Changing the living world

Selective Breeding• Humans use selective breeding to pass desired

traits on to the next generation of organisms:• Nearly all domestic animals and most crop

plants have been produced by selective breeding

Tools for selective breeding

• Hybridization: crossing dissimilar individuals to bring together the best of both organisms

- e.g. Shasta daisies, got its large, white appearance from hybridization by a scientist named Luther Burbank

• Inbreeding: the continued breeding of individuals with similar characteristics

- e.g. Many breeds of dogs are maintained by inbreeding: golden retriever

Risk of inbreeding• Most of the members of a breed are

genetically similar:- Because of this, there is always a chance that

a cross between two individuals will bring together 2 recessive alleles for a genetic defect

Increasing Variability

• Breeders can increase the genetic variation in a population by inducing mutations, which are the ultimate source of genetic variability

• Breeders can increase the mutation rate by using radiation and chemicals

Increasing Variation• Producing new kinds of bacteria: scientists have

been able to develop hundreds of useful bacteria strains

e.g. bacteria that can digest oil• Producing new kinds of plants: scientists use

drugs to produce cells that have double or triple the normal number of chromosomes (polyploid)

e.g. production of bananas