Populations, communities, ecosystems and biomes

Grade 7 Science Worksheet

Circle the best answer.

1. Read this first

   Table (model data)

   Algae per mL and crustaceans per liter. Month 1: 400, 20. Month 2: 600, 22. Month 3: 900, 30. Month 4: 500, 45. Month 5: 350, 40. Month 6: 600, 28.

2. 1.

   Ari counts algae and tiny pond crustaceans, which feed on algae, for six months. What does the table best show?

   • Algae and crustaceans rose and fell in the same months, so they are not related to each other.
   • The crustacean numbers are smaller than the algae numbers, so crustaceans must be the producers.
   • Crustaceans peaked in month 4, after the algae peak in month 3, so they may depend on algae.
   • Algae peaked in month 3, before the crustaceans, so the algae must depend on the crustaceans.

3. Table (model data)

   Deer on an island. Year 1: 20. Year 2: 40. Year 3: 75. Year 4: 120. Year 5: 150. Year 6: 155. Year 7: 150. Year 8: 152.

4. 2.

   Esme reads the deer counts on an island. What does the leveling off after year 5 suggest?

   • The deer will reach 300 soon, because growth was fast in the first four years.
   • Deer stopped being born after year 5, which is why the number stopped growing.
   • Weather set the limit at 150 deer, which the table shows in years 6 to 8.
   • The island's food and space can support about 150 deer, so growth leveled off.
5. 3.

   Jun reads a meadow's energy table: plants hold 8,000 units, first animals about 800 and second animals about 80. A disease cuts the plants to 4,000 units. What is the new energy for second animals?

   • About 4,000 units, because the animals receive the same energy as the plants
   • About 40 units, because every level gets half as much when the plants have half
   • About 80 units, because the second animals are too far up to notice the loss
   • About 400 units, because only the first animals lose energy from the plant loss

6. Simplified biome rules

   Desert: under 250 mm rain, few plants. Grassland: 500 to 900 mm rain, mostly grasses, few trees. Temperate forest: 750 to 1,500 mm rain, trees that drop their leaves in autumn. Tundra: under 250 mm rain, very cold, mosses and low shrubs. Place Q: 1,100 mm rain, tall trees that drop their leaves each autumn.

7. 4.

   Luz compares place Q with the rule table. Which biome fits place Q best?

   • Tundra, because the trees drop their leaves when the weather turns cold each year.
   • Temperate forest, because the rain and the trees that drop their leaves both fit.
   • Desert, because the leaves fall and leave bare branches for part of the year.
   • Grassland, because grasses grow under the trees and the rain is close to the range.

8. Simplified biome rules

   Desert: under 250 mm rain, few plants. Grassland: 500 to 900 mm rain, mostly grasses, few trees. Temperate forest: 750 to 1,500 mm rain, trees that drop their leaves in autumn. Tundra: under 250 mm rain, very cold, mosses and low shrubs. Place R: 180 mm rain, average temperature below 0 °C for many months, mosses and low shrubs.

9. 5.

   Milo compares place R with the rule table. Which biome fits place R best?

   • Grassland, because low shrubs and mosses grow close to the ground like grasses do.
   • Tundra, because the cold and the mosses and low shrubs separate it from a desert.
   • Desert, because 180 mm of rain is under the desert's 250 mm, so it must be a desert.
   • Temperate forest, because the cold months drop the temperature the way autumn does.

10. Simplified biome rules

    Desert: under 250 mm rain, few plants. Grassland: 500 to 900 mm rain, mostly grasses, few trees. Temperate forest: 750 to 1,500 mm rain, trees that drop their leaves in autumn. Rainforest: over 2,000 mm rain, warm all year, tall trees that keep their leaves. Place S: 2,600 mm rain, warm all year, tall trees that keep their leaves, many vines.

11. 6.

    Noah compares place S with the rule table. Which biome fits place S best?

    • Temperate forest, because tall trees grow in both and 2,600 mm is only somewhat more rain.
    • Desert, because warm places with tall trees can still be classed as deserts by their soil.
    • Grassland, because a lot of rain helps grasses grow thick between the vines and the trees.
    • Rainforest, because only it has over 2,000 mm of rain, warmth and tall trees with leaves.
12. 7.

    Pia reads that a town drains part of a wetland where frogs breed, shrinking the pools by 70%. Water birds feed on the frogs. Which prediction is best supported?

    • Frog numbers will rise, because with fewer pools there are fewer frogs to compete for food.
    • The water birds will increase, because fewer frogs means fewer places to hide from them.
    • Frog numbers will stay the same, because frogs can breed anywhere without water.
    • Frog numbers will fall first, and then the water birds will have less food.
13. 8.

    In a field, wild bees carry pollen between clover plants. A change in farming cuts the bees by half. Which prediction follows best, Ren?

    • Clover will make more seeds, because fewer bees means less damage to the flowers.
    • Clover will make the same seeds, because plants do not need other living things to make seeds.
    • Clover will make fewer seeds, but the field will have the same plants next year.
    • Clover will make fewer seeds, so fewer new clover plants may grow in later years.
14. 9.

    Tala reads that heavy rain washes extra plant food into a lake and algae double. Later the extra algae break down and bacteria use up oxygen. Which prediction is best?

    • Fish numbers will rise, because extra algae give each fish more food and more room.
    • Oxygen in the water will stay the same, because bacteria do not use oxygen.
    • Oxygen in the water will rise, because there are more living algae making food.
    • Oxygen in the water will drop, and fish that need a lot of oxygen may become fewer.
15. 10.

    Zee watches a new plant spread fast across a meadow, shading the ground and taking light and water that native flowers use. What is the best prediction for the native flowers?

    • Their numbers will probably fall, because the new plant takes light and water they need.
    • Their numbers will rise, because bees prefer to visit meadows with more kinds of plants.
    • Their numbers will stay the same, because plants do not share light or water.
    • Their numbers will probably rise, because the new plant gives them shade to grow in.