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Assume that there were salamanders living in some grasslands. Suppose, Lamarck argued, that these salamanders had a hard time walking because their short legs 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 wasted away from disuse and the legs thus became small.

passed this acquired trait

legless salamanders evolved

no legs.

by inheriting the acquired characteristic of

Darwin's Background

o have extraordinary talents.

genius, did not at first appear

Darwin disliked school

d observing birds and collecting insects to study.

sent to medical school in Scotland

"intolerably dull

interested in attending natural history lectures.

university at Cambridge, England, in 1827.

Darwin be chosen for the position of naturalist on the ship the HMS Beagle.

to collect specimens, make observations, and keep careful records of anything he observed that he thought significant.

Principles of Geology by Charles Lyell,

In the Andes he observed fossil shells of marine organisms in rock beds at about 4,300 m.

One reason that Darwin was so eager to study life on land was that he suffered from terrible seasickness and couldn't wait to get off the Beagle.

thousands

trekked hundreds of miles through unmapped region.

catalog his specimens and write his notes.

praised by the scientific community.

experts for study.

bird specialist

Darwin's bird collections from the Galapagos Islands, located about 1,000 km west of South America.

13 similar

Other experts

believe that species change over time.

evidence f

In 1837 Darwin began his first notebook on evolution. For several years Darwin filled his notebooks with facts that could be used to support the theory of evolution.

fossils of similar relative ages are more closely related than those of widely different relative ages.

He ran his own breeding experiments and also did experiments on seed dispersal.

How did a group of ground-dwelling flightless dinosaurs evolve to a feathered animal capable of flying?

used its feathered limbs, along with a long, feather-fringed tail, to glide from tree to tree.

new species, Microraptor gui

dated at between 128 to 124 million

four feathered limbs,

birds are most closely related to dromaeosaurids

dromaeosaurs were small, feathered animals with forelimbs similar to those of Archaeopteryx, the oldest known bird at around 150 million years old, and feet with features comparable to modern tree-living birds.