Darwins Theory Chapter 15 Evolution Change over time

Darwin’s Theory Chapter 15

Evolution • Change over time • Process from which modern organisms have descended from ancient organisms • Theory well supported testable explanation for a phenomena

Beagle • 1831 HMS Beagle sailed around the world • Made many observations • Collected much evidence • Proposed a revolutionary hypothesis about how life changes over time • Supported by lots of evidence has become theory of evolution

His Observations • Enormous number of organisms inhabit the earth • Plants and organisms seemed well suited for their environment • Different parts of world with similar types of land had very different biodiversity

Fossils • Collected preserved remains of organisms also • Fossils • Some looked liked ones alive • Others looked very different • Some where not around anymore • Why did they disappear?

Galapagos Islands • West of South America • Very different climates though close together • Tortoises varied in different ways from island to island • Many different birds with very different beaks

Conclusion • Variations on the Islands made him think • Separate species would have evolved from an original South American ancestor species after being isolated on the Island • Could this be?

Ideas that Shaped Darwin • Time when exploration just starting and different views emerging • All things created a few 1000 s of yrs ago and organisms never changed • Then new scientists started to study fossil records • Different periods that eliminated life forms and caused by a catastrophic event • He began questioning this as to be too simple

Imp changes in 18 th and 19 th cent • Hutton and Lyell both scientist findings influence Darwin • Earth is many millions of years old • Processes have changed Earth over time • Same processes are operate in the present

Hutton • 1795 published that geological forces have shaped Earth • Rocks moved in different ways by these forces • Wind rain heat and cold are also forces • Rocks mountains and valleys • These processes work slowly over time

Principles of Geology • Lyell • Release just before Beagle set sail • Must explain past events by processes that can be seen • Explained how geological phenomena could be built up or torn down over time

Lamarck’s Hypothesis • Selective use or disuse of organs • Then organisms acquired or lost certain traits over time • These traits could be passed on to offsrping and lead to changes in the species

Majors Aspects of Lamarck • All organism due to be complex and lean towards perfection (to live in environment) • Can alter size and shape of organs so they work with perfection or not at all if needed (can alter shape and size) • The acquired traits could be past on • Not all true: later learned that behavior has no affect on heritable traits

Population Growth/Malthus • If human population growth continued unchecked we would run out of resources • Natural and others such as disease, war, famine