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1983 1984 1985 1986 1989
ECOLOGY QUESTION 1983: L. PETERSON/ECHS Describe the trophic levels in a typical ecosystem. Discuss the flow of energy through the ecosystem, the relationship between the different trophic levels, and the factors that limit the number of trophic levels. STANDARDS: DESCRIPTION AND SYSTEM RELATIONSHIPS: Max. = 8 points Define and/or identify: __ producers __ consumers (herbivores - carnivores - omnivores) __ decomposers Identification of: __ autotrophs __ heterotrops Define: __ trophic level __ Complex system Comparisons (Pyramids): __ organism (numbers) __ organism (size) __ organism (biomass) __ inverted, numbers and/or biomass __ Material Cycling __ Description of food chain and/or web ENERGY FLOW IN THE SYSTEM: Max. = 6 points __ source __ process (photosynthesis) __ producers support the system __ energy loss __ quantification of loss Use of Energy: __ heat __ metabolic __ building compounds __amount of energy contained (comparative) Relationship of R: __ Prnet __ Prgross LIMITING FACTORS: (No Max.) __ Energy (2 points) __ Change in Prnet __ Change in Prgross __ Biomass (materials) __ Producer numbers __ Efficiency
ECOLOGY QUESTION 1985: L. PETERSON/ECHS Describe the process of ecological succession from a pioneer community to a climax community. Include in your answer a discussion of species diversity and interactions, accumulation of biomass, and energy flow. STANDARDS: DESCRIPTION __ Definition of Succession __ Differentiation (Primary/Secondary) Examples: __ Pioneer __ Climax __ Sere (two or more examples = 2 points) __ Modification of the environment SPECIES DIVERSITY __ Explanation of increase __ Types of Competition (or Niche) __ Examples __ Change in Population Density __ Description of Food Web __ R-Strategists -> K-Strategists (2 points) __ Change in Symbiotic Relationships (increase toward mutualisms) BIOMASS __ Production increase and explanation (2 points) __ Levels of Organizationm (Autotrophs & Heterotrophs) __ Examples of Producers (etc.) __ Pyramid or Explanation ENERGETICS __ Source (Sun) __ Utilization - Photosynthesis __ Explanation of Decrease (entropy -unused) OR Pyramid + Explanation __ Climax Stability (Dynamic Equilibrium) __ P/R toward 1 __ Net Productivity Decrease
ECOLOGY QUESTION 1986: L. PETERSON/ECHS Describe the biogeochemical cycles of carbon and nitrogen. Trace these elements from the point of their release from a decaying animal to their incorporation into a living animal. STANDARDS: The question was divided into two sections for grading, with a maximum number of points of 8 per section. For each maximum assigned, there were more points possible to allow the student several ways to reach the maximum. For the CARBON CYCLE, it was possible to earn points for each of the following statements or ideas: __ Explanation of the role of green plants as producers __ Mention of herbivores in a way that indicated an understanding of their role __ An indication that carnivores obtained C from herbivores __ Discussion of the role of decomposers in returning C to the atmosphere as CO2 __ Mention of CO2 production via respiration of green plants, herbivores or carnivores __ Discussion of the C in oil, natural gas, and coal as originating from the remains of organisms __ Mention of CO2 release to the atmosphere through the burning of fuel or through release of C from limestone. __ Discussion of the existence of dissolved CO2 in the bodies of water on the earth. __ An indication that human activity had a significant impact on the carbon cycle. In the case of the nitrogen cycle, there were 14 possible points from which it was possible for the student to earn the maximum of 8 for that portion of the questions. __ An indication that organic molecules were broken down to amino acids after death __ Discussion of deamination __ Mention of NH4+ as the product of deamination __ Indication that ammonium ion can be converted to nitrate (a second point if there is inclusion of the further oxidation to nitrate) __ Discussion of denitrification __ Mentioning the role of microbes, industry, or lightning in affecting atmosheric nitrogen. __ Understanding that when nitrogen gas is fixed, it is converted to the ammonium ion. __ Indication that nitrate or nitrite or ammonium ions can be taken up by organisms __ Mention of nitrogen loss to living organisms which results from burning or leaching __ Indication that plants use absorbed nitrogen to make proteins __ An understanding of the conversion by animals of plant proteins into animal proteins __ Indication that on death or in excretion organic nitrogen is released into the environment. __ Indication of a significant impact of human activity on the nitrogen cycle.
ECOLOGY QUESTION 1989: L. PETERSON/ECHS Using an example for each, discuss the following ecological concepts. a) Succession b) Energy flow between trophic levels c) Limiting factors d) Carrying capacity STANDARDS: a) SUCCESSION: Max. = 3 points __ Definition: demonstrate process of change in communities through time __ modification of environment/transition of species composition __ Examples: generalized - lake -> marsh -> meadow -> forest specific - lichen -> moss -> herbs -> shrubs -> forest __ Primary - no life/soil -> pioneer organisms/soil development __ Secondary - disturbance -> climax/stable community b) ENERGY FLOW BETWEEN TROPHIC LEVELS: Max. = 3 points __ Examples: grass -> locust -> mouse -> snake grass -> herbivore -> carnivore -> detritivore producer -> 1' consumer -> 2' consumer -> 3' consumer food chain/web - elaboration of trophic levels __ Producers (autotrophs) start energy flow __ Consumers (heterotrophs) acquire energy from primary producers __ Productivity - measure of rate at which energy is converted from radiant to biomass and kinetic energy of action or PG - R = PN __ Efficiency - 10% rule/90% energy loss or pyramid of energy c) LIMITING FACTORS: Max. = 3 points __ Definition: any factor operating to restrict population growth Examples: __ biotic - population density, competition, predation __ abiotic - moisture, temperature, weather/climate, wind, sunlight, soil, topography, geographic location, nutrients __ density-dependent - change birth/death rate as density changes __ density-independent - change birth/death rate regardless of density d) CARRYING CAPACITY: Max. = 3 points __ Definition: number of individuals of a population (species) sustainable by an environment (as long as the environment remains the same) __ Examples: predator/prey; rabbits in Australia; deer on Kaibab; human population; __ Limiting factor(s) determine carrying capacity (competition, waste, predation) __ Population grows -> rate slows -> stabilize (N decreases) or __ Population falls -> growth resumes -> stabilizes (N decreases) or __ dN/dt = rN (K-N/K) with explanation or graph with explanation __ K/r strategies related to carrying capacity