Populations, communities, ecosystems and biomes

Grade 7 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Table (model data)

   Wildflower plants in 1 square meter and rain that year. Year 1: 40 plants, 700 mm. Year 2: 44 plants, 720 mm. Year 3: 15 plants, 250 mm. Year 4: 38 plants, 690 mm.

2. 1.

   Ari counts wildflowers in a meadow each year and records the rain. What does the table best support?

   • Wildflower numbers rose each year, so rain has no effect on the number of plants.
   • Wildflower numbers stay near 40 whatever the rain, so year 3 must be a counting mistake.
   • Wildflower numbers fell in the year with the least rain, so water probably limited the population.
   • Wildflower numbers fell in year 3 because too many insects arrived that year, which the table shows.
3. 2.

   Esme plans four studies of one forest. Which study needs the whole ecosystem, not just a population or a community?

   • How the number of oak seedlings in the forest changes from one spring to the next year
   • How soil moisture and sunlight change how well the forest's plants and insects grow
   • How the forest's beetle population changes in size from one year to the next year
   • How the forest's birds, insects and plants affect each other's numbers over the years
4. 3.

   Jun describes four groups in a pond. Which one is a community, not a population and not an ecosystem?

   • The snails of one kind that live in the pond, counted together as one group
   • The plants, insects, fish and snails that live in the pond together
   • The pond's water, mud, sunlight, plants, insects and fish together as one system
   • One fish that lives in the pond and the spot where it rests during the day

5. Table (model data)

   Bean plants after 6 weeks. Sunny plot: 30 cm tall. Shady plot: 12 cm tall. Both plots: same soil, same watering, same seeds.

6. 4.

   Kira grows beans in two plots. Both plots have the same soil and water. What does the table best show?

   • Sunlight affects how tall these plants grow, because the plots differ only in sunlight.
   • Soil affects how tall these plants grow, because the soil is the same in both plots.
   • The sunny plot's plants were already taller, so they got more sunlight than the shady plot.
   • Water affects how tall these plants grow, because both plots were watered the same way.

7. Table (model data)

   Seeds sprouted out of 100 planted. 10 °C: 12 sprouted. 15 °C: 38 sprouted. 20 °C: 71 sprouted. 25 °C: 74 sprouted.

8. 5.

   Milo plants 100 seeds in soil kept at four temperatures. What is the best conclusion from the table?

   • Warmer soil sprouts more seeds each time, so 40 °C would sprout more than 25 °C.
   • Colder soil sprouted more seeds, since 10 °C had the highest number of sprouts.
   • Warmer soil sprouted more seeds up to about 20 °C, and after that it added little.
   • Soil temperature does not matter, since 25 °C sprouted just 3 more seeds than 20 °C.

9. Table (model data)

   Rain per year and plant cover. Plot A: 300 mm, 20% of the ground covered by plants. Plot B: 900 mm, 70% covered. Plot C: 1,500 mm, 95% covered.

10. 6.

    Noah compares three plots. Which statement does the table support?

    • More rain went with more plant cover across the three plots.
    • Plot A had the most rain, because it had the lowest plant cover of the three plots.
    • Plant cover caused the rain, because the plot with the most plants got the most rain.
    • The three plots had about the same plant cover, because each of the three had some plants.
11. 7.

    A cloudy month cuts a pond's algae in half. Water fleas feed on algae. Pia predicts what happens to the water fleas. Which prediction is best?

    • Their numbers will probably fall, because their food supply shrank.
    • Their numbers will stay the same, because water fleas do not depend on the algae.
    • Their numbers will rise, because less sunlight makes the water cooler for them.
    • Their numbers will probably rise, because with less algae there is less to compete with.
12. 8.

    In a field, energy passes from sunlight to grass, to grasshoppers, to frogs. Which arrows show the path of energy, Ren?

    • Sunlight → frogs → grasshoppers → grass
    • Sunlight → grass → grasshoppers → frogs
    • Frogs → grasshoppers → grass → sunlight
    • Grass → sunlight → grasshoppers → frogs
13. 9.

    Algae in a pond hold 10,000 energy units. About 10% passes to the next level up each time. How many units reach the second level of animals, Tala?

    • 10 units: 10% of 10,000 is 1,000, then 100, then 10 for the second animals
    • 1,000 units: 10% of 10,000 passes up, and that is the whole amount for both animal levels
    • 100 units: 10% of 10,000 is 1,000 for the first animals, and 10% of that is 100
    • 9,000 units: 10% of the energy is used up, so 90% moves to the next level
14. 10.

    Energy units at each level of a meadow. Plants: 5,000. First animals: 500. Second animals: 50. Zee reads an energy table for a meadow. Which statement fits the numbers best?

    • About 10% of the energy at one level reaches the next, so the top level has the least.
    • The first animals hold the most energy, since they are in the middle of the table.
    • Each level has more energy than the one before, because animals are larger than plants.
    • Each level has the same energy, because energy is not used up when it passes along.