13-1 Changing The Living World Section 13-1 Changing the Living World

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.

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

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

Selective Breeding - Hybridization Crossing Dissimilar Individuals To Bring Together The Best Of Both Organisms Often Hardier Than Parents Disease Resistance + Increased Food Producing Capacity

Selective Breeding - Hybridization Postzygotic Barriers Reduced Hybrid Viability Embryos Don’t Develop Reduced Hybrid Fertility Offspring Vigorous but Sterile Hybrid Breakdown 1st Generation Viable & Fertile 2nd Generation Feeble & Sterile

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

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

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

Most Mutations Undesirable Few Mutations Desirable Increasing Variation Most Mutations Undesirable Offspring Destroyed Few Mutations Desirable Breed To Maintain

Increasing Variation – New Kinds of Bacteria Easy To Induce Mutations In Millions At Once Mutations Particularly Useful Produce Oil Eating Bacteria Plastic Eating Bacteria

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

Increasing Variation – New Kinds of Plants Polyploidy May Instantly Produce A New Species Larger & Stronger Than Their Diploid Relatives Bananas, Oats, Cotton, Tobacco, Wheat

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

Allopolyploid Polyploid formed between two species