Competition, predators and prey, and partnerships

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Table (model data)

   Counts per year. Prey line: year 1: 100, 2: 160, 3: 240, 4: 180, 5: 110, 6: 150, 7: 230, 8: 170. Predator line: year 1: 10, 2: 14, 3: 22, 4: 32, 5: 24, 6: 14, 7: 20, 8: 30.

2. 1.

   Ari reads a table of a prey line and a predator line. Which pattern does it show?

   • The prey line rises each year, since its highest value of 240 is bigger than its first value of 100.
   • The predator peaks come before the prey peaks, since the predator line is highest in year 4 at 32.
   • The two lines move in opposite years, with the prey line low whenever the predator line is low.
   • Each predator peak comes a year after a prey peak (years 3 and 4, then 7 and 8), as a cycle.
3. 2.

   Using the same prey and predator table, Bo predicts year 9. The predator line peaked in year 8. What will the prey line most likely do?

   • It should fall again, to about 110, as it did in year 5 after the year 4 predator peak.
   • It should fall to zero, since a high predator line ends the prey line for good in a few years.
   • It should stay at 170, since the prey line stays where it was in the last year of the table.
   • It should rise to a new peak, since the predator line is high and peaks follow peaks in the table.
4. 3.

   Esme stops the predator line after year 8, while the prey's food and space stay plentiful. Using the table, what will the prey line most likely do?

   • It should keep rising and falling in the same cycle, since the cycle does not depend on the predator line.
   • It should fall steadily, since a prey line needs a predator line to stay healthy.
   • It should rise forever, since nothing limits a prey line without a predator line.
   • It should rise for several years, until food or space limits it instead of the predator line.
5. 4.

   40 trees counted in each group. Trees with the vine: 12 healthy. Trees without the vine: 31 healthy. Kira claims a vine helps the trees it grows on because many vine-covered trees looked green. What does the table best support?

   • The vine has no effect, since some vine-covered trees did look healthy and green to the eye.
   • The vine definitely harms each tree it grows on, since just 12 vine trees were healthy.
   • Trees with the vine were healthy less often, so the vine may be harming the trees.
   • Trees with the vine were healthy more often, so the vine helps the trees as the claim says.
6. 5.

   Large fields: 80 bees counted, 5,000 seeds. Small fields: 25 bees counted, 1,400 seeds. Luz finds that fields with more bees also had more seeds, and claims the bees caused the extra seeds. What is the best response?

   • The claim is right, since a table with two rows is enough to show that bees cause the seeds.
   • The claim is right, since fields with more bees had more seeds in each row of the table.
   • The claim is wrong, since seeds are made by plants and bees do nothing to the seeds that form.
   • Field size could explain both counts, so compare same-sized fields with and without bees.

7. Table (model data)

   Ring width added per year, 30 oaks in each group. Oaks with moss on the trunk: 2.1 mm. Oaks without moss: 2.1 mm.

8. 6.

   Milo says moss on oak trunks harms the oaks. Oaks with moss and without moss grew the same amount. What is the best response?

   • Moss still harms the oaks, since an effect can be real even when no growth difference shows up.
   • The oaks with moss grew less, since moss on the trunk blocks light from reaching the leaves.
   • The moss helps the oaks, since the oaks with moss grew as well as the oaks without it.
   • The oaks grew the same, so there is no sign of harm; the moss gains a place to grow.
9. 7.

   Noah says two plants cannot compete because plants cannot move or touch each other. What is the best response?

   • Competition is two living things using the same limited resource, like light; no contact is needed.
   • The claim is right, because plants make their own food and so they do not need limited resources.
   • The claim is wrong, because plants compete by growing their roots right into one another.
   • The claim is right, because competition needs one living thing to push or touch the other one.
10. 8.

    Pia measures an oak with mistletoe for one week, sees no change in growth, and says mistletoe is harmless. What is the best response?

    • The claim is right, because one oak is enough to show what happens to other oaks too.
    • One week is too short to see changes in yearly growth, so the oak should be tracked for years.
    • The claim is right, because no change in one week means mistletoe is harmless in the long run.
    • The claim is wrong, because mistletoe causes the oak to lose leaves within a week of landing.
11. 9.

    Ren wants to test whether weeds reduce lettuce growth. Which plan is best?

    • Grow lettuce in plots with just weeds, and compare the lettuce with lettuce bought in a shop
    • Grow lettuce in plots with weeds and plots without, but give the weedy plots less water to save it
    • Grow lettuce in matching plots with weeds and matching plots without, and measure each weekly
    • Grow lettuce in one plot with weeds and one plot without weeds, and measure both plots one time
12. 10.

    Jun wants to test whether mistletoe slows the growth of oak branches, without differences between trees getting in the way. Which plan is best?

    • Compare the growth of one oak that has mistletoe with one oak that has no mistletoe on it
    • On each of several oaks, compare growth of branches with mistletoe and branches without it
    • Measure the growth of branches with mistletoe and compare it with the weather from last year
    • Compare branches with mistletoe on one tree with branches without it on a different tree