Environmental Systems & Societies

Significant Ideas


The description and investigation of ecosystems allows for comparisons to be made between different ecosystems and for them to be monitored, modelled and evaluated over time, measuring both natural changes and human impacts.
Ecosystems can be better understood through the investigation and quantification of their components.

Knowledge & Understandings
1)
2)
3)
4)
5)
The study of an ecosystem requires that it be named and located ex: Sundarban’s, Bangladesh, a
Mangrove forest along the South-western coastline of
Bangladesh
Organisms in named and located an ecosystem can be identified using a variety of tools including
dichotomous keys, comparisons to herbarium/ specimen collections, technologies and scientific expertise.
Sampling strategies may be used to measure biotic and abiotic factors and their change in space, along an environmental gradient, over time, through succession or before and after a human impact, for example as part of an EIA.
Measurements should be repeated to increase
reliability of data. The number of repetitions required depends on the factor being measured.
Methods for estimating the biomass and energy of trophic levels in a community include measurement of dry mass, controlled combustion, and extrapolation from samples. Data from these methods can be used to construct ecological pyramids.

Knowledge & Understandings
6)
7)
8)
9)
Methods for estimating the abundance of non-motile
organisms include the use of quadrats for making actual counts, measuring population density, percentage coverage, and percentage frequency.
Direct and indirect methods for estimating the
abundance of motile organisms can be described and evaluated. Direct methods include actual counts and sampling. Indirect methods include the use of capture-
mark-recapture with the application of the Lincoln
Index.
Species richness is the number of species in a community and is a useful comparative measure.
Species diversity is a function of the number of species and their relative abundance and can be compared using an index. There are many versions of diversity indices but students are only expected to be able to apply and evaluate the results of the Simpson Diversity
Index. Using its formula, the higher the result, the greater the species diversity. This indication of diversity is only useful when comparing two similar habitats or the same habitat over time.

Application & Skills
1)
2)
3)
4)
5)
6)
7)
8)
9)
Design and carry out ecological investigations.
Construct simple identification keys for up to eight species.
Evaluate sampling strategies.
Evaluate methods to measure at least three abiotic factors in an ecosystem.
Evaluate methods to investigate the change along an environmental gradient and the effect of a human impact in an ecosystem.
Evaluate methods for estimating biomass at different trophic levels in an ecosystem.
Evaluate methods for measuring/estimating populations of motile and non-motile organisms.
Calculate and interpret data for species richness and diversity
Draw graphs to illustrate species diversity in a community over time or between communities.

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

K2:
Dichotomous Keys






Method of identifying an organism
Di chotomous = 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

K2:
Dichotomous
Keys http://www.field-studies-council.org/publications/resources/ks3/images/Liqorice-key.jpg
http://gottalovebio.wikispaces.com/file/view/candy_class._key.jpg/162207257/candy_class._key.jpg


Salamander Keying

Shark Keying

Look at identification book examples and large dichotomous keys on the front table

A2: Creating Dichotomous Keys
• As a group, create a dichotomous key for your bag of hardware store items.
• 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

A2: HOMEWORK



Complete your own dichotomous key of the creatures (sent by email)
Email me a copy of your dichotomous key and make an answer key on the second page.
Your key will be assessed by your peers, we will exchange keys and see if they work.

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
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

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

 Samples taken at fixed intervals
 Set up along an environmental gradient
(e.g. high to low on a mountain, from shoreline)

 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

 Transect line is laid out and a quadrant is placed at each survey interval
 Samples are identified and abundance is estimated
◦
Slow moving animals (limpets, barnacles, snails) are collected, identified then released
◦
For plants an percent coverage is estimated
 Data collection should be completed by one individual as estimates can vary person to person



Square Quadrat – for population density
Size of quadrat determined by size of organism being sampled
(10 x 10 cm = 0.01 m 2 ; 0.5 x 0.5m = 0.25 m 2 ,
1.0 x1.0 m = 1 m 2 or 5.0 x5.0 m = 25 m 2 )

Count all individuals within a randomly placed quadrat


Population density is expressed as number of individuals per square meter
The larger the size and larger the sample the more accurate the results
Species Distribution: Population Density

10 cm
Find the population density

Determine the size of the quadrat (in m 2
)

◦ 10 cm x 10 cm = 100 cm 2 = 0.01 m 2
Count all individuals IN quadrat

◦ 22
Calculate population density number of individuals per square meter

22 𝑓𝑙𝑜𝑤𝑒𝑟𝑠
0.01 𝑚
2
= 2200 𝑓𝑙𝑜𝑤𝑒𝑟𝑠 𝑝𝑒𝑟 𝑠𝑞. 𝑚.



Grid Quadrat
◦ 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)





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%

http://www.slideshare.net/nirmalajosephine1/biology-form-4-chapter-8dynamic-ecosystem-part-3-42839437





Find the percent coverage
Count full squares
Now combine pieces to make full squares
Calculate percentage coverage
% =
= 𝑐𝑜𝑣𝑒𝑟𝑒𝑑
× 100 𝑡𝑜𝑡𝑎𝑙 𝑠𝑞𝑢𝑎𝑟𝑒𝑠
24
× 100 = 24%
100
1 m
18 14 22
24 24
15
1 2 14
3 4 15
17 21 23
19 20
12
13
16
13 17 18 5 6 12
7 8 9 10 11
16
19
21
23 20
22
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 many samples?


Obviously the more samples you collect, the more accurate your estimates for the entire ecosystem.
Generally collect enough quadrats that the number of species collected levels out

Time to Practice



Using Quadrats in Lab find the:
◦ Population Density
◦ Percent Frequency
◦ Percent Coverage
Estimating Percentage Coverage with
Quadrats Wkst
Random Sampling Lab

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!

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
𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥 = 𝑛
1
× 𝑛
2 𝑛 𝑚 𝑛
1
= 𝑛𝑢𝑚𝑏𝑒𝑟 𝑐𝑎𝑢𝑔ℎ𝑡 𝑓𝑖𝑟𝑠𝑡 𝑠𝑎𝑚𝑝𝑙𝑒 𝑛
2
= 𝑛𝑢𝑚𝑏𝑒𝑟 𝑐𝑎𝑢𝑔ℎ𝑡 𝑠𝑒𝑐𝑜𝑛𝑑 𝑠𝑎𝑚𝑝𝑙𝑒 𝑛 𝑚
= 𝑛𝑢𝑚𝑏𝑒𝑟 𝑚𝑎𝑟𝑘𝑒𝑑 𝑜𝑛 𝑠𝑒𝑐𝑜𝑛𝑑 𝑠𝑎𝑚𝑝𝑙𝑒

How to Capture Motile Organisms
REMEMBER: IB Animal Experimentation Policy

Pitfall Traps



Small Mammal Traps
Tullgren Funnels (invertebrates)
Kick Net

Capture – Mark – Recapture




Capture organisms and count
Mark organisms with non-toxic, semipermanent, 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

Assumptions



The population of organisms must be closed, no immigration or emigration.
The time between samples must be small compared to the life span of the organism
The marked organisms must mix completely with the rest of the population during the time between sampling.

Using Lincoln Index

In a woodland, the undergrowth was sampled for snails and 430 were found and marked.
They were then released and the population similarly sampled after a two-week period. This second sampling produced 410 snails, 100 of which were marked.



 n
1 n
2 m
2
= 430
= 410
= 100

N = 430 x 410 = 1763 snails
100

Using Lincoln Index

While studying field voles, an ecologist caught 500 and ringed a foot of each before releasing them. Every day for the next two weeks he examined the waste material found in the nests of their predators. He collected a total of 300 field vole skulls and
15 rings.

How many field voles were probably in the area examined?


N = 300 x 500 = 10,000
15

Use the Lincoln Index to monitor this mountain gorilla population over time:
Year 2003 2004 2005 2006 2007 2008 n
1 n
2 n m
P
23
25
18
26
30
22
27
35
21
16
18
15
18
19
16
17
24
17
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

LAB: Capture-Mark-Recapture &
Lincoln Index (Beans & Rice)

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

Simpson’s Diversity Index
D= N(N-1)
∑n(n-1)


D = diversity index
N = total number of organisms of all species found
 n = number of individuals of a particular species
You are not required to memorize this formula but must know the meaning of the symbols .

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
Daisy
Dandelion
Buttercup
Total (N)
Sample 1
300
335
365
1000
Find the diversity index for sample 1:
Sample 2
20
49
931
1000
𝐷 =
𝐷 =
𝑁(𝑁 − 1)
𝑛(𝑛 − 1)
1000(999)
300∙299 + 335∙334 +(365∙364)
𝐷 = 2.99

Using Simpson’s Index:
Numbers of individuals (n)
Flower Species
Daisy
Dandelion
Buttercup
Total (N)
Sample 1
300
335
365
1000
Sample 2
20
49
931
1000
Now, find the diversity index for sample 2:
𝐷 =
𝐷 =
𝑁(𝑁 − 1)
𝑛(𝑛 − 1)
1000(999)
20∙19 + 49∙48 +(931∙930)
𝐷 = 1.15

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
Orthoptera
(grasshopper)
Orthoptera
(grasshopper)
Lepidoptera
(butterfly)
Lepidoptera
(butterfly)
Coleoptera
(beetle)
Hymenoptera
(wasp)
Hymenoptera
(wasp)
Hymenoptera
(bee)
Description
Green with red legs
Brown with yellow stripe.
Large, blue
Small, blue
Red & Blue
Black
Purple
Striped
Meadow 1
16
5
26
3
12
Meadow 2
25
2
17
9
12
4
5

YOUR TURN Solution
Organism
Orthoptera
(grasshopper)
Orthoptera
Description
Green with red legs
Brown with
(grasshopper)
Lepidoptera
(butterfly)
Lepidoptera yellow stripe.
Large, blue
Hymenoptera
(wasp)
Small, blue
(butterfly)
Coleoptera (beetle) Red & Blue
Black
Hymenoptera
(wasp)
Purple
Hymenoptera (bee) Striped
Meadow 1
16
5
26
3
12
Meadow 2
25
2
17
9
12
4
5
𝐷
1
=
62(61)
16 ∙ 15 + 5 ∙ 4 + 26 ∙ 25 + 3 ∙ 2 + (12 ∙ 11)
=
3782
1048
= 3.6
𝐷
2
=
74(73)
25 ∙ 24 + 2 ∙ 1 + 17 ∙ 16 + 9 ∙ 8 + 12 ∙ 11 + 4 ∙ 3 + (5 ∙ 4)
=
5402
1110
= 4.9

Simpson’s Index

