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

Bird beaks

But what about when these variations are not caused by nature, but by mankind?

Where we come in… Human Intervention

Selective Breeding or Artificial SelectionSelective 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 - DogsDogs 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 CattleGood trail cattle, lean meat

Hereford CattleGood 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 - BeesAfricanized honey bees –high productivity

Selective Breeding Pros and Cons

Pros –• Higher yield in crops

• Healthier Animals –vulnerability to diseases reduced

• More Nutrition Provided

• Breeds Out Harmful Traits

• Variations of Species – more breeds

Cons –• Inhibits Evolution – can

reduce variation

• 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 rattle-snake 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

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.

Problems in Selective Breeding

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