A New Mystery (Sticklebacks)
Investigate the evolutionary mystery of stickleback fish populations: learn how isolated lake populations evolved dramatically different body armor levels compared to their marine ancestors, revealing natural selection in action.
Key Concepts
Scientists are studying Stickleback fish in lakes. Some of these fish have heavy "armor plates" ( Full Armor ), while others have very few ( Low Armor ).
Fossil data and modern observations show a rapid change: in some lakes, the population shifted from mostly Fully Armored to mostly Low Armor in a very short time. We must use our Natural Selection model to explain why.
Common Questions
What makes stickleback fish a useful model for studying evolution?
Marine sticklebacks have heavy armor, but lake populations repeatedly evolved low-armor forms after being isolated. This parallel evolution across many lakes provides powerful evidence that natural selection consistently favors reduced armor in freshwater environments.
Why did lake sticklebacks evolve less body armor?
Lake environments have fewer predators that require bony armor for defense, and the heavy armor uses energy and reduces swimming speed. Natural selection favored fish with less armor in low-predation, food-rich lake environments.
How do sticklebacks connect to Grade 8 evolution concepts?
Sticklebacks demonstrate natural selection, adaptation, geographic isolation, and divergence in a single observable system. Students analyze real population data to trace how environmental differences produced distinct trait distributions.