2 We’ll talk more about these later. EvolutionDefined: the process of biological change by which descendants come to differ from their ancestors.5 factors that lead to evolution:Genetic driftGene flowMutationsSexual selectionNatural SelectionWe’ll talk more about these later.
3 Species lion tiger liger Species: group of organisms that can interbreed and produce fertile offspringDifferent species rarely breedInterspecies (between different species) breeding often results in sterile offspringEx: Horse x Donkey = MuleEx: Lion x Tiger = Ligertigerliger
5 Jean Baptiste de Lamarck Acquired Inheritance: Early theory where organisms could acquire and pass traits after birth.Cause: environmental changes forced individuals to changeProblem: Traits acquired after fertilization cannot be passed to offspringEarly Belief: Giraffes & Long NecksLong necks are result of stretching to reach leavesExtra length was passed on to offspring
6 Geologic Change Early belief: “New” Observations Earth ~6,000 years oldLife remained unchanged“New” ObservationsRock layers (strata) contained differing fossilsDeeper fossils (older) less complexEnvironmental changes thought to affect life characteristicspast geologic events can be explained by phenomena and forces observable today; the classical concept that 'the present is the key to the past'
7 Charles Darwin Observed: Organisms have variations based upon environmentSimilarities between extinct fossils & modern lifeMarine fossils atop mountainsNatural Selection: Process where organisms with favorable traits survive and reproduceMajor concept in biology published in The Origin of Species (1859)
8 Finches are another example. Finches with strong, thick beaks live in areas with a lot of large, hard shell nuts.Finches with delicate beaks live in areas where small insects and fruits are readily available.
9 Adaptation & Variation Variation: Inherited traits that make an individual different from othersGreen, flat wings of the insect aboveAdaptation: Variation increases the chance of survivalAbility to blend with environment
10 Butterflies won'tlay eggs on plantswith fake egg spots
13 Causes of Genetic Variation Genetic variation increases chances some organisms survive in changing environmentsGene Pool: All alleles within a populationTwo main causes of genetic variation:1) Mutations: Random genetic changes may affect phenotypes2) Recombination: During meiosis, genes recombine in varying patterns
14 Variation: 4 Different Gametes ChromatidscopiedCrossing-overCrossing-OverfinishedGenetic variation!Four differing chromatids
15 Quick Review Features of a species can evolve, or change over time Natural selection is when favorable traits allow survival & reproductionVariations allow an organism to be better suited to its environment
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