Mental Model in Biology: Evolution by Natural Selection

Historical Background 

The concept of evolution has long been introduced before Charles Darwin and his fateful voyage to Madagascar. What elevates the theory of Darwin is the evolutionary mechanism called natural selection. Through this, he was able to explain how certain organisms manage to adapt better with their respective environments compared to the others. 

Darwin reached his concept of natural selection through the following key observations:  

● Most traits can be passed by the parent organism to its offspring. 

● Offspring are often produced beyond the number that can be reasonably sustained by their environment. As a result, competition arises over the limited resources available. 

● Offspring that belong to the same generation vary from one another depending on the traits each has inherited from the parent.

● From these observations, Darwin arrived at the following conclusions: 

• Within a given population, certain organisms would inherit key traits that would make them more effective in terms of survival and reproduction compared to the other organisms of the same species who did not receive the same set of traits. 

• Because organisms with the helpful traits produce more offspring, and because these helpful traits are heritable, there will be more organisms bearing these helpful traits, thus making the traits more common within their generation. 

• As time goes by, succeeding generations would be able to better adapt to the environment, making them more successful than their parents were at survival and reproduction. 

The model of evolution that Darwin developed allowed him to make sense of the patterns that he had observed during his trip. For example, different species of Galapagos finches share certain traits because they also share the same ancestors. However, if a certain group of organisms became isolated from the rest for several generations, that particular group develops a distinct set of traits that allowed them to survive and thrive in the environment of the island where they can be found.

As a result, beaks of different shapes and sizes can be observed among the distinct species of finches that live in different islands of Madagascar. 

Over the course of multiple studies conducted on Darwin’s theory, experts on this mental model have managed to boil down its prerequisites into the following: 

1. Replication – The ability to create new copies with a high level of fidelity with the immediate source 

2. Mutation – The ability of the said copies to change in a slight, but potentially significant ways 

3. Fitness – Copies should be able to persist and reproduce at various rates 

When all three elements are present, you can expect the copies to survive and multiply with a high level of success. Copies that lack any of the given elements are likely going to die off, eventually.   


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