KEGS Biology Blog


Daws Hall Day 2
September 27, 2012, 8:09 am
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Daws Hall Day 2: The Return of the KEGS Students.
Upon our arrival we swiftly ventured out to check our mammal traps, much to the disdain of certain members of the group (Hinali). The majority of mammals caught were wood mice, with yellow-necked mice being slightly more uncommon, and bank voles cropping up too. We noticed there were more bank voles in the chestnut coppice than the woodland edge, and this is probably due to the more secluded nature of the coppice, as bank voles are more sluggish than the other two, and therefore can’t escape owls/buzzards/KEGS students as easily.
We also learned another way of measuring diversity, through the Simpson-Yule Diversity Index. This calculates the probability that the next organism in a random selection will be of a different species, a score of 1 (though technically impossible) would mean a high diversity, and 0 would be low.
The formula was as follows: D=1-pi², where pi²=(number of individuals of 1 species ÷ total number of individuals in the sample)².
Finally we headed back to the brook and river to catch our invertebrates, and identify them using a chart. We noticed some were identification species, which meant that that certain species could only be present if all its survival factors were present (for example, Pond Skaters can only be present in slow moving water).
Even those who only caught mud and rocks had an educational day out, we all took something home with us from that day, be it knowledge, or stings (Halima).
Top day 10/10.

Comment by alexgurton

Also, a better formula to use for The Simpson’s Index of Biodiversity would be:-

D = 1-(Σ(n/N)^2)

Comment by Deelan Vadher

We also learnt about the ‘T-test’- http://www.socialresearchmethods.net/kb/stat_t.php

Also the ‘T-Value’ which tells us how different two sets of data are (The T-value depends on how different the two sets of data are e.g usual values are between 3 and 5. If the sets of data are identical however the value will be ‘o

Comment by roobennithi

Alex I love your rendition of day 2 ! And there were other indicator species like the beetle one ? And bloodworm ? Anyone know what mr wren said they were indicators for ?

Comment by halima95

Daws Hall – Day 2 Sumary

Firstly, the two mammal traps and moth trap were checked. As a class, the traps set in the area bordering the woodland and meadow showed that wood mice, yellow-necked mice and bank voles being common. (Highest to lowest frequency stated above). We discovered that the second set of traps downhill in the woodland area displayed identical species richness in that three species stated above were also discovered in this different habitat. However, the species evenness was very different. The first habitat showed signs of much shrubery and low branches of trees (level of plant life near the ground was high), whereas the second area did not have such vegetation near the ground. This could be used to describe the species evenness in the two areas. A higher frequency of wood mice (from our collective sample) were found in the first area because they favour the low branches and bushes to climb up. Bank voles do not- therefore, more were found in the second area where the frequency of ground level plants was lower. We were able to identify many species of moth that were caught in the overnight trap. The UV bulb disorientated the moths and enticed them into the trap. Being dormant during the day, we were able to identify them.

Secondly, in groups of three, invertebrates were caught from both the brook and the river and identified using an Identification Card and Recording Sheet. Again, the species richness was almost identical with every group capturing the same species from both the river and brook. However the species evenness proved to be different. Depending on factors such as oxygen, phosphate, nitrate levels, pH, temperature and turbidity, different proportions of the same species were located in the two freshwater environments.

Comment by Deelan Vadher




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