Fast and slow change, and extinction, in the fossil record

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   A model group of species after a mass extinction (model data)

   time since the mass extinction (million years)	species in the group
   before	100
   0	12
   10	40
   20	70
   30	100

2. 1.

   Ari reads a model table of species after a mass extinction. How long did recovery take, and what share of the species became extinct?

   • 20 million years; 88 percent
   • 30 million years; 12 percent
   • 30 million years; 88 percent
   • 100 million years; 88 percent

3. A model fossil series and the water level in each layer (model data)

   age (million years ago)	mean shell width (mm)	water level (m)
   10	15	50
   8	15	50
   6	15	50
   5	27	32
   3	27	32

4. 2.

   Bo reads a model fossil series beside a record of water level. Which claim and reason fit the table?

   • A quick change came with new conditions; the width jumped as the water level fell
   • Change is slow and steady everywhere; the width rose a little in each layer
   • The species stopped evolving; its flat stretch shows that it cannot change later
   • Change is instant; the width changed with no time passing between layers 6 and 5

5. Mean shell width of two model snail populations after the water level fell (model data)

   population	number of snails	mean width before (mm)	mean width 0.5 million years later (mm)
   large main population	500	30	30
   small cut-off group	20	30	44

6. 3.

   Jun reads a model table of two snail populations after the water level fell. Why could the small group change faster?

   • The small group changed in an instant, with no time passing
   • With a small gene pool, a helpful variation quickly became the usual form
   • Populations change at the same slow, steady rate, so the gap is a mistake
   • The large population was in stasis, so it had stopped evolving for good

7. Notes on the end-Ordovician extinction (real data from Biology 2e)

   topic	note
   number of events	two events about 1 million years apart
   recovery of biodiversity	5 to 20 million years, depending on location

8. 4.

   Kira reads notes on the end-Ordovician extinction. Why might recovery have taken from 5 to 20 million years?

   • One extinction has one recovery time, so the range must be a mistake
   • The two events were 5 to 20 million years apart, so the times differ
   • Life ended in some places, so those places took 20 million years to start again
   • It depended on location, so some places recovered more quickly than others

9. How three mass extinctions are described (real data from Biology 2e)

   mass extinction	how it is described
   Late Devonian	may have unfolded across a fairly long period; causes are poorly understood
   end-Triassic	may have unfolded gradually during the Triassic
   end-Cretaceous	an asteroid impact is the cause understood best; one theropod line continued as birds

10. 5.

    Luz reads how three mass extinctions are described. Which statement fits the table?

    • Each mass extinction ended life on Earth, so nothing continued after it
    • The three extinctions were quick events with the same asteroid cause, one after another
    • After the end-Cretaceous impact, no dinosaur line continued, so birds are unrelated to dinosaurs
    • Some may have taken a long time, and the end-Cretaceous has a well-understood cause

11. Notebook

    Notes on the end-Permian extinction (classmate's notebook), 4 lines. Columns: line, entry. Line 1: The end-Permian extinction was about 251 million years ago. Line 2: About 96 percent of marine species and 70 percent of land species became extinct. Line 3: So life ended completely, and the later species did not come from survivors. Line 4: Tetrapod diversity took about 30 million years to recover.

12. 6.

    Noah reads a classmate's notebook about the end-Permian extinction. Which line has the mistake?

    • Line 4: a recovery cannot take as long as 30 million years to finish
    • Line 1: 251 million years ago is too long ago to be a mass extinction
    • Line 2: 96 percent cannot be a share of the marine species that existed
    • Line 3: some species remained, since the shares are below 100 percent

13. Notebook

    Notes on extinction rates (classmate's notebook), 4 lines. Columns: line, entry. Line 1: The background extinction rate is about 1 extinction per million species per year. Line 2: A model group has 3 million species. Line 3: So about 3 species in the group become extinct each year at that rate. Line 4: A mass extinction has the same rate, so it is just the usual rate.

14. 7.

    Pia reads a classmate's notebook about extinction rates. Which line has the mistake?

    • Line 4: in a mass extinction the rate is far above the background rate
    • Line 1: the background rate is about 1 per thousand species per year
    • Line 2: a model group cannot have as many as 3 million species in it
    • Line 3: 3 million species at 1 per million per year gives 6, not 3

15. A model fossil series for a snail species (model data)

    layer	age (million years ago)	mean shell width (mm)
    1	12	16
    2	9	16
    3	6	16
    4	5.5	28
    5	3	28

16. 8.

    Ren reads a model fossil series. Which claim and reason fit the table?

    • The species changed gradually; evolution is slow and steady in a series like this
    • The species changed in an instant; no time passed between layers 3 and 4
    • The series shows stasis, then a quick change; both patterns can happen
    • The species stopped evolving in layers 1 to 3; stasis cannot be followed by change
17. 9.

    Tala reads a model graph of the extinction rate over time. Which claim and reason fit the graph?

    • A mass extinction occurred near 20 million years; its rate was far above the usual rate of 1
    • Life ended near 20 million years; the rate fell back to 1 because no species were left
    • A mass extinction occurred at 0 million years; the rate there was the lowest
    • Background extinction is shown near 20 million years, since a rate of 8 is the usual rate

18. Notes on the end-Cretaceous mass extinction (real data from Biology 2e)

    topic	note
    when	about 65 million years ago
    species lost	about 75 percent
    dinosaurs	most became extinct, but one theropod line continued as birds
    recovery of biodiversity	on the order of 10 million years

19. 10.

    Zee reads notes on the end-Cretaceous extinction. Which claim and reason fit the notes?

    • Birds descend from a theropod line; that line continued through the end-Cretaceous extinction
    • Dinosaurs became extinct about 10 million years ago; recovery took 65 million years
    • Life on Earth ended; about 75 percent of species became extinct at the end-Cretaceous
    • Dinosaurs left no descendants; most dinosaurs became extinct at the end-Cretaceous