EVOLUTION Chapter 15 Evolution change over time Theory

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 Australiasimilar 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

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