Why do scientists use a classification system? To organize many diverse organisms (biological diversity) What is a theory? A well-supported,testable explanation of phenomena that have occurred in the natural world. What is evolution? Change over time; process by which modern organisms have descended from ancient organisms

Charles Darwin: British scientist who made a significant contribution to the understanding of evolution; traveled with a sailing crew around the world on the H.M.S. Beagle Key Concept: During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.

Key concept: Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galápagos. Patterns of diversity: plants and animals “matched” their environments Fossils of ancient organisms sometimes resembled living organisms (Fig. 15-2) Characteristics of animals on the Galápagos varied from island to island due to climate change (Fig. 15-3)

Darwin’s voyage occurred during a time of great change in the perspective of the natural world. At the time, many people believed that the world was only several thousand years old. Key Concept: Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.

James Hutton and Geological Change Hutton proposed the rock formations occur over millions of years at a very slow rate (Fig. 15-6) Charles Lyell’s Principles of Geology Darwin received a copy of Lyell’s book before his voyage on the Beagle. Lyell proposed that processes that currently shape Earth must be used to explain processes that shaped Earth in the past. Darwin concluded that if Earth takes many years to change, so should life on Earth.

Key Concept: Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species.

Jean-Baptiste Lamarck’s Evolution Hypotheses (c.1809) Tendency toward perfection: all organisms have an innate tendency toward complexity and perfection (i.e. fiddler crabs, Fig. 15-7) Use and disuse: Organs that are not used will decrease in size over generations and finally disappear. Inheritance of acquired traits: these changes are passed on to future generations (i.e. body builders will have children with big muscles too)

Key Concept: Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. Thomas Malthus and Population Growth English economist who stated that war, famine and disease are the only factors working against population growth

Darwin’s On the Origin of Species Darwin waited more than 25 years before he published his thoughts on evolutionary change. He received both positive and negative reviews. What did Darwin’s work actually say?

Darwin observed how breeders used heritable variations in organisms. Artificial Selection Key Concept: In artificial selection, nature provided the variation, and humans selected those variations that they found useful. (Fig )

Natural Selection Population growth would eventually lead to competition for limited resources. Struggle for existence: members of each species compete regularly to obtain food, living space, and other necessities of life.

Natural Selection Fitness: ability of an individual to survive and reproduce in its environment. Adaptation: any inherited characteristic that increases an organism’s chance of survival. Survival of the fittest: Individuals better suited for their environment survive and reproduce more successfully over individuals who are not well suited. Descent with modification: each living species has descended, with changes, from other species over time. (change over time)

Natural Selection Read: 1 st paragraph on page 382 Common Descent: All species, living and extinct, were derived from common ancestors. Did you catch the jump from microevolution to macroevolution?

Key Concept: Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures of living organisms, and similarities in early development, or embryology.

The Fossil Record: comparison of fossils found in old and young rock layers and discovery of transitional fossils (Fig ) Geographic distribution of species: organisms in different geographic locations share similar features due to adaptation to similar climates. (Fig )

Homologous body structures: have different mature forms but develop from the same embryonic tissues (Fig ) Vestigial organs: organs that decrease in size over time (Fig ) Similarities in embryology: many embryos look similar in early stages of development (Fig )