MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Which of the following is a complete and correctly organized food chain?

a. alfalfa ˆ grasshopper ˆ cow ˆ bot fly ˆ barn swallow

b. barley ˆ aphid ˆ ladybird beetle

c. grass ˆ grasshopper ˆ warbler ˆ praying mantis

d. algae ˆ fish ˆ coyote ˆ snake

e. aspen ˆ bacteria ˆ grasshopper ˆ warbler

Correct Answer: b

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Which of these describes a pathway of energy through the living system?

a. Light energy ˆ chemical energy ˆ heat.

b. Light energy ˆ heat ˆ chemical energy.

c. Heat ˆ light energy ˆ chemical energy.

d. Chemical energy ˆ heat ˆ light energy.

Correct Answer: a

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Which of the following statements best describes the work done by decomposers?

a. They provide calcium for plants by taking it from the soil or water.

b. They release carbon from dead bodies in the form of carbon dioxide.

c. They create new sources of oxygen and release free nitrogen.

d. They prevent the escape of energy to outer space.

Correct Answer: b

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Which organisms are most immediately necessary for the survival of primary consumers?

a. Producers

b. Decomposers

c. Secondary consumers

d. Tertiary consumers

Correct Answer: a

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Which of the following statements is true regarding ecosystems?

a. Ecosystems support a larger number of heterotrophs than autotrophs.

b. The presence or absence of carnivores has a greater effect on ecosystems than the presence or absence of producers.

c. There are more organisms in the third trophic level than in the second trophic level.

d. The number of organisms decreases at each level of a food chain in an ecosystem.

Correct Answer: d

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

What happens to the amount of available energy at each level of a food chain?

a. The amount of available energy increases at each level.

b. The amount of available energy decreases at each level.

c. The amount of available energy remains the same at each level.

d. The amount of available energy changes depending on the number of organisms in the level.

Correct Answer: b

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

What would you predict might happen in an ecosystem if the number of organisms in the third trophic level exceeded the number of organisms in the second trophic level?

a. Nothing would change.

b. The number of organisms in the second trophic level would increase.

c. The number of organisms in the third trophic level would continue to increase.

d. The number of organisms in the third trophic level would decrease.

Correct Answer: d

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

In a food chain, which trophic level would have the greatest amount of available energy?

a. First

b. Second

c. Third

d. Fourth

Correct Answer: a

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

In a food chain, which trophic level would contain the greatest number of organisms?

a. First

b. Second

c. Third

d. Fourth

Correct Answer: a

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Which statement most accurately describes what happens to energy as it moves through an ecosystem?

a. It is returned to the environment in the form of heat.

b. It increases as it moves through each level of the food chain.

c. It is used up by the time it reaches the third trophic level.

d. Each organism uses 50% of the energy and stores 50% to be used by other organisms.

Correct Answer: a

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

In order to construct your own food web, what information do you need to know?

a. how many organisms of each species

b. where the organisms live

c. how long they have lived

d. what the organisms consume

Correct Answer: d

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

In areas of southern California where humans have heavily hunted sea lions, killer whales (which normally hunt sea lions) are preying on sea otters. Which statement best describes why killer whales are hunting sea otters?

a. Sea otters are now easier to locate, hunt and kill than sea lions.

b. Sea otters provide more nourishment than killer whales.

c. Sea lions have evolved adaptations that protect them from killer whales.

d. Killer whales prefer sea otters over sea lions.

Correct Answer: a

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Use the following key to answer the questions that follow:

KEY:

a. First-order consumers

b. Second-order consumers

c. Producers

d. Decomposers

_____ 1. Able to capture energy in the process of photosynthesis.

_____ 2. Organisms in a food web most likely to show an increase in number first.

_____ 3. Collects and converts carbohydrates to protein

_____ 4. Mice that eat grass

_____ 5. Hawks that eat mice who eat grass

_____ 6. Mosquitoes that bite cows

_____ 7. Organisms that digest dead plant and animal tissues

_____ 8. Purple bacteria which convert CO2 to cell substances, but utilize H2S instead of H2O

_____ 9. Carbon is made available to most organisms by the activities of these

_____ 10. Has the ability to change light energy to chemical energy

_____ 11. Most of these organisms are microscopic

Correct Answers:

1. c

2. c

3. a

4. a

5. b

6. b

7. d

8. c

9. c

10. c

11. d

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Use the following key to classify the statements below:

KEY:

a. Producers

b. Consumers

c. Both consumers and producers

d. Neither consumers nor producers

_____ 1. Convert light energy into chemical energy

_____ 2. Supply food for consumers

_____ 3. Use the energy of sunlight to manufacture food

_____ 4. Have the ability to create energy

_____ 5. Are unable to make their own food

_____ 6. Have the ability to store energy in chemical bonds

_____ 7. Depend on organic molecules for food

Correct Answers:

1. a

2. c

3. a

4. d

5. b

6. c

7. b

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Arctic terns migrate from their breeding grounds in the Arctic during the summer to South America for the winter. Which statement best describes the function of the migration?

a. Birds are warm blooded, and temperatures are too cold in the Arctic for the birds to survive.

b. Their energy needs can be met at either location; the birds are choosing a new habitat based on changes in weather.

c. The birds require a different habitat for breeding and nesting.

d. Energy requirements for the term cannot be met in the Arctic during the winter.

Correct Answer: d

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Marmots hibernate when temperatures fall below 15.5 degrees Celsius. During hibernation, marmots breathe very slowly, circulation of blood is reduced, body temperature drops, and they are able to survive on their own reserves of fat. Which statement best describes the main adaptive advantage of hibernation?

a. Temperatures in the forest drop too low for the marmot to survive the winter.

b. Hibernation allows the marmotsÕ bodies to recover from the stress of summer.

c. Many predators are active during the winter; hibernation allows the marmot to avoid being eaten.

d. Food sources are scarce in the winter; the marmot would expend debilitating amounts of energy trying to obtain food.

Correct Answer: d

MC	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

When wolves are introduced into a new area, they often will drive resident coyote populations typically decline. Which of the statements below is the best explanation for the wolvesÕ behavior?

a. Coyotes compete with wolves for the same prey base. Because wolves are bigger and stronger, they out compete for coyotes for major food sources.

b. Coyotes and wolves both use dens to protect their young. But wolves quickly occupy all available den sites.

c. If the coyotes do not leave, wolves will actually chase the adults away.

d. Wolves and coyotes are both in the genus Canidae, but because wolves are characteristically social animals, they are able to dominate the coyote population.

Correct Answer: a

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Study the following diagram and answer the questions that follow:

Questions:

1. In this food web, the hawk would be a third-level consumer if he ate

a. Seed-eating birds

b. Pocket gophers

c. Rabbits

d. Snakes

2. In terms of numbers of individuals, you would expect to find more

a. Snakes than gophers

b. Frogs than insects

c. Insects than insect-eating birds

d. Coyotes than rabbits

3. The best examples of primary consumers would be

a. Insects and seed-eating birds

b. Rabbits and owls

c. Gophers and frogs

d. Insects and spiders

4. Spiders and snakes are best classified as

a. Producers

b. Primary consumers

c. Second-level consumers

d. Third-level consumers

5. The role of the shrubs and grasses in the food web is best described as

a. An animal shelter

b. A source of seeds

c. A source of energy

d. A place for nests

6. As diagramed a fourth-level consumer is represented by the

a. Lice

b. Hawks

c. Snakes

d. Frogs

7. The total weight of all the organisms in each group would be the greatest for the

a. Mice

b. Rabbits

c. Grass

d. Decomposers

Correct Answers:

1. d

2. c

3. a

4. c

5. c

6. a

7. c

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

1. In the food web above, which level will be found in greatest numbers?

a. producers

b. level 1 consumers

c. level 2 consumers

d. level 3 consumers

2. Which of the following appear to be level 2 consumers?

a. elk, rabbit, cricket

b. mountain lion, snake, hawk

c. owl, frog, cricket

d. elk, mountain lion, rabbit

3. Which of the following appear to be a third level consumer?

a. mountain lion

b. elk

c. frog

d. hawk

4. At which level will the most energy be available?

a. producers

b. level 1 consumers

c. level 2 consumers

d. level 3 consumers

5. Which level will be found in least numbers?

a. producers

b. level 1 consumers

c. level 2 consumers

d. level 3 consumers

6. At which level will the least energy be available?

a. producers

b. level 1 consumers

c. level 2 consumers

d. level 3 consumers

Correct Answers:

1. a

2. b

3. d

4. a

5. d

6. d

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Questions 1-3 refer to the diagram below. For each question, choose the letter of the word or phrase that best completes the statement or answers the question.

1. The diagram is an example of

a. Biomass pyramid

b. Energy pyramid

c. Food chain pyramid

d. Biomass triangle

2. Suppose 12, 970 kilocalories of energy were available to the organisms at the bottom level of the diagram. How many kilocalories of energy would be available to the organisms at the third level?

a. 1.297

b. 12.97

c. 129.7

d. 1,297

3. Because of the Second Law of Thermodynamics, which statement is true of food chains?

a. Food chains generally do not contain more than four or five levels.

b. Food chains can continue indefinitely.

c. Much of the energy obtained by organisms is stored as heat.

d. Heat given off by organisms can be used by other organisms.

Correct Answers:

1. b

2. c

3. a

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Questions 1-3 refer to the food chain pictured below. Choose the word or phrase that best completes the statement or answers the question.

1. How many trophic levels does the food chain include?

a. one

b. two

c. three

d. four

2. As matter and energy move from grasses to hawks, the amount of available energy

a. always decreases but population size at each level may increase or decrease.

b. always increases and population size at each level always decreases.

c. always decreases and population size at each level always decreases.

d. increases or decreases but population size remains the same.

3. Suppose 100,000 units of energy are available at the level of the grasses. What is the total number of energy units lost by the time energy becomes available to the hawk?

a. 99,000

b. 99,900

c. 900

d. 90

Correct Answers:

1. d

2. c

3. b

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

1. In this illustration of a typical pyramid, the Gambusia fish that were stocked in a pond to control the mosquito larvae would occupy what level?

a. second carnivore

b. first carnivore

c. herbivore

d. producer

2. The algae now blooming in the pond occupy which level?

a. second carnivore

b. first carnivore

c. herbivore

d. producer

Correct Answers:

1. a

2. d

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

The United States has been asked to send relief food supplies to Afghanistan to help that country feed the people who are living in refugee camps. Two choices of relief packages are listed in the table below.

Relief Package A	Relief Package B
Grains such as wheat, oats, barley, rice, corn	Meats, milk, fish products

1. Considering only costs of production and transport per unit of energy and assuming preservation and storage is not a problem, which of the relief packages would be the best choice to send to that country?

a. Package A

b. Package B

2. Essay question: Justify your answer in item #1 by comparing the energy available to the people of Afghanistan for each relief package.

Correct Answers:

1. a

2. Scoring rubric:

3 points Student has correctly identified Relief Package A as the best choice.

3 points Student clearly understands that energy is lost at each level of the food chain and uses that argument to justify his/her choice of Relief Package A.

3 points Student has correctly compared the two relief packages and presented logical arguments for eliminating Relief package B.

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Brown bats have a wide range of heart rates. For example, at rest the heart rate is a little more than 450 beats per minute. The graph below shows what happens to a brown batÕs heart rate during flight and at the end of flight.

1. What is the first change that occurs in the batÕs heart rate during flight?

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. How long does it take for the heart rate to reach its maximum?

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3. How long does the bat fly?

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4. After the flight, how long does it take the batÕs heart rate to stabilize at its resting rate?

____________________________________________________________________________________________________________________________________________________________

5. What hypothesis could you propose to explain the difference between the resting heart rate and the flight heart rate?

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6. What is the advantage of the increased heart rate in meeting the brown batÕs energy requirements?

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Correct Answers:

1. Heart rate increases to 1200 beats per minute.

2. About 1 second to reach maximum rate.

3. About 2.5 seconds

4. About 4 seconds

5. Just as when humans exercise, the high oxygen demand during the batÕs flight requires the heart to beat more rapidly.

6. The energy expenditure required for increased heart rate during flight is balanced by the amount of energy obtained.

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Questions 1-3 refer to the diagram of the diet of black bears in Arizona. Choose the letter of the word or phrase that best completes the statement or answers the question.

Seasonal Black Bear Foods

1. Which food source is used the most during the fall season?

a. Animal matter

b. Grasses, sedges, and herbs

c. Fruits, nuts, and acorns

d. Buds, flowers, and young plants

2. Which statement best explains why the bearsÕ diet changes from spring to summer?

a. Bears prefer animal matter.

b. Animal matter is more readily available in the summer, but not in the spring.

c. Fruit is available in the summer.

d. All the grasses, sedges, and herbs die out in the summer.

3. Which statement best describes how bears obtain energy?

a. Bears eat only certain foods in each season.

b. Bears will selectively search for only those foods that fulfill their nutritional requirements.

c. Bears prefer foods that are high in protein, but will eat other foods.

d. Bears eat a variety of foods based on what is most readily available.

Correct Answers:

1. c

2. b

3. d

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Title: Analysis of a Food Web

Name _______________________________ Period ____________

__________red-tailed hawk coyote badger

__________meadowlark gopher  snake catface spider sagebrush lizard

__________caterpillars grasshoppers beetles mice jackrabbit

__________rabbit brush clovers grasses sagebrush Indian paintbrush

The above organisms belong to a food web found in a typical northern Utah valley.

1. Label each trophic level of the food web (pyramid) shown above in the space provided to the left. Draw arrows indicating the direction of energy flow between the organisms.

2. Describe each of the four trophic levels in the space below.

3. From the food web, choose one food chain and write it in the space below.

4. Describe how energy is stored at the first trophic level and in what form it is transferred through the other levels.

5. If 20 000 units of energy are available at the first level, how much energy would be available for use by organisms at the last level?

6. What will happen to the energy consumed by those at the top of the food web?

7. Does energy cycle through an ecosystem or does it flow through an ecosystem? Explain your answer.

Correct Answers:

1.

Top Carnivores red-tailed coyote  badger

hawk

3rd order consumers

Carnivores meadowlark gopher  snake  catface sagebrush

spider lizard

2nd order consumers

Herbivores caterpillars  grasshoppers beetles  mice  jackrabbit

1st order consumers

Producers rabbit brush  clovers  grasses  sagebrush  Indian

paintbrush

2.

Producers - use photosynthesis to make their own food.

Herbivores (1st order consumers) - eat producers directly

Carnivores - (2nd order consumers) - eat other consumers

Top Carnivores - (3rd order consumers) - end of food chain

3. Example: grass -----> mouse -----> gopher snake -----> red-tailed hawk

4. Grass traps light energy and uses it to produce carbohydrates. The mouse eats grass seeds containing those carbohydrates and uses the nutrients to build muscle tissue. The gopher snake consumes the mouse and digests the muscle tissue for use in making its own protein, muscles, etc.. The hawk consumes the snake and does the same.

5. 6.90% of the energy found at each level is lost to metabolism or to the environment as heat and is not available to the next level. Only 10% is passed to each new level. If producers contained 20 000 energy units, then 2 000 units are available to herbivores, 200 units to carnivores, and only 20 units are available to the coyote, a top carnivore.

6. 90% will again be lost. However, some may be recaptured by decomposers such as bacteria and fungi, or to scavengers such as carrion beetles or fly larvae. Eventually all energy will be lost to the environment as heat.

7. Energy flows through an ecosystem and all of it is eventually lost as heat (random motion of molecules) to the environment.

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

TDN is a commonly used measurement of energy in feed for farm animals. The higher % TDN the more energy is in the feed. Look at the table of TDN in these feeds.

Feed Type	TDN	Cost of Feed
Corn	75%	$110 per ton
Barley	70%	$100 per ton
Oats	60%	$135 per ton
Alfalfa hay	50%	$80 per ton
Grass hay	40%	$60 per ton

1. Which feed is the best buy for energy in terms of monetary costs per unit of energy?

a. corn

b. barley

c. oats

d. alfalfa hay

e. grass hay

2. Assuming that all feeds are digested equally well, which feed will produce the fastest growth?

a. corn

b. barley

c. oats

d. alfalfa hay

e. grass hay

3. Which feed would be the most economical to maintain a mature cow?

a. corn

b. barley

c. oats

d. alfalfa hay

e. grass hay

4. Which feed will produce the least growth per dollar spent?

a. corn

b. barley

c. oats

d. alfalfa hay

e. grass hay

Correct Answers:

1. b

2. a

3. e

4. c

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Use the graph to answer the following questions.

1. Which animal is the least efficient at converting feed into food for humans?

a. cattle

b. pigs

c. turkeys

d. chickens

2. Under optimum conditions, catfish can actually convert two pounds of feed into one pound of meat. Which position would catfish occupy if we included them in this graph?

a. to the left of beef

b. between beef and pork

c. between pork and turkey

d. between turkey and chicken

e. to the right of chicken

3. Since grain and soy are often in limited supply and carry environmental consequences to produce, how can we best conserve the EarthÕs resources and still have enough protein to feed people?

a. increase the amount of poultry and beef produced

b. decrease the amount of beef and increase the amount of pork produced

c. decrease the amount of beef and increase the amount of poultry produced

d. increase the amount of beef and decrease the amount of poultry produced

Correct Answers:

1. a

2. e

3. c

I	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Note to Teacher: You will need to provide nutrition labels from 6 different food items for this question.

Examine the 6 nutrition labels that your teacher has given you and answer the following questions:

1. Which food item contains the most fat per ounce?____________________

2. Which of the food items would you choose if you:

Wanted to consume more iron? _________________

Wanted to consume more Vitamin D? _________________

Wanted to consume more carbohydrates? _________________

Wanted to limit your calories? _________________

Had a family history of diabetes

and wanted to limit your sugar intake? _________________

3. How has science influenced the diet of Americans? Check all that apply.

_____a. Science helps us understand what nutrients are needed for our body to function

properly.

_____b. Science helps us understand how disease and nutrition are related.

_____c. Science tells us exactly what foods and precise amounts each person should eat.

_____d. Science helps us measure the nutrient content of foods.

_____e. Science limits our freedom to choose by telling us what foods are healthy and what

foods are not.

Correct Answers:

1. answer varies

2. answers vary

3. a, b, and d are all correct choices.

E	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Many scientists would like to know whether fish sleep. Some studies indicate that, although fish cannot close their eyes, they do remain immobile for a period of time. At these times, fish exhibit a decreased rate of respiration, a decreased reaction to sound, and a lessened response to the approach of foreign objects.

Propose a hypothesis explaining the adaptive value of sleep for fish in meeting their energy requirements.

Correct Answer: Students should propose that sleep in some way helps fish to conserve energy, either by reducing their sensitivity to external stimuli, reducing movement and thus the expenditure of energy, or reducing fish activity at a time when food sources are not as readily available.

E	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Many people are concerned with the overuse of chemical pesticides. Predict what the long-range environmental consequences in your community could be with the present use of pesticides. (4 consequences)

Possible Answers:

Residue build-up in the soil

Loss of soil life

Pests becoming immune to the chemicals

Potential harmful effect on humans

Damage to water and water life

Scoring Guide:

1 point per consequence

2 points for the way that it will affect environmental relationships/components

P	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

Title: Energy Flow in a Backyard Ecosystem

Introduction

Plants and algae are the world's energy producers. They use a process called photosynthesis to capture sunlight energy to combine simple molecules such as carbon dioxide and water into carbohydrates. All other organisms are called consumers because they are dependent upon the energy stored as carbohydrates by producers for their energy needs. Herbivores are the first level of consumers because they feed on the producers directly. Second level consumers are called carnivores because they fed on herbivores or other consumers. Top carnivores have few or no predators and reign atop the food chain.

Approximately 90 percent of the energy found at each step in the food chain is not passed to the next level, but is lost as heat or waste due to metabolism and maintenance. In other words, if an ecosystem contained 100 tons of plant biomass (producers), it can support only 10 tons of first level consumers (herbivores), 1 ton of second level consumers (carnivores) and only 0.1 tons of top carnivores.

1.Walk through your backyard and observe the many kinds of producers (plants) that are present. Identify and count the number of each specific kind and record those data in the space below.

2.Now search your backyard ecosystem for herbivores, first level consumers, and carnivores, second level consumers. Identify each species observed and write them in the correct category in the space below. Count the number of each kind and record the numbers, or estimate their abundance using the following scale: (A) abundant, (C) common, (U) uncommon, (R) rare. Search carefully in the grass, on flowers, under leaves, and in the soil. One method is to spread a sheet under a bush and then shake the bush. Many small organisms will fall onto the sheet for easy observation.

Herbivores (first level consumers) Carnivores (second level consumers)

3.Top carnivores may be shy to show themselves. Observation through a window for a period of time may allow you to observe and record them. Make a list in the space below.

4.Which trophic or feeding level do you think contains the most biomass (weight of organic material)? Why?

5.Which trophic level do you think contains the least biomass? Why?

6.Does the amount of biomass increase or decrease as the energy moves through the food chain? Why?

7.What happens to the energy after it reaches the top level?

8.Identify decomposers in your backyard ecosystem and describe their role.

9. A food chain describes how energy flows from one organism to the next as food molecules. The direction of energy flow is diagramed below.

sun ---------> producers ---------> herbivores ---------> carnivores -------->top carnivores

Using specific organisms you have observed in your backyard ecosystem, construct a food chain in the space provided.

sun ---------> ----------> ----------> ---------->

10. a. Using the four trophic levels discussed, design a food web (a network of interconnecting

food chains) using the organisms observed in your backyard.

b. Place their names in the proper trophic level. (See attached sheet).

c. Draw arrows from the organisms in the first level to the organisms that feed on them in

the next level. Continue through all trophic levels indicating the direction of energy flow.

P	Biology	Standard: 01
Objective: 01. Summarize how energy flows through an ecosystem.
ILO:

An ecologist studied an area of desert to determine the populations of certain key species. Data from her investigation are recorded in the table below. On a piece of graph paper, construct a bar graph showing the numbers of organisms at each feeding level for each of the three months.

Type of organism	Number of organisms
	May	July	September
Grasshoppers	75	400	90
Birds	25	100	10
Annual grasses	300	500	200
Spiders	50	125	35

1. What is the relationship between population size and time of the year?

2. How could you explain the relationship between population changes and the time of the year?

Correct Answers:

1. Peaks in July. Declines in September.

2. Improving growing conditions for producers increase those populations and thus other populations.

Answer key for bar graph: