Natural Selection

Darwin- A glorious beard & a man who Finches at no question


Darwin and his finches are one of the most famous examples of Natural Selection. These cute little birds are the living, breathing, example of the phenomenal way in which species adapt to ensure the long term survival for their species. Via Natural selection, gene pools of the species of finches become altered as only the fittest of birds can survive. The legend, the man renowned for his glorious beard (and his extraordinary science stuff)- CHARLES DARWIN, observed these finches. While exploring Galapagos Island, Darwin observed many different species of animals. He became particularly interested in the finches he had observed on the island. He found thirteen species of finches on Galapagos Island. Darwin found this quite odd, as to his knowledge the only species of this type of bird was found 600 miles to the east of Galapagos- in South America! Darwin, wanting to know more, went into an intense study of the finches. He hypothesized that the finches had derived from a common ancestor and had changed to do different things and to suit their environments. The main differences in the finches were their beaks size and shape.

The Different Finches and The differences in their beaks


The Large Ground Finch (Geospiza Magnirostris) was the largest species of Finch that Darwin observed. It is the largest both in total size and shape of beak. It has a large, short beak for cracking nuts to get food.


The Medium Ground Finch (Geospiza Fortis) is the first of Darwin's finches that scientists were able to observe evolving in real time. The finch usually ate small and soft seeds, which was reflected by it's small petite beak. But in 1977 a severe drought reduced supply of small soft seeds to Galapagos island, forcing the bird to eat larger, tougher seeds. That led to a 10% change in bird size of the species.


The small tree finch (Geospiza Parvula) differs greatly from the ground finches. They feed primarily on insects. Their beak/bill shape is a lot sharper than ground finches, aesthetically better for their insect diet, as grasping is made a lot easier.


The Green Warbler Finches (Certhidea Olivasea) were the smallest of the finches that Darwin observed. They have much more slender bills than the other finches. They use their long slender, pointed bills to probe amongst moss, bark and leaves for food (such as spiders and insects).

How did their beaks change? How does that relate to natural selection?

Natural Selection and Adaptive Radiation!

Darwin observed that the finches beaks changed due to their diets. He concluded that when the first South American finches reached the Galapagos islands, they all went their separate ways to different environments. Within these different environments, the finches encountered different environments and inhabited different niches. The finches had to adapt to suit the different conditions in their niches. If they did not adapt, they died. So, to accommodate their needs, an individual or group of individuals in the species evolved a new beak shape more suitable for the food sources in their niche.
These individuals then had a competitive advantage over their fellow finch brethren, enabling them to grow and reproduce more successfully, and pass on their more specialized beaks to successive generations. Eventually the characteristic had spread throughout the finch population in that area/niche. The species anatomically changed to suit their niches. The different populations of the finches became reproductively isolated from each-other by adapting to their separate ecological niches. This is called adaptive radiation. The finches with beaks unsuitable died out, making the birds with the suitable beaks in a better condition to mate, and therefore at an advantage to become the dominant species. The finches had to either adapt to the changing food supply or die. The forces of nature are at work, and nature only selects the best adapted finches to survive and reproduce. Viola! Evolution of a species via Natural selection.

Natural Selection and Beak Size Variation Of Finches

Evolution in the Galapagos
Charles Darwin - Galapagos Finches


Horrible Histories - Natural Selection (Charles Darwin)