1. Topic 2.5: Investigating Ecosystems

2. Investigating Ecosystems
Review Zonation and Succession on your notes

3. How do we know what is going on inside an ecosystem?
    
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.

4. Monitoring Abiotic Factors
Ecosystems can be roughly divided into:-
Marine
Freshwater and
Terrestrial systems

5. Monitoring Abiotic Factors
Complete the diagram in your notes

6. 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

7. 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

8. 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.

9. COLLECTING DATA
Two methods used in ecology to determine where to collect a sample are:
Quadrats
Transects.

10. 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

11. 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

12. 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.

13. How do we decide where to measure?
Quadrats
Transects

14. 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%

15. 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)

16. 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%

17. Percent Coverage Percent Coverage Find the percent coverage
1 m
Percent Coverage
Find the percent coverage
Count full squares
Now combine pieces to make full squares
Calculate percentage coverage 18 14 22 24 24 1 2 14 15 3 4 15
1 m 17 21 23 12 19 20 13 13 17 18 5 6 12 16 7 8 9 10 11 22 19 23 20 16 12 21

18. 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

19. 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.

20. 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

21. Transects Look at changes over an environmental gradient e.g. zonation
Need more than 1 for a valuable results. (At least 3)

23. Where to transect? Random number generator. Random direction.
Unless you want to particularly follow a gradient.
Complete a transect of your ecosystem.

24. 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.

25. 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!

26. Primary Productivity
Different methods for terrestrial and aquatic habitats.
Find three identical (ish) areas
Dig up one and calculate its biomass.
Cover one with black plastic, and leave one open.
A set amount of time later measure the biomass of the two site.
Initial – Light = NPP
Initial – Dark = Respiration
Light – Dark = GPP

28. 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.

29. Catching motile organisms
    
Catching motile organisms

30. Terrestrial Aquatic Pitfall Traps Sweep nets Tree Beating
Tullgren Funnels (invertebrates)
Kick sampling

31. Pitfall Trap Insects and other small invertebrates
Placed in a transect
Number of each species recorded
No fluid in the bottom

32. Sweep nets

33. Tree Beating

34. Kick sampling

35. Estimating abundance of motile organisms
Direct methods: actual counts and sampling
Indirect methods: Lincoln index

36. Percentage cover

37. 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

38. Lincoln Index 𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥= 𝑛 1 × 𝑛 2 𝑛 𝑚 Capture-mark-recapture
𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥= 𝑛 1 × 𝑛 2 𝑛 𝑚
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

39. 𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥= 𝑛 1 × 𝑛 2 𝑛 𝑚 Assumptions: Mixing is complete
𝐿𝑖𝑛𝑐𝑜𝑙𝑛 𝐼𝑛𝑑𝑒𝑥= 𝑛 1 × 𝑛 2 𝑛 𝑚
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.

40. Your Turn
Use the Lincoln Index to monitor this mountain gorilla population over time:
Year
2003
2004
2005
2006
2007
2008 n1 23 26 27 16 18 17 n2 25 30 35 19 24 nm 22 21 15 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.

41. 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

42. Species richness and diversity
Richness is the number of species
Diversity is number of species and the individuals in each species.

43. 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

44. Number of individuals of species
𝐷= 𝑁(𝑁−1) 𝑛(𝑛−1)
Simpson diversity index
D = Simpson diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
Calculate the diversity index for both ecosystems
Number of individuals of species A B C
Ecosystem 1: 25 24 21
Ecosystem 2: 65 3 4

45. 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.

46. 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

47. 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
Find the diversity index for sample 1:
𝐷= 𝑁(𝑁−1) 𝑛(𝑛−1)
𝐷= 1000(999) 300∙ ∙334 +(365∙364)
𝐷=2.99

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

49. 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.

50. YOUR TURN
The insects in two meadows are being investigated. The following data was collected. Compare the diversity of the two meadows
Organism
Description
Meadow 1
Meadow 2
Orthoptera (grasshopper)
Green with red legs 16 25
Brown with yellow stripe. 5 2
Lepidoptera (butterfly)
Large, blue 26 17
Small, blue 3 9
Coleoptera (beetle)
Red & Blue 12
Hymenoptera (wasp)
Black
Purple 4
Hymenoptera (bee)
Striped

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

52. How do you identify what you have found?

53. 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

54. Why do we classify? Identify organisms Compare organisms
Identify relationships among organisms
Communicate with others (universal language)
Identify evolutionary relationships

55. 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.

56. Dichotomous keys

57. Dichotomous Keys

58. 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

59. 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.

60. 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.