Darwin's Findings

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard:  Identify chronological patterns of change and communicate that biological evolution is supported by multiple lines of empirical evidence that identify similarities inherited from a common ancestor (homologies).

Article includes ideas, images, and content from Troy Smigielski (2022-01)

Darwin's Findings

(Something was lost? What? What was it?)

Source, 2022-02

Charles Darwin was an English naturalist in the middle of the 1800s who became known as the “Father of Evolution.” 

Much of his work was based on what he learned while in the Galapagos Islands. Darwin noticed how finches on the islands had different beak types, and he described these as adaptations.

An adaptation is any inherited characteristic that increases an organism’s fitness in its environment. Adaptations can come from mutations in DNA or in response to the environment of the animal.

Darwin claimed that the generations of adaptations seen within the different species of finches were present because the finches had evolved into their observed characteristics. He cited how they accessed food as the environmental condition that had led to the adaptations that eventually evolved the birds into different species.

Evolution is the change in the characteristics of a species (or worldview, applications of technology, etc.) over several generations, and it relies on natural selection.

There are two kinds of evolution.

Macroevolution is the idea that all species can trace back to common ancestors. The idea is that adaptation within a species over time eventually leads to separate species that are both (or all) similar to the ancestor.

Microevolution is the process whereby adaptations over time lead to distinct changes within the species. Many examples of microevolution can be cited. As one example, within humans, the average height of eighteen year olds has increased over the last century. Access to nutrition has been pointed to as an environmental opportunity that humans have taken advantage of leading to the change within the species.

So, to summarize, macroevolution is the idea that species change into different species as generations of adaptations take place. Microevolution is the process whereby a species is altered (but remains the same species) by generations of adaptations.

At this point, it's probably worthwhile to define species. Within a taxonomic system, a species is considered to be the level above which reproduction is not possible. Except for a few exceptions wherein hybridization can occur, one species cannot reproduce with another species.

Within the bounds of that definition, Darwin's finches might be better seen through the lens of microevolution. Not only can they reproduce, they do. 

"A new article in Nature by Galápagos finch researchers Peter and Rosemary Grant, “Speciation undone,” confirms [that] Galápagos finch species are capable of interbreeding — but adds a new twist: they’re interbreeding so much that in multiple cases, two “species” may be fusing back into one species" (Source, 2022-02).

Regardless of how the process is defined, Darwin's finches clearly grouped according to how they adapted to (beak shape) the access to and restriction from resources in their environment. 

So, whereas an adaptation is any inherited characteristic that increases an organism’s fitness in its environment and adaptations can come from mutations in DNA or in response to the environment of the animal, we can see in all of creation how different adaptations have evolved to increase the ability of a species to thrive within its environment.

What adaptation did this little guy gain?

Adaptations occur as a result of something. When a resource needed by the organism becomes availalbe in greater quantities, some adaptations take advantage of the change. When something ceases to become readily available, some organisism will adapt in response to the change.

What color mice have the higher fitness?

Adaptations normally increase an organism’s fitness.

What is “fitness”?

Fitness describes the ability of an organism to survive and reproduce in its environment. It is a way to describe how well an organism can thrive.

Fitness is sometimes measured by the number of offspring an organism has.

Would a lion in South Africa with one baby or a lion in Kenya with ten babies show better fitness?

 

So, there is a mechanism within nature that leads to passing on traits that increase fitness. Natural selection is the survival of the fittest; this means that the best fit organisms are the ones that survive and reproduce. The less fit members of the population (possibly) die and do not produce. 

Think about it… if fitness leads to survival and if you have to survive to reproduce, less fit members of a population will not live long enough to reproduce, so the less fit traits will not get passed along!

Darwin was not the first person to use this term (Natural Selection).

Which one of these moths would most likely survive and reproduce in an environment with many trees?

Over time, what would you expect to happen to the green moths? The camouflaged moths?

Note a few things about natural selection…

Natural selection:

• Does not explain the origin of favored traits
  
  
• Takes place outside of human control
  
  
• Leads to an overall increase in a species’ fitness

Natural selection will only occur under specific conditions.

In order for natural selection to occur:

• Genetic variation must be present in a population.
  
  
• Reproduction must occur.
  
  
• Successful genes must reproduce (heredity).
  
  
• There must be a struggle to survive.

So, the if running faster than a lion helps increase fitness, and if some of the antelope slow (yellow to the right) they will not live to pass on their trait. The fast antelope (red to the right) will, and will reproduce, passing their "fastness" to the next generation. 

As adaptations occur, one of two things will happen.

A good adaptation will lead to a high level of fitness, which leads to natural selection.

Remember this guy?

What adaptation did this little guy gain?

His adaptation to blend in increases his ability to survive, and this trait will be passed on as a favorable trait leading to natural selection over many generations.

Snowshoe hare adaptation to change color as temperature gets colder.

The image above shows the progression of the change in coat color exhibited by the snowshoe hare as temperatures get colder.

A good adaptation will give a high level of fitness, which leads to natural selection.

Behaviors Can Also Adapt

Sharks have adapted the behavior to follow ships and boats.

Sharks have adapted the behavior to follow ships for two main reasons:

1. People often throw food/waste overboard.
   
   
2. During the slave trade, sick and/or deceased slaves were tossed overboard. This caused sharks to adapt their behavior to follow ships for food.

So, Back to Darwin…

From his findings, Darwin said that evolution happens through the principle of descent with modification. This says that organisms pass traits to their offspring that often include changes that happened due to mutations or environmental pressures and opportunities.

According to this principle, all species descended from one original species. The species from which all other species derived from is called the common ancestor.