Transcript Lincoln index - cloudfront.net

2.5 Investigating Ecosystems
 Review Zonation and Succession on your notes
Monitoring Abiotic Factors
 Ecosystems can be roughly divided into: Marine
 Freshwater and
 Terrestrial systems
MONITORING BIOTIC (LIVING) FACTORS
 Once the abiotic conditions within an environmental
gradient have been measured, we can begin to ask
questions about the distribution of organisms within
the study area




Which species are present
The size of a particular population of organisms
The productivity in a particular area
The diversity of a particular area
COLLECTING DATA - Where?
 When collecting environmental data, it is almost
impossible to collect every possible data point
 We use sampling methods to make estimations
 These methods enable us to get a random sample
from an entire ecosystem and then use extrapolation
to make estimates and predictions
COLLECTING DATA - Where?
 In order to avoid bias it is important that these
methods are truly random.
 Two methods used in ecology to determine where to
collect a sample are quadrats and transects.
Assumptions Made When Sampling
 The sample is representative of the whole system
 It is necessary to take enough samples so that an
accurate representation is obtained
 It is important to avoid bias when sampling
Estimating Populations of Organisms
 We estimate populations because it would take way
too long to count every living thing in a given
ecosystem.
 We can estimate populations of plants or animals
 Random Sampling: All organisms must have an
equal chance of being captured.
Common Sampling Methods
 Abundance of Non-motile Organisms
 Transects and Quadrants
 Abundance of Motile Organism
 Actual Count (very difficult if large system)
 Lincoln Index

Capture – Mark - Recapture
 Species Diversity
 Simpson Diversity Index

For comparing 2 habitats or the change in one habitat over time
Lincoln Index
n1
N=
x
n2
n3
Measuring abundance of Mobile Organisms
 If the organism is mobile we use a method called the
capture-mark-recapture method
 We then use this data to calculate the Lincoln Index
How to Capture Motile Organisms
 REMEMBER: IB Animal Experimentation Policy
 Pitfall Traps
 Small Mammal Traps
 Tullgren Funnels (invertebrates)
 Kick Net
Estimating Populations of Animals
 Lincoln index (capture-mark-release-recapture)
n1
N=
x
n2
n3
• N = Total number of population
• n1 = Number of animals first (mark all of them)
• n2= Number of animals captured in second sample
• n3= Number of marked animals in second sample
Ex. 40 mice were caught, marked (tail tattoo) and released.
Later, 10 mice were recaptured, 4 of which had tattoo
marks.
Lincoln Index
Example
 50 snowshoe hares are captured in box traps,
marked with ear tags and released. Two weeks later,
100 hares are captured and checked for ear tags. If
10 hares in the second catch are already marked
(10%), provide an estimate of N
 **Realize for accuracy that you would recapture
multiple times and take an average**
Lincoln Index Assumptions
1.
The marked animals are not affected (neither in behavior
nor life expectancy).
2.
The marked animals are completely mixed in the
population.
3.
The probability of capturing a marked animal is the same
as that of capturing any member of the population.
4.
Lincoln Index Assumptions
4. Sampling time intervals must be small in relation to the
total time of experiment of organisms life span.
5. The population is closed (no immigration and
emigration)
6. No births or deaths in the period between sampling.
Some Possible Sources of Error
 Emigration & Immigration
 Natural disaster or disturbance between captures
 Trap happy or trap shy individuals
 Organisms did not have enough time to disperse
back into ecosystem
 Animals lost marks between recapture
Quadrat Sampling
Estimating Populations of Plants
 Quadrat Estimation
 Population Density- The
number of plants within the
given area of the quadrat (m2)
Percentage CoverageHow much of the area of a
quadrat is covered by plants?

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Frequency- How often does a plant occur in each
quadrat?
 Acacia senegalensis was present in 47 of 92 quadrats,
for a frequency of 51%
Square Quadrat Method
 N = (Mean # per quadrat) (total area)
Area of each quadrat
 This estimates the population size in an area
 Ex. If you count an average of 10 live oak trees per
square hectare in a given area, and there are 100
square hectares in your area, then
 N = (10 X 100 hectare2) / 1 hectare2 = 1000 trees in
the 100 hectare2
In addition to population size we can measure…
 Density = # of individuals per unit area

Good measure of overall numbers
 Frequency = the proportion of quadrats sampled that
contain your species
 Assessment of patchiness of distribution
 % Cover = space within the quadrat occupied by each
species
 Distinguishes the larger and smaller species
Grid Quadrate
 Measures percent frequency – the
% of quadrats in which the species
is found
 OR
 Measures percent coverage –the %
of area within a quadrat covered by
a single species

NOTE: When you are looking at one
species at a time
 If not using a 10 x 10, you must
turn into a percentage (squares
covered/total # of squares)
Percent Frequency

http://www.slideshare.net/nirmalajosephine1/biology-form-4-chapter-8dynamic-ecosystem-part-3-42839437
Percent Coverage
1m
 Find the percent coverage
18
 Count full squares
full squares
 Calculate percentage
coverage
1m
 Now combine pieces to make
14 22
24 24 1 2 14
15 3 4 15
17 21 23
19 20 12
13 13 17 18
5 6 12
16 7 8 9 10 11 22
16 19 21 23 20 12
 Percent Coverage
Calculate Population Density
What is the population density of species x ?
What is the population density of species Y?
Quadrat 1= 0.5m2
What is the population density of
species Z?
X
X
X
W
W
W
X
X
W
X
W
X
X
X
X
W
X
W
X
W
W
z
W
W
Y
Calculate Percentage Coverage
What is the percentage of plant
coverage in this quadrat?
Quadrat 1= 0.5m2
X
W
X
X
W
X
W
X
X
X
W
W
X
X
X
W
W
Y
Percentage Frequency
Quadrat 1
What is the frequency
of species X?
What about species V?
X
X
X
W
W
W
W
W
W
X
X
X
Z
X
X
V
W
W
X
X
W
X
X
W
Y
Quadrat 2
Quadrat 3
Z
Z
Z
W
W
X
X
X
W
W
W
Z
Z
Z
Z
W
X
X
W
X
W
Z
Z
W
Z
W
X
X
X
X
W
X
W
Z
W
W
X
W
X
W
W
Z
W
W
Y
W
Z
W
W
Y
How choose quadrat size?
 Think about the size of the organism.
 Think about the area of the system.
 The smaller the quadrat the more accurate, however
the smaller the sample size
 Larger quadrats increase inaccuracy but allow for
broader sample of an area
Measuring Biomass
 Get a sample of the organisms, dry them out
completely in a dehydrating oven (to remove all
water!), find the mass and extrapolate :
 If you collect 10 plants, dry them out and find their
average dry biomass to be 20g, what would the
biomass of a population of 2500 plants be?
 50,000g
 Remember – biomass can be used to create pyramids
of biomass when looking at energy transfers and is
needed for many productivity calculations!
Transets
Transects
 A TRANSECT - A line, strip or profile of vegetation
which has been selected for study. measure any of
these abiotic and/or biotic components of an
ecosystem along an environmental gradient
Transect
 In order to complete a transect, a piece of string or
measuring tape is laid out along the selected
gradient.
Line Transects
 A measured line is randomly placed across the area
in the direction of an environmental gradient
 All species touching the line are recorded along the
whole length of the line or at specific points along the
line
 Measures presence or absence of species
Belt Transects
 Transect line is laid out and a quadrant is placed at
each survey interval
 Samples are identified and abundance is estimated
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Slow moving animals (limpets, barnacles, snails) are collected,
identified then released
For plants an percent coverage is estimated
Belt Transects
 Data collection should be completed by one
individual as estimates can vary person to person
Transect
 These can either be sampled continuously or as an
interrupted transect where samples are taken at
regular, fixed distances along the line.
Transect
 To measure changes in space i.e. zonation, this
technique should be completed within a short space
of time to avoid any daily cycles
 For studies of long term change i.e. succession, the
transect should be repeated at the same time of day
and at regular intervals over a suitable time period
depending on what is being studied or assessed.
Kite Diagrams
 Used to illustrate changes in species over space or
time along an environmental gradient.
 The width of each ‘kite’ represents the percentage
cover or abundance of that species.
Simpson Index
Species Diversity
 The two main factors taken into account when
measuring species diversity
 1. Richness
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A measure of the number of different species present in a
particular area.
The more species present in a sample, the 'richer' the sample.
Takes no account of the number of individuals of each species
present. It gives as much weight to those species which have
very few individuals as to those which have many individuals.
http://www.countrysideinfo.co.uk/simpsons.htm
Species Diversity
 The two main factors taken into account when
measuring species diversity
 2. Relative Abundance

The relative number of individuals of each species present
http://www.countrysideinfo.co.uk/simpsons.htm
How Can We Know Diversity?
Use the Simpsons diversity index below
D = ____________N (N-1)_______________
n1(n1−1) + n2(n2 −1) + n3(n3 −1) +…nk(nk −1)
D = Diversity
N = Total number of organisms of all species
n = number of individuals of a particular species
***The higher the D value the more diverse the
sample is!!!!!
Example Data Calculations
Abundance of Organism
Ecosystem A
Ecosystem B
species 1
3
5
species 2
7
4
species 3
26
12
species 4
9
7
species 5
7
0
Diversity
3.27
How can changes in these populations be measured?
 Necessary because populations may change over
time through processes like succession
 But also because human activities may impact a
population and we want to know how

Impacts include  toxins from mining, landfills,
eutrophication, effluent, oil spills, overexploitation
Analyzing Simpson’s Index
 Used to compare 2 different ecosystems or to
monitor an ecosystem over time
 D values have no units and are used as comparison
to each other
Analyzing Simpson’s Index
 High D Value Indicates:
 Stable and ancient site
 More diversity
 Healthy habitat
 Low D Value Indicates:
 Dominance by one species
 Environmental stress

Pollution, colonization, agriculture
How to Capture Motile Organisms
REMEMBER: IB Animal Experimentation
Policy
 Pitfall Traps
 Small Mammal Traps
 Tullgren Funnels (invertebrates)
 Kick Net
Classification
What is classification?
 Science of grouping organisms based on their
physical characteristics.
What characteristics do we use?
 Structures (morphology)
 Functions (physiology)
 Biochemistry
 Genetics
Why do we classify?
 Identify organisms
 Compare organisms
 Identify relationships among organisms
 Communicate with others (universal language)
 Identify evolutionary relationships
Why do we classify?
 What am I?
 Firefly
 Lightning bug
 Glow Fly
 Blinkie
 Golden Sparkler
 Moon bug
 Glühwürmchen
 Luciérnaga
 Luciole
 We all have different names for the same organism…this
is a problem for communication.
From Aristotle to Linneaus
 Carolus Linneaus (Sweedish botanist)
 (1707-1778)
 Came up with modern classification system
 Used binomial nomenclature (2 word naming system)
 This two word name is called a scientific name
 Composed of the genus name followed by the species name
Scientific Names
 Either written in italics or underlined
 Genus is always capitalized and species is always
lowercase
 Based on Latin
 Examples:
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
Cat: Felix domesticus
Mosquito: Colex pipens
Human: Homo sapien
Funny Scientific Names
 Agra vation (a beetle)
 Colon rectum (another beetle)
 Ba humbugi (a snail)
 Aha ha ( a wasp)
 Lalapa lusa (a wasp)
 Leonardo davinci (a moth)
 Abra cadabra (a clam)
 Gelae baen, Gelae belae, Gelae donut, Gelae fish, and
Gelae rol (all types of fungus beetles)
 Villa manillae, Pieza kake and Reissa roni (bee flies)
Dichotomous Keys
 A series of yes/no questions about an organisms
structure
 Used to identify new and unknown organisms
Step 1: Identify the organism
 Use dichotomous keys, field guides, observe a
museum collection, or consult an expert
 http://www.earthlife.net/insects/orders-
key.html#key
 Sample key for insect ID
Example of Dichotomous Key
 1a. Hair Present…………..Class Mammalia
 1b. Hair Absent……………Go to statement 2
Example of Dichotomous Key
 2a. Feathers present…………..Class Aves
 2b. Feathers absent…………….Go to statement 3
 3a. Jaw Present…………………..Go to statement 4
 3b. Jaw Absent……………………Class Agnatha
Example of Dichotomous Key
 4a. Paired fins present……………Go to 5
 4b. Paired fins absent…………….Go to 6
Example of Dichotomous Key
 6a. Skin scales present………………Class Reptilia
 6b. Skin scales absent……………….Class Ampibia