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13-1 Changing The Living World Section 13-1 Changing the Living World FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT 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. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT 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 FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Selective Breeding • Luther Burbank 1849-1926 –800 Varieties of Plants • Disease Resistant Potatoes FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Selective Breeding - Hybridization Crossing Dissimilar Individuals To Bring Together The Best Of Both Organisms –Often Hardier Than Parents –Disease Resistance + Increased Food Producing Capacity FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT 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 FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT 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 FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Increasing Variation Key Concept: Breeders Can Increase The Genetic Variation In A Population By Inducing Mutations FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Increasing Variation • Selective Breeding Impossible Without A Diverse Gene Pool – Importance Of Diversity In Wild Populations • Mutations Induced Through – Radiation – Chemicals FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Increasing Variation • Most Mutations Undesirable –Offspring Destroyed • Few Mutations Desirable –Breed To Maintain FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Increasing Variation – New Kinds of Bacteria • Easy To Induce Mutations In Millions At Once • Mutations Particularly Useful –Produce Oil Eating Bacteria –Plastic Eating Bacteria FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT 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 FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Increasing Variation – New Kinds of Plants • Polyploidy May Instantly Produce A New Species Larger & Stronger Than Their Diploid Relatives –Bananas, Oats, Cotton, Tobacco, Wheat FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT 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 FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Allopolyploid Polyploid formed between two species FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
