EVOLUTION Chapter 15

Evolution - change over time Theory – a well-supported testable explanation of phenomena in the natural world

Charles Darwin

The variety of living things… BIOLOGICAL DIVERSITY Darwin found a huge variety of living things, each well adapted to their environment

Voyage of the Beagle 1831

Patterns of Diversity Visited Argentina and Australia-similar grassland ecosystems those grasslands were inhabited by very different animals.

Patterns of Diversity Darwin asked questions… Why no rabbits in Australia, despite the presence of habitats that seemed perfect for them? Why no kangaroos in England?

Living Organisms and Fossils Darwin collected the preserved remains of ancient organisms, fossils. Some of the fossils resembled organisms that were still alive today.

Living Organisms and Fossils   Others looked completely unlike any creature he had ever seen. As Darwin studied fossils, new questions arose. Why had so many of these species disappeared? How were they related to living species?

The Galapagos Islands Islands close together but had very different climates

The Galapagos Islands The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited.

More Galapagos Animals

The Journey Home Darwin Observed that characteristics of many plants and animals vary greatly among the islands Hypothesis: Separate species may have arose from an original ancestor

Darwin’s Tree of Life

Ideas that shaped Darwin’s Thinking James Hutton: 1795 Theory of Geological change *Forces change earth’s surface Changes are slow *Earth much older than thousands of years

Evidence for Hutton and Lyell

Ideas that Shaped Darwin’s Thinking Charles Lyell Geographical features can be built up/torn down Darwin thought if earth changed over time, what about life?

Population Growth Thomas Malthus- English economist If population grew… Insufficient living space Food runs out War, famine, disease limit population Darwin applied theory to animals and plants

Publication of On the Origin of Species 1859 after 25 years of study, thought, struggle It outlined his theories of natural selection and evolution over time

His Studies of Variation Darwin didn’t know about genes He DID observe traits being passed to offspring He knew about Artificial Selection – nature provides variation, humans select variations they find useful Dogs, pigeons, crops, horses, cows

Natural Selection There is a struggle for existence…living things need food, living space Some individuals are better adapted for their environment Adaptation – any inherited characteristic that increases an organism’s chance of survival SURVIVAL OF THE FITTEST

Can you think of any adaptations? Check out these examples of adaptations

Lamarck’s Theory of Evolution Tendency toward Perfection (Giraffe necks) Use and Disuse Theory of Acquired Traits (characteristics)

Descent with Modification Darwin proposed that living things changed over long periods of time because of natural selection It implies that all living organisms are related Living things evolved from a common ancestor

Descent w/ Modification (cont.) Common Descent – all species, both alive and extinct, came from common ancestors. Tree of Life links all living things

Evidence of Evolution Fossil Record Geographic Distribution of living things Homologous structures Vestigial organs Similarities in embryology

Darwin saw fossils as a record of the history of life on Earth. Fossil Record Darwin saw fossils as a record of the history of life on Earth. He proposed that Earth was many millions of years old.

Geographic Distribution of Living Things Darwin found different species of animals on different continents He recalled similar environments and sometimes similarities in different animals

Geographic Distribution

Homologous Structures have different mature forms but develop from same embryonic tissues Vestigial organs are traces of homologous organs Ex. Legs in skinks (p. 385)

Similarities in Embryology -Similar in early stages…common ancestry? -Embryonic cells develop in same order and pattern -Common cells produce homologous structures