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Dogs and More Dogs

Classroom Activity

Materials | Procedure | Activity Answer | Links & Books | Standards  Print this Teacher's Guide (PDF, 7 pages)

Objective
To learn through an evolution card game how selective pressures can affect an organism's evolution.

• copy of the "From Wolf to Dog" student handout (PDF or HTML)
• copy of the "Examining the Game" student handout (PDF or HTML)
• copy of the "Wolf Deck" student handout (PDF or HTML)
• scissors
• 1 die

1. Scientists know all dogs descended from the gray wolf, but they don't know exactly how that happened. Tell students that in this activity they are going to engage in a simulation to learn how selective pressures can affect an organism's evolution.

2. Review with students the concepts of gene, gene pool, selective pressure, mutation, species, and genetic isolation (see Activity Answer for definitions).

3. Tell students that they will make a deck of cards that will represent the entire gene pool for a hypothetical group of genes responsible for temperament in a population of wolves. Each card will represent an individual gene and each six-card hand will represent the collection of genes that contribute to temperament for one wolf.

4. Organize students into teams of four and provide each team with a set of materials (teams of smaller size will need to use dummy hands to complete the activity). Have each team cut out and create a 24-card deck from the cards on its "Wolf Deck" student handouts. Assign half of the teams to be Wolf Group A and the other half to be Wolf Group B.

5. Have students do the activity as outlined on their student handouts. Students will calculate the new deck average for the 5^th, 10^th, and 20^th rounds. At the end of the game, compare the final deck averages for each team. Have they all evolved from their original average? How much do the final averages from Group A and Group B teams differ from one another? Discuss with students how the selective pressures of each of their groups contributed to each population's evolution.

6. To conclude, have a class discussion about the difference between the conditions in this simulation and those occurring in nature. (Selective pressures in the simulation occurred randomly; in nature, selective pressures would occur as a result of specific environmental influences.)

7. As an extension, have students research and write a position paper regarding the controversy involving wolf-dog hybrids. Find more information at

   www.nal.usda.gov/awic/newsletters/v5n4/5n4wille.htm

You may want to review the following terms with students:

gene: A segment of DNA that codes for a particular protein.

gene pool: All the genes of all the members in a population.

selective pressure: Any environmental factor that favors one trait over another.

mutation: A random change in a gene or a group of genes.

species: Any group of organisms, the members of which successfully breed with each other, producing healthy, fertile offspring.

genetic isolation: What occurs when two groups of one species are prevented from breeding with each other.

inherited trait: An inherited characteristic—such as hair and eye color or muscle and bone structure—that has been passed on from a previous generation.

acquired trait: An acquired characteristic—such as the ability to ride a bike or do karate—that is attained throughout life. Acquired traits are not passed on genetically.

This activity modeled the evolution of just one trait that contributes to making dogs the species that they are; many additional anatomical, physiological, and behavioral traits contribute to differentiating a dog from a wolf. And while there are dogs that are bred for aggressiveness, the activity addresses the evolution of genetic tameness in dogs as a species.

In the card game students played, higher hand totals represent wolves with genes that contribute to tame behavior; lower hand totals indicate fewer genes for tame behavior. Students were organized into two groups—Group A students modeled a wolf population that continued to have an intermediate temperament found in a wild wolf population. While this group underwent random mutations, the selective pressures of the wild continued to select for the average wolf. Group B students modeled a wolf population that evolved into dogs. Random mutations allowed Group B wolves to evolve past what would have been the tamest wolf in the wolf population (Canis lupus) and into the subspecies of increasingly tamer dogs (Canis lupus familiaris).

Sample Results

In terms of the game, genetically isolating dogs and wolves means that the cards from the wolves-evolving-into-dogs decks are never mixed with the pure-wolf decks. If wolves and dogs were allowed to regularly interbreed, one prediction might be that the dog's tameness would be reduced and the wolf's tameness would be increased. In terms of real life, it would mean the two groups would be prevented from breeding (e.g., exchanging genes) with each other.

If dogs and wolves had not been isolated, the small number of "tameness" genes that arose in the population evolving into dogs would likely have been lost in the much larger wolf gene pool, where they would be selected against by the wolf's way of life. This would have made it very unlikely for dogs to ever evolve.

Web Sites

NOVA Web Site—Dogs and More Dogs
www.pbs.org/nova/dogs/
In this companion Web site for the NOVA program, discover why there are so many breeds, read about why dogs are an evolutionary success, view a photo gallery of working dogs, and match breeds with their countries of origin.

American Kennel Club
www.akc.org/
Contains information about purebred dogs, including a list of recognized breeds, information on how to choose a puppy, and facts about DNA testing to prove dog parentage.

Dog Breed Info Center
www.dogbreedinfo.com/
Provides an alphabetical listing of dog breeds with additional information describing each breed and listing information about its temperament, living conditions, exercise requirements, and health conditions.

The Dog Genome Project
mendel.berkeley.edu/dog/manifesto.html
Outlines the goals of the dog genome project, similar to the human genome project, which is aimed at mapping all the chromosomes in dogs.

The Genetics of ... Dogs
www.discover.com/issues/apr-03/departments/featscienceof/
Looks at some of the genetic problems faced by purebred dogs, such as bulldogs with heads too large to fit through the birth canal and crippled German shepherds, and humans' influence on these problems through artificial selection.

The Human Role in Dog Evolution
www.nationalgeographic.com/xpeditions/lessons/08/g912/dogsevolution.html
Presents a lesson that asks students to investigate and consider the human role in the domestication and evolution of ancient and modern dog breeds.

The Truth About Dogs
www.theatlantic.com/issues/99jul/9907dogs.htm
Presents author Stephen Budianski's view on how dogs have evolved into a species uniquely adapted to getting food and shelter from people.

The Wolf-Dog Hybrid: An Overview of a Controversial Animal
www.nal.usda.gov/awic/newsletters/v5n4/5n4wille.htm
Reviews some of the anatomical and physiological differences between dogs and wolves and presents some of the breeding, genetic, and legal issues associated with wolf-dog hybrids.

Books

Budiansky, Stephen. The Truth About Dogs: An Inquiry into the Ancestry, Social Conventions, Mental Habits, and Moral Fiber of Canis Familiaris. New York: Viking Press, 2000.
Draws on evidence from behavioral science, archeology, biology, and neuroscience to probe how the relationship between humans and dogs developed.

Coppinger, Raymond and Lorna. Dogs: A Startling New Understanding of Canine Origin, Behavior, and Evolution. New York: Scribner, 2001.
Focuses on how dog breeds have evolved and examines how the dog became a distinct species from the wolf.

Padgett, George A. Control of Canine Genetic Diseases. New York: Howell Book House, 1998.
Includes chapters on modes of inheritance, tables and probabilities, genetic disease predisposition by breed, and definitions of canine genetic disorders.

Ritvo, Harriet. The Animal Estate: The English and Other Creatures in the Victorian Age. Cambridge, Massachusetts: Harvard University Press, 1989.
Discusses the role of animals in Victorian England and looks at selective breeding.

Serpell, James (editor). The Domestic Dog: Its Evolution, Behaviour and Interactions with People. New York: Cambridge University Press, 1995
Explores the natural history of the dog and its evolution, behavior, and interactions with humans.

The "From Wolf to Dog"" activity aligns with the following National Science Education Standards.

Grades 5-8

	Science Standard C: Life Science

Reproduction and heredity:

• Every organism requires a set of instructions for specifying its traits. Heredity is the passage of these instructions from one generation to another.

Diversity and adaptation of organisms:

• Biological evolution accounts for the diversity of species developed through gradual processes over many generations.

Grades 9-12

	Science Standard C: Life Science

The molecular basis for heredity:

• Changes in DNA (mutations) occur spontaneously at low rates.

Biological evolution:

• Species evolve over time. Evolution is the consequence of (1) the potential for a species to increase its numbers, (2) the genetic variability of offspring due to mutation and recombination of genes, (3) a finite supply of the resources required for life, and (4) the ensuing selection by the environment of those offspring better able to survive and leave offspring.

Classroom Activity Author

Charles Low has taught biology at Malden High School in Massachusetts for 37 years. He regularly participates in science research projects, and is currently involved with a Tufts University School of Engineering program.