Question

1. What is evolution?

2. Summarize Lamarck's hypothesis of evolution.

3. Summarize Darwin's voyage on the Beagle.

4. Explain how adaptations arise from natural selection.

5. What did Darwin mean by the phrase "descent with modification"?

6. What observations and corresponding inferences did Darwin make from the results of artificial selection?

7. Summarize the experiment conducted on soapberry bugs.

8. Explain how drug-resistant pathogens are an example of ongoing natural selection.

9. Explain the difference between homologous and analogous structures.

10. How does the study of biogeography support evolution?

Answer 1

1. In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

• The theory of evolution is based on the idea that all species are related and gradually change over time.
• Evolution relies on there being genetic variation in a population which affects the physical characteristics (phenotype) of an organism.
• Some of these characteristics may give the individual an advantage over other individuals which they can then pass on to their offspring.

2. Jean-Baptiste Lamarck was a French scientist who developed an alternative theory at the beginning of the 19th century. His theory centred on two ideas:

• the law of use and disuse
• the law of inheritance of acquired characteristics

His theory stipulated that a characteristic which is used more and more by an organism becomes bigger and stronger. One that is not used disappears eventually. Any characteristic of an organism that is improved through use is passed to its offspring.

These lists summarise the two different explanations for long necks in giraffe.

1. a giraffe stretches its neck to reach food high up
2. the giraffe's neck gets longer because it's used a lot
3. the giraffe's offspring inherit its long neck

3.  In 1831, Charles Darwin received an astounding invitation: to join the HMS Beagle as ship's naturalist for a trip around the world. For most of the next five years, the Beagle surveyed the coast of South America, leaving Darwin free to explore the continent and islands, including the Galápagos. He filled dozens of notebooks with careful observations on animals, plants and geology, and collected thousands of specimens, which he crated and sent home for further study.

Darwin later called the Beagle voyage "by far the most important event in my life," saying it "determined my whole career." When he set out, 22-year-old Darwin was a young university graduate, still planning a career as a clergyman. By the time he returned, he was an established naturalist, well-known in London for the astonishing collections he'd sent ahead. He had also grown from a promising observer into a probing theorist. The Beagle voyage would provide Darwin with a lifetime of experiences to ponder—and the seeds of a theory he would work on for the rest of his life.

A Stunning Invitation

Returning from a trip in August 1831, Darwin received a letter from his Cambridge professor and mentor, J. S. Henslow offering a chance of a lifetime: an invitation to go on a trip around the world as a naturalist on the HMS Beagle.

A Very Small Vessel

Darwin knew that life would be cramped aboard the Beagle, but it was still a shock to see how small the ship was: just 90 feet long.

A Five-Year Journey

The captain and crew of the HMS Beagle originally planned to spend two years on their trip around the world. Instead, the voyage took nearly five years, from December 1831 to October 1836.

But What to Bring?

With little time to prepare before the ship departed, Darwin hurriedly shopped for supplies. His most important possessions were his scientific instruments, such as his clinometer, a tool for measuring angles and elevations that he needed for geological observations.

An Emerging Mind

Darwin began the Beagle voyage green and inexperienced, but he finished a seasoned naturalist. On the Beagle he grew from a wide-eyed observer into a profound analytical thinker who increasingly found patterns in what he saw.

A Ship and its Captain

Captain Robert FitzRoy had extremely high standards for any ship he intended to command--and the money to back up his wishes. What the Admiralty wouldn't pay for, he bought out of his own pocket.

Fossils and Living Species

Fossils raised many questions about the origin of species: They showed that in past ages, the world had been inhabited by different species from those existing today. Fossils also revealed that new species tended to appear where similar species had previously lived.

A Long Way From Home

Darwin sent numerous letters and specimens home by boat throughout the voyage. Darwin's lengthy letters home are filled with detailed, enthusiastic observations.

Neighboring Species

The puzzling distribution of plants and animals in South America and the Galpagos would later make Darwin question how species originated. The pattern of geographic separation he observed was exactly what one would predict if new species evolved from existing ones.

Island Species

The strange plants and animals of the Galpagos Islands puzzled Darwin. Many lived only on the Galpagos--sometimes only on one island. How had they gotten there? Why weren't they the same as those on similar islands around the world?