15-2IDEAS THAT SHAPED DARWIN’S THINKING

Objectives1) How did Hutton and Lyell

describe geological change?2) According to Lamarck, how did

species evolve?3) What was Malthus’s theory of

population growth?

People during Darwin’s era thought the world was created only a few thousand years ago

People didn’t believe living species or the Earth had ever changed

Scientists were discovering new evidence to disprove common beliefs

INTRODUCTION

AN ANCIENT, CHANGING EARTH

2 scientists formed important theories based on evidence suggesting that Earth was very old and had changed slowly over time

• Hutton and Lyell

AN AN CIENT, CHAN GIN G EARTH CO N T’D

Hutton and Lyell helped scientists recognize that

• Earth is manly millions of years old

• Processes that changed Earth in the past are the same processes that operate in the present

Hutton published a detailed hypothesis about the geological forces that have shaped Earth in 1795

HUT TON AND GEOLOGICAL CHANGE

Proposed• Layers of rock form

very slowly• Moved up by forces

beneath Earth’s surface

• Buried • Pushed up from the

sea floor to form mountain ranges

HUTTON AND GEOLOGICAL CHANGE CONT’D

• Rocks are shaped by a variety of natural forces• Rain• Wind• Heat• Cold temperatures

• Operate extremely slow

Because of this he proposed that Earth had to be much more than a few thousand years old

HU T TO N AND GEO L OGICAL CHANGE CO N T’D

LYELL’S PRINCIPLES OF GEOLOGY

Darwin was given a copy of Lyell’s book Principles of Geology shortly before his voyage on the H.M.S. Beagle.

This book inspired Darwin to ask questions• If the Earth could change over time, might life change as well?• Wouldn’t it have taken many, may years for life to change in the

way Lyell suggested? • This would only be possible if the Earth were extremely old

What are some ways the Earth has changed over time?

BLUE TICKET QUESTION

LAMARCK’S EVO LUTION HYPO THES ES

French naturalist

Jean-Baptiste Lamarck

Among the 1st scientist to recognize

• Living things have changed over time

• All species were descended from other species

• Organisms were somehow adapted to their environment

LAMARCK’S EVO LUTION HYPO THES ES

Lamarck proposed • Selective use or disuse of organs, organisms acquired or

lost certain traits during their lifetime• Traits could then be passed on to their offspring

• Led to change in a species over time

All organisms have an innate tendency toward complexity and perfection

• Continually changing and acquiring features that help them live more successfully in their environments

TENDENCY TOWARD PERFECTION

USE AND DISUSE

Organisms could alter the size or shape of particular organs by using their bodies in new ways

Acquired characteristics could be inherited• If during its lifetime an animal somehow altered a body

structure, then it would pass that change on to its offspring

INHERITANCE AN D ACQ UIR ED TRAITS

Lamarck’s hypotheses had flaws• He did not know how traits

are inherited• An organism’s behavior has

no effect on its heritable characteristics

He was one of the 1st to develop a scientific hypothesis of evolution and realize that organisms are adapted to their environments

EVALUATIN G L AMARCK’S HYPO THES ES

POPULATION GROWTH

Thomas Malthus• Reasoned that if the human population continued to grow unchecked,

sooner or later there would be insufficient living space and food for everyone

POPULATION GROWTH CONT’D

• This hasn’t happened because humans produce fewer offspring

• Other organisms• Majority of

offspring die• Only a few

offspring succeed in reproducing

15.2 EXIT TICKET