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Darwins Finches

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Biology

Darwin’s finches are a classic example of how evolution happens through natural selection. We will discuss Darwin’s observations on the Galapagos finches and how they helped inform the theory of evolution by natural selection.

Voyage of the Beagle to the Galapagos Islands

From 1831-to 1836, Charles Darwin embarked on a voyage on the H.M.S Beagle. Their mission: survey the South American coastline. Although he was hired as a geologist, Darwin spent a lot of time observing and collecting animals, plants, and fossils.

After five years of the voyage, the Beagle stopped over at the Galapagos Islands, a group of volcanic islands 900 km west of South America. The Galapagos Islands are home to diverse, endemic animal life, including blue-footed boobies, giant land tortoises, and the Galapagos finches.

His observations during his visit to the Galapagos Islands would later become the foundation for his theory of evolution by natural selection.

Darwin’s Finches and Their Beaks

While in the Galapagos Islands, Darwin noticed that organisms were similar from island to island but had certain features that distinguished them from each other.

Finches, in particular, caught Darwin’s attention. He found that over a dozen species of finches inhabited the islands. While the finches were similar in size and color, Darwin observed that their beak shapes varied.

Darwin attributed the unique beak shapes to the food sources available in their specific environment. Their distinct shapes gave them a higher chance of survival. Some finches had broad, blunt beaks, which helped them crack nuts and seeds. Other finches had long, pointed beaks, which helped them snatch insects (Fig. 1).

Darwin's Finches: a Diagram

Darwin's Finches, A diagram comparing the beaks of four species of Galapagos finch, StudySmarter

Figure 1. A diagram comparing the beaks of four species of Galapagos finch. Source: John Gould, Public domain, via Wikimedia Commons.

Traits and behaviors that help organisms survive and reproduce are called adaptations. Darwin noted that the finches’ beak shapes were adaptations that helped them obtain food in their habitat. By explaining how these unique finch species came to be, Darwin was able to formulate his theory of evolution by natural selection.

Darwin's Finches: a Short Activity

Here's a short activity you can do to understand how different beak shapes are adapted to collect specific food types.

You will need the following materials:

  • Food sources, like sunflower seeds, grapes, hard-boiled eggs, and yogurt

  • Tools: a toothpick, a pair of tweezers, a spatula, and a fork

  • Paper plates

Methodology:

  1. Fill a plate with sunflower seeds. This plate will be called Plate A.

  2. Leave Plate B empty.

  3. For 30 seconds, try to transfer as much content from Plate A to Plate B using each tool.

  4. Weigh Plate B and write in the table below how much you were able to transfer.

  5. Repeat the process for each of the food sources.

Toothpick

Tweezers

Spatula

Fork

Sunflower seeds

Grapes

Hard-boiled eggs

Yogurt

Answer the following questions:

  1. What tool was the best for collecting sunflower seeds? Grapes? Hard-boiled eggs? Yogurt? Why?

  2. What tool was the worst for collecting each of the food sources? Why?

  3. How would you relate this activity to the finches' beak shapes as adaptations?

  4. What do you think would happen to finches with beak shapes that are unsuitable for the available food source? How about finches with the most suitable beak shapes?

Darwin's Finches and His Theory of Evolution by Natural Selection

Darwin theorized that all of the different finch species on the Galapagos Islands came from one parent species (a common ancestor) that first colonized the islands millions of years ago. Darwin explained that, as populations of the parent species spread from one uninhabited island to the next, they adapted to different ecological niches and rapidly evolved into many descendant species.

How Does Natural Selection Cause Evolution?

In any habitat, resources are limited, so organisms have to compete to survive. Organisms with better-suited traits have a higher chance of survival.

For example, there is an area in the Galapagos Islands where cactuses are the most viable food source. What beak shape do you think would be more favorable for the survival of finches in this area: broad, blunt beaks or long, pointed beaks?

Finches with long, pointed beaks have a higher chance of survival because their beaks allow them to probe the cactus flowers and fruits without being pricked by cactus spines.

Because they have a higher chance of survival, organisms with favorable traits can also reproduce and pass on these traits. Darwin called this the process of natural selection, which is more popularly known as "the survival of the fittest.Natural selection is the process where organisms with better traits tend to survive and reproduce at higher rates than other individuals because of those traits.

This means that organisms with favorable traits will outnumber those with less favorable traits in the succeeding generation. Over time, species with better adaptations to their habitat are formed. This is how natural selection leads to evolution.

Evolution is the gradual and cumulative change in heritable traits of a population of organisms. This change takes place over the course of several generations.

Speciation is the process where a new species is formed in the course of evolution.

What Accounts for the Many Different Species of Galapagos Finch?

The number of different species of finches in the Galapagos presents an interesting case because speciation tends to produce one new species from a parent species over a long period.

In the case of the Galapagos finches, they underwent a burst of evolution, producing a large number of different descendant species in a relatively short time. This is a type of speciation called adaptive radiation. Adaptive radiation is the process by which a single species rapidly evolves into many species adapted to different ecological niches or the role that a species plays in a habitat.

To illustrate how adaptive radiation might have taken place:

  • Let’s say Finch Population A occupies one area.

  • Over time, Finch Population A adapts to its new environment and becomes different from its parent species.

  • Finch Population B from the same parent species enters the same area and competes with Finch Population A.

  • There is pressure on both Populations A and B to adapt to different niches.

  • They pass on traits suited to each niche.

  • When this process happens several times in one area, several new species may be formed from a single parent species in a short period.

This explains how over a dozen different finch species evolved from one parent species in a relatively short time in the Galapagos Islands (Fig. 2).

Darwin's Finches, A diagram showing how a parent species of finch rapidly formed several new species of finch with different beak shapes and feeding habits, StudySmarter

Figure 2. A diagram showing how a parent species of finch rapidly formed several new species of finch with different beak shapes and feeding habits. Source: National Human Genome Research Institute's Talking Glossary

Significance of Darwin's Finches

Darwin's discovery that different species of Galapagos finch had unique beak shapes adapted to the food sources available in their specific habitats led to the idea that life forms are not perfect and unchanging. Instead, they were changing over time in response to their environment. Such changes manifest in observable traits, such as the beak shapes of Galapagos finches. He argued that traits change in a population because individuals that inherit traits that are better adapted to the environment have better chances of survival and reproduction; thus, these traits have better representation in succeeding generations. These insights became the foundation for Darwin's theory of evolution by natural selection.

Another key insight that Darwin had drawn from his observations is the process of adaptive radiation. Morphological similarities among the species of Galapagos finches led him to believe that they all descended from a common ancestor but rapidly diversified and speciated because each population adapted to a different ecological niche.

Darwin's Finches - Key takeaways

  • Charles Darwin’s observations on the Galapagos Finches led to the formulation of his theory of evolution by natural selection.

  • Darwin observed that the different finch species on the Galapagos Islands each had unique beak shapes. He noticed that their beak shapes were suited to the food available in their habitat.

  • Darwin theorized that organisms with better traits have a higher chance of survival and reproduction; they can pass on these traits to the next generation. He called this natural selection.

  • Over time, species with better adaptations to their habitat are formed. This is why natural selection is the mechanism for adaptive radiation.

Darwins Finches

The different species of Darwin's finches descended from one common ancestor. Populations of the same ancestor species colonized different ecological niches. Over time, species with specific traits adapted to their specific habitat were formed.

Darwin's finches are significant because his discovery that different species of finch had unique beak shapes adapted to their specific habitats became the foundation for his theory of evolution by natural selection.

Yes, Darwin's finches consist of over a dozen species of finch.

The ancestor population of Darwin's finches colonized different ecological niches and underwent a burst of evolution, producing a large number of different descendant species in a relatively short period of time. This is a type of speciation called adaptive radiation.

Darwin's finches are significant because his discovery that different species of finch had unique beak shapes adapted to their specific habitats became the foundation for his theory of evolution by natural selection.  

Final Darwins Finches Quiz

Question

What did the different beak shapes among Darwin's finches imply?

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Answer

The different beak shapes among Darwin's finches implied that the different populations of finch adapted to the food available in their specific environments. A long, pointed beak was an advantage to insect-eating finches and a broad, blunt beak was an advantage to seed-eating finches.



Show question

Question

How did Darwin's finches adapt to their environment?

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Answer

The beak shape and feeding habits of different Galapagos finch populations changed over the course of several generations according to the demands of its specific environment.

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Question

What is an ecological niche?

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Answer

An ecological niche is a role that a species plays in a habitat.

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Question

What did the similarities among Darwin's finches imply?

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Answer

The similarities among Darwin's finches implied that they were closely related species and that they likely had the same ancestry.

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Question

What did Darwin notice about the Galapagos Finches?

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Answer

Darwin noticed that although the Galapagos were similar in size and color, their beak shapes were different.

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Question

What was the most important distinguishing feature of Darwin's finches?

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Answer

Their beaks

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Question

How did adaptive radiation occur in the Galapagos finches?

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Answer

Darwin theorized that all of the different finch species on the Galapagos Islands came from one parent species that first colonized the islands millions of years ago. As populations of the parent species spread from one uninhabited island to the next, they adapted to different ecological niches and rapidly evolved into many descendant species.

Show question

Question

Darwin's observations on Galapagos finches led him to what theory?

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Answer

Darwin's observations on Galapagos finches led to the formulation of his theory of evolution by natural selection.

Show question

Question

How did speciation occur among Darwin's finches?

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Answer

Speciation occurred when different populations of the ancestor finch species adapted to different ecological niches on the Galapagos Islands.  

Show question

Question

Why did Darwin's finches have different beak shapes?

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Answer

Darwin's finches had different beak shapes suited to their feeding habits.

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Question

What is the significance of Darwin's Finches?

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Answer

The Galapagos finches inspired Darwin’s theory of evolution by natural selection.

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Question

How did Darwin's finches adapt to their local environment?

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Answer

Darwin's finches had different beak shapes that were adapted to their local environment.

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Question

Why were the geological features of the Galapagos Islands important to Darwin's discovery of evolution?

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Answer

Different isolated habitats are found across the Galapagos Islands, making the Galapagos Islands high in biodiversity. This is why over a dozen species of finch are found on the Islands.

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Question

How did the beak shapes of Darwin's Finches increase their chance of survival?

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Answer

The unique beak shapes of Darwin's Finches helped them access their food. Long, pointed beaks helped insect-eating finches stab their prey, while blunt, broad beaks helped seed-eating finches crack seeds and nuts.

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Question

What are inherited traits and behaviors of organisms that help them survive and reproduce in their specific environments called?

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Answer

Adaptation

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Question

What is the process when a single species rapidly evolves into a large number of species adapted to different ecological niches called?

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Answer

Adaptive radiation

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Question

What is the formation of new species in the course of evolution called?

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Answer

Speciation

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