ECOLOGY QUESTION 1989:			L. PETERSON/AP BIOLOGY

	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 -> 10 consumer -> 20 consumer -> 30 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