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
   • 18 mm, from layer 4
   • 16 mm, from layer 3
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?

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

   • 15 million years
   • 3 million years
   • 9 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?

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

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?

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

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?

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

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

14. Word card (definition from Biology 2e)

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

15. 8.

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

    • 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
    • A species that stays fixed for good and cannot evolve again later
16. 9.

    Tala reads a word card about dinosaurs. What does the card say about birds?

    • Birds come from another group, because dinosaurs left no descendants
    • Birds became extinct along with most dinosaurs
    • Birds are a kind of theropod that became extinct
    • Birds descend from a theropod line of dinosaurs
17. 10.

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

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