Darwin, Evolution & Natural Selection

Key Concepts

• Evolution

• Darwin- The father of evolution

• The voyage of the beagle

• Observations from the Galapagos

• Tortoises of the Galapagos

• Darwin’s finches

Introduction

Evolution states that various types of plants, animals, and other living organisms on Earth have their origin in pre-existing life-forms. The distinguishable differences are due to modifications or adaptations in successive generations. In simple terms, evolution can be defined as change over time. 

Modern scientists have altered this definition of evolution as the genetic change in a population over time. 

Explanation:

Ideas revolving around natural selection and evolution began to be discussed in earnest in the early nineteenth century. Many scientists and philosophers have put forward their theories of evolution over the course of time; Charles Darwin was one of them. 

Even though he was not the first person to talk about evolution, he was the first person to write the most comprehensive collection of evidence supporting evolution. 

Who was Darwin? 

Charles Darwin (1809-1882) was an English naturalist of the 19th century. A naturalist is someone who examines the natural world, such as plants, rock formations, and animals. He is popularly known as the father of evolution due to his contribution to the establishment of the theory of evolution. 

After returning from his journey around the world aboard HMS Beagle, Darwin formulated his theory in private in 1837–39, but it was not until two decades later that he finally published it in his book “On the Origin of Species (1859)”, a book that has profoundly influenced modern Western society and thought. 

His theory appalled the Victorian religious society by suggesting that animals and humans shared a common ancestry. Before he published his book, he was very much influenced by C. Lyell (Geologist), who believed that the natural forces that existed in the past are the same as those existing at present. 

Darwin – The Father of Evolution 

Darwin’s theory of evolution helped to eliminate all of the ancient beliefs that the origin of various species was a supernatural occurrence or act of the Almighty.  

His theory provided a more reasonable explanation of the creation of new species. According to his theory, various species originated from a single species as a result of adaptation to change in environmental conditions. 

The voyage of the Beagle: 

In December 1831, Charles Darwin was only 22 when he went on a voyage on the HMS Beagle, a British military ship. The Beagle sailed from England to South America and other parts of the world.  

Darwin traveled the world extensively for 5 years from 27th December 1831 to October 1836 and returned to England. The HMS Beagle sailed from England to South America and other parts of the world to provide maps for navigation. The voyage of the Beagle nearly took five years.  

Darwin spent time in South America, visiting remote islands such as the Galápagos Islands. 

The Galapagos Islands: 

On his journey, Darwin spent his time exploring South America and its remote islands, like the Galapagos. The Galápagos Islands are located around 1000 kilometers off the coast of Ecuador (South America).  

The majority of Darwin’s time on these islands was spent studying nature, gathering samples of unknown plants and animals, and writing about places and organisms that few others had ever seen.  

Darwin’s observations: 

Darwin was amazed by the variety of species found on the Galapagos islands. He made extensive observations and detailed notes of the biology and geology of the locations that he visited. He noticed various new animals and plants that had not been recorded prior to this trip. 

He collected several samples of flora and fauna from the Galapagos. 

Darwin became particularly fascinated in comparing the similarities and differences among the animals and fossils of animals from the different islands of the Galapagos. On comparing them, he realized that many of the turtles, birds and lizards on the Galápagos were similar but not identical to organisms that he found on the South American mainland.  

Darwin concluded from these observations that perhaps some of the animals and plants on the Galápagos originally came from South America, and over time, they evolved to be different. 

Tortoises of the Galapagos Islands: 

During his voyage, Darwin made interesting observations of the giant Galápagos tortoises.  

He found tortoises on all of the Galápagos Islands and nowhere else that he visited. The tortoises were enormous in size.  

Darwin was fascinated by the fact that the tortoises varied from island to island in the Galápagos.  

He wondered why all the tortoises were so different despite the fact that they lived on islands only 80 kilometers apart. 

In the above picture, we can see that the shape of the shell is unique in the two different tortoises. 

Darwin found that tortoises that had dome-shaped shells and short necks were found in places where they primarily ate low-growing plants.  

But the tortoises feeding on high-growing cacti had saddle-shaped shells that allowed their long necks to reach the cactus pads. 

Darwin reasoned that perhaps the different tortoises “descended with modification” from a common ancestor in South America. The population would change genetically with each generation until a trait for long necks emerged. 

Darwin’s finches: 

On the Galápagos Islands, Darwin also made significant observations of birds called finches. These birds were unlike any he had seen before in other parts of the world. He described 13 finch species, although, at the time, he believed they were all the same species.  

Similar to the tortoises, Darwin was amazed by the diversity of finches on the different islands. The variety of beak size and shape in the finches piqued his interest the most. Beaks ranged from small to large, and each beak type was well-suited for eating a particular food. 

For example, the large ground finch had a large beak that was ideal for cracking large open seeds on the ground.  

The small tree finch had a long and narrow beak that was suitable for catching insects in the trees. The long beak of the cactus finch enables it to eat the fruit of the prickly pear cactus.  

Darwin later explained that if individuals from an ancestral species in South America were separated for a long period of time, the future generations or the descendants on different islands might look and behave differently.  

Thus, in a similar way to the tortoises, the finches became different because genetically, they fit the different habitats on the islands. 

After his voyage, Darwin returned to England and thought about his observations. He collected more evidence by performing different experiments and studying different breeds of dogs and varieties of flowers. 

In the 1800s, he developed his theory of evolution based on these observations and thoughts, which is now widely accepted. 

Summary

• Evolution is defined as change over time. New age scientists refer to evolution as genetic change in a population over time.

• Charles Darwin (1809-1882) was an English naturalist of the 19th century.

• He is popularly known as the father of evolution due to his contribution to the establishment of the theory of evolution.

• Darwin’s theory of evolution helped to eliminate all of the ancient beliefs that the origin of various species was a supernatural occurrence or act of the Almighty.

• In December 1831, Charles Darwin was only 22 when he went on a voyage on the HMS Beagle, a British military ship.

• The Beagle sailed from England to South America and other parts of the world. Darwin spent time in South America, visiting remote islands such as the Galapagos Islands.

• The Galapagos Islands are located around 1000 kilometers off the coast of Ecuador (South America).

• Darwin compared the similarities and differences among the animals and fossils of animals from the different islands of the Galapagos.

• On comparing them, he realized that many of the turtles, birds and lizards on the Galapagos were similar but not identical to organisms that he found on the South American mainland.

• Darwin later explained that if individuals from an ancestral species in South America were separated for a long period of time, the future generations or the descendants on different islands might look and behave differently.

• Thus, in similar ways, the tortoises, as well as the finches, became different because genetically, they fit the different habitats on the islands.