The conditions for natural selection
Grade 9 Science Worksheet
Circle the best answer.
Read this first
Moths on soot-darkened trees: each survivor leaves 2 young like itself (model data)
moth color generation 1 survived to breed generation 2 dark 20 16 ? light 80 24 ? Ari fills in generation 2 with the model rule in the title. How many dark moths are in generation 2?
- 16 dark moths: the survivors, with no young counted
- 40 dark moths: 20 moths leave 2 young each, whether or not they survived
- 32 dark moths: 16 survivors leave 2 young each
- 36 dark moths: 20 dark moths plus 16 survivors
Finches on a model island after a drought (model data)
bill type generation 1 survived to breed small-billed 60 12 large-billed 40 28 Bo predicts generation 2, assuming bill size is inherited and survivors breed. Which prediction fits the table?
- The shares stay 60 and 40, since young copy their parents
- Surviving small-billed finches will grow deeper bills, so the shares change
- Large bills will appear in the young because the drought made them necessary
- Most young will be large-billed, since 28 of the 40 survivors are
A model meadow study (model data)
observation result plants in the meadow heights from 20 to 60 cm seeds per tall plant and per short plant 40 and 10 seeds that find room to grow 5 of 100 offspring of tall and of short plants, grown in one soil 30 cm average for both Jun reads a model study. Tall plants leave more seeds, yet generation 2 is not taller. Which condition is missing?
- Differential reproduction: tall and short plants leave equal seeds
- Variation: the plants do not differ in height
- Overproduction: the meadow makes fewer seeds than it has room for
- Inheritance: the height difference is not passed on
A model patch of purple-flowered plants (model data)
observation result petal colors among the plants purple only alleles for petal color the same pair in each plant seedlings that find room 20 of 100 seedlings that match their parent plants 20 of 20 Kira reads a model patch. Natural selection cannot change petal color here. Which condition is missing?
- Overproduction: the patch makes fewer seedlings than it has room for
- Variation: the plants carry the same alleles, so petal color does not differ
- Inheritance: the seedlings do not match their parent plants
- Differential survival: white seedlings survive worse than purple ones
Model moths on soot-darkened trunks (model data)
moth color moths survived to breed dark 40 28 light 40 4 Where soot darkened tree trunks, dark peppered moths became more common. Milo reads model counts. Which explanation fits?
- Dark moths were stronger, so a larger share of them survived
- Soot made the moths mutate toward dark so they would match
- Dark moths matched the dark trunks, so a larger share survived and passed on the trait
- Light moths turned dark on the sooty trunks, so each one matched
Finches in the 1977 drought on Daphne Major (real pattern from Concepts of Biology)
observation what was found seeds after the drought far fewer; small, soft seeds declined more than large, hard seeds survival the following year large-billed finches survived better than small-billed finches average bill size measured afterward larger inheritance of bill size survivors with large bills tend to have offspring with large bills Noah reads the pattern from the 1977 drought. Which explanation fits the data and the conditions for natural selection?
- Large-billed finches survived better, and bill size is inherited, so young tended to have larger bills
- The finches needed larger bills, so larger bills appeared in the young
- The drought made each finch's bill grow deeper, so the average rose
- Large bills are the better trait in any year, so they were favored
Bacteria carrying a resistance gene, per 10,000 bacteria (model data)
sample carrying the gene before any antibiotic 4 after one round of antibiotic and regrowth 8,200 Pia reads a model sample of bacteria. Which explanation fits the change from 4 to 8,200 per 10,000?
- The antibiotic caused new resistance mutations in the bacteria it touched
- The gene was already present at a low count, and the antibiotic let those bacteria multiply
- The bacteria needed resistance, so more of them mutated to carry it
- Each bacterium became resistant after it met the antibiotic
Seedlings on a salty beach plot, 40 of each kind planted (model data)
kind survived to breed A 28 B 4 Ren compares equal groups of seedlings on a salty beach plot. How many times as many kind A as kind B survived to breed?
- 24 times, since 28 − 4 = 24
- 0.14 times, since 4 ÷ 28 is about 0.14
- 32 times, since 28 + 4 = 32
- 7 times, since 28 ÷ 4 = 7
Finches per 100 on a model island (model data)
trait generation 1 generation 2 generation 3 small-billed 75 60 35 large-billed 25 40 65 Tala compares generations. By how many per 100 did small-billed finches change from generation 1 to generation 3?
- Down by 15, from generation 1 to generation 2
- Up by 40, the change in the large-billed finches
- Down by 25, from 60 to 35
- Down by 40, from 75 to 35
Two plant types in a model patch (model data)
type plants in generation 1 young surviving to breed per plant A 20 6 B 20 2 Zee applies the model rule that young match their parent type. How many type A plants are in generation 2?
- 26, since 20 plants plus 6 young
- 120, since 20 plants leave 6 young each
- 160, since 120 type A and 40 type B
- 20, since the count of type A stays the same