Chapter 16 16

Darwin’s Voyage of Discovery & Ideas That Shaped His Thinking Section 16.1 Section 16.2

Learning Targets  State Darwin’s contribution to science.  Describe the 3 patterns of biodiversity noted by Darwin.  Identify the conclusions drawn by Hutton & Lyell about

Earth’s history.  Describe Lamarck’s hypothesis  Describe Malthus’s view of population growth.

Darwin’s Epic Journey  Charles Darwin  1809, a time when science was dramatically

changing  Geologists & biologists suggest that earth

AND life have changed over time  EVOLUTION is defined as change over time.

Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through decent from common ancestors.

The HMS Beagle  In his 20’s, Darwin was asked to join a 5 year journey.  The captain and crew of the HMS Beagle were planning to

chart the coastline of South America—  Darwin had plans to collect specimen of plants and

animals.  No one knew it then, but what Darwin was about to do, was

going to change the face of Biology.

Darwin’s Observations 1.

Species vary globally  Different, yet ecologically similar animal species inhabited

separate, yet ecologically similar habitats around the globe. 

Rheas vs. Ostriches

South America



Africa

What did this pattern of distribution mean?

2.

Species Vary Locally  Different, yet related animal species often

occupied different habitats within a local area.  Different niches  Rheas in S.A.

• Tortoises & Finches

3. Species vary over time  Noticed that some fossils of extinct animals

were similar to living species.  And other fossils looked NOTHING like

anything currently alive.  What caused certain animals to continue living

while others are now extinct?

 On the way home, after 5 years of observations and

detailed note taking Darwin began to put the pieces of the puzzle together…  Certain members of the scientific community were

buzzing with excitement and curiosity—others were skeptical.

An Ancient & Changing Earth  It was believed that Earth was only a few thousand years old

and relatively unchanged.  Geology—a relatively new science, started to support ideas

of Earth’s history that did not support the current beliefs.  Two geologists suggested that Earth is actually very old and

was shaped by various processes that are still at work today.

Hutton  1785, made connections between geological

processes and features.  Mountains & valleys  Rock types & formations (lava, vs. sedimentary)

 Proposed that forces beneath/within the Earth can tilt, push

and twist rock layers.  Proposed that other forces, like rain, wind, cold, heat can

erode surfaces.  Erosion, tectonic movement is very slow  In order to shape Earth that we recognize; Earth much

be much older than a few thousand years.  Hutton proposed “deep time”—the idea that our

planet is much older than we ever thought possible.

Lyell  1830, introduced the idea of “uniformitarianism”  Geological processes NOW, work the same way they

did “way back then”  Another “universal law”, like the law of gravity

Lamarck  1809—proposed two hypotheses 1.

Organisms can change during their lifetime by using/not using certain parts of their bodies.

2.

Individuals could pass these acquired traits to their offspring.  Called this “acquiring” characteristics

Malthus  1798, economist noting changes in the human population.  He argued…  IF the human population grew “unchecked” we would soon run

out of food and living space.  BUT…  There are forces that work against population growth, like war, famine

and disease.

The Influence On Darwin  From England to S.A., there was a lot of “free time” 

Darwin read to pass the time…  Specifically, he read of the work of Hutton, Lyell,

Lamarck and Malthus.  What he didn’t know, was that their work would later shape

his thinking when he organized his research on the journey back home.

 Hutton & Lyell (the geologists)  Darwin saw first hand how an earthquake shapes the earth   A quake in S.A. knocked him to the ground, as he saw the earth raise 3

feet from where it was

 He observed aquatic fossils towards the tops of mountains.

Darwin was seeing proof that Hutton & Lyell were correct! If the EARTH could change over time, is it possible that LIFE could change too?

 Lamarck (the naturalist)  While a lot of his ideas were “incorrect” he paved the

way for Darwin.  He suggested that species can and do change over time  He was the first to try an explain evolution as a

process.  He also recognized the link between an organism’s

environment and body structures.

 Malthus (the economist)  Darwin realized Malthus’s thoughts could be

applied to other species other than humans  If all species grew unchecked, they would

eventually run all other species to extinction.

Darwin had become convinced that evolution occurs.

Why do some individuals die? Why do some survive…and HOW??

Now he needed a mechanism—a natural explanation or process to explain why evolution occurred.