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Selective Breeding
Notes
(Artificial Selection)
Let’s recap from last time!
• Natural selection - The process by which
individuals that are better adapted to the
environment survive and reproduce more
successfully than other members of their
species
• These adaptations are incredibly varied, but
are caused by nature.
• Crash Course – Natural Selection
Examples:
Counter shading in fish
But what about when
these variations are not
caused by nature, but
by mankind?
Bird beaks
Where we come in… Human Intervention
Selective Breeding or Artificial Selection
Selective breeding is the process of breeding plants
and animals for particular genetic traits.
• Parent organisms are bred by people to produce the
desired traits in the next generation
• Domestic animals are commonly bred for various
traits.
• Domestic animal: animal that has been tamed and
kept by humans for work, food or as a pet.
Let’s explore a few examples of selective breeding
Selective Breeding - Dogs
Dogs are bred for
many reasons
such as their
intelligence,
trainability, and
good looks
Dogs are all the
same species, just
varieties!
Selective Breeding - Livestock
Longhorn Cattle
Good trail cattle,
lean meat
Hereford Cattle
Good beef
Aryshire Cattle
High milk
producer
Selective Breeding -Food Crops
How does this work?
• From one species,
in this case, a
common wild
mustard, people
have selective
bred plants over
generations to
provide a variety
of different foods
Selective Breeding - Flowers
Selective Breeding - Bees
Africanized honey bees –high
productivity
Selective Breeding Pros and
Cons
Pros –
Cons –
• Higher yield in crops
• Inhibits Evolution – can
reduce variation
• Healthier Animals –
vulnerability to diseases
reduced
• More Nutrition Provided
• Breeds Out Harmful Traits
• Variations of Species – more
breeds
• Harmful Pathogens – maybe
new pathogens could arise
• In Breeding Risks
• Food sources change – such as
when breeding plants, other
animals may be unable to feed
from these new plants
Problems from Selective Breeding –
undesirable traits
Africanized honey bees, known as "killer
bees," are hybrids of the African honey
bee with various European honey bees bred for their high productivity
•accidentally released from an apiary
Brazil in 1957
•far more aggressive than the European
subspecies
•500 bee stings are equivalent to a rattlesnake bite
Problems with Selective
Breeding – undesirable traits
• Undesirable traits sometimes appear
when trying to produce desired traits
• Common examples:
• Hip Dysplasia in dogs
• a disease in which the ball and socket
joint is malformed.
• Purebreds are more prone to this
disease than cross-breeds (mutts)
• Inbreeding encourages negative traits
– the gene pool is less diverse
Problems in Selective Breeding
WHITE GREAT DANES, DEAFNESS
AND EYE ANOMALIES
DANES PREDOMINATELY WHITE ARE
TYPICALLY DEAF AND MAY HAVE VARIOUS
EYE ANOMALIES.
THE HEALTH ISSUES ARE NOT CONFINED TO
SKIN COLOR, APPARENTLY THE GENES FOR
COLOR ARE “PAIRED” WITH OTHER GENES
THAT CAUSES THESE DEFECTS.
Dalmatians
• The urinary tract is a major weakness in
Dalmatians, who are prone to forming
urinary stones throughout their life. This
is because all Dalmatians are born with a
defective urinary system that can't break
down uric acid, which occurs when dogs
digest food.
• Another problem? About 33% of all
Dalmatians (1 of every 3) are born deaf in
one or both ears.
Evolutionary history of dogs:
• Dogs belong to a single species, Canis familiaris, but that species is comprised of
about 400 different breeds.
• Since they are a single species, they can mate and have viable offspring. Recognized
dog breeds take generations to establish through selective breeding or artificial
selection.
• Many of the breeds we have today are the result of people's desire to have dogs with
specific features that make them suitable for performing particular tasks, such as
retrieving, protection, assistance, hunting, and companionship, to name just a few.
• The process of breeding a new type of dog often involves identifying desired
features, finding dogs with those features, then performing a series of matings to
produce offspring with the appropriate combination of traits.
• After a number of generations, a new breed may be established.
Activity – Selective Breeding of Dogs
• You will begin by examining canine features and their
functions.
• Then you will be given a scenario that describes the type of
task they need a new breed of dog to perform.
• Then select two existing breeds that will most likely
produce a successful new breed and determine the
resulting offspring's characteristics.
"How to Get an American Foxhound and Why"
• What are your thoughts?
"How to Get an American Foxhound and Why"
• The American Foxhound is half descended from the English Foxhounds that were brought to
America in 1650. The English hounds were crossed with a French hound.
• The combination breed became an excellent hunter of wild animals. The American
Foxhound has great speed and an excellent sense of smell. It can run at high speed for long
periods and has a musical bay that is easy to follow. American Foxhounds are still used as
hunting dogs today but are also used as companions and watchdogs.
Designing a Dog Breed
• Describe the features or
abilities of dogs for which
humans might breed.
• How do you decide what type
of dog you want or need?
Let’s make a dog breed!
• I will put up pictures and we need to identify
which traits would match what we are looking for
Which traits? We need a dog to hear a
polar bear and then alarm the bear
What did we pick?
• Pointed ears are good for hearing and a loud bark will
travel a longer distance. Long fur will help the dogs
stay warmer out in the cold.
• Which traits are probably not very important? (eye
color).
• Which breeds would probably be best to cross?
(Breed 1 and Breed 3)
Physical Traits
• Physical traits serve a
very specific function for
dogs.
• Each of these could play
an important role, or
have significance for
humans when they need
a dog to perform a
particular function.
Dog Breed Packets
• Techer will pass out the "Dog Packet."
• Each group will be trying to artificially select a new dog
with certain traits by crossing two existing breeds.
• Once you have your packets and group:
• Take out the "Ownership Card“ (which you will fill in)
and the “Dog Breeds” – this contains the breeds your
group may use
• Follow instructions to complete the activity