Theory of Evolution Chapter 15

15.1 Key Concepts What was Charles Darwin’s contribution of science? What pattern did Darwin observe among organisms of the Galapagos Islands?

15-1 The Puzzle of Life’s Diversity Biological diversity- variety of living things How did they arise? Related? Evolution- change over time; process by which modern organisms have descended from ancient organisms Theory- well-supported testable explanation of phenomena that have occurred in the natural world

Charles Darwin Charles Darwin (1809-1882)- Englishman Voyage aboard H.M.S. Beagle (1831) 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 Collected plant and animal specimens while ship was anchored

Darwin’s Observations Well suited for environment Many ways for survival and production of offspring Puzzled by where species lived and did not live Gathered fossils Resembled organisms still alive Others looked completely different Galapagos Islands were very close together, but had very different climates Tortoise shells

Journey Home Time spent thinking Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos

15-2 Ideas That Shaped Darwin’s Thinking Fossils caused Darwin to be skeptical of people’s views Earth created only a few thousand years ago Robin had always been a robin Discoveries challenged fundamental beliefs held at that time

Lyell and Hutton James Hutton Charles Lyell Earth had to be much more than a few thousand years old 1795, hypothesis about geological forces that have shaped Earth Internal forces- mountains, valleys, rocks- affected by natural forces- rain, wind, heat and cold temps Charles Lyell Gave book to Darwin Processes that shaped the Earth millions of years earlier continue in present Fossils of marine animals above sea level Influence?: If the Earth could change over time, might life change as well? It would have taken many, many years for life to change in the way he suggested. This would have been possible only if the Earth were extremely old

Jean- Baptiste Lamarck Living things have changed over time 1809- hypothesis (1st to develop) Tendency toward perfection- continually changing and acquiring features that help them live more successfully in their environments Use and disuse- organisms could alter the size or shape of particular organs by using their bodies in new ways Inheritance of acquire traits- pass on traits to offspring Evaluation of hypothesis Did not know how traits are inherited Did not know that behavior has no effect on heritance

Thomas Malthus 1798- human population Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone Influence What causes death of so many individuals? What factor/factors determine which ones survive and reproduce, and which do not?

15-3 Darwin Presents His Case 1858- Alfred Wallace sent short essay which contained thoughts on evolutionary change 1859- Darwin publishes his book On the Origin of Species

Inherited Variation and Artificial Selection Inherited variation- differences that are passed from parents to offspring Larger fruits on plants; some cows give more milk Today: caused by variations in their genes Then: revolutionary idea because variations thought to be minor defects Artificial selection- selection by humans for breeding of useful traits from the natural variation among different organisms Animal breeders used heritable variation to improve livestock and crops

Evolution by Natural Selection Malthus- high birth rates and shortage of life’s basic needs would eventually force organisms into a competition for resources Survival of the Fittest Fitness- ability of an individual to survive and reproduce in its specific environment Result of adaptation- any inherited characteristic that increases an organism’s chance of survival Can be anatomical (structural) or physiological (functions)

Evolution by Natural Selection Central to process of evolution by natural selection Individuals compete to survive and produce offspring Low levels of fitness = death High levels of fitness = survival Survival of the fittest (natural selection)- process by which individuals that are better suited to their environment survive and reproduce most successfully (takes place without human control or direction) Can only be seen in time over successive generations Only certain individuals of a population produce new individuals

Descent with Modification Principle that each living species descended with changes, from other species over time Look different from ancestors Implies that all living organisms are related to one another Common descent- principle that all species were derived from common ancestors “Tree of life” links all living things

Evidence of Evolution Fossil Record Geographic Distribution Fossils = record of history of Earth Compare fossils of older rock layers and fossils of younger rock layers told us that life on Earth has changed over time # of fossils has increased since Darwin, but we still have gaps Geographic Distribution Finches- similar but distinctly different Slightly different from mainland (S. America) Same ancestor with modifications Different species on continents of S. America and Australia Similar environments = similar features; different ancestors

Evidence of Evolution Homologous Body Structures Limbs vary greatly in form and function, yet constructed from same basic bones Homologous structures- structures that have different mature forms but develop from the same embryonic tissue Descent with modification Group organisms to how recently they last shared a common ancestor Vestigial organ- organ that serves no useful function in an organism

Embryology Early stages, or embryos, of many animals with backbones are very similar The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates

Summary of Darwin’s Theory Individual organisms differ, and some of this variation is heritable Organisms produce more offspring than can survive, and many that do survive do not reproduce Because more organisms are produced than can survive, they compete for limited resources