Populations, communities, ecosystems and biomes
Grade 7 Science Worksheet
Circle the best answer.
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.
Ari counts algae and tiny pond crustaceans, which feed on algae, for six months. What does the table best show?
- 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.
- The crustacean numbers are smaller than the algae numbers, so crustaceans must be the producers.
- Algae and crustaceans rose and fell in the same months, so they are not related to each other.
Table (model data)
Plants per 10 square meters. Year 1: Species A 10, Species B 60. Year 2: A 20, B 45. Year 3: A 35, B 30. Year 4: A 50, B 15.
Bo counts two plant species growing in one field for four years. Which statement fits the data best?
- As Species A grew, Species B fell, which fits the two competing for light, water or space.
- Species A and B help each other, since the total number of plants stayed near 65 to 70 in each year.
- Species A feeds on Species B, which is why B fell each year as A grew and spread across the field.
- The counts show no pattern, because one species went up while the other species went down.
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.
Esme reads the deer counts on an island. What does the leveling off after year 5 suggest?
- The island's food and space can support about 150 deer, so growth leveled off.
- 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 deer will reach 300 soon, because growth was fast in the first four years.
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 P: 800 mm rain, grasses and scattered shrubs, no tall trees.
Kira compares place P with the rule table. Which biome fits place P best?
- Grassland, because grasses and no tall trees fit, even though the rain also fits a forest.
- Temperate forest, because 800 mm of rain is inside the forest's range of 750 to 1,500 mm.
- Tundra, because scattered shrubs and no tall trees match the tundra's plants and low growth.
- Desert, because the shrubs and the bare spots between them show that the place has few plants.
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.
Luz compares place Q with the rule table. Which biome fits place Q best?
- Grassland, because grasses grow under the trees and the rain is close to the range.
- Desert, because the leaves fall and leave bare branches for part of the year.
- Temperate forest, because the rain and the trees that drop their leaves both fit.
- Tundra, because the trees drop their leaves when the weather turns cold each year.
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.
Milo compares place R with the rule table. Which biome fits place R best?
- Desert, because 180 mm of rain is under the desert's 250 mm, so it must be a desert.
- Tundra, because the cold and the mosses and low shrubs separate it from a desert.
- Grassland, because low shrubs and mosses grow close to the ground like grasses do.
- Temperate forest, because the cold months drop the temperature the way autumn does.
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.
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.
- Grassland, because a lot of rain helps grasses grow thick between the vines and the trees.
- Desert, because warm places with tall trees can still be classed as deserts by their soil.
- Rainforest, because only it has over 2,000 mm of rain, warmth and tall trees with leaves.
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 fewer seeds, so fewer new clover plants may grow in later years.
- Clover will make fewer seeds, but the field will have the same plants next year.
- 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.
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 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.
- Oxygen in the water will stay the same, because bacteria do not use oxygen.
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 rise, because the new plant gives them shade to grow in.
- Their numbers will probably fall, because the new plant takes light and water they need.
- Their numbers will stay the same, because plants do not share light or water.
- Their numbers will rise, because bees prefer to visit meadows with more kinds of plants.
