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Section 15.1 Notes 2015
Revised on 1/28/15
Basic Vocab
Species – a group of organisms that can breed
together and produce fertile offspring
Population – all of the individuals of a species that
live in a certain area, at a certain time
Gene Pool – all of the genes, including all of the
different alleles for each gene, that are present in a
population
Selective Breeding
Selective breeding (also called artificial
selection) is a way in which humans manipulate
the gene pools of populations
Selective breeding – when humans select which
organisms will reproduce/pass their genes to
the next generation
Selective Breeding
• Human uses of selective breeding
-making new varieties of cultivated plants
-domestication of animals
Examples of Selective Breeding
• Modern day corn is descended from a grass
called teosinte
*Taken from http://evolution.berkeley.edu/evolibrary/news/070201_corn
Examples of Selective Breeding
• Dog Breeds – all breeds of dogs are descended from
wolf-like ancestor
*taken from http://visual.merriam-webster.com/animal-kingdom/carnivorous-mammals/dog-
breeds_1.php
Selective Breeding
• Hybridization
-crossing dissimilar individuals to bring
together the best of both organisms
-the offspring are often hardier than the
parents
-many hybrids combined the disease
resistance of one plant with the foodproducing capacity of another
Selective Breeding
• Inbreeding
-the continued breeding of individuals with
similar characteristics
-inbreeding is used to maintain the desirable
characteristics in a line of organisms
-can be a risky practice because it increases
the chances that offspring will have two
recessive alleles for a genetic defect
Increasing variation
• Biotechnology – the application of a
technological process, invention, or method to
living organisms
• Selective breeding is considered a type of
biotechnology
• However, sometimes breeders want more
variation than can be achieved through
selective breeding
Increasing Variation
• Mutations – heritable changes in DNA
• Mutations occur spontaneously in nature
• Breeders can increase the mutation rate of an
organism by using radiation or chemicals
• Mutations are usually harmful to the organism
but sometimes breeders can create mutations
in organisms that are useful to humans
Increasing variation
• The application of radiation or chemicals to
create useful mutations has been very
successful with bacteria
• This technique has allowed scientists to
develop hundreds of useful bacterial strains
Polyploid plants
• Polyploid – organisms that contain more than
two sets of chromosomes
• Polyploidy in plants can naturally occur (it is rare
in animals and if it does occur is usually fatal)
• Drugs that prevent the separation of
chromosomes during meiosis are very useful in
plant breeding. These drugs can produce cells
that have many times the normal number of
chromosomes
Polyploid Plants
• Polyploidy can quickly produce new species of
plants that are larger and stronger than their
diploid relatives.
• Several important crop plants such as bananas
and some citrus fruits have been produced
this way
Polyploid Plants