13-1 Changing The Living World

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13-1 Changing The Living World

• Section 13-1Changing the Living World

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Selective Breeding

• The Wide Variety of Animals Plants Used By
  Humans, Have Been Developed By Selective Breeding
  Allowing Only Those Animals Plants With
  Desired Characteristics Are Allowed To Reproduce.

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Selective Breeding

• Key Concept
• Humans Use Selective Breeding To Pass Desired
  Traits On To The Next Generation of Organisms
• Apples, Corn, Potatoes
• Dogs, Cattle, Mice, Yeast

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Selective Breeding

• Luther Burbank 1849-1926
• 800 Varieties of Plants
• Disease Resistant Potatoes

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Selective Breeding - Hybridization

• Crossing Dissimilar Individuals To Bring Together
  The Best Of Both Organisms
• Often Hardier Than Parents
• Disease Resistance Increased Food Producing
  Capacity

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Selective Breeding - Hybridization

• Postzygotic Barriers
• Reduced Hybrid Viability
• Embryos Dont Develop
• Reduced Hybrid Fertility
• Offspring Vigorous but Sterile
• Hybrid Breakdown
• 1st Generation Viable Fertile
• 2nd Generation Feeble Sterile

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Selective Breeding - Inbreeding

• Used To Maintain A Desired Characteristic
• Dog Breeds
• Higher Risk of Homozygous Recessive Alleles for
  Genetic Defect.
• Blindness Joint Problems In German Shepherds
  Golden Retrievers

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Increasing Variation

• Key Concept
• Breeders Can Increase The Genetic Variation In A
  Population By Inducing Mutations

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Increasing Variation

• Selective Breeding Impossible Without A Diverse
  Gene Pool
• Importance Of Diversity In Wild Populations
• Mutations Induced Through
• Radiation
• Chemicals

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Increasing Variation

• Most Mutations Undesirable
• Offspring Destroyed
• Few Mutations Desirable
• Breed To Maintain

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Increasing Variation New Kinds of Bacteria

• Easy To Induce Mutations In Millions At Once
• Mutations Particularly Useful
• Produce Oil Eating Bacteria
• Plastic Eating Bacteria

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Increasing Variation New Kinds of Plants

• Drugs Disrupt Chromosomal Separation During
  Meiosis
• Offspring 2X or 3X Chromosomes (Polyploidy)
• Usually Fatal For Animals
• Tolerated Useful In Plants

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Increasing Variation New Kinds of Plants

• Polyploidy May Instantly Produce A New Species
  Larger Stronger Than Their Diploid Relatives
• Bananas, Oats, Cotton, Tobacco, Wheat

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Increasing Variation New Kinds of Plants

• Allopolyploid
• Two Different Species Form A Polyploid Hybrid
• Bread Wheat Triticum aestivum
• 8000 years ago
• Cultivated Wheat Wild Grass

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Allopolyploid
Polyploid formed between two species