Prentice Hall—2005
Authors
Various
Selective Breeding
Darwin studied other examples of changes in living things to help him understand how evolution might occur. One
example that Darwin studied was the offspring of animals produced by selective breeding. English farmers in
Darwin’s time used selective breeding to produce sheep with fine wool. Darwin himself had bred pigeons with large,
fan-shaped tails. By repeatedly allowing only those pigeons with many tail feathers to mate, breeders had produced
pigeons with two or three times the usual number of tail feathers. Darwin thought that a process similar to selective
breeding might happen in nature. But he wondered what process selected certain traits.
Selective Breeding Race horses are
selectively bred to obtain the trait of speed.
Funny Cide’s father, Distorted Humor, and
great-grandfather, Seattle Slew
Natural Selection: Genetic techniques have enabled people to produce organisms with desirable traits. Selective
breeding, cloning, and genetic engineering are three methods for developing organisms with desirable traits.
The process of selecting organisms with desired traits to be parents of the next generation is called selective
breeding. Thousands of years ago, in what is now Mexico, the food that we call corn was developed in this way. Every
year, farmers saved seeds from the healthiest plants that produced the best food. In the spring, they planted those
seeds. By repeating this process over and over, farmers developed plants that produced better corn. People have
used selective breeding with many different plants and animals. Two selective breeding techniques are inbreeding and
hybridization.
Inbreeding Turkeys such as the one with white feathers were developed by inbreeding. Breeders started with wild
turkeys.
Inbreeding : The technique of inbreeding involves crossing two individuals that have similar characteristics. For
example, suppose a male and a female turkey are both plump and grow quickly. Their offspring will probably also have
those desirable qualities. Inbred organisms have alleles that are very similar to those of their parents.
Inbred organisms are genetically very similar. Therefore, inbreeding increases the probability that organisms may
inherit alleles that lead to genetic disorders. For example, inherited hip problems are common in many breeds of dogs.
Hybridization
In hybridization (hy brid ih ZAY shun), breeders cross two genetically different individuals. The hybrid organism that
results is bred to have the best traits from both parents. For example, a farmer might cross corn that produces many
kernels with corn that is resistant to disease. The result might be a hybrid corn plant with both of the desired traits.
Hybridization McIntosh and Red Delicious
apples were crossed to produce Empire
apples.
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http://www.sciencedaily.com
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Horse breeding
Horse breeding refers to reproduction in horses, and particularly the human-directed process of planned mating of
animals.
While feral and wild horses breed successfully without human assistance, it can be beneficial to domesticated
horses.
Humans can increase the chances of conception, a successful pregnancy, and successful foaling. The male parent of
a horse, a stallion, is commonly known as the sire and the female parent, the mare, is called the dam.
Both are genetically important, as each parent provides 50% of the genetic makeup of the ensuing offspring, called a
foal. Contrary to popular misuse, the word "colt" refers to a young male horse only.
Though many amateur horse owners may simply breed a family mare to a local stallion in order to produce a
companion animal, most professional breeders use selective breeding to produce individuals of a given phenotype,
or breed.
Sunflower Genome Holds the Promise of Sustainable Agriculture
ScienceDaily (Jan. 14, 2010) — As agricultural land becomes increasingly valuable, the need to maximize its
utilization increases and decisions about what crops to plant and where, become extreme.
The sunflower family includes a number of valuable food crops, with sunflower seed production alone valued at
about $14 billion annually. Yet the sunflower family is the only one of a handful of economically important plant
families where a reference genome is not available to enable the breeding of crops better suited to their growing
environment or consumers tastes.
A new research project, largely funded by Genome Canada, and the US Departments of Energy and Agriculture will
create a reference genome for the sunflower family -- currently the world's largest plant family, containing 24,000
species of plants, including many crops, medicinal plants, horticulture plants and noxious weeds.
One of the potential applications of this research includes a hybrid variety of sunflower, grown as a dual-use crop.
The wild Silverleaf species of sunflower, known for its tall, woody stalks that grow 10 to 15 feet tall and up to 4
inches in diameter in a single season, could be crossbred with the commercially valuable sunflower plant that
produces high quality seeds, capitalizing on the desirable traits of both species.
"The seeds would be harvested for food and oil, while the stalks would be utilized for wood or converted to ethanol.
As a dual-use crop it wouldn't be in competition with food crops for land," says project leader, Dr. Loren Rieseberg
(University of British Columbia).
In addition, this fast growing annual crop will be highly drought resistant, thanks to desirable traits from the
Silverleaf variety, and would therefore be suitable for use in subsistence agriculture in places like Sub-Saharan
Africa, as well as in much of North America.
Alternatively, a breeder could, using individuals of differing phenotypes, create a new breed with specific
characteristics.