Unpacking Goals

After working through Chapter 6 and looking at the content standards again, I've taken another look at my big ideas, the stated or implied real-world performances that go with the standards, and the essential questions that fit best with the standards.

BIG IDEAS:

1. Interconnections between species
2. The flow and cycling of resources (energy and nutrients) in ecosystems
3. Ecosystem responses to disturbance

REAL-WORLD PERFORMANCES:

Students should be able to...

• ANALYZE changes in an ecosystem.
• REPRESENT energy flow through an ecosystem, as in an energy pyramid.
• DISTINGUISH accommodation within individuals from genetic adaptation in a population. (I'm saving this for Unit 3 when we get into evolution.)
• DETERMINE the fluctuations in population size caused by birth, immigration, emigration, and death.

UNDERSTANDINGS:

Students should understand that...

• Ecosystems include a variety of different roles that can interact in complex ways. (Big Idea #1)
• Both negative interactions (competition, predation) and positive interactions (cooperation, mutualism) are important in shaping the structure of ecological communities. (#1)
• Different species use different survival strategies, which can be successful in very different ways (e.g., r-selection vs. K-selection; Type I, II and III survival curves).
• Species' populations can be regulated from the "bottom up" (by resource limitation) or from the "top down" (by predation and disease). (#1, #2)
• Nutrients cycle within the biosphere: carbon, nitrogen, oxygen, and water are reused again and again, with little "new" input or loss (though human CO2 production is a major exception!). (#2)
• Ecosystems are open-ended with respect to energy: producers obtain it from one source (almost always the sun) and pass it up the food chain, losing some energy to heat at every step. (#2)
• Some ecosystems depend on "keystone species", and that threatening these species threatens the entire structure of the community. (#3)
• Outside disturbance can upset the balance of an ecosystem, and that the degree of upset depends on both the magnitude of the disturbance and the robustness of the ecosystem. (#3)

ESSENTIAL QUESTIONS:

• How are different species dependent on each other?
• Why is preserving biodiversity important?
• What makes an ecosystem stable or vulnerable?
• How do resource needs constrain the structure of ecological communities?
• How can we protect ecosystems from damage, and when should we do so?

PERFORMANCE TASK IDEAS:

• Have students plot the flow of resources and/or interaction webs in sample ecosystems.
• Write the "biography of a nitrogen atom" (or a carbon atom, etc.) as it journeys through its nutrient cycle.
• Examine population data to determine if a species is at its carrying capacity in a particular ecosystem.
• Identify populations that are under "bottom-up" or "top-down" regulation.
• Study real-world systems where dramatic shifts have occurred in community structure, and identify likely causes for the change.
• Research an exotic species that has been introduced to California (chosen from a list) and present a report explaining whether it has become invasive, how they can tell, and what is being done to combat it (if anything).

At this point I think my Stage 1 picture looks pretty clear. Assuming that my coaches agree, I'll be ready to jump into Stage 2: designing the assessments that will allow my students to demonstrate their understanding of the material.