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?

   • Overproduction: the patch made more seedlings than it can support
   • Inheritance: the seedlings match their parents in petal color
   • Variation: the seedlings differ in petal color
   • 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?

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

5. 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

6. 3.

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

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

7. 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

8. 4.

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

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

9. 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

10. 5.

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

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

11. Dark color in a moth population (model data)

    question	answer
    Is dark color passed from parent moths to their young?	yes
    Is survival to breed higher in sooty woods?	yes, for dark moths

12. 6.

    Milo reads a card on dark moth color. Which term names an inherited trait that raises survival and reproduction in the current environment?

    • Fitness: how strong and large an individual is
    • Variation: a difference that may or may not be inherited
    • Mutation: a change in DNA that appears when a trait is needed
    • Adaptation: an inherited trait that helps survival and reproduction

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
    • Inheritance: copying DNA from parent to young creates new alleles
    • Selection: sorting individuals by survival 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
    • Neither: both plants survived the season
    • Plant P: more of its seedlings survived to breed
    • Plant Q: it is taller, so it is the stronger plant

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 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
    • The individuals: each light moth turned dark in its life

19. Seeds from two sets of plants grown in the same poor soil (model data)

    parent plants	parent height (cm)	offspring height (cm)
    grown in rich soil	60	30
    grown in poor soil	30	30

20. 10.

    Zee grows seeds from rich-soil plants and poor-soil plants in the same poor soil. What does the table show about the extra height?

    • The extra height was inherited, so the offspring should be taller
    • Soil does not affect height, since the offspring match
    • The extra height came from the soil and was not inherited
    • The rich-soil plants evolved extra height during their lives