Darwin’s Theory Darwin’s Observations - PowerPoint Presentation

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Darwin’s Theory

Darwin’s Observations

Background Info: Charles DarwinSet sail on the HMS Beagle

5 year trip around the worldNaturalist: a person who studies the natural worldHe wanted to learn about the living things he saw on the voyage

He made many stops along the coast of South America then to the Galapagos islands

His important observations included

Diversity of living thingsThe remains of ancient organismsThe characteristics of organisms on the Galapagos Islands

Diversity

Darwin was amazed by the tremendous diversity of living thingsScientists have observed 1.7 million species of organisms on EarthSpecies

A groups of similar organisms that can mate with each other and produce fertile offspring

Fossils

FossilPreserved remains or traces of an organism that lived in the past

Galapagos Organisms

Darwin observed the greatest diversity of organisms on the Galapagos IslandsComparisons to South American Organisms

Many Galapagos organisms were similar to organisms on mainland South AmericaDarwin hypothesized that the ancestors of Galapagos animals and plants came from mainland South AmericaBlown out to sea during a storm?

Set adrift on a fallen log?

Comparisons Among the Galapagos Islands

Darwin traveled from island to islandHe noticed many differences among the organismsDome-shaped tortoise shells

Saddle-shaped tortoise shells

Adaptations

The finches Darwin saw on the islands were noticeably differentMost obvious difference was the size and shape of their beaksFinches that ate insects: narrow, needle-like beaks

Finches that ate seeds: strong, wide beaksAdaptationA trait that helps an organism survive and reproduce

Evolution

Darwin reasoned that plants or animals that arrived on the Galapagos Islands faced conditions different from mainland South AmericaHe hypothesized the species gradually changed over time

Organisms became better adapted to the new conditionsEvolutionThe gradual change in a species over time

Scientific Theory

A well-tested concept that explains a wide range of observations

Darwin’s Theory of Evolution

Selective Breeding

Breeding animals by only allowing certain animals to mateExampleRace horses are selectively bred to obtain the trait of speed

Darwin bred pigeons with ONLY large, fan-shaped tail feathers

Natural Selection

Book by Charles Darwin, The Origin of Species

Explanation of how evolution COULD occur in natureNatural SelectionThe process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other member of the same species

Factors that affect the process of natural selection

Overproduction

Competition Variations

Overproduction

Effect cause by species producing more offspring than can surviveExampleInsects

Variations

Differences between individuals of the same speciesExampleDifferent foods eaten by the same species of insects

Competition

Effect caused by limited food and other resourcesExampleDirect (physical fights)

Indirect (not finding enough food to eat)

Environmental Change

Environment can affect an organism’s ability to surviveThis can then lead to selectionMonkey Flowers

Can’t grow in soil with high concentration of copper

Genes and Natural Selection

Darwin could not explain what caused variations or how they were passed onScientists later learned, variations can result from mutation and the shuffling of alleles during meiosis

Genes are passed from parents to offspringOnly traits inherited, or controlled by genes can be acted upon by natural selection