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EVOLUTIONARY THEORY

EVOLUTIONARY THEORY. So what is biological evolution?. Successive genetic changes in a population over many generations. New species result as genetic characteristics are modified due to: Mutation: change to DNA(random, predictable)

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EVOLUTIONARY THEORY

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  1. EVOLUTIONARY THEORY

  2. So what is biological evolution? • Successive genetic changes in a population over many generations. • New species result as genetic characteristics are modified due to: • Mutation: change to DNA(random, predictable) • Isolation: events that separate populations • New allele combinations: results in variety w/in populations • Environment: constant or changing • Reproduction: sexual/asexual, rates • Implies natural processes are at work

  3. Humans have been manipulating the genetics of populations since we first domesticated animals and plants SELECTIVE BREEDING results in ARTIFICIAL SELECTION Rather than allowing natural events to determine the combination of genes, we select for specific traits to combine This process results in new varieties of dogs, cats, horses, tomatoes, corn, etc

  4. Evolutionary theory suggests the same genetic mechanisms are at work in nature…but through Natural Selection

  5. History of Evolutionary Thought Jean –Baptiste Lamarck(1744-1829) Theorized that acquired traits can be inherited. Environmental change causes changes in the needs of organisms Changing needs causes changing behavior Altered behavior leads to changes in the use of a structure Greater use structure gets bigger, disuse would cause structure to get smaller or disappear.

  6. Lamarck did see that organisms do change over time and that the environment drives the change… however, his “use/disuse” mechanism is completely WRONG!!!

  7. Thomas Malthus(1766-1834) Was a political economist Observed that animals and plants produced far more offspring than can survive Populations will grow to a size that can be supported by the environment related these concepts to human populations, poverty and famine. .

  8. Alfred Wallace(1823-1913) 19th century's leading expert on thegeographical distribution of animalspecies Best known for independently proposing a theory of evolution due to natural selection that prompted Charles Darwin to publish his own theory.

  9. Noted that natural barriers like water, mountains, canyons etc, resulted in greater diversity in populations. • Observed that similar environments result in similar adaptations even though populations have different geographical origins.

  10. OSTRICH EMU RHEA AFRICA AUSTRALIA S AMERICA Wallace theorized the birds have similar structures because their environments are similar

  11. Charles Darwin(1809-1882) Developed and published a unified theory of evolution by natural selection in 1858 Based upon observations made in South America and the Galapagos Islands in 1835

  12. Darwin’s Observations • It’s a struggle to survive: species must compete for food, space, water, mates, etc

  13. Living organisms over produce: incorporated from Malthus

  14. There is variation within species: genetic differences exist w/in organisms of same species • Genetic • raw • material for • change

  15. Environment determines which traits are successful: become adaptations

  16. Two main aspects of the Theory DESCENT WITH MODIFICATION Newer species appear to be descended from older species Species may be descended from one or a few original species CHAP STICK

  17. NATURAL SELECTIONMechanism for divergence Characteristics of the environment “select” traits that increase a population’s ability to survive Those organisms with favorable traits (adaptations) are best suited and are more likely to survive to reproduce and pass those traits to offspring giving them an adaptive advantage. Those that do not possess favorable traits more likely to die thus not reproduce and remove those traits from gene pool Over time organism’s variation increases from the original population, the species has diverged genetically or evolved. CANDLE

  18. Take into consideration… • Mutation, degree of variation, and recombination of genes affect organisms characteristics, thus affecting change(if any) that may occur • Rate of environmental change directly affects selection(stable-little change, unstable- more change, or extinction) • Generally, the more complex(amt of DNA) the organism the slower the process: bacteria: single strand DNA-many generations very short time, greater change(resistance) elephants: lots o’ DNA- few generations in very long time(2 yrs to make 1!), less change

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