The conditions for natural selection

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Petal colors of seedlings in one wildflower patch (model data)

   petal color	seedlings
   white	12
   pink	18
   purple	10

2. 1.

   Ari counts the petal colors of seedlings in one wildflower patch. Which condition for natural selection does the table show?

   • Inheritance: the seedlings match their parents in petal color
   • Variation: the seedlings differ in petal color
   • Overproduction: the patch made more seedlings than it can support
   • Differential survival: pink seedlings survived better than white ones

3. One patch in one season (model data)

   measure	number
   seeds made	200
   plants the patch has room and water for	20

4. 2.

   Bo compares the seeds one patch makes with the plants it has room for. Which condition for natural selection does the table show?

   • Differential reproduction: some plants made more seeds than others
   • More offspring than can survive: 200 seeds, room for 20 plants
   • Inheritance: the plants pass their traits to their seeds
   • Variation: the seeds differ in a trait that can be counted

5. Petal color of 20 seedlings from each kind of parent plant (model data)

   parent plants	purple seedlings	white seedlings
   purple-petaled	17	3
   white-petaled	2	18

6. 3.

   Esme compares seedlings with their parent plants. Which condition for natural selection explains why the seedlings tend to match their parents?

   • Inheritance: seedlings tend to match their parents' petal color
   • Acquired traits: parents pass on the petal color they gained from soil
   • Differential survival: purple seedlings survived better than white ones
   • Variation: the seedlings differ in petal color

7. Moths in a sooty woodland, per 100 moths (model data)

   trait	generation 1	generation 2	generation 3
   dark moths	10	24	58
   light moths	90	76	42

8. 4.

   Jun reads a generation table for a sooty woodland. How many dark moths are there per 100 in generation 3?

   • 58 per 100, the dark moths in generation 3
   • 10 per 100, the dark moths in generation 1
   • 42 per 100, the light moths in generation 3
   • 24 per 100, the dark moths in generation 2

9. Finches on a model island, per 100 finches (model data)

   trait	generation 1	generation 2	generation 3
   large-billed	30	42	60
   small-billed	70	58	40

10. 5.

    Kira reads a generation table for finches on a model island. Which trait became more common from generation 1 to generation 3?

    • Small-billed: each finch's bill grew deeper, so fewer have small bills
    • Large-billed: from 30 to 60 per 100 finches
    • Small-billed: from 70 to 40 per 100 finches
    • Neither trait: the total is 100 in each generation

11. Finches before and after a drought on a model island (model data)

    bill type	finches before	finches surviving
    small-billed	40	8
    large-billed	40	24

12. 6.

    In 1977 a drought on Daphne Major left far fewer seeds. Luz reads model counts of the pattern. How many large-billed finches survived?

    • 8, the small-billed finches that survived
    • 16, the drop in large-billed finches
    • 24, the large-billed finches that survived
    • 40, the large-billed finches before the drought

13. A rare form of a resistance gene in a bacteria sample (model data)

    measure	number of bacteria
    bacteria in the sample	10,000
    bacteria carrying the rare form, tested before any antibiotic was added	4

14. 7.

    Noah reads a card about a rare form of a gene in bacteria. What is the original source of a new allele such as this one?

    • Mutation: a change in the DNA sequence of a gene
    • Need: the environment changes genes in individuals that need new traits
    • Selection: sorting individuals by survival creates new alleles
    • Inheritance: copying DNA from parent to young creates new alleles

15. Two plants over one season (model data)

    plant	height in cm	seedlings that survived to breed
    Plant P	30	12
    Plant Q	45	3

16. 8.

    Pia compares two plants. In natural selection, which plant has the higher fitness, and why?

    • Plant Q: its height shows it is the fittest plant
    • Plant P: more of its seedlings survived to breed
    • Plant Q: it is taller, so it is the stronger plant
    • Neither: both plants survived the season

17. Moths in a sooty woodland, per 100 moths (model data)

    trait	generation 1	generation 2	generation 3
    dark moths	20	45	70
    light moths	80	55	30

18. 9.

    Ren reads the moth table. What changed between generation 1 and generation 3?

    • The individuals: each light moth turned dark in its life
    • The population: dark moths became a larger share
    • Nothing: the total is 100 in each generation
    • The moths: they changed color on purpose to match the trees

19. A population and one finch (model data)

    measure	first value	second value
    population average bill depth: generation 1 then generation 10 (mm)	9.0	9.6
    one finch's bill depth: age 1 year then age 3 years (mm)	9.1	9.1

20. 10.

    Tala reads model bill depths for a finch population and for one finch. What does the table show about change?

    • Each finch's bill grew deeper, which raised the population's average
    • The population's bills deepened because the finches needed deeper bills
    • The population's average rose, while the one finch's bill stayed the same
    • Nothing changed, since the one finch had 9.1 mm both times