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Introduction

Biology Internal Assessment DCP and CE “Ecological Niches of Caterpillars” 2013 Design Aim To investigate whether the Window and Notching caterpillar share the same ecological niche. Research Question How does the shape of the feeding bite as measured by the distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site indicate whether the Window and the Notching caterpillar share the same ecological niche? Variables Independent Variable – Shape of feeding site Range: Window or Notch Dependant Variable The distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site. Results Raw Data Table showing the distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site (mm) of 50 samples from notched and window shaped feeding sites on cabbage tree leaves. Shape of Feeding site The distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site. (mm) (±1mm) Notch 7 9 8 12 12 6 12 10 11 10 9 6 11 4 5 Notch 7 6 8 11 11 6 7 8 9 6 8 7 8 7 6 Notch 4 13 5 9 6 12 7 14 10 13 10 10 12 8 6 Notch 9 5 7 11 9 Window 5 10 8 7 6 3 2 5 10 5 10 1 5 5 7 Window 6 2 11 5 1 3 10 11 3 5 5 7 6 5 3 Window 5 7 4 6 8 3 2 8 3 9 5 5 10 4 6 Window 9 4 3 1 10 Key Colour used to indicate the raw data used to calculate example mean Colour used to indicate the raw data used to calculate example standard deviation Observations: * Notches were mostly at the edges of leaves but were quite deep. ...read more.

Middle

The Window and Notching caterpillar both have the same fundamental niche (the area which a population can occupy in ideal conditions¹), yet the competition which occurs in this fundamental niche has resulted in the caterpillar species inability to co-exist in the same habitat as eventually one caterpillar species will outcompete and eliminate the other. Thus our results can be explained by Gauses competitive exclusion principal which states: “if species are to coexist in the same habitat, their niches cannot be exactly the same².” In the case of the two caterpillars, they both have different physical adaptations have enabled them to coexist because they feed on different parts of the leaves. The notching caterpillar mouthparts which enable it to bite, so eats from the edge of the leaf. While the window caterpillar has a rasping radula³ that scrapes holes in the leaf close to the midrib. Thus the caterpillars can successfully exist on the same cabbage tree leaf while not in sharing the same niche, as their adaptations reduce competition creating different realised niches in the same fundamental niche. However my results are reflected by these other experiments such as the one a found online which directly measured the frequency of different types of feeding sites against the distance from the midrib. Their results are shown in the graph belowâ´. I also found another similar studyâµ which looks at the caterpillar feeding sites on flax, this also supports my findings. The findings though not as extreme were very similar to my own, as the window feeding sites were located closer to the midrib while the notches were closer to the edges of the leaves. Therefore I can conclude that my findings and my explanation is correct as it is confirmed by outside sources. ...read more.

Conclusion

Thus significantly effecting our reliability and validity of our results. Once we had taken measurements from a leaf we could place a small sticker brought (http://www.amazon.com/Map-Dot-Stickers-Red-Diameter/dp/B003M6WPPW) on the tip of that leaf to indicate that we had already taken measurements then we could move onto the next leaf. Once we had collected all 50 samples we could return and remove all of the stickers. We had some difficulty in telling where the midrib was. This would have caused our mean to be inaccurate. As our distances to the feeding sites would have altered if we had an incorrect starting point due to our inability to determine where the midrib was. This would have significantly effecting our reliability and validity of our results. As the midrib is easier to view on the underside of the leaf. Therefore we would undertake all of our measurements using the underside of the leaf. The leaves taper to a point so depending on where we measure the distance to the midrib from the feeding site will be less. This would have caused our mean to be inaccurate. As our distances to the feeding sites would have altered getting smaller as the leaf tapered off. Therefore it would not be clear if we measuring a feeding site which was extremely close to the midrib or it was actually in the middle of the leaf but the leaf was narrower at that point. This would have significantly effecting the validity of our results. If we were to do this experiment again I would not include any results from the first 15cm of the leaf or the first 15cm from the base to make the distance from the midrib to the outside more equal. Sources 1)https://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&ved=0CIkBEBYwDQ&url=http%3A%2F%2Fstudents.kaikourahigh.school.nz%2Fbiology%2F12resources%2Feniche.doc&ei=VWmMUu3POInyiAeUvYGwCw&usg=AFQjCNH42DsZ8PV29T6nuBoMtADGCOS4EA&sig2=fMwOpmm0LcJoP5tVn6ZsiA&bvm=bv.56643336,d.aGc&cad=rja 2) http://www.nobraintoosmall.co.nz/students/biology/NCEA_Level2/pdfs/bio2_90461_habitats.pdf 3) http://wiki.answers.com/Q/What_is_the_difference_in_the_mouthparts_of_a_notch_and_a_window_flax_caterpillar#ixzz2lAbEk3no 4)https://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CDsQFjAC&url=http%3A%2F%2Fcarmel.ultranet.school.nz%2FModules%2FResources%2FDownload.aspx%3FID%3D1795&ei=GGeMUr7uHqWiigfnrID4Dg&usg=AFQjCNFrkoI9ZNmdgiAOu587ghFW8Rweig&sig2=oQQROaX6cZ0934xfrqdcoA&bvm=bv.56643336,d.aGc&cad=rja 5) http://eng.keitemohiokoe.tki.org.nz/Overview-of-Biology/Harakeke-5/Activity-Friend-or-Foe-Are-harakeke-caterpillars-fighting-for-the-same-food ...read more.

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