Name________________________________
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Sampling techniques homework 3
1. Two groups of ecologists carried out a pitfall trap survey in a woodland. Group A set
one trap while group B set 5. The results of both groups are shown in the tables below.
Group A concluded that there were four different kinds of invertebrate and that thrips
were least common.
Animals found
Group A
Rove beetle
Ground Beetle
Wolf Spider
Thrips
Animals found
Group B
Rove beetle
Ground beetle
Wolf spider
Thrips
Centipedes
Snails
1
4
0
6
2
1
1
Number
8
2
2
1
Trap Number
2
3
4
1
2
2
0
3
1
8
10 8
2
2
3
1
0
1
0
0
0
5
6
2
8
1
2
0
Total
Average
a) Calculate the average number of each type of insect sampled by Group B and write
your results in the table.
2
b) How many kinds of small animal did Group B find in the woodland?
__________________________
1
c) What type of small animal did Group B find to be most and least common?
Most common_______________________ Least common_______________________
2
d) Both groups saw many wasps in the wood but none were caught in the traps. Why?
__________________________________________________________________________________
1
e) Both groups were trying to obtain a specimen of a very rare beetle which is known to
live in the woodland. Why did neither group catch one?
__________________________________________________________________________________
1
f) How could the groups improve their chances of catching a rare beetle?
__________________________________________________________________________
1
g) Which groups data do you think is more reliable and why?
__________________________________________________________________________
1
2. A comparison was made between the types of invertebrate animals living on the
branches and leaves of an oak tree with those living on a beech tree. Samples were
collected as shown.
a) Give two variables which must be kept constant to keep this comparison valid.
1. ________________________________________________________________________
2. ________________________________________________________________________
2
b) The samples collected were not representative of all the invertebrates living on the
trees. Suggest a reason for this.
__________________________________________________________________________
1
3. Name two biotic and two abiotic factors
Biotic ________________________________ and ________________________________
2
Abiotic ________________________________ and ________________________________
2