Biodiversity and why it keeps ecosystems steady

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Plants counted in one meadow (model data)

   species	plants
   clover	120
   yarrow	40
   plantain	20
   dandelion	20
   total plants	200

2. 1.

   Kira reads the table. What share of the plants in the meadow belongs to the most common species?

   • 60%: 120 out of 200 plants
   • 25%: 4 species share the plants evenly
   • 20%: 40 out of 200 plants, the second species
   • 75%: 120 out of 160, the two largest counts

3. Three model communities (model data)

   community	species	share of the commonest species (%)
   X	8	90
   Y	8	15
   Z	4	25

4. 2.

   Milo reads the table. Which community is the most diverse?

   • Community X: its commonest species has the biggest share, 90%
   • Community Y: it has 8 species and none of them dominates
   • Communities X and Y tie: each has 8 species
   • Community Z: its species are the most evenly shared, 25% each

5. Growth in two plots (model data)

   plot	species	before the dry year	during the dry year
   D	16	480	360
   L	1	320	160

6. 3.

   Jun reads the table. By what percent did the growth of plot D change in the dry year?

   • It fell 33%: 120 ÷ 360
   • It fell 0%: a plot with many species does not change
   • It fell 75%: 360 ÷ 480, the share left
   • It fell 25%: 120 ÷ 480
7. 4.

   Noah reads the table. By what percent did the growth of plot F change in the dry year?

   • It fell 25%: 160 ÷ 640, the change of plot E
   • It fell 52%: 130 ÷ 250, the share left
   • It fell 48%: 120 ÷ 250
   • It fell 92%: 120 ÷ 130
8. 5.

   Zee reads the table. Which plot’s growth changed by the larger percent in the dry year?

   • Neither: the two plots changed by the same percent
   • Plot H: it fell 50%, against 25% for plot G
   • Plot G: it had more growth left, 600 against 150
   • Plot G: it lost more growth, 200 grams against 150 grams

9. Growth in one plot (model data)

   time	growth (grams per square meter)
   before the dry year	400
   during the dry year	300
   a year later	390

10. 6.

    Resistance is how little a plot changes during an event. Pia reads the table. Which comparison shows the plot’s resistance?

    • Growth before the dry year, by itself: 400
    • A year later against before: 390 against 400
    • The dry year against before: 300 against 400
    • A year later against the dry year: 390 against 300

11. Growth in two plots (model data)

    plot	before the dry year	during the dry year	a year later
    many-species plot	400	300	380
    one-species plot	400	200	380

12. 7.

    Ari reads the table. Which statement does the table support?

    • The many-species plot did not change during the dry year, so it had nothing to recover
    • The one-species plot recovered more because it rose 180 grams, against 80
    • Both plots reached 380 a year later, so recovery here did not depend on diversity
    • The many-species plot recovered faster because it fell less in the dry year

13. Growth in four plots (model data)

    plot	species	normal	dry year	a year later
    P1	1	300	150	300
    P2	2	500	260	500
    P3	16	1000	750	1000
    P4	32	800	624	800

14. 8.

    Luz reads the table. Which statement fits the table?

    • Plot P1 was the most resistant because it lost the fewest grams, 150
    • The four plots were equally resistant because all ended at their normal growth
    • Plots with more species recovered faster, since they lost less in the dry year
    • Plot P4 was the most resistant, losing 22%, and all four plots were back to normal a year later

15. Gene versions in two wildflower populations (model data)

    version of the gene	population P plants	population Q plants
    version 1	40	100
    version 2	30	0
    version 3	20	0
    version 4	10	0

16. 9.

    Esme reads the table for two populations of one wildflower species. Which has more genetic diversity?

    • Neither: genes inside one species do not count as diversity
    • Population Q: it has the most plants with one version, 100
    • Population P: its plants carry 4 versions of the gene, against 1 in Q
    • The same: both populations are one species, so their species diversity is equal

17. Dry-year growth by gene version (model data)

    gene version	growth per plant (grams)	population P plants	population Q plants
    version A	20	90	100
    version D	50	10	0

18. 10.

    Kira reads the model data. Which population grew more in total in the dry year?

    • Population P: 3,500 grams, counting 35 grams for each plant
    • The same, 2,000 grams: each population has 100 plants
    • Population P: 2,300 grams, against 2,000 for Q
    • Population Q: 2,000 grams, against 1,800 for P