Unit 3 - AOS 1 - CH 3 - Measuring species & biodiversity, Conservation status etc. Flashcards
Sampling using quadrats + info on size and number
Using a small area of habitat
- Most widely used means of obtaining quantitative info about composition & structure of plant or sessile (attached) animal species.
- If the size and position are appropriate = reliable info
Size: depends on height and density of species present
Number: ecologists suggest should cover 10% of area being studied.
Types of sampling - PLANTS
Random sampling: plots are placed randomly within the study area
Systemic sampling: quadrats are placed in line as evenly as possible.
- Belt transect: small quadrats joined in a line
Sampling edge effects
- When plant crosses edge decision if should be counted or not. (if not discussed = overestimation of population)
Circle quadrat:
- Minimises edge effect because ratio of edge to area is lower
- But is harder to calculate area.
Sampling - MAMMALS
INDIRECT SIGNS: droppings, tracks, feeding signs, burrows, food remains, body remains
SPOTLIGHTING: walk along tracks at night; listening for movement or spot mammal with light ( red=less disturbing)
DIRECT OBSERVATION: species observed during the day/setting up camera traps
LIVE TRAPPING: small mammals trapped alive in collapsible aluminium Elliot traps or wire mesh cage traps with suitable bait. (data = sex + weight)
CAPTURE MARK RECAPTURE: Sample of population is captured, marked and released. Later repeated with second sample mark individuals counted.
(number of individuals marked in 2nd sample should be proportional to number of whole population)
*Smaller # of individuals marked in 2nd capture = larger population.
Mark-recapture formula
M x n
N = ———-
m
N = estimation of population size
M = # of individuals initially marked
n = total size in second sample
m = # marked in second sample
Species abundance
“The number of individuals in a species”
Relative abundance
“Evenness of distribution of individuals among species in a community.”
Species richness
“The number of different species present in a particular region”
Why could using species richness data be not fully accurate
- Ignoring genetic variation that may be present in a species
- Partially represents ecosystem diversity
- Ranks all species equally (rare, common, introduced species)
Species diversity
“Takes into account the relative species abundance (# of individuals) & species richness (# of species)”
Definition of equitability & what makes a community diverse and non-diverse.
“Extent to which each species contributed to the ecology of the community”
Diverse community: species in a particular trophic level are present in roughly equal #.
Non-diverse community: a trophic level is dominated by only a few species.
SID = Simpsons index of diversity
“Based on probability of 2 specimens belonging to the same species”
0 = low diversity
1 = high diversity
Degree of endemism
“The level of endemism of the species present”
Endemism: species native to one area only
Vegetation structure
“Physical structure of the vegetation, size & shape”
1. height
2. projective foliage cover (% of the ground shaded by foliage of the plants in the stratum)
e.g., tropical rainforests 90% & grasslands 10%
2 developed researched to assess risk of extinction
- THEORY OF ISLAND BIOGRAPHY
- Lager island will have greater number of species compared to a small island
- Larger habitat loss will result in ^ loss of species
- generalised results that change depending on habitat type.
- predicts the possible effect of habitat loss & fragmentation.
- High levels of uncertainty. - COLLECTIONS AT HERBARIUMS AND MUSEUMS
- Organisms are considered extinct when they haven’t been collect for ~50 yrs
- Assumes collections are random (not actually the case in practice)
- There have been species that have been found (live) even after considered extinct.
- provides estimate of relative threat
- Most effective when used along with current data.
- both not reliable
