artificial selection. homework recap variation + inheritance = inherited variation overreproduction...

Artificial Selection

Homework

Recap

Variation + Inheritance = Inherited VariationOverreproduction + Limited Resources = CompetitionInherited Variation + Competition = Traits confer reproductive advantage or disadvantage = Natural Selection


One kind of natural selection has another name that it sometimes goes by, “artificial selection.” Artificial selection IS natural selection, the only difference is what environment it happens in.The environment for artificial selection:


In artificial selection, we humans are the environment that drives the evolution of something else.

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Artificial selection is the process by which heritable traits favored by human actions become more common in successive generations.Also called “selective breeding.” Very well known to farmers and breeders, artificial selection is how they harness evolution to produce the varieties of plants and animals that they want.

Artificial selection can be intentional, or unintentional on our parts.

Examples: IntentionalAll of our domesticated species - pets, crops, farm animals - evolved through artificial selection. In many cases, it was intentional.Selective breeding is natural selection in which a trait gives its bearer a reproductive advantage because it’s a trait that the human breeder likes.Animal A has trait A which the breeder likes, so he breeds Animal A with many mates. Animal B has a trait the breeder doesn’t like, so he doesn’t let Animal B breed. Thus, trait A is more frequent amongst the babies.

ExamplesCorn, or maize, is the result of domestic breeding of teosinte by Mesoamerican famers ~9,000 years ago.

Video: Dr. Kingston on maize, Ch 5-11


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ExamplesWolves are Canis lupus of the subspecies lupus. Dogs are Canis lupus of the subspecies familiarus. DNA studies show that dogs were domesticated ~50,000 years ago.One trait that varies among wolves is their pacifism, sociability, and ability to interpret human gestures…

Video: Dr. Kingston on dogs, Ch 13-18




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Examples

Felis silvestris, Kalahari Wild Cat, and modern day cat phylogeny.





Examples

Artificial selection applied to the wild mustard, Brassica oleracea:



ExamplesDarwin devoted nearly a whole chapter to the selective breeding of pigeons, which has produced many varieties from a single species, Columba livia, the Rock Pigeon. QuickTime™ and a

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Examples

Artificial selection is how we make our vaccines. We select for attenuated (weakened) viruses for measles, polio, and smallpox vaccines. Smallpox has been eradicated, polio only remains in four countries, and measles had been eradicated in the Americas some 10 years ago but since then it’s come back due to many parents now choosing not to vaccinate their children.

Examples: Unintentional

There have also been many cases where we’ve imposed a selective pressure on a population without even knowing it. These cases can also be called artificial selection.Most cereal crops were unintentionally developed 12,000 years ago. There’s no evidence that the first farmers premeditated and decided to breed certain plants in order to keep and enhance their desired traits, they just kept those juicier plants because they liked them.


Heikegani or “Samurai Crabs,” Heikea japonica. Crabs thrown back into the bay after the battle of Dan-no-Ura, April 1185.The crab went from a normal-shelled crab to this:




Since the advent of major urban areas, we’ve been seeing changes in the allele frequencies amongst inhabitants such as rats and cockroaches.With your partner: What traits probably give rats or cockroaches a reproductive advantage in cities, that would therefore become more common as time goes on?






Important, don’t forget!Artificial selection is natural selection, they are the same process. The ONLY difference is that in artificial selection, the environmental factor that makes a trait advantageous or disadvantageous is a human action.

Artificial SelectionTo be done for the day, you must interview with me to demonstrate that you understand natural and artificial selection.I will give you a scenario, like an MCAS question would. You must explain to me how this result came about, or what will likely happen in the future as a result. Use the following vocab: variation, inheritance, over-reproduction, competition, reproductive advantage OR disadvantage, allele frequency, generation, natural OR artificial selection.

• A town in ancient Afghanistan is given a herd of greyish horses as a gift. In this culture, bright coat colors - like white, black, and red - are most valuable.

• Three hundred years later, the horse descendents of that herd are all brightly colored, not grey.

• Explain how this happened.

• In 1985, Spiny Dogfish in the Gulf of Maine were being fairly regularly fished, but then new laws and nets came into play. Fishermen were limited in terms of the number of dogfish that they could catch, and they had a wide choice of nets, ranging from nets that are best at catching small prey to nets that are best at catching large prey.

• Over the last 20 years, the average age of dogfish hasn’t changed, but their average size has. One-year-old dogfish are smaller on average than they were, two-year-old dogfish are smaller on average, etc. Explain this.

• Before humans arrived, members of a parrot species were generally very brightly colored. The brighter your feather colors, the more likely you were to attract a mate, which made you more likely to have many brightly-colored offspring.

• But human poachers came and they also valued the most brightly-colored parrots. Not for mating, of course, but because their feathered and stuffed carcasses fetched a better price. They hunted the most brightly colored birds and wouldn’t go much out of their way for the individuals whose colors were a little more dull.

• Explain what you think will happen to the allele frequencies of different feather colors.

• A dog kennel in Victorian era England has many wealthy gentlemen as clients. These gentlemen like to hunt for sport, and will pay handsomely for hunting dogs that look good and will help them win at hunting games. This kennel has been doing good business breeding slender little dogs that are good for rabbit hunts, because they can get down into burrows and follow the rabbits through thick underbrush.

• But then, rabbit hunting became passé and boar hunting became popular. The kennel has a variety of rabbit dogs, but clients aren’t buying them now because they’re too small and weak for boars.

• What should the kennel do to get boar dog babies out of these rabbit dog breeding parents? Why?

• A loud rattle once lent rattlesnakes a survival and reproductive advantage. Predators that would otherwise have bitten the snake are scared away from it, saving both predator and snake the problem of a bite.

• In the last hundred years, rattler round-ups have become a cultural mainstay amongst the descendents of European immigrants to the Western U.S. Participants use long metallic prongs to capture snakes without much risk to themselves, and are rewarded for how many rattlers they’re able to bag in a day or night. Biting and venom don’t help rattlers against these round-ups, their only hope is to not be noticed by the human hunters.

• Predict what’s probably happening to the allele frequencies for rattle loudness amongst U.S. rattlesnakes.

artificial selection. homework recap variation + inheritance = inherited variation overreproduction...

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artificial selection

examples artificial

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examples wolves

examples darwin

examples corn

examples felis silvestris

human breeder