Transcript 13-1 Changing The Living World

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