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 two lines move in opposite years, with the prey line low whenever the predator line is low.
   • 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.
   • Each predator peak comes a year after a prey peak (years 3 and 4, then 7 and 8), as a cycle.
3. 2.

   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 fall steadily, since a prey line needs a predator line to stay healthy.
   • It should rise for several years, until food or space limits it instead of the predator line.
   • It should rise forever, since nothing limits a prey line without a predator line.
   • It should keep rising and falling in the same cycle, since the cycle does not depend on the predator line.
4. 3.

   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.
   • Trees with the vine were healthy less often, so the vine may be harming the trees.
   • The vine definitely harms each tree it grows on, since just 12 vine trees were healthy.
   • Trees with the vine were healthy more often, so the vine helps the trees as the claim says.
5. 4.

   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?

   • Field size could explain both counts, so compare same-sized fields with and without bees.
   • The claim is wrong, since seeds are made by plants and bees do nothing to the seeds that form.
   • 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.

6. 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.

7. 5.

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

   • The oaks grew the same, so there is no sign of harm; the moss gains a place to grow.
   • Moss still harms the oaks, since an effect can be real even when no growth difference shows up.
   • The moss helps the oaks, since the oaks with moss grew as well as the oaks without it.
   • The oaks with moss grew less, since moss on the trunk blocks light from reaching the leaves.
8. 6.

   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 competition needs one living thing to push or touch the other one.
   • 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.
9. 7.

   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 wrong, because mistletoe causes the oak to lose leaves within a week of landing.
   • One week is too short to see changes in yearly growth, so the oak should be tracked for years.
   • The claim is right, because one oak is enough to show what happens to other oaks too.
   • The claim is right, because no change in one week means mistletoe is harmless in the long run.
10. 8.

    Tala wants to test whether a root fungus helps pine seedlings. Which plan is best?

    • Plant seedlings with the fungus in matching pots and measure how tall they grow after 8 weeks
    • Plant seedlings with the fungus in sun and seedlings without it in shade, then compare their heights
    • Plant one seedling in each of several types of soil and compare their heights after 8 weeks
    • Plant equal seedlings in matching pots with and without the fungus, and compare heights at 8 weeks
11. 9.

    Zee wants to measure competition among bean plants for light and water. Which plan is best?

    • Plant 8 seeds in one pot and count how many of the 8 seeds sprout in the soil
    • Plant 1, 2, 4 and 8 seeds in pots, but give the biggest pots the most light and water
    • Plant 4 seeds in one pot and measure the total mass of the plants that grow in it
    • Plant 1, 2, 4 and 8 seeds in matching pots, and measure the average mass of one plant
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?

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