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 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.
   • Place X, because plenty of water and year-round warmth let many kinds of plants grow.
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 color of the sky on a sunny day in the middle of summer, as seen from the center of the place
   • The rain total again, measured carefully for one more year, to confirm what the rain gauge shows
   • The number of people who live nearby and how much of the land around the place they use for homes
   • Whether the plants are mostly grasses or tall trees that drop their leaves in autumn
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 yearly average temperature, since tundra stays cold and deserts are often warmer
   • The color of the soil at the surface, which can look different between the two places
   • 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
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?

   • 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
   • 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
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?

   • Ten years is too short a time, because real patterns appear after a hundred years of data
   • The data show the two rose together but never test whether fertilizer reached the lake
   • The algae rose, and algae are living things, so they cannot be counted as data in the study
   • Fertilizer is sold in stores, so it cannot have any effect on a lake in the same county
7. 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 claim is wrong, because ponds cannot hold more than a few dozen fish at one time or place
   • The claim is right, because a count that stays level for six years cannot change after that
   • The data show a level for six years, but a change in rain or food could change the limit
   • The claim is right, since 300 is a round number that matches the pond's size and shape very well
8. 7.

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

   • Put several tanks in the sun and change how much plant food each one gets over the weeks
   • 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
   • 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 different kinds of water in each tank
   • 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
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 20,000 plants
    • About 10 plants
    • About 50 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 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 extra seeds and the same water, kept in full sun for a longer time
    • A tray with the same soil, water and seeds, kept in full sun with no shade