Download Darwin`s Background

Darwin's Theory of Evolution
Scientists at the beginning of the 1800s suspected that some kind of evolution had given rise to living things around them. However,
they had no unifying theory to explain how evolution might have occurred. Two scientists led the way in the search for a mechanism
of evolution. The first was Jean Lamarck. The second was one of the greatest figures in biology, Charles Darwin.
Evolutionary Theory Before Darwin
The first systematic presentation of _______________ was put forth by the French scientist Jean Baptiste de Lamarck (1774-1829) in
1809. Lamarck described a mechanism by which he believed evolution could occur. This mechanism was known
as "the inheritance of __________________________________."
Assume that there were salamanders living in some ____________________. Suppose, Lamarck argued, that
these salamanders had a hard time walking because their ______________couldn't trample the tall grasses or
reach the ground. Suppose that these salamanders began to slither on their bellies to move from place to place.
Because they didn't use their legs, the leg muscles _______________________ from disuse and the legs thus
became small. Lamarck's theory said that the salamanders passed this ________________________ to their offspring. In time the
salamander's legs were used so rarely that they _____________. Thus, Lamarck argued, legless salamanders evolved from
salamanders by inheriting the acquired characteristic of having no legs. Lamarck presented no experimental evidence or observation
and his theory fell out of scientific favor. The next significant idea came from the ____________________________Charles Darwin.
Darwin's Background
Charles Darwin (1809-1882), like many people of genius, did not at first appear to have extraordinary talents. From
a young age Darwin _______________ school and preferred observing birds and ____________ insects to study.
He was sent to medical school in _________when he was 16. Young Darwin found medicine "intolerably dull." He
was much more interested in attending ______________________ lectures. Seeing that Darwin lacked enthusiasm
for becoming a doctor, his father suggested he study for the clergy. Darwin was agreeable to the idea and enrolled
in the university at Cambridge, England, in 1827. Here again, Darwin admitted, "My time was wasted, as far as the academic studies
were concerned." However, Darwin found that his friendship with John S. Henslow, professor of botany, made life in Cambridge
extremely worthwhile. Through long talks with Henslow, Darwin's knowledge of the natural world ______________. Henslow
encouraged Darwin in his studies of natural history. In 1831 Henslow recommended that Darwin be chosen for the position of
naturalist on the ship the ___________________________.
The Voyage of the Beagle
The Beagle was chartered for a five-year mapping and collecting expedition to South America and the South Pacific.
Darwin's job as ship naturalist was to collect specimens, make observations, and keep careful records of anything he
observed that he thought significant. At the beginning of the voyage Darwin read a geology book given to him by
Henslow. This book, Principles of _________________ by Charles Lyell, spurred his interest in the study of land
forms. In Chile Darwin observed the results of an earthquake: the land had been lifted by several feet. In the Andes he observed fossil
shells of marine organisms in rock beds at about 4,300 m. He came to agree with Lyell that over millions of years earthquakes and
other geologic processes could change the ___________ of the land. Because the land changed, new habitats would form. Darwin
realized that animals would have to adapt to these changes. During the Beagle's five-year trip the ___________ often dropped Darwin
off at one port and picked him up months later at another. One reason that Darwin was so eager to study life on land was that he
suffered from ______________ seasickness and couldn't wait to get off the __________. During his time on land Darwin trekked
___________________________ through unmapped region. He observed thousands of species of organisms and collected many
different types of _________________. On the long sea ___________ he used his time to catalog his specimens and write his notes.
Darwin in England
When Darwin returned to England in October 1836, the scientific community ______________ his collections from the voyage.
Darwin sent many specimens to experts for _________. A bird specialist, or ______________________, studied Darwin's bird
collections from the ___________________________, located about 1,000 km west of South America. He reported that Darwin had
collected 13 similar but separate species of ____________. Each finch species had a distinctive bill specialized for a particular food
source. Other experts studied Darwin's fossils and classified them as remains of ________________ mammals. The fossils included
rodents the size of __________________________. The similarities of the Galapagos finches led Darwin to infer that the finches
shared a common ______________. The similarities between the fossil mammals Darwin collected and modern mammals led him to
believe that species _____________________________________.
In 1837 Darwin began his first notebook on evolution. For several years Darwin filled his _______________________ with facts that
could be used to support the theory of evolution. He found ________________ from his study of the fossil record: he observed that
fossils of ________________ relative ages are more closely related than those of widely different relative ages. Comparing
___________________ structures, vestigial organs, and embryological development of living species gave him additional evidence of
evolution. He consulted animal and plant breeders about changes in domestic species. He ran his own breeding and on seed dispersal
experiments.