus reproduction 


I had forgotten that Darwin did not "Invent"evolution, but instead described how it had happened. This means that the allelic frequencies changed because those with non beneficial phenotypes were those who were less likely to reproduce

Riley Hajek
April 02, 2014 at 8:46pm

Riley taught me that in order to "see" the results of evolution, it takes many years.  Small traits can change from parent to offspring, but in order to realize the benefits of these changes, many incremental changes need to be added up and passed along over a long period of time.  I learned that it was observations made by Darwin that formed his theory of Natural Selection.  These observations are that populations vary by traits, traits are inherited from parents, all species can overproduce offspring and due to limited food supply/disease etc, many offspring do not survive.

Tracy Hajek

Riley Hajek

I learned more about what led Darwin to the idea of evolution.  1) Descent with modification  so basically species change over time (over generations).  2)change in Gene frequencies in a population.                  3) population evolve, not individuals.

Madison Boggan
January 28, 2015 at 4:06pm

Parent: Evolution is species changing over time. Darwin that there are individual traits, traits are inherited, species overproduce and there is both competition and scarcity. I am wondering how he (and his predecessors) were able to piece together the significance of these observations.

Student: I described and solidified in my own mind the following:

-evolution is like a: liquidy cake turning into a baked cake with the heat representing time

-individual variation: one cake is white frosting while another has brown 

-surplus: there are a lot of cakes in the world and people are still making more

-competition & scarcity: the resources for a cake are limited, especially in some parts of the world, so some people cannot make them at all 


Lauren Masters
April 30, 2016 at 3:06pm

Student: My mom knew about evolution and natural selection so this ETD was pretty easy for me to teach her. She understood my concepts pretty well and knew that evolution is 1) descent with modification 2)species changing over generations and 3) change in gene frequencies in a population over generations. Also Darwin's 4 big observations made a lot of sense to her and she saw how natural selection and evolution are linked. Populations evolve, individuals do not.

Parent: I knew about Darwin and natural selection. Survival of the fittest makes sense. Those that adapt survive, those that can't/don't adapt do not.

Makaila Heifner
June 10, 2016 at 8:43am

Student: it was interesting talking to my stepdad about this, because he knew what evolution was but he didn't know the specifics of it. We went over Darwin's four big observations and why he came up with these ideas. After this discussion we talked about why people believed it or not and talked about our own views.  

Parent: Evolution means descent with modification, which can also mean new trait's acquired over time. Drawin's observations are descent with modification, species changing over generation, change in gene frequencies, and surplus reproduction.

Madeleine Magana
February 05, 2018 at 5:12pm


I explained to my dad about Darwin's 4 observations that led him to conclude that evolution occurs by natural selection. I thought it was interesting that Darwin's observations seemed basic but he connected them to form a valid conclusion. I also summarized his observations so that I would remember them better: no copied individuals, kids have similar traits as parents, too many offspring for nature, competition between individuals.



Mainly covered Darwin’s 4 foundational observations.

  1. There are no exact clones from generation to generation.

  2. Genetic traits are inherited from living organisms.

  3. Surplus population will dwindle when scarcity of resources like food dwindles.

  4. Survival of the fittest will propagate a populations longevity.

Also covered the role micro changes in organisms that can help explain variations between species on a genetic level.

Also covered the role of macro changes between organisms that can help explain variations between species on a anatomical level.


Jacob Michaels
February 05, 2018 at 6:07pm

Parent- Evolution is descent with modification.  A simple definition is species change over time, while an AP definition is the change in gene frequencies in a population over generations.

1. Individual variation

2. Traits are inherited

3. There is competition for limited resources

4. Surplus reproduction

Student- I described what evolution is to my dad at the AP level. I also told him about Darwin's 4 big observations. Individuals show variation in their traits, hence why everyone in the class looks different. Traits are inheritable from parents to kids, (variation inheritable). Competition for limited resources is fairly self explanatory, there is a set amount of resources and many different organisms want them. Surplus reproduction, making way more babies then is really necessary because many of them will not survive, like spores of fungi.

Emilia Barkdull
January 28, 2020 at 1:03am

Student: I described what evolution is by first using the general statement that overall it is descent with modification. Meaning that a species change over time meaning that each generations trait variation from mutations and natural selection. I went into more depth talking about how it's in more complex terms a change in gene frequency over an entire population. Specifically that populations evolve and not individuals, through survival of the fittest. I also covered Darwin's 4 big observations.

Parent: Emilia described that evolution is descent with modification, with a detail description about how species change over time and that evolution occurs in a population, not an individual.  She also described Darwin's 4 observations:  (1) Individual variation, (2) Traits are inherited, (3) Surplus reproduction, and (4) Competition for resources (scarcity). 

Zach Holtz
February 09, 2020 at 10:39pm

Student:   It was nice to review about evolution.  I had forgotten about descent with modification.  That is when species change over generations.  It was also nice to review that evolution is a change in gene frequency in a population over time as well.  And the four major observations were good to remember.  Individuals vary, traits are inheritable, surplus reproduction, and competition.

Parent: Darwin's 4 observations of evolution are: 1) Individual traits vary (not a carbon copy) 2) Traits are inherited (variable) 3) Surplus Reproduction (make more kids than nature can handle 4) Competition (resources are limited).  It's not the individual that evolves, it's the population.  

Alaina Brady
February 11, 2020 at 11:57pm

Parent: Evolution is basically descent with modification.  There is a species, it's environment changes, and it adapts to it's new environment.  Darwin noted 4 observations that led him to this theory.  1.  Variation in traits in a population - cats come in many colors 2.  Variations are heritable, passes on to the next generation  3.  Populations over reproduce and 4.  Competition for survival - species compete for food, resources, etc... 

Student: I explained to my mom that evolution is descent with modification. Populations change over time due to natural selection, which leads to evolution. I explained Darwin's 4 main observations that led to this idea. Variation in traits exist, those traits are heritable, populations overreproduce, and there is competition to survive with limited resources.

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