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Racing the Dry Spring: Field Mustard at Thistledown Farm

Grade 8 natural selection practice: use a farm's field mustard data from a dry year and a wet year to explain how flowering time affects reproduction.

Grade 8ScienceInteractive · Printable

Aligned toMS-LS4-4

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Single worksheet
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1 NGSS standard
Printable answer key
10 questions
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Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students calculate percents and seed shares to compare plants with different inherited flowering times.
Students explain how a dry year and a wet year favor different variations in flowering time.

How to use

Read the passage together and check that students know what each table column counts; allow calculators for the percent questions before the written explanation.

Curriculum

NGSS standard covered

MS-LS4-4

Explain how genetic variation in traits makes some individuals more likely to survive and reproduce.

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Name Date

Racing the Dry Spring: Field Mustard at Thistledown Farm

Use flowering and seed data to explain which plants pass on their genes.

Part 1: The dry year

Read the passage and Table 1, then answer questions 1–4.

Weeds Along the Field Edge

1Thistledown Farm grows vegetables and keeps a herd of dairy cows in a valley where most of the year's rain falls in winter and spring. In a normal year the rains last into May. Each January, after the first heavy rains, field mustard sprouts along the edges of the farm's fields. Field mustard is a weedy relative of the turnip with small yellow flowers. Each plant lives for only one season: it sprouts, grows, flowers, fills its seed pods and dies. Its seeds drop into the soil and sprout the next winter.

2Bartholomew Pemberton-Asante, an eighth grader whose family runs the farm, joined a project led by Ms. Priyanka Draganova, a scientist with the county farm office. In January they put a numbered flag beside 150 young mustard plants along one field edge. Every few days they checked each plant and recorded how many days passed from sprouting to its first open flower. Plants growing side by side differed a lot: some opened their first flower about 35 days after sprouting, and others took 55 days. Bartholomew tied a strip of colored tape to each flag on the day that plant's first flower opened. Every flagged plant had opened its first flower by the end of February.

3That year turned out to be dry. The spring rains stopped about a month early, and by early April the soil along the field edge was dry and hard. A mustard plant needs moist soil for several weeks after its first flowers open, while its seed pods fill and ripen. Many plants wilted and died with green, unripe pods. In May the team checked each flagged plant for ripe seeds and counted them (Table 1).

4Ms. Draganova had flagged 150 other mustard plants along the same edge the year before, which was a wet year with rain into May. Those results are in Table 2, in Part 2.

5To find out whether flowering time is passed on, the team planted seeds from early-flowering plants and seeds from late-flowering plants in the school greenhouse. All of the pots had the same soil, light and water. The young plants from early-flowering parents opened their first flowers after an average of 37 days. The young plants from late-flowering parents took an average of 52 days.