Transcript Topic 2.5: Investigating Ecosystems

Topic 2.5: Investigating
Ecosystems
Investigating Ecosystems
• Review Zonation and Succession on your notes
How do we know what is going on
inside an ecosystem?
• In order to understand an ecosystem properly we
need to measure various biotic and abiotic factors.
Monitoring Abiotic Factors
• Ecosystems can be roughly divided into:• Marine
• Freshwater and
• Terrestrial systems
Monitoring Abiotic Factors
• Complete the diagram in your notes
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
IB Animal Experimentation Policy
• You may not perform an experimentation using animals
that involves:
• Pain, undue stress, damage to health of animal
• Death of animal
• Drug intake or dietary change beyond those easily tolerated
by the animal
• Consider:
• Using cells, plants or simulations instead
• If using humans you MUST have written permission
• AISD safety contracts apply at ALL times during ALL labs
• No experiments may be done that have any risk of
transferring blood-borne pathogens
COLLECTING DATA
• It is almost impossible to collect every possible data
point
• Use sampling methods to make estimations
• Use random sample from an entire ecosystem
• In order to avoid bias it is important that these methods
are truly random.
• All organisms must have an equal chance of being
captured.
COLLECTING DATA
• Two methods used in ecology to determine where
to collect a sample are:
• Quadrats
• 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
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
Homework:
Measuring abiotic factors
• Choose a one factor from each type of ecosystem and
research how it is measured.
• Produce a detailed methodology with supporting
diagrams if necessary.
Marine: Salinity, pH, temperature, dissolved oxygen,
wave action.
Freshwater: Turbidity, flow velocity, pH, temperature,
dissolved oxygen.
Terrestrial: Temperature, light intensity, wind speed,
particle size, slope, soil moisture, drainage, mineral
content.
How do we decide where to
measure?
• Quadrats
• Transects
Estimating Populations of Plants
• Quadrat Estimation
• Population Density- The
• number of plants within the
• given area of the quadrat (m2)
• Percentage Coverage• How much of the area of a
• quadrat is covered by plants?
• Frequency- How often does a plant occur in each quadrat?
• Acacia senegalensis was present in 47 of 92 quadrats, for a
frequency of 51%
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
• Find the percent frequency
• Count number of squares with flowers
• 15 (note one square has 2 flowers)
• Count total number of squares
• 36
• Calculate percentage
•
15
36
× 100 = 42%
Percent Coverage
• Percent Coverage
18
1m
• Find the percent coverage
• Count full squares
• Now combine pieces to
make full squares
• Calculate percentage
coverage
1m
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
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
How do we know where to place
the quadrat/sample?
• “Throw it over your shoulder”
• Draw a grid over your sample area.
• Use a random number generator.
• This is the square that you sample.
• If your habitat has two (or more) different
habitats/vegetation types then samples should be
taken in each area.
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
Transects
• Look at changes over an environmental gradient
e.g. zonation
• Need more than 1 for a valuable results. (At least 3)
Where to transect?
• Random number generator.
• Random direction.
• Unless you want to particularly follow a gradient.
• Complete a transect of your ecosystem.
What to measure?
• Biotic and Abiotic Factors
• You have (for HW) explained how to measure
various abiotic factors, we are going to discuss
some of the biotic factors.
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!
Primary Productivity
Different methods for terrestrial
and aquatic habitats.
1) Find three identical (ish) areas
2) Dig up one and calculate its
biomass.
3) Cover one with black plastic,
and leave one open.
4) A set amount of time later
measure the biomass of the two
site.
5) Initial – Light = NPP
6) Initial – Dark = Respiration
7) Light – Dark = GPP
Secondary Productivity
• GSP = food eaten – faecal loss
• NSP = GSP – Respiration
• Take the mass of herbivore.
• Measure all the food it eats and its faeces.
• After a certain amount of time measure the mass
of the animal again.
Catching motile organisms
Terrestrial
• Pitfall Traps
• Sweep nets
• Tree Beating
• Tullgren Funnels
(invertebrates)
Aquatic
• Kick sampling
Pitfall Trap
• Insects and other small
invertebrates
• Placed in a transect
• Number of each species recorded
• No fluid in the bottom
Sweep nets
Tree Beating
Kick sampling
Estimating abundance of motile
organisms
• Direct
methods:
actual counts
and sampling
• Indirect
methods:
Lincoln index
Percentage
cover
Capture – Mark – Recapture
• Capture organisms and count
• Mark organisms with non-toxic, semi-permanent,
substance that will not increase the likelihood of
harm to the organism
• Release organism back into environment
• The time before you do another capture will
depend on; the mobility of the organism, r or K
strategists
Lincoln Index
• Capture-mark-recapture
• 𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥 =
𝑛1 × 𝑛2
𝑛𝑚
n1 = the number caught in the first sample
n2 = the number caught in the second sample
nm = the number caught in the second sample that
we marked
𝑛1 × 𝑛2
𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥 =
𝑛𝑚
• Assumptions:
•
•
•
•
•
Mixing is complete
Marks do not disappear
Marks are not harmful or advantageous
It is equally easy to catch every individual
There is no immigration, emigration, births or deaths in
the population between the times of sampling
• Trapping the organisms does not affect the changes of
being trapped a second time.
Your Turn
Use the Lincoln Index to monitor
this mountain gorilla population
over time:
Year
n1
n2
nm
2003
23
25
18
2004
26
30
22
2005
27
35
21
2006
16
18
15
2007
18
19
16
2008
17
24
17
P
Gorilla hunting is illegal in some regions and carefully controlled in
others, though there is a high demand for illegal bush-meat.
•Deduce between which two years illegal hunters were active in
the forest.
•Explain the long recovery time for the population.
Some Possible Sources of Error with
Capture – Mark – Recapture
• 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
Species richness and diversity
• Richness is the
number of
species
• Diversity is
number of
species and the
individuals in
each species.
Species Diversity
• The two main factors taken into account when measuring
species diversity
• 1. Richness
• 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.
• 2. Relative Abundance
• The relative number of individuals of each species present
http://www.countrysideinfo.co.uk/simpsons.htm
𝑁(𝑁 − 1)
Simpson
diversity 𝐷 =
𝑛(𝑛 − 1)
index
• D = Simpson diversity index
• N = total number of organisms of all species found
• n = number of individuals of a particular species
Number of individuals of species
A
B
C
Ecosystem 1:
25
24
21
Ecosystem 2:
65
3
4
• Calculate the diversity index for both ecosystems
Simpson diversity index
• Both ecosystems have the same species richness
(3), however one is far more diverse.
• High D-values associated with stable ancient sites
• Low D-values associated with disturbed ecosystems
• Crop fields will have very low D-value (farmers do not
want other species competing with there crops)
• NOTE: low values for D in Artic tundra may
represent ancient stable sites as growth is so slow
there and diversity is low.
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
• 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
Using Simpson’s Index:
Numbers of individuals (n)
Flower Species
Sample 1
Sample 2
Daisy
300
20
Dandelion
335
49
Buttercup
365
931
Total (N)
1000
1000
Find the diversity index for sample 1:
𝑁(𝑁 − 1)
𝐷=
𝑛(𝑛 − 1)
𝐷=
1000(999)
300∙299 + 335∙334 +(365∙364)
𝐷 = 2.99
YOUR TURN Solution
Organism
Orthoptera
(grasshopper)
Orthoptera
(grasshopper)
Lepidoptera (butterfly)
Lepidoptera (butterfly)
Coleoptera (beetle)
Hymenoptera (wasp)
Hymenoptera (wasp)
Hymenoptera (bee)
Description
Green with red legs
Meadow 1
16
Meadow 2
25
Brown with yellow
stripe.
Large, blue
Small, blue
Red & Blue
Black
Purple
Striped
5
2
26
3
12
17
9
12
4
5
62(61)
3782
𝐷1 =
=
= 3.6
16 ∙ 15 + 5 ∙ 4 + 26 ∙ 25 + 3 ∙ 2 + (12 ∙ 11) 1048
𝐷2 =
74(73)
25 ∙ 24 + 2 ∙ 1 + 17 ∙ 16 + 9 ∙ 8 + 12 ∙ 11 + 4 ∙ 3 + (5 ∙ 4)
5402
=
= 4.9
1110
•
Sample 1 has a higher Simpson’s Biodiversity
index than Sample 2 even though it has the same
number of species present and the same number
of total individuals because there is more even
distribution of the organisms through the species.
YOUR TURN
The insects in two meadows are being
investigated. The following data was collected.
Compare the diversity of the two meadows
Organism
Description
Orthoptera
(grasshopper)
Orthoptera
(grasshopper)
Lepidoptera
(butterfly)
Lepidoptera
(butterfly)
Coleoptera (beetle)
Green with red
legs
Brown with
yellow stripe.
Large, blue
Hymenoptera
(wasp)
Hymenoptera
(wasp)
Hymenoptera (bee)
Black
Small, blue
Red & Blue
Purple
Striped
Meadow 1
Meadow 2
16
5
26
3
12
25
2
17
9
12
4
5
YOUR TURN Solution
Organism
Orthoptera
(grasshopper)
Orthoptera
(grasshopper)
Lepidoptera (butterfly)
Lepidoptera (butterfly)
Coleoptera (beetle)
Hymenoptera (wasp)
Hymenoptera (wasp)
Hymenoptera (bee)
Description
Green with red legs
Meadow 1
16
Meadow 2
25
Brown with yellow
stripe.
Large, blue
Small, blue
Red & Blue
Black
Purple
Striped
5
2
26
3
12
17
9
12
4
5
62(61)
3782
𝐷1 =
=
= 3.6
16 ∙ 15 + 5 ∙ 4 + 26 ∙ 25 + 3 ∙ 2 + (12 ∙ 11) 1048
𝐷2 =
74(73)
25 ∙ 24 + 2 ∙ 1 + 17 ∙ 16 + 9 ∙ 8 + 12 ∙ 11 + 4 ∙ 3 + (5 ∙ 4)
5402
=
= 4.9
1110
How do you identify what you
have found?
Dichotomous Keys
• Method of identifying an organism
• Dichotomous = divided in two parts
• Numbered series of pairs of descriptors
• One matches the species, the other is clearly wrong
• Each pair leads to another pair of descriptors OR to
an identification
• Features chosen for descriptors should be easily
visible and observable
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.
Dichotomous keys
Dichotomous
Keys
http://gottalovebio.wikispaces.com/file/view/candy_class._key.jpg/162207257/candy_class._key.jpg
http://www.field-studies-council.org/publications/resources/ks3/images/Liqorice-key.jpg
Creating Dichotomous Keys
• REMEMBER:
• There are always only 2 choices (1a or 1b)
• You may start with a branching diagram but this must
be turned into a outline form for final draft
• It is easiest to start by grouping all objects into 2
groups, then take one group and divide into 2 again
until you get to individual items.
• Traits should be used that ANYONE would be able to
observe and come to the same conclusion
• When naming your organisms they should have a
Genus species name
Create your own key
• Using the species in front of you create a dichotomous key for 8 species.
• Avoid using words like “big”.
• Use quantitative, comparative descriptors.
• Don’t over complicate things.
Alternatives
• Photos and illustrations
• DNA analysis
• Field guide
• Consider habitat
• Even though two things
looks similar they may
live in different habitats.
• Allows certain species to
be eliminated.