BIOL112 Animal Biology


The experiment was carried out using the Evobeaker (r) computer simulation program (“How the Guppy Got His Spots”) (Simbio Virtual Labs) (Biology 112, 2017.

It had five study locations: Upper West Stream (Lower West Stream), Lower West Stream (Upper East Stream), Lower East Stream (Upper East Stream), Meir Creek) and one holding cooler. Three tanks were also included.

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Simulations were run for between four and eight generations, both before and afterwards the removal of prey and before or after transplantation.

Randomly sampling 15 males, their spot brightness was recorded using a scale between 0-20 for each simulation.

Each simulation was reproduced 21 times. Results were visualised using histograms. Two-sample t tests were also performed.

To test the hypothesis of male spot lighting being determined by adult predation risks (AH1) we showed that a decrease in or increase of predation would cause a change in average male brightness over time (P1). We measured male spot brightness before and after adding a predator (Cichlid A to Upper East Stream) and before and after 1000-days after removing a predator from Lower East Stream.

East Stream

To test the hypothesis that male spots brightness is determined primarily by sexual selection, (AH2) we predicted that average male brightness would rise over time in a population that has been free from adult predators (P2): 800 days later, male spot luminosity was recorded after 15 females were removed and 15 dull males (brightness score =7) were brought to a tank that had no predators.

To test the hypothesis of male spot lighting being determined by geographical location (AH3) we predicted that male spot brightness would increase over time in a population that is free of predators (P2): male spot brightness was recorded in the Upper West Stream after all fish had been removed from Upper West Stream. This was done prior to transplantation of all fish from the Lower East Stream into the Upper West Stream.

1000 days following the transplantation event, male spot brightness in Upper West Stream had been recorded.

We also tested the hypothesis that male spots are determined by predation, sexual selection, geographical location (AH4) or that they are random with respect to predation, selection, and geographical location. (AH5). AH4 is supported if at least two of the predictions above are true. AH5 is supported if none.

Answer to Question: BIOL112 Animal Biology

Charles Darwin presented a theory that would allow for descent and modification in his theory.

This theory holds that if an organism’s population exhibits inheritance, variation or differential reproductive success, then there are high chances that this population will change from one generation onwards (Laland et. al., 2014.).

Guppies, Poecilia reticulata, are aquarium fish with unusual patterns. Guppies are found in their natural habitat of mountain streams found in tropical forests in northeasternTrinidad, Margarita Island, Venezuela, and Tobago (Banet et al., 2016).

Wild males may not be extravagantly ornamented, but they are nonetheless stunning.

They are known for wearing spots, stripes, splashes and splashes of many vibrant colours (Kodric Browne, 1985).

John Endler was an evolutionary biologist who studied the stupendous colouful patterns that wild guppies displayed in Trinidad in the 1970s.

Deacon, Magurran, 2016, noted that males living in one swimming pool had large orange and blue dots on their tails while those living downstream only had small dots.

Furthermore, the distribution patterns of guppy prey were different.

Endler proposed that the population variation could be attributed to predators found in the aquatic ecosystems.

This theory was born out of the fact that guppys who lived in streams with predatory fish cichlids had smaller spots than those who lived with Rivulus (Endler 80).

The laboratory work presented here was intended to challenge learners to design studies that allow for the documentation and analysis of natural selection in nature.

The field exploration was conducted on wild guppies to determine the variation among males across a range of wild populations.

John Endler’s final study of natural selection among guppies prompted the EvoBeaker simulations.

This research was conducted to examine the variation among male guppy guppies in different populations.


The study revealed that the average brightness of male spots is significantly decreased by adding predators to the stream.

Alternately, when predators were eliminated from a stream, the average brightness in the male spot rose significantly.

The first hypothesis was accepted, corresponding to adult predation risk (AH1) being the reason for male spot brightness.

This prediction, that increasing or decreasing risk of predation will lead to respective reductions or elevations of the average brightness of male spot over time (P1), was proved true.

Similar to P1, introducing males and/or females into a predator-free tank resulted in a significant increase of the average brightness in male spot at the end.

Thus, the second hypothesis which explains how male spot brightness is determined by sexually selecting (AH2) was accepted.

P2 was a prediction that the average brightness of spots in males within a group will rise over time with no predators that are adults (P2) proved to be true.

Also, there was no significant difference in the average brightness for male spots between the transplanting and post-transplanting factors.

The difference in average brightness of spot between males of Lower East Stream and Upper West Stream was significant after the transplantation of the Upper West Stream males.

The hypothesis that spot brightness was determined geographically (AH3) was therefore discredited.

The prediction that spot brightness would increase in a new location if males were incorporated (AH3) was incorrect.

The fourth view was based on the determination spot brightness in males by combined risk, sexually select and geographic location (AH4).

AH4 was approved because it fulfilled two out of three of the predictions.

The results of this study support the theory natural selection, particularly the sexual selection.

Sexual selection is a form or natural selection where some organisms produce offsprings with better traits than they do, so that they have greater chances of mating (West Eberhard, 2014).

Guppies believe in sexual selection because they fight for the right partner to mating.

One or two offspring result from the struggle between male guppies in order to possess females.

Evolutionary pressures drive male guppies brighten their abilities to attract females (Wilson. et. al., 2014.).

A male guppy that is brighter would mean that a female will prefer him over him, which would give him the chance to pass his genes on to her future generations.

If there is a high risk of predators, the evolutionary pressure on the guppy is to hide so they don’t fall prey to them.

As the priority is survival and not reproduction, the body spots’ brightness is not important (Tefertiller and co., 2016). Wright et al., (2017) had tested the model of sex chromosome evolution using genome and transcriptomeresequencing data in the guppy.

This study proved that there are long-standing models in sex catalysis. It also suggests that sexual selection is possible.

According to Darwin’s natural selection theory, spots in guppies can be attributed to Darwin.

It also supports the theory of sexual selectivity.References:Banet, A. I., Svendsen, J. C., Eng, K. J., & Reznick, D. N. (2016).

Linking reproduction to locomotion and habitat usage in the Trinidadian-guppy (Poecilia.reticulata). Oecologia, 181(1), 87-96.Deacon, A. E., & Magurran, A. E. (2016).

15 How behaviour contributes to the success an invasive poeciliid fishing species: The Trinidadian Guppy (Poecilia reticulata), as a model species.

Biological Invasions & Animal Behaviour. 263.Endler, J. A. (1980).

Natural selection of color patterns in Poeciliareticulata. Evolution, 34(1), 76-91.Hooker, D., Kiesewetter, K., Heath, R., Marsh, L., & Bowser, B. (2016).

How color and size influence the choice of poeciliareticulata for a mate.

Journal of Introductory Biology Investigations. 5, 4.Kodric-Brown, A. (1985). Female preference and sexual selection for male coloration in the guppy (Poeciliareticulata).

Behavioral Ecology & Sociobiology (17(3)), 199-205.Laland, K., Wray, G. A., & Hoekstra, H. E. (2014).

Are evolutionary theories in need of revision? Nature, 514(7521), 161.Tefertiller, L., Taylor, M., Rose, M., Saunders, G., & Hanna, A. (2016).

Studying male guppy mate selection behavior.

Journal of Introductory Biology Investigations.West-Eberhard, M. J. (2014).

Darwin’s forgotten thought: The social nature of sexual selection. Neuroscience & Biobehavioral Reviews, 46, 501-508.Wilson, A. D., Krause, S., James, R., Croft, D. P., Ramnarine, I. W., Borner, K. K., … & Krause, J. (2014).

Dynamic social network dynamics in guppies. (Poecilia.reticulata).

Behavioral ecology & sociobiology. 68(6), 915-925.Wright, A. E., Darolti, I., Bloch, N. I., Oostra, V., Sandkam, B., Buechel, S. D., … &Mank, J. E. (2017).

Convergent reproduction suppression suggests the role of sexual selectivity in guppy-sex chromosome generation.

Nature Communications, 8, 14251.

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