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4.2.1 Biodiversity (Sampling Techniques (Sweeping nets: walk through…
4.2.1 Biodiversity
Sampling Techniques
Sweeping nets: walk through habitat with stout net and make figures of eight to catch small invertebrates; works better in long grass or ponds; empty out net onto white sheet and count organisms before they fly away
Pitfall traps: trap set in soil to trap small animals; small container buried in soil with a small amount of water to stop animal climbing out; covered with leaf litter so animal walking on top will fall in
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Tullgram funnels: to collect small animals from leaf litter; place leaf litter in a funnel and animals follow the light and fall down a mesh screen and are trapped
Kick-sampling: kick the edge of a water stream gently to disturb small organisms present and collect them with a net
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Point frame: place it on the ground and record the plant species touching each of the frames (10) needles
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Biodiversity levels:
habitat biodiversity: range of habitats in which species live e.g. sand dunes, woodland, meadows, streams
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genetic biodiversity: variation between individuals belonging to the same species e.g. different breeds within a species
genetic biodiversity of small isolated populations is small e.g. captive animals in zoos, or rare breeds in animals
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can look at observable physical traits to measure biodiversity, or look at differences of alleles for particular loci
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Biodiversity: measure of all the different plant, animal, fungus, and microorganism species worldwide, the genes they contain, and all the ecosystems of which they form a part.
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Sampling
Random sampling: sample sites are randomly selected e.g. using a random number generator to generate coordinates of the sample sites
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--- may not cover all areas of habitat equally; may lead to underestimate or overestimate of biodiversity
Non-random sampling:
opportunistic
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researcher makes sampling decisions based on prior knowledge e.g. they sample an area they know has high biodiversity
stratified
+++ ensures all different areas within a habitat is sampled; less likely of an underestimate of species
--- may lead to over representation of some species as areas sampled are not proportional in size to each other
dividing a habitat into areas that appear different and sampling each area separately e.g. in a meadow longer grass vs shorter grass
systematic
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--- only species that happen to be on the line are recorded; species may be missed leading to underestimate
samples are taken at fixed intervals across the habitat e.g. using an interrupted belt or line transect
Sampling a habitat means a small portion of the habitat is studied and numbers of individual species are measured, then multiplied to give an estimate of total numbers of individual species within a habitat
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