EVOLUTION Charles Darwin Question for Thought Earth has

EVOLUTION

Charles Darwin

Question for Thought Earth has millions of other kinds of organisms of every imaginable shape, size, and habitat. This variety of living things is called biological diversity. How did all these different organisms arise? n How are they related? n

Darwin’s Theory of Evolution n Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms. n A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

How do you think Darwin came up with his theory?

Voyage of the Beagle

Voyage of Beagle Dates: February 12 th, 1831 n Captain: Charles Darwin n Ship: H. M. S. Beagle n Destination: Voyage around the world. n Findings: evidence to propose a revolutionary hypothesis about how life changes over time n

Patterns of Diversity n Darwin visited Argentina and Australia which had similar grassland ecosystems. u u those grasslands were inhabited by very different animals. neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands.

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

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

Fossils

The Galapagos Island n The smallest, lowest islands were hot, dry, and nearly barren-Hood Island-sparse vegetation n The higher islands had greater rainfall and a different assortment of plants and animals-Isabella- Island had rich vegetation.

Animals found in the Galapagos n Land Tortoises n Darwin Finches n Blue-Footed Booby n Marine Iguanas

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

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

Ideas that Shaped Darwin’s Thinking n Charles Lyell n Book: Principles of Geography Geographical features can be built up or torn down Darwin thought if earth changed over time, what about life? n n

Lamarck’s Theory of Evolution n Tendency toward Perfection(Giraffe necks) Organisms Are Continually Changing and Acquiring Features That Help Them Live More Successfully In Their Environment Use and Disuse (bird’s using forearms) Acquired traits -> traits that developed over time by a species.

Lamarck’s Mistakes n Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) n Genes Are NOT Changed By Activities In Life n Change Through Mutation Occurs Before An Organism Is Born copyright cmassengale 20

Population Growth n n Thomas Malthus 19 th century English economist If population grew (more Babies born than die) u Insufficient living space u Food runs out u Darwin applied this theory to animals

Publication of Orgin of Species n Alfred Russel Wallace wrote an essay summarizing evolutionary change from his field work in Malaysia n Gave Darwin the drive to publish his findings

Natural Selection & Artificial Selection n Natural Variation--differences among individuals of a species Natural selection --is the gradual, non-random process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. Artificial selection- nature provides the variation among different organisms, and humans select those variations they find useful.

Evolution by Natural Selection n The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities n Survival of the Fittest-Some individuals better suited for the environment

Survival of the Fittest n Fitness u n Ability of an Individual To Survive & Reproduce Adaptation u Inherited Characteristic That Increases an Organisms Chance for Survival. (can be physical or behavioral) copyright cmassengale 26

Struggle For Existence & Survival of The Fittest

Survival of the Fittest Key Concept Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment copyright cmassengale 28

Descent n Descent with Modification-Each living organism has descended, with changes from other species over long periods of time. Ex) body structures, niches, habitats. n Common Descent- All species, living and extinct, were derived from common ancestors

Descent n Divergent evolution: is the process of two or more related species becoming more and more dissimilar. u Ex) Adaptive radiation-When a single form of life successfully expands into many environments, the process is termed "adaptive radiation. " n Convergent Evolution: unrelated species become more and more similar in appearance as they adapt to the same kind of environment

Evidence of Evolution n The Fossil Record n Geographic Distribution of Living Things n Homologous Body Structures n Similarities in Early Development

Evidence for Evolution n n The Fossil Record. Layer show change Geographic Distribution of Living Things Homologous Body Structures Similarities in Early Development

Evidence of Evolution n n The Fossil Record Geographic Distribution of Living Things-similar environments have similar types of organisms Homologous Body Structures Similarities in Early Development

Homologous Structures n Homologous Structures-structures that have different mature forms in different organisms, but develop from the same embryonic tissue.

Analogous Structures § Structures of different species having similar or corresponding function but not from the same evolutionary origin

Evidence for Evolution - Comparative Embryology (Similarities In Embryonic Development) n. Embryo – early stages of vertebrate development 36

Evidence for Evolution n Not All Serve Important Functions u Vestigial Organs: organs that serve no useful function in an organism t Appendix In Man t Legs On Skinks 37

Summary of Darwin’s Theory n Individuals in nature differ from one another n Organisms in nature produce more offspring than can survive, and many of those who do not survive do not reproduce. n Because more organisms are produce than can survive, each species must struggle for resources

Summary of Darwin’s Theory n Each organism is unique, each has advantages and disadvantages in the struggle for existence n Species change over time Individuals best suited for the environment survive and reproduce most successful Species alive today descended with modification from species that lived in the past All organisms on earth are united into a single family tree of life by common descent n n n