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Hairy Leaves and Hungry Slugs: Four Generations in the Garden

Grade 8 natural selection math: compute survival rates and trait percents for hairy and smooth plants over four generations in a school garden.

Grade 8ScienceInteractive · Printable

Aligned toMS-LS4-6

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
11 questions
Classroom-ready

Details

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

About this worksheet

What students practice

Students calculate survival rates and the percent of a population with a trait across generations.
Students use a control line and generation data to explain how natural selection changes a trait's share.

How to use

Read the passage and walk through one row of Table 1 together, then let students use calculators for the percent questions before the written explanation.

Curriculum

NGSS standard covered

MS-LS4-6

Use math and data to explain how natural selection changes the share of a trait in a population over time.

Preview

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Name Date

Hairy Leaves and Hungry Slugs: Four Generations in the Garden

Track the share of hairy plants over four generations and explain the change.

Part 1: The garden line

Read the passage and the tables, then answer the questions.

The Slug Bed Experiment

1The garden club at Harmon Ridge Middle School grows a fast-growing plant in the mustard family. It goes from seed to seed in about six weeks, so the club can raise four generations in one school year. Some plants have tiny hairs on their leaves and stems, and others are smooth. In an earlier test, hairy parents mostly had hairy offspring and smooth parents mostly had smooth offspring. The raised bed beside the school greenhouse has many slugs, which come out at night to eat young leaves.

2The two kinds of plants are easy to tell apart. Under a hand lens, a hairy seedling has many tiny white hairs along the edges of its first leaves and on its stem, while a smooth seedling has none. Hairy and smooth plants grew to about the same height in the greenhouse and made flowers at about the same age.

3Club leader Yusuf Brandvold and their teacher, Ms. Celeste Amadi, set up two lines of plants that started from the same bag of mixed seeds. For each generation of the garden line, the club planted 200 seeds in trays in the greenhouse. After 7 days, before any slug could reach them, students used hand lenses to count the hairy and smooth seedlings. Then the trays went into the slug bed for 10 nights. Plants that still had at least two healthy leaves counted as survivors, and the club brought them back into the greenhouse to flower.

4Inside, students moved pollen between all of the survivors with cotton swabs, giving each plant the same number of strokes. They mixed all of the seeds the survivors made, and 200 seeds drawn at random became the next generation. Table 1 shows the garden line.

5The greenhouse line was handled the same way, with one difference: it never went outside, so no plants were lost to slugs. Table 2 shows its seedling counts.

6Every plant in both lines grew in the same potting mix, under the same grow lights, and was watered on the same schedule. The project ran from September to May. After each generation, Yusuf posted the new counts on the club bulletin board, and by spring several students had noticed that the slug bed looked fuzzier than it had in the fall.