Transcript Selective Breeding

Selective Breeding
or
Artificial Selection
Selective Breeding
The process of breeding plants and animals for particular
traits. This is synonymous with Artificial Selection.
• This selection process is "artificial" when human
preferences for specific traits have an effect on the
changes in a population or species.
Domestication and Selective
Breeding
• Domestication: Accentuating plant and animal traits at the genetic
level as desired by humans.
– How does this picture portray both domestication and taming?
– Why is domestication different than taming?
Answer: It differs from taming in that a change in the genetics and physical traits
of the animal occurs. Taming is the process by which animals become used to the
presence of humans.
Advantages of Selective
Breeding
• Selective breeding establishes and maintains certain stable
traits that animals will pass to the next generation.
• Traits that humans find desirable in domesticated species
such as:
– disease resistance, strength, calmness, more lean meat,
endurance, etc.
• In many cases, this makes the species stronger.
Disadvantages of Selective
Breeding
• Breeding from too small of a gene pool can lead to the
following:
– Passing on of undesirable characteristics
– Collapse of a breed population due to what is called inbreeding depression
• Breeding for only one trait, over all others, can cause
problems.
– For example, certain roosters bred for fast growth or heavy muscles did
not know how to perform the typical rooster courtship dance. The dance
bonds the roosters to the hens. No mating dance led the roosters to kill the
hens after reproducing with them. This is not a trait which encourages
survival of the species!
Examples of Selective
Breeding
Carrots in a variety of colors
http://commons.wikimedia.org/wiki/File:Carrots_of_many_colors.jpg
Examples of Selective
Breeding
Variegated ears of maize (Indian corn)
http://commons.wikimedia.org/wiki/File:Indian_corn.jpg
Examples of Selective
Breeding
Charolais cattle produce beef that has more red
meat and less fat.
http://commons.wikimedia.org/wiki/File:Charolais_cow_with_calf,_Penuwch,_Ceredigion_-_geograph.org.uk_-_924969.jpg
Examples of Selective
Breeding
Chihuahuas and Great Danes are bred for size.
http://commons.wikimedia.org/wiki/File:Big_and_little_dog_1.jpg
Selective Breeding and Natural
Selection
• The main difference between natural selection and
selective breeding is human involvement.
• In natural selection, the reproduction of organisms with
certain traits is attributed to improved survival or
reproductive ability (survival of the fittest).
• In selective breeding, humans favor specific traits and
control breeding for those traits. It is goal oriented.
Historical Connection to the
Contribution of Scientists
• Scientists, such as Charles Darwin, have proposed that natural
selection and selective breeding both serve as evidence of
genetic variation in species and populations over time. Examples
cited are the Galapagos finches and domestic animals.
– Examples of selective breeding: pigeons, dogs, horses, and
cattle
http://commons.wikimedia.org/wiki/File:Pigeons_(5198253339).jpg