Module: Succession
DCI: LS2.C (A) A complex set of interactions within an ecosystem
can keep its numbers and types of organisms relatively constant over long
periods of time under stable conditions. If a modest biological or physical
disturbance to an ecosystem occurs, it may return to its more or less original
status (i.e., the ecosystem is resilient), as opposed to becoming a very
different ecosystem. Extreme fluctuations in conditions or the size of any
population, however, can challenge the functioning ecosystems in terms of
resources and habitat availability.
PE: HS-LS2-2 Use mathematical representations to support and revise
explanations based on evidence about factors affecting biodiversity and
populations in ecosystems of different scales.
PE: HS-LS2-6 Evaluate the claims, evidence, and reasoning that the
complex interactions in ecosystems maintain relatively consistent numbers and
types of organisms in stable conditions, but changing conditions may result in
a new ecosystem.
[Clarification
Statement: Examples of mathematical representations include finding the
average, determining trends, and using graphical comparisons of multiple sets
of data.] [Assessment Boundary: Assessment is limited to provided data.]
[Clarification
Statement: Examples of changes in ecosystem conditions could include modest
biological or physical changes, such as moderate hunting or a seasonal flood;
and extreme changes, such as volcanic eruption or sea level rise.]
No idea why this module is called "Succession". The content here is about how ecosystems respond to disturbances or remain stable. It is more like "homeostasis". Succession is a natural progression or change in biodiversity. Succession may start in response to an even (forest fire) but the term describes the kinds of plants that first grow in a region and how they change over time.
The ideas in this standard are:
The ideas in this standard are:
- interactions within an ecosystem help keep the number of organisms relatively constant over long periods of time under stable conditions.
- interactions within an ecosystem help keep the types of organisms relatively constant over long periods of time under stable conditions.
- if a modest biological disturbance occurs, it may return to its original status
- if a modest physical disturbance occurs, it may return to its original status
- extreme fluctuations in conditions can challenge the functioning ecosystem
- extreme fluctuations in the size of any population can challenge the functioning ecosystem
So we also need to focus on the fact that in many cases, the ecosystem will remain stable. We should have students looking at population numbers, habitat distribution, availability of resources, etc in order to represent the factors that affect changes to populations or biodiversity. We can also have them come up with evidence that would support that the ecosystem is remaining stable over time, or that a change in conditions may result in a shift in the ecosystem. We should not simply be asking students to list the steps in primary or secondary succession, or comparing the two, etc.
Possible Questions:
We might be able to get away with one or two "general" questions. Something like...
"What is the most reasonable prediction for what would be observed in a stable ecosystem two years after (modest disturbance)?
correct answer - types and number of organisms will be the same as before the earthquake
"Which of the following events is most likely to have an effect on the numbers and types of organisms living in a seashore habitat?"
"What is the most reasonable prediction for what would be observed in a stable ecosystem two years after (modest disturbance)?
correct answer - types and number of organisms will be the same as before the earthquake
"Which of the following events is most likely to have an effect on the numbers and types of organisms living in a seashore habitat?"
correct answer - a sea level rise of several inches over a few years
incorrect answer - high wind speeds as the result of a tropical storm
We should ask more than one question about "What data would be needed to evaluate the claim that (some change) affects (some aspect of an ecosystem?"
Perhaps, also, some data on populations of different organisms that fluctuate over several years. Most of it is minor ups and downs. Some data shows a reaction to something. We ask what claim the data will support.
The correct answer would be something like "grazing by cattle in the area reduced resources available to some organism"
We should ask more than one question about "What data would be needed to evaluate the claim that (some change) affects (some aspect of an ecosystem?"
Perhaps, also, some data on populations of different organisms that fluctuate over several years. Most of it is minor ups and downs. Some data shows a reaction to something. We ask what claim the data will support.
The correct answer would be something like "grazing by cattle in the area reduced resources available to some organism"
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