Competition, predators and prey, and partnerships

Grade 7 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Table (model data)

   Plants per plot. Kind A alone: 40. Kind A with Kind B: 70. Kind B alone: 30. Kind B with Kind A: 55.

2. 1.

   Ari counts two kinds of plants alone and together in garden plots. Which interaction do the counts show?

   • Mutualism, because both kinds have more plants when they grow together
   • Commensalism, because one kind gains while the other kind stays the same
   • Parasitism, because one kind gains by taking something from the other kind
   • Competition, because two kinds that share a plot affect each other's numbers

3. Table (model data)

   Plants per plot. Kind C alone: 50. Kind C with Kind D: 28. Kind D alone: 60. Kind D with Kind C: 31.

4. 2.

   Bo counts two kinds of plants alone and together in garden plots. Which interaction do the counts show?

   • Parasitism, because one kind gets smaller while the other kind grows larger
   • Commensalism, because one kind is not changed by the other kind
   • Competition, because both kinds have fewer plants when they share a plot
   • Mutualism, because both kinds are affected by the other kind in the plot

5. Table (model data)

   Yearly growth of oak branches. Without mistletoe: 20 cm. With mistletoe: 12 cm. Mistletoe grows only on host trees such as oaks, about 6 clumps per branch.

6. 3.

   Esme measures oak branches with and without mistletoe. Which interaction does the table show?

   • Commensalism, because the mistletoe gains while the oak is not changed
   • Parasitism, because the mistletoe gains from the oak while the oak grows less
   • Mutualism, because the oak and the mistletoe both gain from living together
   • Competition, because the oak and the mistletoe both lose when they share a branch

7. Table (model data)

   Ferns grow on 18 oak branches out of 20, and on 4 bare rock ledges out of 20. Yearly oak branch growth: 21 cm with ferns, 21 cm without ferns.

8. 4.

   Jun compares oak branches with and without ferns on them. Which interaction does the table show?

   • Mutualism, because the ferns and the oak both get something useful from living together on the branch
   • Commensalism, because the ferns gain a place to grow while the oak's growth stays the same
   • Parasitism, because the ferns gain a place to grow and the oak is harmed by having them on its branches
   • Competition, because the ferns and the oak use the same branches and both of them end up losing
9. 5.

   Squash plants make more fruit when bees visit their flowers. A spray removes the bees from Kira's garden. What will most likely happen to the squash fruit?

   • Fruit numbers will fall, because the plants lose the bees that carry pollen.
   • Fruit numbers will stay the same, because plants make fruit without help from other living things.
   • Fruit numbers will rise, because the plants no longer share their nectar with the bees.
   • Fruit numbers will rise, because the bees were competing with the plants for water.
10. 6.

    Orchids grow on the branches of a tree and take nothing from it. Luz removes the orchids. What will most likely happen to the tree's growth?

    • Little change, because the orchids neither helped the tree nor harmed it.
    • The tree will grow faster, because the orchids were hiding its leaves from the sun.
    • The tree will grow slower, because the tree needs the orchids to grow well.
    • The tree will grow faster, because the orchids were taking light and water from it.
11. 7.

    Mistletoe takes water and minerals from the oak it grows on. Milo removes the mistletoe from one oak. What will most likely happen to that oak's growth?

    • Its growth should fall, because the oak will lose the shade that the mistletoe was giving it.
    • Its growth should rise, because the mistletoe was taking water and minerals from it.
    • Its growth should stay the same, because a plant living on an oak cannot affect the oak.
    • Its growth should fall, because the oak needs the mistletoe to grow well and stay healthy.
12. 8.

    Two kinds of plants share one bed and use the same light and water. Noah pulls out Kind B. What will most likely happen to Kind A?

    • Kind A should stay the same, since plants do not share light or water in a bed.
    • Kind A should grow more, since it no longer shares light and water with Kind B.
    • Kind A should grow less, since the bed will have fewer plants to hold the soil.
    • Kind A should grow less, since Kind A needs Kind B to grow well.
13. 9.

    Bees counted. 30 flower patches: Species A 120, Species B 90. 15 flower patches: Species A 60, Species B 40. Pia compares two bee kinds before and after half the flower patches are cut. What do the counts best show?

    • Flower patches limit both kinds, since both counts fell by about half when the patches were halved.
    • Water limits both kinds, since bees need water to live in a meadow and the table has water too.
    • Sunlight limits both kinds, since the table shows that sunlight changed when the patches were cut.
    • Species A limits Species B, since Species A has more bees than Species B in both rows.

14. Table (model data)

    Fish in the tank. 4 hiding places: Kind F1 has 20, Kind F2 has 16. 8 hiding places: Kind F1 has 38, Kind F2 has 33.

15. 10.

    Zee counts two fish kinds in a tank with different numbers of hiding places. Eight more hiding places are added to the 8. What is the best prediction?

    • Kind F1 should rise and Kind F2 should fall, because F1 had more fish.
    • Both kinds should increase, because hiding places limit both of them.
    • Both kinds should fall, because more hiding places mean more room to compete in.
    • Both kinds should stay the same, because 8 places were already enough for them.