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

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Mean shell width of a model snail species by rock layer (model data)

   layer	age (million years ago)	mean shell width (mm)
   1	10	12
   2	8	14
   3	6	16
   4	4	18
   5	2	20

2. 1.

   Ari reads a model fossil series for a snail species. What was the mean shell width in the layer that is 6 million years old?

   • 14 mm, from layer 2
   • 6 mm, from layer 3
   • 16 mm, from layer 3
   • 18 mm, from layer 4
3. 2.

   Bo reads a model graph of clam shell length through rock layers. What was the mean shell length 6 million years after the oldest layer?

   • 50 mm
   • 6 mm
   • 30 mm
   • 20 mm

4. Mean leaf length of a model plant species by rock layer (model data)

   layer	age (million years ago)	mean leaf length (mm)
   1	12	40
   2	9	44
   3	6	48
   4	3	52

5. 3.

   Esme reads a model fossil series for a plant species. How many million years separate the oldest layer from the youngest layer?

   • 9 million years
   • 3 million years
   • 15 million years
   • 12 million years

6. Mean shell height of a model mussel species by rock layer (model data)

   layer	age (million years ago)	mean shell height (mm)
   1	10	30
   2	8	33
   3	6	36
   4	4	39
   5	2	42

7. 4.

   Jun reads a model fossil series for a mussel species. Which pattern of change does the series show?

   • Stasis: the height stays the same through the series
   • Punctuated: long flat stretches with one quick jump
   • Gradual: small steady steps from layer to layer
   • Extinction: the species is missing from the later layers

8. Mean beak length of a model bird species by rock layer (model data)

   layer	age (million years ago)	mean beak length (mm)
   1	8	14
   2	6	14
   3	4	14
   4	3.5	22
   5	1.5	22

9. 5.

   Kira reads a model fossil series for a bird species. Which pattern fits the series?

   • Gradual: small steady steps through the whole series
   • Punctuated: the beak changed in a single moment, with no time passing
   • Stasis: the beak length stays the same through the series
   • Punctuated: long stasis, then a quick change, then stasis again

10. Mean leaf width of a model plant species by rock layer (model data)

    layer	age (million years ago)	mean leaf width (mm)
    1	9	20
    2	7	20
    3	5	20
    4	3	20
    5	1	20

11. 6.

    Luz reads a model fossil series for a plant species. Which statement fits the series?

    • Stasis: little change through 8 million years
    • Punctuated: the width jumps once between layers
    • Gradual: the width rises a little in each layer
    • No evolution: a species in stasis cannot change later

12. The five mass extinctions (real data from Biology 2e Table 47.2)

    mass extinction	time (million years ago)
    end-Ordovician	450–440
    Late Devonian	375–360
    end-Permian	251
    end-Triassic	205
    end-Cretaceous (K–Pg)	65.5

13. 7.

    Milo reads the table of the five mass extinctions. Which one is the most recent?

    • End-Cretaceous, at 65.5 million years ago
    • End-Triassic, at 205 million years ago
    • End-Permian, at 251 million years ago
    • End-Ordovician, at 450–440 million years ago

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

    topic	note
    when	about 65 million years ago
    cause scientists understand best	an asteroid impact off the coast of the Yucatán Peninsula
    dinosaurs	most became extinct, but one theropod line continued as birds
    recovery of biodiversity	on the order of 10 million years

15. 8.

    Pia reads notes on the end-Cretaceous mass extinction. What do the notes say about the dinosaurs?

    • They were not affected, and other groups became extinct
    • Most became extinct, and one theropod line continued as birds
    • They became extinct and left no descendants, so birds come from another group
    • One theropod line became extinct, and the other lines continued as birds

16. Word card (definition from Biology 2e)

    word	where it is used
    punctuated equilibrium	a model of how quickly species change in the fossil record

17. 9.

    Ren reads a word card. Which meaning fits punctuated equilibrium?

    • A species that stays fixed for good and cannot evolve again later
    • A new species that appears at once, with no time passing
    • Long stretches of little change, broken by quick changes
    • Change in small steady steps through the whole history
18. 10.

    Zee reads a word card. Which meaning fits mass extinction?

    • A time when life ended everywhere and nothing recovered after it
    • A slow, steady loss of one species over a very long time span
    • A period when species became extinct at a rate far above usual
    • One species becoming extinct at the usual background rate, in a quiet year