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Transcript
15-3: Darwin Presents His Case Part 1 Biology 2 Introduction • Darwin returned to England is 1836, with lots of information • Brought back many specimens of what he studied (plants and animals) • Found that every Galapagos island, and continent, had its own species On The Origin of Species • 1859: Published book – On The Origin of Species • Proposed natural selection causes evolution • Showed evidence that evolution has been happening for millions of years-and continues now Inherited Variation and Artificial Selection • Darwin saw that species naturally vary – Example: Some cows give more milk than others • Sometimes parents pass these traits to offspring • Wild plants and animals vary • Domestic plants and animals vary Inherited Variation and Artificial Selection • Darwin said the variation is VERY important – Others thought it was an accident, or something wrong • Farmers and breeders use variations to improve crops and livestock – Example: Only breed fastest horse, cows that produce more milk, plants that give bigger food • ARTIFICIAL SELECTION: selection by humans for breeding of useful traits from the natural variation among different organisms Evolution by • STRUGGLE FOR EXISTENCE: Natural competition among members of a Selection species for food, living space, and the other necessities of life • Members of same species have to compete for food, shelter – Predators that move faster or hunt better catch more prey – Prey that hides better, protects themselves or can avoid being caught lives longer Evolution by • Important to struggle for existence is how well living Natural organisms “fit” their environment Selection • FITNESS: ability of an organism to survive and reproduce in its environment • ADAPTATION: inherited characteristic that increases an organism's chance of survival • BETTER ADAPTATION = BETTER FITNESS! Evolution by Natural Selection • SURVIVAL OF FITTEST: process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection • Living organisms that have better adaptations have better fitness – Better fitness = more offspring! Evolution by Natural Selection • NATURAL SELECTION: process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest • Only certain individuals can survive and reproduce offspring! Evolution by Natural Selection • In natural selection better adaptations = better fitness • Better fitness = more offspring • More offspring = increase in population with better adaptations! • Causes change in population – More individuals with better adaptations increase over time • More individuals without adaptations will die and decrease