Download Interactive Reader 10.1

section
Ideas
10.1 Early
About Evolution
Key Concept There were theories of biological and
geologic change before Darwin.
Early scientists proposed ideas about evolution.
Evolution is the process of biological change by which descendants*
come to differ from their ancestors. Much of today’s understanding of
evolution is based on Charles Darwin’s work in the 1800s. But Darwin
did not come up with the idea of evolution himself. Many other scientists contributed important ideas to the study of evolution. Several
historical ideas—about species, geology, and the mechanisms of evolution—are described below. Like all
science, the modern understanding of biological evolution builds on hundreds of years of study and research.
Species
In the 1700s, a botanist named Carolus Linnaeus came
up with a system to organize and name all of the
different known types of organisms, or species. A
species is a group of organisms that can reproduce and
have fertile* offspring. Linneaus’ classification system
grouped organisms according to physical similarities.
His system also shows evolutionary relationships, and
is still in use today.
In Linnaeus’ time, there was a common belief that
the organisms that lived on earth were fixed, or that
species did not change. Linneaus proposed that species
could change. For example, he observed in experiments
that two different plant species could cross, and make a
new type of plant.
There is great diversity in
different species of birds.
* Academic Vocabulary
descendant offspring, or an organism that is related to another organism from the past
fertile able to breed and have offspring
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McDougal Littell Biology
In the 1700s, it was also a common belief that Earth was only 6000 years
old. But several geologists began to challenge this idea. The geologists
believed they had evidence that Earth was much older. The evidence of
the old age of Earth was important to Darwin’s development of his ideas.
Mechanisms of Evolution
Many scientists in the 1700s did not believe that species could go
extinct*. But many scientists thought species could change, or evolve.
There were many different ideas, however, about the mechanism of
evolution, or how evolution happens. For example, different scientists
had different ideas about how environmental changes affect evolution,
how changes get passed on to offspring, and what causes biological
variation.
How does history affect the development of scientific ideas?
Theories of geologic change set the stage for
Darwin’s theory.
The study of fossils led some scientists to conclude that species do go
extinct. Fossils are traces of organisms that existed in the past. The
locations of fossils in different rock layers provide clues about Earth’s
past. But how did those rock layers form? Geologists held different ideas
about geologic change.
• Catastrophism (kuh-TAS-truh-fihz-uhm) is the
idea that past natural disasters—like floods and
volcanic eruptions—shaped landforms, and
caused species to become extinct in the process.
• Gradualism (GRAJ-oo-uh-lihz-uhm) is the
idea that landforms were shaped by very slow
changes over a long period of time, and not by
natural disasters.
The formation of mountains, shown here,
results from slow changes over long periods
of time.
* Academic Vocabulary
geology the study of rocks, minerals, and landforms
extinct no longer existing
Interactive Reader
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• Uniformitarianism (yoo-nuh-fawr-mih-TAIR-ee-uhnihz-uhm) is the idea that the same processes that shaped
landforms in the past also shape landforms today. In
other words, the geologic processes that shape Earth are
uniform, or the same, through time. Uniformitarianism
became the favored theory of geologic change and played
an important role in the development of Darwin’s theory.
VISUAL VOCAB
Uniformitarianism proposes that
present geologic processes are the key
to the past.
Which idea about geologic change became the
accepted theory?
10.1 evolution
species
fossil
Vocabulary Check
catastrophism
gradualism
uniformitarianism
Mark It Up
Go back and highlight
each sentence that
has a vocabulary
word in bold.
1. Name three ideas about geologic change.
2. What is the term for a group of organisms that can reproduce and
have fertile offspring?
3. What is the term for the process of biological change by which
organisms come to differ from their ancestors?
10.1 The Big Picture
4. How are catastrophism and gradualism different?
5. How did the ideas of scientists before Darwin influence Darwin’s
ideas?
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McDougal Littell Biology
Every layer of rock
was formed by the
uniform laying down
of sediment that
still occurs today.