Chapter 15.1: The Puzzle of Life’s Diversity and Chapter 15.2: Ideas That Shaped Darwin’s Thinking

Biological Diversity Variety of living things  A result of evolution (change over time)  Process by which modern organisms have descended from ancient organisms

Charles Darwin  Naturalist  Sailed on boat called the HMS Beagle  Collected, studied and stored specimens of life found around the world.

Patterns of Diversity  Darwin was: –Intrigued by the fact that so many plants and animals seemed remarkably well suited to whatever environment they inhabited –Impressed by the many ways in which organisms survived and reproduced offspring –Puzzled by where different species lived (and did not live)  Why no rabbits in Australia? No kangaroos in England?

Galapagos Islands  Set of 13 islands found 1000 km off the west coast of South America  Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos

Original Ideas  People, prior to Darwin and his ideas, believed that the Earth and all the life that had been created only a thousand years ago  They also believed that the planet, nor the animals on it, changed over time

The Earth Does Change  1795  James Hutton proposed that layers of rock are moved by forces beneath the Earth’s surface –Rock layers bend, twist, and are buried –Shaped from rain, heat, and cold –Very slow process

 Charles Lyell – wrote book called Principles of Geology  said the Earth is constantly changing over time  Hutton and Lyell helped scientists recognize that the Earth is millions of years old, and the processes that changed the Earth in the past are the same processes that operate in the present

Jean Baptiste Lamarck  Preceded Darwin  Said living things change over time and all species are descended from other species Proposed that by selective use or disuse of organs, organisms acquire certain traits during their lifetime  these traits could then be passed to their offspring

Lamarck’s Hypothesis 1. He proposed that all organisms have an innate tendency toward complexity and perfection; thus always changing 2. Due to search for perfection, the organism can alter its body in new ways – making some body parts more useful and making other body parts obsolete 3. These new characteristics can be passed down to the offspring of the altered organism

Struggle for Existence  Thomas Malthus  human population was growing faster than the food supply –Reasoned if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone –Darwin used this idea on life forms  Many organisms die before maturity  struggles for food, space, escape from predators and ability to find shelter  Only certain individuals survive these struggles.