Competition, predators and prey, and partnerships

Grade 7 Science Worksheet

Circle the best answer.

1. Read this first

   Table (model data)

   Percent of the plot covered. Week 1: Grass A 40, Grass B 10. Week 2: A 35, B 25. Week 3: A 25, B 40. Week 4: A 15, B 55.

2. 1.

   Ari measures how much of a plot two grasses cover. Which interaction does the pattern fit, and why?

   • Mutualism, because both grasses are growing in the same plot over the weeks of the study.
   • Commensalism, because Grass A is not changed while Grass B gains more and more cover.
   • Parasitism, because Grass B is living on Grass A and taking things from it as it grows.
   • Competition, because as Grass B gained cover, Grass A lost cover from the same plot.

3. Table (model data)

   Plants and bees per hectare. Year 1: 20 plants, 8 bees. Year 2: 28 plants, 12 bees. Year 3: 40 plants, 20 bees. Year 4: 55 plants, 30 bees.

4. 2.

   Bo counts flowering plants and bees in a meadow for four years. Which interaction does the pattern fit best?

   • Commensalism, because the plants gain while the bees stay the same.
   • Competition, because the plants and the bees are both using the same meadow.
   • Parasitism, because the bees rose while the plants were being used up.
   • Mutualism, because both populations rose together over the four years.
5. 3.

   Yearly branch growth. 0 mistletoe clumps: 24 cm. 2 clumps: 19 cm. 4 clumps: 13 cm. 6 clumps: 8 cm. Esme compares oak branches with different amounts of mistletoe. What does the table best support?

   • Branch growth has no link to mistletoe, since both are found together on the same branches.
   • More mistletoe clumps went with more branch growth, which fits a partnership between the two.
   • More mistletoe clumps went with less branch growth, which fits mistletoe harming the oak.
   • Slow branch growth caused the mistletoe to grow, since weak branches attract mistletoe seeds.

6. Table (model data)

   Lettuce leaf area. Week 1: 10. Week 2: 20. Week 3: 32. Week 4: 40. At week 4, weeds start to grow in the plot and use the same light, water and space.

7. 4.

   Kira grows lettuce in a plot, and weeds start to grow there after week 4. What will the lettuce line most likely do next?

   • The line will drop to zero in week 5, because weeds remove lettuce right away.
   • Growth will speed up, because the weeds will shade the soil and keep it moist.
   • Growth will stay on the same path, because weeds and lettuce are different plants.
   • Growth will slow or flatten, because the weeds will take light, water and space.
8. 5.

   Bean plant height after 6 weeks. Plots with root bacteria: 30 cm. Plots without root bacteria: 12 cm. Bean plants grow with bacteria in their roots that give them nitrogen. Luz removes the bacteria from one plot. What will most likely happen to the beans there?

   • They should grow less, since they lose the nitrogen the bacteria gave them.
   • They should grow more, since the bacteria were taking nitrogen from the beans.
   • They should grow more, since the roots will have more room for water.
   • They should grow the same, since roots do not need help from other living things.

9. Table (model data)

   Kind A plants per bed. Week 1: 40. Week 2: 36. Week 3: 32. Kind B plants per bed rose from 10 to 30 in those same weeks.

10. 6.

    Kind A and Kind B share a bed and use the same resources. Milo pulls out Kind B after week 3. What will the Kind A line most likely do?

    • Kind A should stay at 32 plants, since plant counts stop changing after the third week.
    • Kind A should fall faster, since Kind B was helping Kind A grow and is now gone from the bed.
    • Kind A should keep falling at the same speed, since Kind B had no effect on Kind A to begin with.
    • Kind A should stop falling and start to rise, since it no longer shares resources with Kind B.
11. 7.

    Year 1: 2 clumps, oak growth 20 cm. Year 3: 4 clumps, 17 cm. Year 5: 7 clumps, 13 cm. Noah tracks an oak and its mistletoe. If the clumps keep rising to 10 by year 7, what will the oak's yearly growth most likely be?

    • Exactly 13 cm, since growth stays at the last measured value however many clumps grow.
    • Higher than 13 cm, since more clumps share the load of taking water and minerals from the oak.
    • Back near 20 cm, since trees recover when more mistletoe grows on them over the years.
    • Lower than 13 cm, since more mistletoe takes more water and minerals from the oak.

12. Table (model data)

    Lettuce leaf area. Plot A: week 1: 8, week 2: 14, week 3: 18, week 4: 26, week 5: 34. Plot B: week 1: 8, week 2: 14, week 3: 18, week 4: 19, week 5: 17. Same sun and watering.

13. 8.

    Pia compares two lettuce plots. Weeds were pulled from Plot A in week 3 but left in Plot B. What does the difference show?

    • Lettuce grew more where the weeds were left, so the weeds were helping the lettuce along.
    • The plots were the same until week 5, so the weeds made no difference to the lettuce at the end.
    • Plot A got more sun than Plot B, so the sun explains why Plot A grew more than Plot B did.
    • Lettuce grew more where the weeds were pulled, so the weeds were competing with the lettuce.

14. Table (model data)

    Average mass of one plant after 6 weeks. 1 seed per pot: 12 g. 2 seeds per pot: 9 g. 4 seeds per pot: 5 g. Same soil, water and light in every pot.

15. 9.

    Tala grows beans in pots with different numbers of seeds. What does the table best show?

    • Pots with more seeds got more light, which explains the mass of each plant in the pots.
    • Each plant grew smaller as more seeds shared a pot, which fits crowding and competition.
    • Each plant grew larger as more seeds shared a pot, which fits a partnership among the plants.
    • The pots show no pattern, since the mass of one plant changed in each of the pots.

16. Table (model data)

    Host growth over 4 weeks. Hosts with dodder: 9 cm. Hosts without dodder: 15 cm. Dodder cannot grow without a host.

17. 10.

    Zee compares host plants with and without dodder, a plant that wraps around its host and takes water from it. What does the table show?

    • The hosts with dodder grew less, so the dodder and the host are partners that both gain.
    • The hosts with dodder grew less, so the dodder gains from the host while the host loses.
    • The hosts with dodder grew less, so the host gains from the dodder and the dodder loses.
    • The hosts with dodder grew the same, since both groups were measured over the same 4 weeks.