Populations, communities, ecosystems and biomes

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   Climate cards (model data). Place X: 2,400 mm rain a year; monthly average temperature 23 to 28 °C all year. Place Y: 300 mm rain a year; monthly average temperature from −5 to 25 °C over the year.

2. 1.

   Ari compares two places. Which place likely supports more kinds of plants, and what is the best reason?

   • Place Y, because the big change in temperature through the year leaves room for many kinds of plants.
   • Place X, because plenty of water and year-round warmth let many kinds of plants grow.
   • Place X, because 2,400 mm is a bigger number and so there must be more plants growing there.
   • Place Y, because 300 mm of rain is a less crowded amount of water for plants to share.

3. Table (model data)

   Average rain per year and plants seen. 1990s: 820 mm, tree seedlings common, grasses few. 2000s: 640 mm, seedlings fewer, grasses more. 2010s: 480 mm, seedlings rare, grasses common.

4. 2.

   Bo reads thirty years of data from one site. Which claim is best supported?

   • Trees no longer need water, which is why tree seedlings became rare over the years at the site.
   • The change is just a coincidence, so the plants at this site tell us nothing about the rain there.
   • The grasses made the rain fall, since the grasses became common as the rain went down over time.
   • As rain fell, the plants shifted from tree seedlings toward grasses, which fits a drier biome.
5. 3.

   Two places each get under 250 mm of rain. One is a desert and one is tundra. Jun can take one more measurement. Which separates them best?

   • The yearly average temperature, since tundra stays cold and deserts are often warmer
   • The rain total, measured again with the same rain gauge for another full year to check it
   • The number of plant species counted in one small square of ground at each of the two places
   • The color of the soil at the surface, which can look different between the two places
6. 4.

   Luz finds that county fertilizer sales and lake algae both rose for ten years, and claims fertilizer caused the algae. What is the weakest part of the claim?

   • Ten years is too short a time, because real patterns appear after a hundred years of data
   • Fertilizer is sold in stores, so it cannot have any effect on a lake in the same county
   • The algae rose, and algae are living things, so they cannot be counted as data in the study
   • The data show the two rose together but never test whether fertilizer reached the lake
7. 5.

   Milo counts birds only near a feeder on three mornings and finds four kinds. Milo says the whole park has few kinds of birds. What is the best response?

   • Three mornings are too many, since counts should be made on a single morning of the year
   • Four kinds is a good result, because any count of birds shows the park's kinds accurately
   • Feeders bring in each bird that lives in the park, so the count of four kinds is complete
   • Counts at one spot near a feeder may not represent the whole park, so sample more places
8. 6.

   Noah sees a pond's fish count level off at 300 for six years and claims the pond can hold 300 fish forever. What is the best response?

   • The data show a level for six years, but a change in rain or food could change the limit
   • The claim is wrong, because ponds cannot hold more than a few dozen fish at one time or place
   • The claim is right, since 300 is a round number that matches the pond's size and shape very well
   • The claim is right, because a count that stays level for six years cannot change after that
9. 7.

   Pia wants to test whether light affects how fast duckweed spreads on water. Which plan is best?

   • Use one tank in the sun and one tank in the shade, with different water in each of the tanks
   • Use one tank in the sun and count the plants one time, at the end of the month of growing
   • Put several tanks in the sun and change how much plant food each one gets over the weeks
   • Use several identical tanks, put some in sun and some in shade, and count the plants weekly
10. 8.

    Ren wants to test whether road salt in water changes how many pond snails survive. Which plan is best?

    • Put equal snails in tanks with different salt amounts and different kinds of water in each tank
    • Put many snails in one tank with a large amount of salt and count how many remain at the end
    • Put equal snails in tanks with different salt amounts and count the snails in just one of the tanks
    • Put equal snails in several tanks with different salt amounts, one with none, and count them
11. 9.

    Tala counts clover in 5 random squares of 1 square meter: 12, 8, 10, 11 and 9 plants. The meadow is 2,000 square meters. Which estimate is best?

    • About 10 plants
    • About 50 plants
    • About 100,000 plants
    • About 20,000 plants
12. 10.

    Zee tests whether shade changes how many seeds sprout. Which tray is the best control for the experiment?

    • A tray with the same soil and seeds, kept in the shade and given half as much water
    • A tray with the same soil, water and seeds, kept in full sun with no shade
    • A tray with no seeds, kept in shade so that the soil can be watched
    • A tray with extra seeds and the same water, kept in full sun for a longer time