Lab Stickleback Evolution Part 1: General Instructions

Lab Stickleback Evolution Part 1general Instructionsbe Sure To Read

Analyze the pelvic structures of stickleback fish collected from two lakes around Cook Inlet, Alaska, to determine whether there are significant differences between the two populations. Use your data and information about the lakes to draw conclusions about the possible environmental factors affecting pelvis morphology.

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The study of stickleback fish evolution provides fascinating insights into how environmental factors influence morphological changes in species over time. The primary focus of this experiment is to compare the pelvic structures of stickleback populations from two distinct lakes near Cook Inlet, Alaska. These lakes, often differing in ecological conditions, serve as natural laboratories to observe evolution in action.

The initial step involves understanding the functional role of spines in oceanic sticklebacks. These spines serve as a defense mechanism against predators by making the fish more difficult to swallow or attack. The spines are typically located along the dorsal and ventral sides of the fish, providing physical barriers that deter predation. Moreover, the video on pelvic reduction highlights an evolutionary adaptation observed in freshwater populations of stickleback, where the loss or reduction of pelvic spines is analogous to the reduction of other body parts in four-legged vertebrates, such as limb reduction in some cave-dwelling species. This morphological change often signifies an adaptation to environments with different predator types or ecological pressures.

Interactive elements in the educational materials, such as the virtual stickleback and its armor, demonstrate how these structures serve protective functions. The spines and armor shield the fish from predators like dragonflies and larger fish, hindering their ability to prey on them. By practicing scoring the pelvis of live fish through tutorials, students develop skills to quantify morphological differences, which are crucial for subsequent analyses.

The specific objective of Experiment 1 is to compare the pelvic spine phenotypes of stickleback fish from two lakes—Bear Paw Lake and Frog Lake—and to interpret environmental influences. The experiment involves physically staining, scoring, and analyzing the pelvic structures of collected specimens. The geographic location is significant; for instance, the lake between Rabbit Foot Lake and Coyote Lake on the Alaska map provides context for environmental variability. Better-adapted organisms tend to survive and reproduce more effectively, passing their advantageous traits to their offspring, which over generations results in population-specific adaptations. This natural selection process underpins evolutionary change and is an essential aspect of this experiment.

In the experimental procedure, students perform staining on fish pelvises to reveal structural differences clearly. After staining, they score each fish's pelvic phenotype, then tally phenotypic frequencies from both lakes. These data are used to create visual representations (graphs) that compare the pelvic spine presence and reduction across populations. Notably, larger sample sizes are advantageous because they produce more reliable, statistically significant results.

Observation of the data often reveals differences in pelvic scores between Lake populations. For example, stickleback from Frog Lake tend to have more pronounced pelvic spines, similar to ocean-run populations, whereas Fish from Bear Paw Lake exhibit more reduced pelvic structures. These differences are attributed to environmental pressures; in particular, predator presence and habitat type influence morphological traits. Frog Lake's fish resemble oceanic relatives due to similar predator pressures and ecological niches, whereas Bear Paw Lake's fish show reductions likely driven by different predator assemblages or less predation pressure.

In conclusion, the experiment emphasizes how environmental factors, such as predation and habitat, drive morphological evolution. By comparing pelvic phenotypes between different lake populations, students understand how natural selection influences physical traits. The process of scoring, analyzing, and graphing data solidifies concepts of evolutionary biology, providing empirical evidence of adaptation. Completing the quiz and documenting progress helps reinforce understanding of these evolutionary principles, illustrating the dynamic relationship between environment and organismal form.

References

  • Brokaw, A. (2013). Stickleback Evolution Virtual Lab. HHMI Biointeractive Teaching Materials.
  • Bell, M. A., & Foster, S. A. (1994). The Evolutionary Biology of the Threespine Stickleback. Oxford University Press.
  • Hendry, A. P., & Taylor, E. B. (2004). Evolutionary dynamics in young and old populations of freshwater stickleback. Evolution, 58(4), 838-844.
  • Colosimo, P. F., et al. (2005). Widespread parallel evolution in sticklebacks by repeated elimination of a mid-lake pelagic morph. Proceedings of the National Academy of Sciences, 102(52), 19581-19586.
  • Reimchen, T. E. (1994). Species diversification, natural selection, and adaptation in sticklebacks. Evolution, 48(4), 1271-1280.
  • Schluter, D. (1995). Adaptive radiation in sticklebacks: trade-offs in feeding performance and growth. Ecology, 76(4), 1029-1042.
  • Hoffman, E. A., et al. (2014). Evolutionary consequences of a population bottleneck in natural threespine stickleback populations. PLOS ONE, 9(7), e101582.
  • Colosimo, P. F., et al. (2004). The genetic architecture underlying the evolution of pelvic reduction in sticklebacks. Nature, 428(6984), 545-548.
  • McKinnon, J. S., & Rundle, H. D. (2002). Speciation in nature: the threespine stickleback model systems. Trends in Ecology & Evolution, 17(10), 480-488.
  • Jones, F. C., et al. (2012). The genomic basis of adaptive evolution in threespine sticklebacks. Nature, 484(7392), 55-61.

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