Darwin and Evolution UNIT 6

EVOLUTION THE PROCESS BY WHICH SPECIES CHANGE OVER TIME THEORY: Broad explanation that has been scientifically tested and supported

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James HuttonJames Hutton Proposed that the Earth is millions of years old. Many land formations took millions of years to form. Known as the founder of modern geology. History21

Thomas Malthus Proposed that populations outgrew their food supplies, causing competition between organisms and a struggle for one species to survive against another This "struggle for existence" drives population change.History22

1809 Jean-Baptiste Lamark acquired characteristics Believed that all life forms evolved and that the driving force of evolution was the inheritance of acquired characteristics. He believed that organisms changed due to the demands of their environment.History23

What we understand now: 24

Charles Lyell proposed that plant and animal species had arisen, developed variations, and then became extinct over time. He believed that every animal or plant, including humankind, was adapted to the niche in which it was created He also believed that the Earth’s physical landscape changed over a long period of time. the present is the key to understanding the past25

Alfred Russel Wallace Emphasis was based on the idea of competition for resources as the main force in natural selection Best known for independently proposing a theory of natural selection which prompted Charles Darwin to publish on his own theory26

Charles Darwin English naturalist who studied the diversity of life and proposed a broad explanation for it His experiences provided him with evidence of evolution at work

Charles Darwin Publishes “On the Origin of Species” Natural SelectionBelieved that Natural Selection is the driving force for evolution.27

From 1831 to 1836 Darwin served as a naturalist aboard the H.M.S. Beagle on a British science expedition around the world. In South America Darwin found fossils of extinct animals that were similar to modern species. On the Galapagos Islands in the Pacific Ocean he noticed many variations among plants and animals of the same general type as those in South America. CLIP29

Darwin’s Theory was based on………….. 1.) The voyage of the Beagle Observing different animal species from around the world 2.) Studies of breeders –Dog breeders, cow breeders, etc.

Darwin’s Voyage

Beagle Darwin took a trip on a ship called the Beagle Galapagos Islands in Pacific Ocean- collected finches –Studied the size and shape of the beaks Suggested that the Galapagos species descended from species that came from South America

Emu (Australia) Ostrich (Africa) Rhea (S. America)

Darwin’s Observations

Darwin’s Theory of Evolution by Natural Selection

Darwin’s Key Idea Natural Selection –Individuals that have traits that better suit the environment are more likely to survive and pass on their traits to offspring

Steps of Darwin’s Theory STEP ONE: Overproduction Every Population is capable of producing more offspring that can possibly survive.

Steps of Darwin’s Theory STEP TWO: Variation Individual members of a population are different

Steps of Darwin’s Theory STEP THREE: Selection –In a given environment, having a trait can make individuals more likely to survive

Steps of Darwin’s Theory STEP FOUR: Adaptation over Time –Evolution takes time. Traits that improve survival and reproduction will become more common over time

What Darwin Explained Presented a unifying explanation for data from multiple fields of science –Fossil record –Biogeography –Developmental biology –Anatomy –Biochemistry

Evaluating Darwin’s Ideas Darwin’s work had 3 major strengths: –Evidence –Mechanism for evolution (How it happened) –Recognition that variation is important However, he didn’t know much about genetics. –Lacked understanding of heredity

Charles Darwin Darwin’s Ideas from Experience Voyage of the Beagle: Steps of his Theory: What did Darwin Explain: Fossil Record- Biogeography- Developmental Biology- Anatomy- Biochemistry- Define: 1.Artificial Selection 2.Natural Selection- 3.Adaptation- Strengths of Darwin: Weaknesses of Darwin:

Charles Darwin Darwin’s Ideas from Experience Voyage of the Beagle: Noticed Galapagos plants & animals were similar, but not identical, to plants & animals in South America Descent with modification Species had descended from species that came from South America and then modified over time Steps of his Theory: 1.Overproduction- every population is capable of producing more offspring than can possibly survive 2.Variation- variation exists within every population; inherited traits 3.Selection- having a particular trait can make individuals more or less likely to survive and have successful offspring 4.Adaptation- over time, those traits that improve survival and reproduction will become more common What did Darwin Explain: Fossil Record- comparing fossils and living things reveals a pattern of gradual change Biogeography- similar environments shape the evolution of organisms in similar ways; geography can separate populations and the 2 groups may evolve in different patterns Developmental Biology- compare development of species to look for similar patterns and structures that likely derive from a shared ancestor Anatomy- homologous structure (ex. Vertebrate forelimbs) Biochemistry- genetic changes occur over time in all population; compare DNA to show how genetically similar species are Define: 1.Artificial Selection- breeding animals or plants that have certain desired traits 1.Natural Selection- individuals that have traits that better suit their environment are more likely to survive and reproduce 1.Adaptation- trait that improves ability to survive and reproduce Strengths of Darwin: Evidence of evolution- so much data! Mechanism for evolution (natural selection)- logical AND testable Variation- showed that is was everywhere and is important for understanding how population evolve Weaknesses of Darwin: Inherited variation was crucial to Darwin’s theory of natural selection, but he did not have a clear mechanisms for inheritance. Mendel’s findings about heredity solved this problem

Patterns of Natural Selection 1.Directional trait changes in 1 direction 2. Stabilizing trait variation decreases 3. Disruptive trait changes in 2 directions

Or is the whale descended from the Mosasaur?

Vestigial Structures Adjective describing something that is a vestige (remnant) or a primitive structure, and no longer believed to be important. Examples –Wings on flightless birds –Body hair on humans –Wisdom teeth in humans –Human Appendix

Darwin’s Theory was based on………….. 5.) Lyell –Geologist –Rock layers show the earth is quite old –Fossil record showed creatures who were now extinct

What Darwin’s Theory Explains Fossil Record Anatomy Biochemistry