Energy Flow in Ecosystems: a full term of science

Ten ready-to-teach lessons for Year 7 Biological sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards or exit tickets, an assessment kit and worked answers.

Start here: five minutes to Monday

1. Skim the term at a glance on the next page.
2. Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, cards or tickets.
3. Gather the few items under “You need” on the plan. Most come from the classroom or the supermarket.
4. Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
5. Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.

For any Year 7 science teacher

The pack suits a science specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: energy enters an ecosystem when producers capture sunlight and flows one way through food chains and webs, with most of it lost as heat at every step, while matter cycles round again through decomposers. Because every species is linked, a change to a living (biotic) or non-living (abiotic) factor ripples through the populations, and a food web lets us predict how.

Two ways to run each lesson

Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Look ahead: the decomposition bags set up in Lesson 4 are scored two weeks later in Lesson 6, the salt test set up in Lesson 6 is read in Lesson 7, and Lesson 8 needs a dry day outdoors.

Safety and care in one look

The decomposition bags are sealed with tape and never opened; the teacher puts them in the bin still sealed, and anyone with asthma or a mould allergy only looks. Salt water and seeds are never tasted. Outdoors, students wear hats and gloves, move small animals only with a spoon, never touch a spider, and leave the quadrats as they found them. Everyone washes their hands after soil, plants and bags.

The term at a glance

One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.

How the sequence builds

Lessons 1 to 3 build the model: chains, a web, and the energy that shrinks at every level. Lesson 4 adds the decomposers and the cycle of matter. Lessons 5 to 7 test the model against changes: predators and prey, abiotic and biotic factors, and a salt test on the producers at the base of the web. Lesson 8 builds a real web from the school grounds, Lesson 9 uses webs to explain what invaders did in Australia, and Lesson 10 brings it together.

Curriculum links (Australian Curriculum V9)

The whole term teaches the Science Understanding descriptor AC9S7U02 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:

Assessment in this pack

• Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 7 voice, with working.
• The assessment sheet near the front has a class observation checklist and a three-level rubric.
• Lesson 10 is the summative pair: predictions for a river food web, plus the “Show what we know” check.

Materials for the whole term

One gathering session covers all ten lessons. Most lessons need only the cards and sheets in this pack; Lessons 4, 6 and 8 need a few things from the supermarket and the garden centre, and some borrowed equipment. Plan the dates too: Lessons 4, 5 and 6 should fall a week apart, because the bags are scored one and two weeks after they are sealed; Lesson 7 reads the salt test a week after Lesson 6; and Lesson 8 needs a dry day.

The one-trip list

• From the classroom: scissors, glue sticks, A3 paper, calculators, rulers, coloured pens, magnifiers, white trays, plastic spoons, clipboards, cups and droppers.
• From the supermarket: an apple for each group, zip-lock bags, sticky tape, table salt, cling wrap and paper towel.
• From the garden centre: radish seeds, 100 for each group, and a small bag of garden soil.
• To borrow: kitchen scales, a measuring jug or cylinders, five saucers or Petri dishes per group, string and tent pegs or metre rulers, and gloves for every student.

Safety and care in one look

• Decomposition bags are sealed with tape and never opened; the teacher bins them still sealed, and students with asthma or a mould allergy only look.
• Salt water and seeds are never tasted; used seeds and paper towel go in the bin.
• Outdoors: hats, sunscreen and gloves; small animals are moved only with a spoon, no one touches a spider, logs and bricks go back as they were, and students allergic to stings record from the path.
• Everyone washes their hands after soil, the bags, the seeds and the survey.

Assessment without extra work

The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the river task, with its web checked by a partner, and the final check. This sheet is the place to note what you see along the way.

The three levels

Class observation checklist

A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.

Word wall cards

Cut out the cards and build the wall as the words arrive: producer, consumer and food chain in Lesson 1; food web in Lesson 2; energy pyramid and trophic level in Lesson 3; decomposer and nutrient in Lesson 4; predator and prey in Lesson 5; abiotic and biotic factor in Lesson 6; quadrat and population in Lesson 8; introduced species in Lesson 9.

Dear families

This term in science, Year 7 studies how energy and matter move through ecosystems. Students build food chains and webs for an Australian woodland, work out why only about a tenth of the energy passes up each feeding level, and find out how decomposers return nutrients to the soil. Then they use their webs to predict what happens when something changes: a drought, salty soil, a new predator, or an introduced animal such as the rabbit or the fox.

Along the way your student will seal apple slices in bags to watch decomposers at work, graph twelve years of rabbit and fox counts, test how salt affects seeds, survey a square metre of the school grounds, and study two real experiments in which removing foxes had effects nobody wanted.

Try this at home

• Trace a meal back to the Sun: what ate what, and where did the energy start?
• Look under a log or a pot plant, without touching anything. Which animals there feed on dead leaves?
• Find out which introduced animals live near you, and what they eat.
• Count the birds in one tree for five minutes on two different days. Are the numbers the same? Why might they differ?

What to ask your scientist

• Why are there so few top predators, such as eagles?
• What would happen to a forest with no decomposers?
• Why can removing a pest make things worse?
• How did your class estimate the number of snails in a garden bed?

A small note on care: the decomposition bags stay sealed and are binned unopened, salt water and seeds are never tasted, and in the schoolyard survey students wear gloves and leave spiders alone.

Warm regards,

The Year 7 science team

Printed from the free seegongsik Energy Flow in Ecosystems teaching pack · seegongsik.com/au/y7/biological/AC9S7U02/pack

Who eats whom?

Every living thing needs energy. Producers, such as grasses and trees, capture it from sunlight; consumers get it by eating other living things. A food chain shows one path the energy takes, and its arrows point from the living thing that is eaten to the one that eats it, the way the energy travels. Pairs use thirteen diet cards from a eucalypt woodland to build food chains, then name each link by its feeding level: producer, primary consumer, secondary consumer and up.

We are learning to

• build food chains from information about what each living thing eats,
• draw the arrows the way the energy flows, from the eaten to the eater,
• name the producer and the level of each consumer in a chain.

Success criteria

• I can write a food chain with every arrow pointing from the eaten to the eater.
• I can name the producer and each consumer level in my chain.

You need

• the diet cards (third sheet), cut out, one set per pair,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the breakfast trace, the demo chain and Part A in Session A, and the board, Part B and Part C in Session B.

Watch for these ideas

• Arrows drawn towards the food (“the hawk eats the snake, so the arrow points to the snake”). The arrow shows where the energy goes: into the eater.
• “The Sun is a producer.” The Sun is the energy source; producers are the living things that capture its energy.
• “Every animal has one level.” An animal that eats at several levels, such as the kookaburra, belongs to more than one.

Make it easier, make it bigger

• Easier: hand each pair the two producer cards first, and build every chain upwards from them.
• Bigger: find the longest chain the cards allow, and count its links.

Answers and look-fors

• Part A, any four of the 8 chains: Native grass → Eastern grey kangaroo → Dingo; Native grass → Grasshopper → Australian magpie; Native grass → Grasshopper → Eastern blue-tongue lizard → Eastern brown snake → Laughing kookaburra; Native grass → Grasshopper → Eastern blue-tongue lizard → Laughing kookaburra; Native grass → House mouse → Eastern brown snake → Laughing kookaburra; Native grass → House mouse → Laughing kookaburra; Gum tree → Christmas beetle → Australian magpie; Gum tree → Common brushtail possum → Powerful owl.
• Part B: the first card is the producer; then primary, secondary, tertiary and quaternary consumers in order, for example native grass (producer), grasshopper (primary consumer), eastern blue-tongue lizard (secondary consumer), eastern brown snake (tertiary consumer), laughing kookaburra (quaternary consumer).
• Part C: 1. Only producers can capture energy from sunlight; every consumer’s energy came from a producer first. 2. The eastern brown snake (levels 3 to 4) and the laughing kookaburra (levels 3 to 5): each eats animals from more than one level. 3. Native grass → Grasshopper → Eastern blue-tongue lizard → Eastern brown snake → Laughing kookaburra.
• Bigger: 5 links, Native grass → Grasshopper → Eastern blue-tongue lizard → Eastern brown snake → Laughing kookaburra.

Who eats whom?

A. Four food chains

Start every chain with a producer. Draw each arrow from the living thing eaten to the one that eats it.

B. The levels in one chain

C. Questions

Woodland diet cards

Cut out the cards. Each one says what the living thing eats in this woodland. Build food chains, starting with a producer.

Teacher note: keep the cards. Lesson 2 joins every chain into one food web, and Lesson 9 adds introduced animals to it.

Weaving a food web

In a real woodland, food chains cross: the grasshopper is eaten by the magpie and by the lizard, and the kookaburra eats at three different levels. Joining every chain into one food web shows how each living thing is connected. Groups lay all thirteen diet cards on A3 and draw every feeding arrow, then use the web to predict which animals a loss would reach, first directly and then further up. The web also shows why animals with several foods cope better than specialists.

We are learning to

• join food chains into a food web that shows every feeding link,
• use the web to predict the direct and knock-on effects of losing a species,
• explain why a living thing with several foods is less affected by a loss.

Success criteria

• Our web has an arrow for every link on the cards, each pointing from the eaten to the eater.
• I can predict which animals lose food first when a species disappears, and which feel it later.

You need

• the Lesson 1 diet cards, a sheet of A3 paper and glue per group of three,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet), cut into four.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Weave the web in Session A. Show the board and do Parts A to C and the ticket in Session B.

Watch for these ideas

• “Only the animals that eat it are affected.” The effect travels further up, and the living things it ate can increase.
• “Every animal that loses a food dies out.” Animals with other foods, such as the magpie, can switch.
• Arrows that skip a level, such as grass straight to the kookaburra. Draw only the links on the cards.

Make it easier, make it bigger

• Easier: build the web in two halves, the grass side and the gum-tree side, then join them.
• Bigger: the grasshoppers disappear. Which of their foods might increase, and what could that do to the other grazers?

Answers and look-fors

• Part A: eat more than one food: Australian magpie, eastern brown snake, laughing kookaburra. Eaten by more than one animal: native grass, gum tree, grasshopper, house mouse, eastern blue-tongue lizard.
• Part B1, no grasshoppers: directly Australian magpie, eastern blue-tongue lizard; then eastern brown snake, laughing kookaburra.
• Part B2, no gum trees: directly Christmas beetle, common brushtail possum; then Australian magpie, powerful owl. The powerful owl is hit hardest: the possum is its only food here, while the magpie still has grasshoppers.
• Part C: a chain shows one path, so it misses the other foods an animal has and the other animals a loss reaches; the web shows both. Bigger: with fewer grasshoppers eating it, the grass may grow more, so the kangaroos and mice could have more food.
• Exit ticket: eastern brown snake, laughing kookaburra; yes, both eat other animals as well (lizards, and the kookaburra also eats snakes).

Weaving a food web

A. The busiest members

B. Predict the ripple

Use your web. For each loss, list the animals that lose food directly, then those affected further up.

C. Web or chain?

Exit tickets

Cut into four. Students answer on their own, from their web.

Teacher note: the answers are on this lesson’s plan.

Energy up the levels

Energy enters a food web when producers capture sunlight, but it is not passed on whole. At each step only about a tenth reaches the next level: the rest is used for living (moving, growing, keeping warm), lost as heat, or left in parts that are not eaten or digested. Students use this rule of thumb to work out how much energy reaches each consumer in the woodland web, compare a short route and a long route to the kookaburra, and explain why there are many more plants than plant-eaters and so few top predators.

We are learning to

• calculate the energy reaching each feeding level, using the one-tenth rule of thumb,
• draw a pyramid of energy and explain its shape,
• explain why food chains rarely have more than five links.

Success criteria

• I can work out the energy at each level of a chain and show my working.
• I can say where most of the energy goes at each step.

You need

• calculators, the worksheet (next sheet), one per student, and the exit tickets (third sheet), cut into four.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the rule and Parts A and B in Session A, and the pyramid, Part D and the ticket in Session B.

Watch for these ideas

• “The energy is used up and gone.” Energy is not destroyed; it is changed, mostly to heat, which spreads into the surroundings.
• “Big animals are at the top.” Kangaroos are big but are primary consumers; levels depend on what an animal eats, not its size.
• Taking a tenth of the starting amount at every level, instead of a tenth of the level just below.

Make it easier, make it bigger

• Easier: start with 1000 units, so each level is one zero shorter.
• Bigger: an animal eats both plants and mice. Is it a primary or a secondary consumer, and how does that change the energy it can get?

Answers and look-fors

• Part A: native grass 10 000 units; grasshopper 1000 units; eastern blue-tongue lizard 100 units; eastern brown snake 10 units. Each level is the level below divided by 10.
• Part B: short route (native grass, house mouse, laughing kookaburra) 100 units; long route (native grass, grasshopper, eastern blue-tongue lizard, eastern brown snake, laughing kookaburra) 1 unit. The short route delivers 100 times as much.
• Part C: three bars, widest at the bottom (10 000), then 1000 and 100; widths need not be to scale, but each bar must be narrower than the one below.
• Part D: 1. Used for moving, growing and keeping warm, lost as heat, and left in parts not eaten or digested. 2. Each magpie needs the energy of many grasshoppers, and only about a tenth passes up, so there is energy for far fewer magpies. 3. After four or five steps so little energy is left that it cannot support another level.
• Exit ticket: 500 units (two steps: 50 000 ÷ 10 = 5000, then ÷ 10 again); about nine-tenths; heat.

Energy up the levels

Rule of thumb: about one-tenth of the energy at one level passes to the level above.

A. The energy table

B. Two routes to the kookaburra

Short route: native grass → house mouse → laughing kookaburra. Long route: native grass → grasshopper → eastern blue-tongue lizard → eastern brown snake → laughing kookaburra. The grass captures 10 000 units each time.

C. A pyramid of energy

D. Why so short?

Exit tickets

Cut into four. Students answer on their own.

Teacher note: the answers are on this lesson’s plan.

Decomposers and the cycle of matter

When living things die, or drop leaves and droppings, decomposers such as fungi and bacteria break the dead matter down, helped by earthworms and slaters that chew it into smaller pieces. The nutrients go back into the soil, where producers take them up again: matter cycles round. Energy does not cycle; it flows one way and leaves as heat. Groups seal apple slices in four bags that differ in soil and temperature, to see what speeds decomposers up, and draw the cycle of matter.

We are learning to

• explain what decomposers do and why an ecosystem needs them,
• plan a test that changes one factor at a time and keeps the others the same,
• explain the difference between matter cycling and energy flowing.

Success criteria

• I can name the factor that differs between two of our bags, and what we kept the same.
• I can draw the cycle of matter and say why energy is not in it.

You need

• for each group: four zip-lock bags, an apple cut into four equal slices, six teaspoons of garden soil, a cup of water and a dropper, sticky tape and gloves; space in a fridge and a warm cupboard,
• the bag labels and decay scale (third sheet), and the worksheet (next sheet), one per student.

Safety: bags are sealed with tape and never opened again; at the end the teacher puts them in the bin still sealed. Students with asthma or a mould allergy observe only. Gloves for soil; everyone washes their hands.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Set up the bags in Session A. Show the board and do the cycle of matter in Session B.

Watch for these ideas

• “Things just rot away to nothing.” The matter becomes gases, water and nutrients in the soil; nothing vanishes.
• “Mould is the apple going bad by itself.” Mould is a fungus, a living decomposer, feeding on the apple.
• “Energy is recycled too.” Matter cycles; energy flows through once and leaves as heat.

Make it easier, make it bigger

• Easier: set up only bags A and B, one changed factor.
• Bigger: plan a fifth bag to test whether moisture matters, and say what it must keep the same.

Answers and look-fors

• Part A: A and B differ in temperature (room against fridge); A and C in soil (with and without); A and D in temperature (room against warm). Kept the same: the size of the apple slice, the drops of water, the amount of soil where there is soil, the kind of bag, sealing. Expected order, fastest first: D, A, C, B, because decomposers come from the soil and work faster when warm.
• Part B, in order round the loop: Producers → Consumers → Dead matter and droppings → Decomposers → Nutrients in the soil → back to producers.
• Part C: 1. Nutrients would stay locked in dead matter, so new plants could not grow and the whole web would run down. 2. Matter is reused again and again; energy enters as sunlight and leaves as heat at every step, so it must keep coming in.

Decomposers and the cycle of matter

A. Our bag test

B. The cycle of matter

Word bank: Consumers, Dead matter and droppings, Decomposers, Nutrients in the soil, Producers. Write one in each box, in order round the loop.

C. Matter and energy

Bag labels

Cut out a label for each bag and tape it on. Every bag holds one apple slice and a few drops of water. Write your group name and today’s date.

The decay scale (for Lessons 5 and 6)

Teacher note: score the bags through the plastic, without opening them, one week and two weeks after today.

Predators and prey

A predator and its prey are a biotic factor for each other. When prey are plentiful, more predators survive and raise young; as predator numbers climb, they eat more prey and the prey fall; with less food, the predators fall too, and the prey recover. The two populations rise and fall in turn, with the predators a step behind. Students graph twelve years of illustrative spotlight counts of rabbits and foxes on one farm, find the lag between the peaks, and explain it as a loop.

We are learning to

• graph two populations over time and describe the pattern in each,
• identify the lag between a predator’s and its prey’s peaks,
• explain how each population affects the other, step by step.

Success criteria

• My graphs have scales, labelled axes and accurately plotted points joined by lines.
• I can explain, in four linked steps, why the fox numbers rise and fall after the rabbit numbers.

You need

• rulers and sharp pencils, the worksheet (next sheet), one per student, and the exit tickets (third sheet), cut into four,
• the Lesson 4 bags, for a one-week score at the start.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Score the bags, show the board and graph the counts in Session A. Read the pattern and explain the loop in Session B.

Watch for these ideas

• “The foxes eat all the rabbits.” Prey numbers fall but rarely reach zero; as they get scarce, predators find fewer and go hungry.
• “Both rise and fall at the same time.” Look at the peak years: the predators lag behind.
• Joining the points with a smooth curve that misses them. Use straight lines from point to point.

Make it easier, make it bigger

• Easier: give the axes already scaled, and plot only years 1 to 8.
• Bigger: these counts are illustrative. Name two other factors, one abiotic and one biotic, that could change a real farm’s counts.

Answers and look-fors

• Part A: points plotted at each year and joined with straight lines; rabbit axis 0 to 100, fox axis 0 to 12.
• Part B: 1. rabbits peak in years 4 and 11; foxes in years 5 and 12. 2. about 1 year each time. 3. year 7. 4. the rabbits rise again first, then the foxes.
• Part C, the loop: more rabbits mean more food, so more foxes survive and breed; more foxes eat more rabbits, so the rabbits fall; with fewer rabbits, the foxes go hungry and fall; with fewer foxes, the rabbits recover.
• Bigger: abiotic, such as drought or a hard winter cutting the grass; biotic, such as a rabbit disease or people baiting foxes.
• Exit ticket: 1. the predator’s line. 2. Predators survive and breed better only after their prey have increased, so their numbers rise later. 3. Its food.

Bag check: expect little change yet in bag B (the fridge), and the most in bag D.

Predators and prey

Spotlight counts on one farm, taken on the same night each year (illustrative data).

A. Graph the counts

B. Read the pattern

C. Explain the loop

Exit tickets

Cut into four. Students answer on their own.

Teacher note: the answers are on this lesson’s plan.

Abiotic and biotic factors

Populations change when the factors around them change. Abiotic factors are non-living: rainfall, temperature, light, fire, salty soil. Biotic factors are living: predators, prey, competitors, disease. The decomposition bags show both at once: warmth (abiotic) and the decomposers in the soil (biotic) set how fast the apple broke down. Students score the bags, sort twelve real changes into abiotic and biotic and predict their effects, then set up a salt test on radish seeds, an abiotic factor acting on the producers, to read next lesson.

We are learning to

• tell abiotic factors from biotic factors,
• use results to decide which factor made the biggest difference,
• plan a fair test with one changed variable, one measured and the rest controlled.

Success criteria

• I can sort a change as abiotic or biotic and predict its effect on a population.
• I can name the independent, dependent and controlled variables in our salt test.

You need

• the Lesson 4 bags and their one-week scores; the factor cards (third sheet), one set per group,
• for the salt test, per group: five saucers or Petri dishes, paper towel, 100 radish seeds, cling wrap; for the class: table salt, kitchen scales, a 250 mL jug, measuring cylinders or a measuring cup,
• the worksheet (next sheet), one per student.

Safety: the bags stay sealed and go in the bin still taped at the end of the lesson. Salt water and seeds are not tasted. Wash hands.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Score the bags and sort the changes in Session A. Set up the salt test in Session B.

Watch for these ideas

• “Fire is biotic because it burns living things.” Fire itself is not alive: it is an abiotic factor.
• “Abiotic factors only affect plants.” A heatwave or a flood acts on animals directly, and on all of the web through the plants.
• Changing more than one thing between dishes. Only the salt may differ.

Make it easier, make it bigger

• Easier: sort the cards first, then score the bags; leave the salt solutions made in advance.
• Bigger: one card could be argued either way. Find it and argue it.

Answers and look-fors

• Part A, example class scores (one week, two weeks): A 2, 4; B 0, 1; C 1, 2; D 3, 5. Fastest D, slowest B: warmth sped the decomposers up and cold slowed them, and with no soil (bag C) there were fewer decomposers to start with, so temperature made the biggest difference.
• Part B: abiotic A, C, E, F, H, K, L; biotic B, D, G, I, J. Predictions should follow the web; for example, card A: Less grass grows, so grazers have less to eat.
• Part C: independent variable, the amount of salt; dependent, the number of seeds sprouted after a week; controlled, the kind and number of seeds, the volume of solution, the paper towel, the light, the temperature and the time. A sensible prediction: more salt, fewer seeds sprout.
• Bigger: card G (a grass that cattle will not eat) is biotic, but students may argue that it changes the soil or shade; card L (a cloudy month) is abiotic even though it acts through living plants.

Abiotic and biotic factors

A. The decomposition bags

B. Abiotic or biotic?

C. Our salt test

Factor cards

Cut out the cards. Lay down the two grey heading cards and sort each change.

Dish labels for the salt test

Teacher note: 7 cards are abiotic and 5 biotic.

Salt and seedlings

Salt is an abiotic factor that matters in Australia: in some farming districts, clearing deep-rooted native plants let the water table rise and bring salt to the surface, a problem called dryland salinity. Groups count the radish seeds that sprouted in each salt strength, work out percentages, draw a line graph of germination against salt, and use the woodland web to predict what salty soil would do to the animals that depend on the plants.

We are learning to

• turn counts into percentages and graph them,
• describe the trend in a graph and spot any odd result,
• predict how an abiotic change to producers ripples through a food web.

Success criteria

• My graph has the salt along the bottom, the percentage up the side, and points joined by straight lines.
• I can predict, with two linked steps, how salty soil would affect a consumer in the web.

You need

• the Lesson 6 seed dishes, magnifiers, calculators,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet), cut into four.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Count and work out the percentages in Session A, and graph and answer Part C in Session B.

Watch for these ideas

• “A little salt helps plants grow.” Plants need some minerals, but table salt in the soil makes it harder for roots to take up water.
• Plotting the salt values evenly spaced (0, 0.5, 1, 2, 4 as equal steps). Use the scale on the grid.
• Only predicting for the plants. The effect travels to the grazers and then to their predators.

Make it easier, make it bigger

• Easier: use the example results, and plot only 0, 1, 2 and 4.
• Bigger: the steepest fall is between two strengths. Plan an extra test to find more precisely where germination fails.

Answers and look-fors

• Part A, example results: 0 g, 18 of 20 = 90%; 0.5 g, 17 of 20 = 85%; 1 g, 12 of 20 = 60%; 2 g, 5 of 20 = 25%; 4 g, 0 of 20 = 0%.
• Part C: 1. The more salt, the fewer seeds sprouted; on the graph the steepest fall is between 0.5 and 1 g (25 points in 0.5 g); the biggest drop between tested strengths, 1 to 2 g (35 points), is spread over 1 g; none sprouted at 4 g. 2. In the example, none stands out; in class data, a dish that dried out or got more seeds may.
• Part C: 3. Fewer plants grow, so the grazers (eastern grey kangaroo, grasshopper, house mouse) have less food and fall; then their predators have less food too. 4. More seeds per dish, repeat dishes for each strength, more strengths between 0.5 and 2 g, and check every dish stays equally moist.
• Exit ticket: 7 of 20 is 35%; the trend falls as salt rises; fewer producers means less food, and so less energy, for every level above.

Salt and seedlings

A. Our results

B. Graph it

C. What it means

Exit tickets

Cut into four. Students answer on their own.

Teacher note: the answers are on this lesson’s plan.

A schoolyard web

The woodland web is a model; the school grounds hold a real web. No one can count every living thing in a habitat, so ecologists sample it with quadrats, squares of a set size placed in several spots, and scale up from the average. Groups survey a 1 m by 1 m quadrat, record the plants, the animals and the signs they leave, then use a field guide to build a food web of what they found and estimate the size of a population.

We are learning to

• sample a habitat with a quadrat and record what we find,
• build a food web from our own observations,
• estimate the size of a population from several quadrats.

Success criteria

• Our tally gives a number for every living thing in our quadrat, and lists the signs we found.
• I can estimate a population from quadrat counts and explain why more quadrats give a better estimate.

You need

• for each group: 4 m of string and four tent pegs (or four metre rulers) to mark a 1 m square, a clipboard, a white tray, two plastic spoons, a magnifier and gloves; hats and sunscreen,
• the field-guide cards (third sheet), one set per group, A3 paper, and the worksheet (next sheet), one per student.

Safety: walk the survey area first for broken glass, bees and ants’ nests. Gloves on; animals are moved with a spoon onto the tray and back, and no one touches a spider. Lift a log or brick away from you and put it back as it was. Students allergic to stings record from the path. Everyone washes their hands afterwards.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Brief and survey in Session A. Build the web and answer Parts B and C in Session B.

Watch for these ideas

• “We found nothing, so there is no web.” Signs count: chewed leaves, webs, casts and shells show who lives and feeds there.
• “Decomposers are not part of the web.” Magpies eat earthworms, and decomposers return nutrients that the grass takes up again.
• Arrows drawn from the eater to the eaten. Read each arrow aloud as “is eaten by”.

Make it easier, make it bigger

• Easier: count only plants and animals bigger than an ant, and build the web from four cards.
• Bigger: compare two quadrats in different spots, such as a sunny lawn and a shady garden bed, and name an abiotic factor that could explain the difference.

Answers and look-fors

• Part A depends on the quadrat. Look for numbers rather than ticks, and for signs recorded as well as animals seen.
• Part B, for the full field guide: producers lawn grass, clover; decomposers slater, earthworm, feeding on dead leaves and droppings; the longest chain is clover → aphid → jumping spider → garden skink → Australian magpie.
• Part C: 1. 3 + 0 + 2 + 5 + 1 + 1 = 12 snails in 6 m², an average of 2 per square metre; the bed is 8 m × 5 m = 40 m², so about 2 × 40 = 80 snails. 2. One quadrat could land on a crowded or an empty patch; the average of several evens out the differences.
• Part C: 3. The spray kills the insects: ants, aphids, caterpillars and ladybirds. The jumping spiders lose all their food, the aphids and caterpillars, so they fall. The garden skinks lose their caterpillars and then their spiders, so they fall too. The magpies lose the caterpillars and some skinks but still have earthworms, so they cope better. With fewer aphids and caterpillars eating it, the clover may grow more.

A schoolyard web

A. Our quadrat

B. Our web

Draw your web on A3, with arrows from the eaten to the eater. Then answer.

C. Estimate and predict

An example class counted the garden snails in six quadrats on one garden bed, 8 m long and 5 m wide. Their counts: 3, 0, 2, 5, 1, 1.

Field guide: who eats what

Twelve living things a schoolyard quadrat often turns up. “Dead leaves” means dead leaves, droppings and dead animals.

Teacher note: the diets are cut down to the twelve cards; real animals eat more kinds of food.

Invaders in the web

Many of the biggest changes to Australian food webs since 1788 came from animals that people brought in. An introduced animal joins a web it did not evolve in: it eats native species, competes with them for food, or poisons the animals that try to eat it, and the natives have had little time to adapt. Groups add one invader to their Lesson 2 woodland web and predict its effects, then use data from two real field experiments to see what happened when one invader was removed, and advise a reserve.

We are learning to

• predict how an introduced species changes the populations in a food web,
• use data from field experiments to test a prediction,
• give advice backed by evidence and reasoning.

Success criteria

• I can name a population an invader eats or poisons, and one that loses food to it, and explain each.
• My advice gives a claim, evidence from the experiments and reasoning from the web.

You need

• each group’s Lesson 2 woodland web and a pen in a new colour,
• the invader cards (third sheet), one sheet per group, and the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the dates, the invader and the report in Session A, and the experiments and the advice in Session B.

Watch for these ideas

• “An invader only harms what it eats.” It also takes food from natives that eat the same things, and a poisonous one harms whatever eats it.
• “Removing an invader always helps native animals.” At Heirisson Prong it did not: the foxes had been keeping the cats down.
• “Introduced animals are a problem because they are not from here.” Ask for the arrow in the web that does the damage.

Make it easier, make it bigger

• Easier: every group starts with the rabbit, and the class fills row 1 of Part A together.
• Bigger: in 1950 the myxoma virus killed most rabbits at first. Predict what happened next to the foxes, to the grass, and to the native animals foxes eat.

Answers and look-fors

• Five dates: the 1950 and 1995 diseases were released to control the rabbits of 1859, and the 1935 toads to control a beetle pest; the foxes spread with the rabbits, their food.
• Part A: European rabbit: falls, native grass; loses food, eastern grey kangaroo, grasshopper, house mouse; could rise, dingoes, with more prey to hunt. Red fox: falls, house mouse, eastern blue-tongue lizard, common brushtail possum; loses food, eastern brown snake, laughing kookaburra, powerful owl; could rise, native grass, grasshopper, gum tree, eaten less. Feral cat: falls, house mouse, eastern blue-tongue lizard, grasshopper; loses food, eastern brown snake, laughing kookaburra, Australian magpie, eastern blue-tongue lizard; could rise, native grass, eaten less. Cane toad: falls, grasshopper, Christmas beetle, eastern blue-tongue lizard, eastern brown snake; loses food, Australian magpie, eastern blue-tongue lizard; could rise, native grass, gum tree, eaten less.
• Part B: 1. Foxes eat rabbits; with the foxes gone, more young rabbits survived to breed. 2. The foxes had been keeping the cats down; with the foxes gone, the cats rose and hunted the small mammals. 3. So that any change could be put down to the control, not to rain or the season, which affected every area alike.
• Part C, for example: control foxes and cats together (claim); at Heirisson Prong small mammals fell by 80% when only foxes were controlled but rose when both were (evidence); foxes and cats hunt the same small animals, so removing one leaves more food for the other (reasoning); rabbits may rise, as at Namadgi, so count them too (risk).
• Bigger: the foxes lose their main food and fall a year or two later; the grass and seedlings recover; in the meantime hungry foxes may hunt more native animals.

Invaders in the web

A. An invader joins the web

B. Removing an invader

C. Our advice

A reserve plans to bait foxes to protect its bandicoots. Advise it.

Five dates

The invader cards

Each group works on the invader the teacher gives it; the other cards help with row 2 of Part A.

Teacher note: the Part A answers are on this lesson’s plan.

Show what we know

The last lesson brings the term together. Students build a food web for a river they have not met, from eight cards, and use it to calculate and predict. Then each student sits the final check on their own, and the class finishes with the unit quiz on the board.

We are learning to

• build a food web for an unfamiliar ecosystem and use it to predict,
• calculate energy flow and explain changes in populations,
• show what we know about food webs on our own.

Success criteria

• Every arrow in my river web points from the eaten to the eater, and each prediction gives a reason from the web.
• I can back each answer on the final check with a link in a web, a calculation or a reason.

You need

• the river task (next sheet) and the final check (third sheet), one each per student,
• the interactive unit open for the closing quiz.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the river task and the swap in Session A, and the final check and the class quiz in Session B.

Watch for these ideas

• “The platypus is at the top, so it has the most energy.” The top level has the least: about a tenth passes up at each step.
• Arrows drawn from the eater to the eaten. Ask the student to read each arrow aloud as “is eaten by”.
• “A drought is biotic because it kills living things.” Water and temperature are not alive: a drought is abiotic.

Make it easier, make it bigger

• Easier: give the first two arrows, from the algae to the mayfly nymph and to the shrimp, and let students build from there.
• Bigger: the Murray cod also eats smaller fish. Add a small fish that eats mayfly nymphs. At which levels does the cod now feed?

Answers and marking guide

• Task, Part A, the eight arrows: algae → mayfly nymph; algae → freshwater shrimp; water plants → yabby; mayfly nymph → platypus; freshwater shrimp → platypus; freshwater shrimp → Murray cod; yabby → Murray cod; yabby → rakali (water rat).
• Task, Part B: producers: algae, water plants; primary consumers: mayfly nymph, freshwater shrimp, yabby; secondary consumers: platypus, Murray cod, rakali (water rat).
• Task, Part C: 1. The platypus is 2 steps above the algae: 40 000 ÷ 10 ÷ 10 = 400 units. 2. The Murray cod and the rakali (water rat) lose food; the water plants could increase; the cod may eat more shrimp, leaving the platypus less food. 3. Abiotic; for example, shallow, warm water holds less oxygen, so the mayfly nymphs and shrimp fall and the platypus and cod have less food. 4. Bacteria or fungi (yabbies help too, eating rotting leaves): arrows from the dead remains of every member to the decomposer, and nutrients back to the algae and water plants.
• Check: 1. the eaten to the eater. 2. grass 60 000, mouse 6000, snake 600, hawk 60 units: divide by 10 at each step. 3. a fox. 4. Less grass means less food for the rabbits, so they fall; with fewer rabbits to eat, the foxes fall too, a little later.
• Check: 5. fungus. 6. 6 + 2 + 4 + 0 + 5 + 7 = 24 in 6 m², so 4 per square metre; 4 × 150 = 600 slaters. 7. Predators breed well only after their prey have become plentiful, so their numbers rise later; they then eat the prey down and go hungry, so they fall later too. 8. Decomposers break the leaf into nutrients that a new plant takes up, so its matter goes round again; its energy was used or lost as heat along the way and never returns, so new energy must keep arriving as sunlight.
• Scoring: 1 mark each for 1, 3 and 5; 2 marks each for 2, 4, 6, 7 and 8. The rubric near the front of the pack turns the task and the check into a level.

A river web

A. Draw the web

B. Sort the eight into levels

C. Use the web

Show what we know

Show what you know about food webs, energy and populations. Read each item, then circle or write.

Teacher note: the marking guide is on this lesson’s plan; the rubric near the front of the pack turns the score into a level.