Pre-Visit Activity: Coincidental Colonization
In this game of chance, students will learn how organisms colonized the Galápagos Islands, experiencing how chance plays a role in the successful dispersal of species to new areas.
In this game of chance, students will:
- learn how organisms colonized the Galápagos Islands.
- experience how chance plays a role in the successful dispersal of species to new areas.
- Our Only Chance at Colonization game boards (one half-sheet per pair of students)
- Teacher Reference Sheet
- Organism Cards
- small objects to mark squares, such as paperclips, coins, beans, poker chips, etc. (60)
- wooden craft sticks or coffee stirrers (15)
- cup (1)
- six-sided die (optional)
- oceanic island: an island that was produced by the eruption of underwater volcanoes, and therefore began as a rocky terrain with no original plants and animals
- colonize: to migrate to and settle in (noun form = colonization)
- disperse: to spread from one place to another (noun form = dispersal)
- isolated: separated from others, especially due to distance or physical barriers
- Print out Our Only Chance at Colonization game boards. Cut the sheets in half. One pair of students will share the organism on the top half; another pair will play with the bottom half.
Print out Organism Cards, cut out each one, and distribute one to each pair of students.
- Copy each of the 15 phrases listed on the Teacher Reference Sheet onto its own wooden coffee stirrer or craft stick. Place the sticks in a cup.
Tell your students that when they visit the California Academy of Sciences, they will check out an exhibit describing a famous group of tropical islands, located hundreds of kilometers from any continent. Have students brainstorm their impressions of such an environment: What plants and animals might you find there? What is on the ground and in the sky? How is the weather? Last but not least, how would you travel to these isolated islands? What if you weren’t a person, but rather a lizard, a bird, or a flower?
- Introduce the Galápagos Islands by indicating their position on the map. Briefly describe their volcanic formation, explaining that such an island had no plants or animals to begin with—only barren volcanic rock.
- Distribute one Our Only Chance at Colonization sheet, one Organism Card, and three marker objects to each pair of students. Tell students that these sheets represent plants and animals that live on the Galápagos Islands today whose ancestors successfully reached the islands from other places long ago. Reaching an isolated island involves experiencing chance events beyond one’s control. Organisms with characteristics that help an individual survive these unintended situations are more likely to survive the journey. Therefore, this game involves linking a series of characteristics and chance events experienced by particular organisms, resulting in their current residence on the Galápagos Islands.
- Brief the class on potential modes of dispersal: (1) floating on the ocean’s surface; (2) flying using one’s own wings; (3) swimming in a strong current; (4) getting carried by the wind; (5) or traveling in the gut of a bird. Have pairs share which method they hypothesize was taken by an ancestor of their organism, confirm the answer using the Teacher Reference Sheet, and instruct students to write this in the appropriate box on their worksheet.
- Conduct the game like bingo, pulling out a stick, reciting the event, and returning the stick to the cup. (Consider walking from pair to pair, allowing students to play the role of Fortune). Instruct students to place a marker over the space if the event applies to their organism, but note that the events are sequential: the first space must be marked before moving on to the second space, etc.
- Each time a pair reaches the island, have them announce their organism and tell what characteristics and chance events made their dispersal possible.
- Allow successful pairs to continue playing, sending another individual on the trip. Consider creating a list of successful organisms and tallying the population size of their colonies on the board.
Discuss with the students:
- Only a few small mammals, like bats and rats, made it to the Galápagos Islands. Amphibians, like frogs and newts, also found the journey difficult. What makes the trip more difficult for these animals? (mammals lose water easily and digest food quickly, so they wouldn’t last on a long trip; amphibians have skin that can’t tolerate salt water and prolonged sunlight)
- Assuming you survive the long journey and land on the volcanic islands, what else might be necessary for your species to grow and reproduce in this new area? (varies by organism, but possibilities include food, fresh water, fertile soil, a mate of the opposite gender, a pollinator, a safe home, etc.)
For a longer exercise that integrates the conditions necessary for colonization after reaching the island, give each group that successfully crosses the ocean the opportunity to roll a die 7 times. Write a table on the board similar to the one below, and have the class consult it for the ‘contestant’ hoping to colonize. To survive and reproduce, the group must roll all four numbers that represent their organisms’ requirements, as indicated. If not, the individual perishes, and, without reproducing, the species cannot colonize! Another from the mainland must begin the journey anew.
|land on fertile||soil meet a mate and reproduce|
|-||drink fresh water|
|absorb fresh water||-|
|-||settle in a safe habitat|
|get pollen and reproduce||-|
|avoid predation by animals||find a source of food|
Assess students by having them choose 2 organisms from any place or time that might successfully colonize an isolated island, and 2 that would find it particularly difficult. Have students provide written support for their selections, describing the physical traits, behaviors, or requirements that aid or hinder successful dispersal and colonization.
- Adapted from Monalaua Gardens Foundation. (2005). Dispersal Bingo: Draft. Retrieved April 2, 2008, from http://www.mgf-hawaii.org/PDF/invasives/
- Constant, P. (2000). The Galapagos Islands. Hong Kong: Odyssey Publications Limited.
California Content Standards
- 3a. Students know plants and animals have structures that serve different functions in growth, survival, and reproduction.
- 3d. Students know when the environment changes, some plants and animals survive and reproduce; others die or move to new locations.
- 3b. Students know that in any particular environment, some kinds of plants and animals survive well, some survive less well, and some cannot survive at all.
- 3c. Students know many plants depend on animals for pollination and seed dispersal, and animals depend on plants for food and shelter.
The Galápagos Islands formed millions of years ago over a volcanic hotspot at the intersection of three tectonic plates. Underwater volcanoes spewed forth magma, which built up a cone-like formation that eventually breached the water’s surface. Lava cooled upon contact with the air, forming an island of volcanic rock devoid of all life. This barren land, isolated from the coast of South America by 965 km (600 miles) of Pacific Ocean, was populated entirely by organisms originating from far away.
Safe transportation to a remote island is a challenge for the majority of plants and animals. An organism might have to survive weather fluctuations, temperature extremes (whether riding in cold air currents or rafting in the hot sun all day), and submergence in salt water. Additionally, an organism must be able to subsist on minimal provisions or lower its metabolism. Some common methods of dispersal to the Galápagos Islands include:
- Floating or rafting: Light, salt-tolerant seeds can float, as can the shell of a large tortoise. Reptiles, small mammals, insects, and plants may be carried on floating vegetation or logs, hopefully reaching the islands via currents within a few weeks.
- Flying: Only strong seabirds, migratory birds, and hardy insects can make the trip, as lighter birds would be blown off-course.
- Swimming: Penguins, marine mammals, fish, and the larva of invertebrates can catch a ride in a current, saving energy otherwise expended by swimming. Several currents pass along the Galápagos Islands, potentially depositing organisms on their shores.
- Being carried by wind: The spores and seeds of flowers, ferns, and mushrooms are often transported by strong winds, sometimes facing cold temperature high in the sky, and ultimately drop to the ground with the condensing moisture from the clouds. Small, light insects and some birds are also blown to the Galápagos.
- Traveling in the gut of a bird: Seeds from tasty fruits are eaten by migratory birds and deposited when the animal excretes the material.
It is important to emphasize the random nature of these dispersal events. The odds that any individual will reach an oceanic island are slim; moreover, basic food, water, and habitat may not be present upon their arrival. The diversity found on the Galápagos Islands today is a result of successful colonization events that took place over a large span of time.
The islands are closest to South America, so most of the iguanas, tortoises, and sea birds that inhabit the Galápagos came from this mainland. However, the variety of ocean currents surrounding the archipelago brought life from several regions. Examples include sea lions from North America, penguins from Antarctica, and finches from the Caribbean.