The Puzzle of Life’s Diversity

Objectives What was Charles Darwin’s contribution to science? According to Lamarck, how did organisms acquire traits? What was Malthus’s theory of population growth? Darwin found fossils of many different organisms that were different from any living species. How would this finding have affected his theory of evolution?

Voyage of the Beagle In 1831, Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world. Darwin went ashore and collected plant and animal specimens for his collection and filled many notebooks with his observations and thoughts.

During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. That hypothesis has become the theory of evolution. Evolution (change over time) is the process by which modern organisms have descended from ancient organisms. A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

Darwin’s Observations Darwin observed that many plants and animals were well suited to the environments they inhabited. He was impressed by the ways in which organisms survived and produced offspring. Darwin was puzzled by where different species lived and did not live.

Ideas that Shaped Darwin’s Ideas Darwin’s voyage came during one of the most exciting periods in the history of Western science. As a result, Darwin was powerfully influenced by several scientists. The work of these scientists along with his numerous observations led him to his theory of evolution. (What type of ideas/thoughts/technologies influence our thinking TODAY?)

Ideas that Shaped Darwin’s Ideas 1. Geology During the 18th and 19th centuries, James Hutton and Charles Lyell gathered information suggesting: Earth is VERY old, and the processes that changed Earth in the past are the same processes that operate in the present (Uniformitarianism). Earth changed slowly over time (gradualism). James Hutton 1726-1797 Charles Lyell 1797-1875

Ideas that Shaped Darwin’s Ideas This understanding of geology influenced Darwin: If the Earth could change over time, life might change as well. It would have taken many years for life to change in the way Lyell suggested. This would have been possible only if the Earth was extremely old.

Ideas that Shaped Darwin’s Ideas 2. Lamarck’s Early Evolution Hypotheses Jean-Baptiste Lamarck (1744-1829) recognized that: living things have changed over time. all species were descended from other species. organisms were adapted to their environments.

Lamarck’s Assumptions a. A Desire to Change- organisms change because they “want” to better themselves Example: Giraffes could stretch their neck by wanting to feed on the tall trees b. Use and Disuse: organisms could alter their appearance by using them or not using them

Lamarck’s Assumptions c. Passing on Acquired Traits: if an animal acquired a trait during their lifetime, they could pass on that trait to their children Example: If a man toned up and had large muscles, his offspring would have large muscles.

A male fiddler crab uses its front claw to ward off predators and to attract mates. Lamarck proposed that the selective use or disuse of an organ led to a change in that organ that was then passed on to offspring. This proposed mechanism is shown here applied to fiddler crabs. (1) The male crab uses its small front claw to attract mates and ward off predators. (2) Because the front claw has been used repeatedly, it becomes larger.

Because the front claw is used repeatedly, it becomes larger. This characteristic (large claw) is passed onto its offspring.

Ideas that Shaped Darwin’s Ideas Lamarck’s hypotheses of evolution are incorrect in several ways. Lamarck did not know: how traits are inherited. that an organism’s behavior has no effect on its heritable characteristics.

Ideas that Shaped Darwin’s Ideas 3. Population Growth: In 1798, Thomas Malthus published a book in which he noted that babies were being born faster than people were dying. The only forces he observed that worked against this growth were war, famine, and disease.

Ideas that Shaped Darwin’s Ideas Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. (Struggle for existence) When Darwin read Malthus’s work, he realized that this reasoning applied to plants and animals. If all the offspring of almost any species survived for several generations, they would overrun the world. This information was central to Darwin’s explanation of evolutionary change.

Answer these Objectives now…: What was Charles Darwin’s contribution to science? According to Lamarck, how did organisms acquire traits? What was Malthus’s theory of population growth? Darwin found fossils of many different organisms that were different from any living species. How would this finding have affected his theory of evolution?