Darwin’s VoyageOf the HMS Beagle and Finches

The HMS Beagle

• Set sail in 1831 on a voyage around the world

• Mission: Chart the poorly known South American coastline

• Charles Darwin was the ship’s naturalist

• He collected thousands of specimens of South American plants & animals

• He also observed different land forms and fossils

• Maintained extensive journals of his travels

The Route

The Three Patterns

• Darwin observed three patterns on his journey as he studied the biodiversity and fossils of the world:• Species Vary Globally• Species Vary Locally• Species Vary Over Time

Species Vary Globally• Darwin noticed that distantly related

species living in similar habitats in different part of the world looked similar and had acted in similar ways. E.g. Large flightless birds in different grasslands: Rhea (SA), Ostrich (AF) and Emu (AUS)

Species Vary Globally• He noticed that some places had unique

organisms not found anywhere else. E.g. Marsupials in Australia

Species Vary Globally• He also noticed that South American plants

and animals were very different from species from Africa and Europe. E.g. A tropical SA lizard was more like a SA desert lizard than an African tropical lizard.

Species Vary Locally• Darwin noticed that related

animal species that occupied different habitats within a local environment had different features. Especially on Islands E.g: Galapagos Archipelago• Tortoises on Isabella vs. Española• Many different Finch species even

though they look like they are from bird different families

• Most of the unique species were similar to a mainland species. Therefore, Darwin inferred that the mainland species had changed after colonizing this new environment

Species Vary Locally

• Darwin noticed that related animal species that occupied different habitats within a local environment had different features. Especially on Islands E.g: Galapagos Archipelago• Tortoises on Isabella vs. Española• Many different Finch species even though they

look like they are from bird different families• Most of the unique species were similar to a

mainland species. Therefore, Darwin inferred that the mainland species had changed after colonizing this new environment

Species Very Over Time

• Darwin noticed that the fossils he found in SA were very different from those discovered by other naturalists elsewhere.

• They were uniquely South American

• This supported the idea that species living in SA were descended from ancestral species on that continent

• E.g. Armadillo vs Glyptodon fossils

Geological Change• Darwin was reading Lyell’s

Principles of Geology on his trip

• He experienced an earthquake in the Andes and observed underwater land move above the water level.

• He had also collected fossils of marine organisms in the mountains

• He reasoned that earthquakes had gradually lifted the rock containing those marine fossils from the sea floor based on Lyell’s ideas

The road to Darwin’s Theory

• In 1838, Darwin read an essay on human population by Thomas Malthus who said that much of human suffering was due to human population’s potential to grow faster than the rate at which resourced to support that population can be produced.

• Darwin recognized that these ideas applied to all species and this concept helped him propose a mechanism of evolutionary change

Resemblance to Other Animals

• How closely do we resemble some animals?

Fish?

Frog?

Alligator?

Eagle?

Wolf?

Monkey?

Chimps?

The race to Publish

• In 1844, Darwin wrote a 200-page essay that outlined his idea of evolution but didn’t release it to public.

• Instead he tried to accumulate more evidence to support his idea. But his friend wanted him to publish his work before someone else did

• In 1858, Alfred Wallace (Brit) came to the same conclusion and sent Darwin a letter about it

• Within a month, both writings were jointly presented to the public.

• Darwin published The Origin of Species a year later

The Origin of Species

• Darwin made two main points in this book:• All species of organisms living on earth today

are descended from ancestral species i.e. species evolve over time

• The mechanism that causes them to change over time is called Natural Selection

Descent with Modification

• Darwin proposed that the descendents of the earliest organisms spread into various habitats over a geological time scale

• In these habitats they accumulated different modifications, or adaptations, to diverse ways of life

• He called this process “descent with modification”

• He never used the term Evolution

• E.g. Jackrabbit vs Snowshoe hare