Download The Evolution of Canis pedatus

STANDARD V: Objective 1
Title: The Evolution of Canis pedatus
Background Knowledge: Students need no prior knowledge. This is an introductory activity.
Objective: Students will evaluate an isolated population and infer the effects of natural selection
and reproductive isolation. They will identify environmental forces that drive evolution. They will
also investigate the definition of a species.
Equipment and Supplies: colored pencils, unlined paper
Safety Issues: None
Duration: Two 50 minute class periods with optional 3rd class period for presentation of results
Procedures for Teachers:
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Make a copy of student sheet
Divide students into groups of 4
Assign each group an island
Read through activity with students and answer any questions
Allow students 2 full class periods to work on this assignment
You many want to have students present their work to the class in a 3 rd class period
Answers to Questions:
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5.
Answers will vary.
Answers will vary.
Answers will vary.
Answers will vary.
Because the animals were placed in very different environments and allowed to roam free for
an extended period of time this most likely would lead to the formation of four different
species. If the species from each island were introduced to each other again they probably
would not interbreed. There may be physical, social or even genetic barriers that prevent
them from producing fertile offspring.
6. The larger the dog population the more genetic variability is present. The larger the gene
pool the more likely the species is to survive in its new habitat. This is because there is a
larger number of alleles in the population and more chance of some being beneficial. If the
population was small it wouldn’t be likely to survive the environmental pressures of the new
environment.
7. Selective breeding is a controlled change in a population. A person selects for a desired trait
and then breeds those organisms which possess that trait so that the presence of the trait
increases in future generations. This happens independent of the environment. Natural
selection is driven by pressures in the environment which make some individuals better fit
and more likely to survive and pass on their genes to future generations, thus increasing the
frequency of the beneficial trait in the species.
8. Mutation provides the raw material for evolution. Without mutation evolution could not occur.
Usually mutations are harmful but some are beneficial and can make an organism better
adapted for its environment. Recombination allows for increased diversity in the gene pool
as opposed to asexual reproduction. This again allows for more chances that organisms may
be better fit for their environment.
9. If the population were an asexually reproducing population then it would reproduce much
faster. However if the bacteria was not well suited for the environment it may die out very
quickly because there is not a great deal of diversity in the gene pool. Without this diversity it
makes adaptation difficult.
10. Answers will vary.
Scoring Guide:
Questions are valued at 5 points each for a total of 50 points. You may also want to include a group
participation grade of 15 points.
Student Sheet
The Evolution of Canis pedatus
Name:__________________________________________________ Period:_______________
Introduction: In this activity you will imagine that 800 years ago an international expedition
discovered a previously unknown dog-like creature. The expedition's leaders, all from different
Islands of the world, each took several hundred of the species on board their vessels and returned
to their own lands. The animals were originally held in captivity and allowed to mate randomly. Their
numbers increased and eventually most of them were set free to roam. You are to decide if the
animals could have survived in their new habitat and then, if they had survived, how the animals
could have changed over 8 centuries as they adapted to their new environments.
Objectives: The purpose of this activity is to decide:
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If a population of the species Canis pedatus would survive being relocated to a new
environment;
If the species Canis pedatus would show adaptations to its new environment over a period of
four hundred years;
Whether the animals with those adaptations still belong to the species Canis pedatus.
Background information on the species Canis pedatus:
Height: medium, similar to a spaniel
Hair: medium length, brown, white, black mix
Tail: bushy, hangs down to its heels
Snout: long, similar to a collie, with medium-sized teeth
Ears: short and pointed
Feet: unusually large, with small sharp claws
Poor night vision
Moderate runner: runs at speed of the average house cat
Omnivorous, but has a particular liking for small birds
Environments:
Island A
The island is fairly flat, with an occasional hill. The ground is soft dirt, and several species of shrubs
grow towards the center of the island. There is no animal life on land, but the water is teaming with
fish. The island is surrounded by a coral reef, which keeps the predators out. The shore is sandy
with no algal growth. Fresh water is available.
Island B
The island has a rocky shoreline. Numerous tide pools dot the island along the shore where the
wave action is somewhat sheltered by rock outcrops. The tide pools host barnacles, abalone, sea
urchins and crabs. Algae grows all around the island; however, it is quite sparse in the tide pools
where the various animals feed. The current is quite strong along the rocky outcrops where the
algae grows best. Fresh water is available.
Island C
The island is somewhat barren. A few species of cactus thrive on the bare rocks. A large cactuseating tortoise inhabits the island. A species of very large bird nest on the island annually. They
build their nests on the rocks, and protect their eggs from the sun by standing over the nests with
outspread wings. The nests are always found on the windy side of the island which is somewhat
cooled by offshore breezes.
Island D
The island is an extinct volcano. Vegetation on the island changes with the altitude moving up the
volcano. Grasses grow at the base. Further up the slope the grasses give way to low shrubs. Half
way up, the island becomes quite lush; tropical plants and trees dominate the landscape. At this
altitude, the island experiences frequent rain showers. There are two species of birds that inhabit
the island. One is a raptor, which preys upon the smaller birds. The other fishes the waters
approximately one mile offshore. Both nest in trees.
Procedures: You will be assigned to groups and each group will be given a letter that corresponds
to an environment. As a group you must complete the following tasks and questions.
1. As a group, decide if the species could have survived after being allowed to roam in the wild,
given their characteristics and lifestyle. Explain your decision.
2. Examine the traits the dog population began with. Describe how each trait might be
influenced by natural selection and the environmental factors that provided the pressure for
change. Record every change that could have occurred, together with a statement to explain
the functional benefit of the change.
3. Provide a written description of the animal and its lifestyle. Include a food web, a discussion
of energy use and conservation, nocturnal or diurnal, habitat etc.
4. Include a colored sketch that shows your "new and improved" appearance for this animal.
The animal should appear in its ecosystem.
5. Briefly look at the descriptions of the other habitats. The dogs began as a single species but
they were then reproductively isolated. What effect do you think this had on the individual
populations on each island after 800 years.
6. Explain how the adaptations and evolution of this species is influenced by the number of
dogs that were introduced to the island. In other words, how does genetic variation affect a
species ability to adapt to a changing environment?
7. How are the forces of natural selection different than selective breeding of dogs and the
practices used in agriculture?
8. What role does mutation and recombination play in the evolution of this species?
9. How would the evolution differ if this were an asexually reproducing bacteria instead of a
sexually reproducing mammal?
10. Is this modern animal still a Canis pedatus? Defend your answer based on the definitions of
a species.