Lab 5: Adaptations and Invasive Species — Fashion a Fish

1. Natural selection is the mechanism of evolution. It operates on three conditions: (1) Variation — individuals in a population differ in heritable traits. (2) Selection — some traits improve survival and reproduction more than others. (3) Inheritance — favorable traits are passed to offspring.
2. An adaptation is a heritable trait that improves an organism's fitness (survival + reproductive success) in its specific environment. Adaptations evolve over many generations through natural selection — no individual organism evolves.
3. Fish adaptations to aquatic environments include: streamlined body shape (reduces drag), lateral line system (detects vibrations in water), gills (extract dissolved oxygen), swim bladder (controls buoyancy), camouflage coloration (avoids predation), and specialized mouth shapes (linked to diet).
4. Environment determines which adaptations confer fitness. A deep-sea fish adapted to darkness (large eyes, bioluminescence) would have low fitness in a shallow, turbulent river. Adaptations are environment-specific, not universally 'better.'
5. Invasive species are non-native organisms introduced (intentionally or accidentally) into ecosystems where they did not evolve. Without natural predators, parasites, or competitors from their home range, invasive species often outcompete native species.
6. Invasive fish examples: Asian carp in the Mississippi River basin (filter-feed so efficiently they outcompete native filter feeders; leap from water and injure boaters); snakehead fish in Mid-Atlantic states (breathe air, can cross land between water bodies, eat almost any small organism); lionfish in the Atlantic (venomous spines deter predators that evolved with Pacific fish).
7. The lionfish in the Atlantic provides a clear case study in how adaptations cause harm outside the native range: native Atlantic prey fish never evolved fear of the lionfish, so they are captured easily. The lionfish's venom works against predators but Atlantic predators avoid the unfamiliar spines.
8. Prevention is the most effective management for invasive species — once established, eradication is rarely achieved. Regulations prohibit releasing aquarium fish, bait fish, or ballast water without treatment.

Netiquette from the syllabus: address ideas, not people. Complete sentences, correct spelling. Personal matters go to email, never the board.

Ask at home: Imagine a new disease appeared that killed only dark-colored moths in your neighborhood. What would the moth population look like in 20 years — and what principle explains that change?

En español: Imagina que apareciera una nueva enfermedad que matara solo a las polillas de color oscuro en tu vecindario. ¿Cómo se vería la población de polillas en 20 años — y qué principio explica ese cambio?