AP Environmental Science Free-Response Question



AP Environmental Science Free-Response Question

Section II

Time---22 minutes

Directions: Answer the whole question, which is weighted equally. Write all your answers on notebook paper. BE SURE TO LABEL EACH SECTION OF THE QUESTION AND TO ANSWER EACH SECTION. Where calculations are required, clearly show how you arrived at your answer. Where explanation or discussion is required, support your answers with relevant information and/or specific examples.

1. A food web is made of many different niches: decomposers, consumers (primary, secondary, tertiary…), and producers. Discuss each of these niches in the following ways:

a) Explain what each niche’s job is in the ecosystem.

b) Diagram a food chain containing at least 4 real organisms AND identify the niche of each.

c) Diagram a trophic pyramid using the same 4 organisms.

d) Assume the biomass of the organism at the bottom of your trophic pyramid is 5,000 lbs. Predict the approximate mass of each of the remaining levels, and explain WHY the mass is changing. (Where calculations are required, clearly show how you arrived at your answer.)

Scoring Guidelines

(a) 3 points possible

A food web is made of many different niches: decomposers, consumers (primary, secondary, tertiary…), and producers. Discuss each of these niches in the following ways:

(a) Explain what each niche’s job is in the ecosystem.

1 point each for correctly identifying each organism’s niche.

|Producers (autotrophs) |make their own food from compounds and energy obtained from their environment |

| |most species capture sunlight to produce carbohydrates by photosynthesis |

|Must include the 1st or 2nd bullet to |are the source of all food chains |

|gain a point. |on land, most producers are green plants |

| |in freshwater & marine ecosystems, algae and plants are the major producers near shorelines |

| |in open water, the dominant producers are phytoplankton |

|Consumers (heterotrophs) |organisms that get energy & nutrients they need by feeding on other organisms or their remains |

| |primary consumers (herbivores), such as rabbits & zooplankton, eat producers |

|Must include the 1st bullet & depict |secondary consumers (carnivores), such as foxes & fish, feed on herbivores |

|b/w 1, 2, & 3rd consumers to gain a |tertiary & higher level consumers are carnivores that feed on other carnivores |

|point. |omnivores play dual roles by feeding on both plants and animals. |

|Decomposers |mostly certain types of bacteria & fungi |

| |are specialized consumers that recycle nutrients in ecosystems |

|Must include the 2nd or 3rd bullet to |they secrete enzymes that digest or biodegrade living or dead organisms into simpler inorganic compounds that producers can |

|gain a point. |take up from the soil and water and use as nutrients |

| |other consumers called detritivores are insects and other scavengers that feed on the wastes or dead bodies of other |

| |organisms |

| |in natural ecosystems, there is little or no waste--one organism’s wastes serve as resources for other organisms, as the |

| |nutrients that make life possible are recycled again and again. |

(b) 3 points possible

(b) Diagram a food chain containing at least 4 real organisms AND identify the niche of each.

Producers

Decomposers

Primary consumer

Secondary consumer

2 points for correctly identifying four organisms of a food chain/web AND showing the proper connections.

1 point each for the following:

• identifying 4 suitable organisms in a food chain

• placing arrows in the correct direction of energy flow (arrows point to the eater)

• labeling trophic levels

_______________________________________________________________________

(c) 1 point possible

(c) Diagram a trophic pyramid using the same 4 organisms.

OR

1 point for the following:

• producer on the bottom

• labeling of trophic levels

• must show biomass loss with each tier (must form a pyramid—size in tiers decrease as you move up)

__________________________________________________________________________________________________

(d) 3 points possible

(d) Assume the biomass of the organism at the bottom of your trophic pyramid is 5,000 lbs. Predict the approximate mass of each of the remaining levels, and explain WHY the mass is changing. (Where calculations are required, clearly show how you arrived at your answer.)

1 point each for the following:

• clearly showing calculations

• correctly labeling the biomass amounts at each trophic level with units

• explanation of the 10% rule

|10 percent rule or ecological |The percentage of usable energy transferred as biomass from one trophic level to the next is called ecological efficiency |

|efficiency |where 10% is typical—only 10% of biomass at one level is transferred to usable biomass at the next level (90% is lost as |

| |mostly heat). |

|Must include at least the 1st bullet |Energy transfer is not efficient—with each transfer energy is degraded and lost to the environment as low-quality heat (2nd |

|to gain a point OR include the 2nd & |law of thermodynamics). |

|3rd bullets together. |Only a small portion of what is eaten & digested is actually converted into an organism’s bodily material or biomass, and |

| |the amount of usable energy available to each successive trophic level declines. |

| |The more trophic levels in a food chain or web, the greater the cumulative loss of usable energy as energy flows through the|

| |trophic levels. |

| |This explains why food chains and webs rarely have more than four or five trophic levels--too little energy is left after |

| |four or five transfers to support organisms feeding at these high trophic levels. |

-----------------------

coyotes

rabbits

plants

Decomposers are found at each consumer trophic level.

5 lbs.

50 lbs.

5,000 lbs.

500 lbs.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download