2.5 investigating ecosystems notes

IB Environmental Systems and Societies p. 1
Topic 2: Ecosystems and Ecology (25 hours)
2.5 Investigating Ecosystems
Significant Ideas:
➔ The description and investigation of ecosystems allows for comparisons to be made between different
ecosystems and for them to be monitored, modeled, and evaluated over time, measuring both natural
change and human impacts.
➔ Ecosystems can be better understood through the investigation and quantification of their
components.
Knowledge & Understanding: Use these notes to familiarize yourself with ESS terminology and concepts.
2.5.1 The study of an
ecosystem requires that it
be named and located, for
example Deinikerwald in
Baar, Switzerland – a mixed
deciduous – coniferous
managed woodland.
Name a protected and studied ecosystem in your home country (or Tanzania!).
Name:
Location (draw map in box):
Biome type:
Famous/protected flora and fauna:
Other significant features:
Original Source: International School of Prague
https://sites.google.com/site/environmentalsystemssocieties/home
Modified by Brad Kremer, May 2017

2.5.2 Organisms in an
ecosystem can be identified
using a variety of tools
including keys, comparison
to herbarium or specimen
collections, technologies
and scientific expertise.
Why is species identification an important part of studying an ecosystem and its
biodiversity?
A. Dichotomous Key
B. Herbarium
C. Specimen collection
2.5.3 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).
Briefly fill in the following table:
Sampling Method Target Organism(s) Resulting Information
TRANSECTS
(line or belt)
QUADRATS
Non-motile (non-
moving) e.g. plants,
sea urchins
CAPTURE - MARK -
RECAPTURE
Motile organisms
(birds, fish,
mammals)

2.5.4 Measurements should
be repeated to increase
reliability of data. The
number of repetitions
required depends on the
factor being measured.
Using the targets below as a metaphor for experimental data, use the terms
valid/invalid and reliable/not reliable to describe each set of “data”. [hint: valid
is how close the data comes to the true value (also called accuracy) and reliable
is how repeatable each data point is (also called precision)]
2.5.5 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.
Explain the reason behind the inverted biomass pyramid from the English
Channel.

2.5.6 Methods for
estimating the abundance
of non-motile organisms
include the use of quadrats
for making actual counts,
measuring population
density, percentage cover
and percentage frequency.
For each measurement, explain what the term means, the units of measure,
and any applicable formulas. Recall your experience with the random sampling
stations in class. Use the sample quadrats below to help you drawn an example
of how each measurement could be taken.
POPULATION DENSITY:
PERCENT COVER:
PERCENT FREQUENCY:

2.5.7 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.
Estimate the size of the population of mice using the circles below. Calculate the
percent error.
2.5.8 Species richness is the
number of species in a
community and is a useful
comparative measure.
Which ecosystem (A or B) is more RICH? Explain. Which ecosystem is more EVEN
and what does this mean?

2.5.9 Species diversity is a
function of the number of
species and their relative
abundance and can be
compared using an index.
Students are only expected
to be able to apply and
evaluate the result of the
Simpson diversity index.
Using this formula, the higher the result (D), the greater the species diversity.
This indication of diversity is only useful when comparing two similar habitats,
or the same habitat over time.
Define each variable in this formula. Explain which term represents evenness
and which term represents richness.
Applications and skills – these will be addressed with practice labs, class and/or field investigations, and real
exam questions – you may leave the spaces blank for now.
2.5.AS1 Design and carry out ecological investigations.
2.5.AS2 Construct simple identification keys for up to eight species.
2.5.AS3 Evaluate sampling strategies.
2.5.AS4 Evaluate methods to measure at least three abiotic factors in an ecosystem.
2.5.AS5 Evaluate methods to investigate the change along an environmental gradient and the effect of a
human impact in an ecosystem.
2.5.AS6 Evaluate methods for estimating biomass at different trophic levels in an ecosystem.
2.5.AS7 Evaluate methods for measuring or estimating populations of motile and non-motile organisms.
2.5.AS8 Calculate and interpret data for species richness and diversity.
2.5.AS9 Draw graphs to illustrate species diversity in a community over time, or between communities.

2.5 investigating ecosystems notes

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