Evolution

Vocabulary Evolution = process by which modern organisms have descended from ancient organisms. Scientific Theory = well-supported, testable explanation of phenomena that have occurred in the natural world.

Charles Darwin **In 1831, Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world. **During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. (natural selection)

Darwin’s Observations 1.Darwin observed and was impressed by many plants & animals were well suited to the environments & how they survived and produced offspring. 2. Darwin collected preserved remains of ancient organisms, called fossils. »Some of the fossils resembled organisms that were still alive. »Others looked completely unlike any creature he had ever seen.

The Galápagos Islands The Galápagos Islands are close together but have different climates. Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galápagos. »Had the animals living on different islands once been members of the same species?

Influential People Hutton & Lyell – Geologists –Earth is millions of years old & the processes that changed Earth in the past are the same processes that operate in the present. So……their impact on Darwin….. –If the Earth could change over time, life might change as well……

Influential People Lamarck –Inheritance of acquired characteristics So……his impact on Darwin….. –Traits can be passed down from generation to generation

Malthus – Economist –If the human population continued to grow unchecked, sooner or later there would not be enough living space and food for everyone. So……his impact on Darwin….. –What if plants and animals continued to grow unchecked???? Would they run out of resources too? Influential People

On the Origin of Species Darwin published his work, On the Origin of Species (1859) because a fellow naturalist, Alfred Wallace, was also working on a similar biological concept. In this book, Darwin proposed a mechanism for evolution called natural selection. »Presented evidence that evolution has been taking place for millions of years—and continues in all living things.

Natural Vs. Artificial Selection Natural Selection = Selection by nature of the most advantageous traits to be passed on to the next generation Frog with a long tongue, owls with better sight, etc. Artificial selection = Selection by humans for breeding of useful traits from the natural variation among different organisms. Breeding the largest horses, fastest horses, cows that produce the most milk, ect.

Evolution by Natural Selection 1.Struggle for existence High birth rates and overcrowding cause organisms to compete for resources (food, living space, etc.)

Evolution by Natural Selection 2. Survival of the fittest Fitness – ability of an individual to survive & reproduce Prey that are better camouflaged, faster, better protected (porcupine), avoid being caught will be more likely to survive What determines an organism’s fitness? »Adaptations = any inherited characteristic that increases an organism's chance of survival. Nature selects those with desired traits to reproduce

Evolution by Natural Selection 3. Descent with modification Species today look different from their ancestors Each species has descended with changes over time Example: Tigers, panthers, and cheetahs have common ancestors

Evidence of Decent with Modification 1.Fossil Record Comparing fossils from older rock layers to fossils from younger rock layer shows changes over time 2. Geographic Distribution Different animals live in different regions, but animals exposed to similar conditions have similar anatomies and behaviors

Evidence of Decent with Modification 3. Homologous Body Structures Homologous Structures = structures that have different mature forms but develop from the same embryonic tissues Not all homologous structures serve important functions. Vestigial Organs = organs that have shrunk in size because they serve no purpose (appendix, tailbone, legs etc.)

Evidence of Decent with Modification 3. Similarities in Embryology Early stages (embryos) of animals with backbones are very similar

Summary 1. Organisms differ 2. Variation is heritable 3. Limited resources force competition 4. Adapting advantages allow organisms to live longer and reproduce more 5. Able to pass on that adaptation more times (more offspring) 6. Natural selection causes change over time 7. Species today have descended with some changes from ancestral species