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. Show
Voyage of the Beagle to the Galapagos IslandsFrom 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 BeaksWhile 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 DiagramFig. 1 - A diagram comparing the beaks of four species of Galapagos finch 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 ActivityHere'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:
Methodology:
Answer the following questions:
Darwin's Finches and His Theory of Evolution by Natural SelectionDarwin 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 nichesand 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:
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). Fig. 2 - A diagram showing how a parent species of finch rapidly formed several new species of finch with different beak shapes and feeding habits Significance of Darwin's FinchesDarwin'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
What were Darwin's observations of finches on Galapagos Islands?On the Galapagos Islands, Darwin also saw several different types of finch, a different species on each island. He noticed that each finch species had a different type of beak, depending on the food available on its island. The finches that ate large nuts had strong beaks for breaking the nuts open.
What observation did Charles Darwin make about finches in the Galapagos Islands quizlet?He noticed that the birds had different beaks in different parts of the island. He also noticed that tortises have different shells depending where they are.
How Charles Darwin used his observations of finches on the Galapagos Islands to develop his theory of natural selection?However, the Galapagos finches helped Darwin solidify his idea of natural selection. The favorable adaptations of Darwin's Finches' beaks were selected for over generations until they all branched out to make new species. These birds, although nearly identical in all other ways to mainland finches, had different beaks.
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