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 300 mm of rain is a less crowded amount of water for plants to share.
   • Place X, because 2,400 mm is a bigger number and so there must be more plants growing there.
   • Place X, because plenty of water and year-round warmth let many kinds of plants grow.
   • Place Y, because the big change in temperature through the year leaves room for many kinds of plants.
3. 2.

   A place gets 800 mm of rain a year, which fits both grassland and temperate forest. Esme wants to separate them. Which observation helps most?

   • The number of people who live nearby and how much of the land around the place they use for homes
   • The rain total again, measured carefully for one more year, to confirm what the rain gauge shows
   • Whether the plants are mostly grasses or tall trees that drop their leaves in autumn
   • The color of the sky on a sunny day in the middle of summer, as seen from the center of the place
4. 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 rain total, measured again with the same rain gauge for another full year to check it
   • The color of the soil at the surface, which can look different between the two places
   • The yearly average temperature, since tundra stays cold and deserts are often warmer
   • The number of plant species counted in one small square of ground at each of the two places
5. 4.

   Kira counted fewer frogs in one pond in a drought year and says the drought caused the drop. Which added evidence would best support that claim?

   • More photos of the same pond taken in the same drought year, to show how dry it looked
   • A neighbor's opinion that the pond looked emptier than it did in the year before the drought
   • Frog counts from several ponds over many drought years and many normal years
   • Frog counts from the same pond in the drought year, counted a second time by the same person
6. 5.

   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?

   • The data show the two rose together but never test whether fertilizer reached the lake
   • Fertilizer is sold in stores, so it cannot have any effect on a lake in the same county
   • Ten years is too short a time, because real patterns appear after a hundred years of data
   • The algae rose, and algae are living things, so they cannot be counted as data in the study
7. 6.

   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. 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 count the plants one time, at the end of the month of growing
   • Use one tank in the sun and one tank in the shade, with different water in each of the tanks
   • 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
9. 8.

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

   • Put equal snails in several tanks with different salt amounts, one with none, and count them
   • Put equal snails in tanks with different salt amounts and count the snails in just one of the tanks
   • 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 different kinds of water in each tank
10. 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 20,000 plants
    • About 100,000 plants
11. 10.

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

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