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

   • 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
   • A quick change came with new conditions; the width jumped as the water level fell
   • Change is instant; the width changed with no time passing between layers 6 and 5

5. Table

   Species counts on a model island around a mass extinction (model data), 4 rows. Columns: time | group X species | group Y species. Row 1: before | 6 | 1. Row 2: just after | 0 | 1. Row 3: 5 million years later | 0 | 4. Row 4: 10 million years later | 0 | 9.

6. 3.

   Esme reads a model table for an island around a mass extinction. Which statement fits group X and group Y?

   • Group Y became extinct, and group X branched from one species into 9
   • Both groups became extinct, so the 9 species of group Y must be a mistake
   • Group X recovered to 6 species, while group Y stayed at one species
   • Group X became extinct, and group Y branched from one species into 9

7. 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

8. 4.

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

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

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
    • 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
    • The three extinctions were quick events with the same asteroid cause, one after another

11. Notebook

    Notes on a model fossil series (classmate's notebook), 4 lines. Columns: line, entry. Line 1: The width stayed at 18 mm in the layers from 9 to 5 million years ago. Line 2: It then reached 30 mm in the layer at 4.5 million years ago. Line 3: So the change took 0.5 million years or less, a short time next to the stasis. Line 4: A quick change in a punctuated pattern means the species changed in an instant.

12. 6.

    Milo reads a classmate's notebook about a model fossil series. Which line has the mistake?

    • Line 4: a quick change still takes time, here up to 0.5 million years
    • Line 1: a species cannot stay at one width for as long as 4 million years
    • Line 3: a change cannot be called short next to a stasis of 4 million years
    • Line 2: a width cannot rise by 12 mm within as short a time as 0.5 million years

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 3: 3 million species at 1 per million per year gives 6, not 3
    • 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

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 stopped evolving in layers 1 to 3; stasis cannot be followed by change
    • The species changed in an instant; no time passed between layers 3 and 4
    • The species changed gradually; evolution is slow and steady in a series like this
    • The series shows stasis, then a quick change; both patterns can happen
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
    • A mass extinction occurred at 0 million years; the rate there was the lowest
    • Life ended near 20 million years; the rate fell back to 1 because no species were left
    • 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?

    • Dinosaurs became extinct about 10 million years ago; recovery took 65 million years
    • Birds descend from a theropod line; that line continued through the end-Cretaceous extinction
    • 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