Convergence, Natural Selection, "Survival of the Fittest"

Convergence, Natural Selection, and "Survival of the Fittest"

What is convergent evolution? Convergent evolution is when species share a trait or character not from a common ancestor. In "Improbable Destinies" one of the convergent characters is the human eye versus the octopus eye. 

If we look at the figure for convergent evolution, we can observe that the most recent common ancestor for humans and octopuses occurred many, many, years ago. This ancestor is known to not have eyes! 

Octopuses and Humans have specially evolved photoreceptors that allow us to view the world more clearly. When you look at scientific models of each eye you will notice they are almost identical! You can see from the above image, that several characters look and have the same function. The iris is in the same place, surrounding the lens, on both. There are specialized photoreceptors, nerve fibers, and an optic nerve for transmitting sight to the brain. 

Eyes could have evolved due to species relying on photoreceptors to detect prey or predators. Over generations, the individuals with more evolved eyes tended to survive and reproduce whereas individuals with less evolved eyes, or no eyes, did not.

On the contrary, Divergent evolution is when two or more species sharing the same character split or diverge from a single common ancestor. In the divergent evolution figure we see several species that have eyes and originate from the same ancestor, this is reminiscent of a clade on a family tree. 

 

An easier way to think of Divergent evolution comes from dogs. All breeds stem from a single common ancestor, the wolf. We see hundreds of dog breeds from this species with the help of selective breeding and time. 


 

Comments

  1. Abby DeckerSeptember 19, 2024 at 6:28 PM

    You did so great on your visuals, they look so nice and help someone understand the concept so much! Good Job!

    ReplyDelete
  2. JodieSeptember 20, 2024 at 1:05 PM

    Very cool visuals and explanation of convergent evolution. Dogs do show a great deal of diversity. For them to be an example of divergent evolution they would need to evolve into different species. At present they are a weirdly diverse single species (kind of unbelievable!). - Dr. W

    ReplyDelete

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