Transcript Selective Breeding

Selective Breeding
or
Artificial Selection
What is
Selective Breeding?
 Selective breeding is the process of breeding
plants and animals for particular traits. The term
selective breeding is synonymous with artificial
selection.
 This selection process is "artificial" when human
preferences for specific traits have a significant
effect on the changes in a particular population
or species.
Domestication and
Selective Breeding
 Domestication is the process whereby a
population of animals or plants, through a
process of artificial selection, is changed at the
genetic level, accentuating traits desired by
humans.
 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.
Historical Support for
Selective Breeding
 Charles Darwin wrote how selective breeding
had been successful in producing change over
time in his book, On the Origin of Species.
 The first chapter of the book discusses
selective breeding and domestication of such
animals as pigeons, dogs, and cattle.
 Selective breeding was used by Darwin as a
way to introduce the theory of natural
selection and to support it.
Advantages of
Selective Breeding
 Selective breeding tries to establish and
maintain certain stable traits that animals
will pass to the next generation.
 These are 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 a gene pool can lead to
the passing on of undesirable characteristics or
even a 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
Examples of
Selective Breeding
Variegated ears of maize (Indian corn)
Examples of
Selective Breeding
Charolais cattle produce beef that
has more red meat and less fat.
Examples of
Selective Breeding
Chihuahuas and Great Danes are bred for
size.
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 artificial selection, humans favor specific
traits and control breeding for those traits.