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

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?

   • 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
   • Differential reproduction: some plants made more seeds than others

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?

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

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

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

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?

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

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?

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

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

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