Charles Darwin How one man’s observations and ideas helped to change the world.

Charles Darwin

How one man’s observations and ideas helped to

change the world

Darwin continued…

As a young boy, Darwin preferred collecting insects, hunting and fishing to attending school lessons. He loved the outdoors.

Darwin’s father and grandfather were both physicians and hoped Darwin would follow in their footsteps.

Yet Darwin’s time at medical school was short lived as he was completely nauseated by the operating room (anaesthetics were not yet in use).

He instead studied to be a clergyman.

Darwin continued…

On August 24th 1831, shortly after he had graduated from his studies, Reverend John Henslow sent a letter to Darwin informing him that he had been recommended as a naturalist on a voyage to South America.

Although Darwin had no formal training, Henslow considered him to be “the best qualified person I know of …for collecting, observing and noting anything worthy to be noted in natural history.”

Darwin continued…

Darwin accepted the

offer and set sail on

the HMS Beagle on

December 27th 1831.

The captain of the ship (Captain Robert FitzRoy) accepted Darwin on board the ship in hopes that he would find evidence to support biblical creation.

The voyage of the Beagle 1831 - 1836

The Beagle set sail on her voyage on 27th December 1831, with Charles Darwin aboard, and returned to England on October 2nd 1836. The voyage lasted 5 years.

The mission of the ship was to map the coastline of South America and everywhere it went Darwin took detailed notes of what he saw and collected many specimens.

The Galapagos Islands

Charles Darwin arrived in the Galapagos, a group of volcanic islands off the coast of Ecuador, South America on September 15th 1835.

The observations Darwin made during his visit were to be influential in the formation of his scientific theories.

The Galapagos Islands During his time on the islands, Darwin collected

specimens of many of the different plants and animals he observed, and detailed drawings were also made.

As well as his observations of the species on the islands, Darwin also wrote descriptions of the geography and geology of each island in his diary.

He found that most of the animal species live no where else in the world, although they resemble species on the South American mainland (found this same trend in the Cape Verde islands off the coast of Africa)

The Galapagos Islands

Darwin began to wonder why continents that were very far apart had species that were entirely different occupying similar ecological niches? For example, why would species in the grassland areas of South America be similar to those of a nearby island rather than those occupying the grassland areas of Africa?

Darwin observed that each island had its own unique mixture of plants and animals. These were often adapted to survive in the different conditions found on each island.

The Galapagos Islands One species which

Darwin wrote many observations about was the Galapagos giant tortoise.

“It was confidently asserted, that the tortoises coming from different islands in the archipelago were slightly different in form; and that in certain islands they attained a larger average size than in others”

Darwin’s Finches

Darwin made detailed studies of one group of birds, the finches, because of their strong similarities and subtle differences.

He noticed that the different finch species varied in size, beak size and shape, and behaviour. He thought that these differences could be best explained if the finches had gradually become adapted to suit the conditions on the island they inhabited.

He presumed therefore that all 13 species of finch found on the islands must be closely related.

He also deduced that the individuals with the best set of adaptations for each island’s habitat would be most likely to survive and breed.

Darwin’s Finches

Upon his return, Darwin had the bird specimens he had collected analyzed by ornithologist John Gould.

Gould discovered that the birds were in fact different species (Darwin did not realize this at first. He thought he was observing variation within one species)

This suggested to Darwin that a single ancestor had come from a nearby land and given rise to several distinct species, especially when isolated on separate islands.

Importance of adaptation and survival!

Glyptodon and Megatherium

While in Patagonia, Darwin discovered fossils of giant organisms that closely resemble much smaller modern animals

Upon his return, these fossils were analyzed by palaeontologist Richard Owen who confirmed that they were larger versions of armadillo and sloth which are still found in the area.

Darwin figured these must be ancestral forms of organisms currently occupying the area

Glyptodon

Armadillo

Megatherium

Sloth

The Origin of Species

When Darwin returned to England (1836), he continued to study and collect information about what he had seen and experienced on his journey.

About seven years later he presented a paper to trusted colleagues that proposed his theory of evolution

However, he knew it would be met with great opposition and so he continued to gather evidence and add to his work

The Origin of Species

In 1858, he received a letter from naturalist Alfred Russell Wallace who was working in Indonesia. Wallace had independently arrived at the same conclusions as Darwin!

Wallace’s work was much more sketchy as he had written his theory in 2 days, while Darwin had compiled 22 years of research!!!

Yet Wallace was ready to publish and present his ideas

The Origin of Species

Darwin’s friends and colleagues urged him to present a paper along with Wallace.

On July 1, 1858 both men’s papers were presented jointly

A year later, in 1859, Darwin published his book On the Origin of Species By Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life (also known as the Origin of Species).

The Origin of Species The book sold out on the first day. Why was it so influential?

a) His theory suggested that all living things are here as a result of descent, with

modification, from a common ancestorb) His observations could be explained through his theory of evolution but not through

creationist theoriesc) Although evolution was not a new idea, he

was the first person to propose a reasonable mechanism of how evolution occurred.

The theory still stands today.