Worksheet

Tassels, Silks and Monarch Eggs

Grade 6 life science: seed-corn ear tests and a monarch egg count explain how wind-pollinated flower structures and egg-laying behavior aid reproduction.

Grade 6ScienceInteractive · Printable

Aligned toMS-LS1-4

Play online Play as a game

PrintLetter-size worksheet Answer keyPrintable answers

Assign to classAssign to your classes, or get a join code

What’s included

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

Details

Format: Interactive · Printable
Grade: Grade 6
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use kernel counts to explain how tassels, pollen and silks help corn reproduce by wind.
Students use egg counts to explain how a monarch's egg-laying behavior helps its young survive.
Students argue from evidence why making large amounts of pollen raises the chance of reproduction.

How to use

Show a real ear of corn with its silks, or a photo, before reading; then let students work through the tables in pairs and write the final argument alone.

Curriculum

NGSS standard covered

MS-LS1-4

Explain how animal behaviors and plant structures help them reproduce successfully.

Preview

OwlSheets.com

Name Date

Tassels, Silks and Monarch Eggs

Explain how plant structures and animal behaviors help reproduction.

Pollen in the seed-corn field

Read the passage and Tables 1 and 2, then answer the questions.

A Summer on the Detasseling Crew

1Lorenzo Hakimi, who is 13, spent his first summer job on a detasseling crew in a seed-corn field outside his town in Iowa. The field, the people and the numbers here are made up, but they are based on real farm studies. On the first morning, crew leader Annika Brandvold explained what the crew was doing and why.

2A corn plant has two kinds of flowers. The tassel at the very top holds the male flowers, which release pollen. The ear, lower on the stalk, holds the female flowers. Each future kernel on the ear is joined to its own long thread, called a silk, that grows out of the tip of the husk. Silks are covered with fine, sticky hairs. Corn flowers have no petals, no nectar and no scent. A tassel sheds millions of tiny, light pollen grains over about a week, and the wind carries them. Most grains settle within a few dozen meters of the plant.

3In this field, four rows of one corn variety, the seed rows, alternate with one row of a second variety, the pollen row. Rows are about 0.75 m apart. The crew pulls the tassels off every plant in the seed rows before they shed pollen, so that the seeds on those plants are a cross between the two varieties.

4Plant scientist Dr. Ingrid Mwale tagged ears on plants in the seed rows to show the crew how kernels form. She bagged the ears in Groups B, C and D before their silks appeared and treated them in different ways (Table 1). In the table, “shedding ended” means the day the pollen rows stopped shedding pollen. She also tagged ears on tasselless seed-row plants in a strip running away from the field's last pollen row (Table 2).

5Wildflowers and milkweed grow along the field's edges. A female monarch butterfly lays eggs one at a time, gluing each to a leaf, and may lay several hundred in her life. Before laying, she often lands on a leaf and drums on it with her front feet, which have taste receptors. Monarch caterpillars eat milkweed leaves and no other plants. A newly hatched caterpillar is about 2 mm long and chews soft, young leaves more easily than tough, older ones. Milkweed mowed in June grows back as young plants with soft leaves and no flowers, while unmowed plants are tall, older and in flower. In July, Lorenzo helped Dr. Mwale search 40 plants of each kind along one edge for eggs (Table 3).

Table 1. Tagged Ears in the Seed Rows (20 ears in each group)
Group	Bags on the silks	Kernels per ear (avg.)
A	None (left open)	540
B	On the whole time	0
C	On; tassel pollen shaken in once	486
D	Removed 10 days after shedding ended	6

Use Table 1.

The average Group C ear had % as many kernels as the average Group A ear.

Which two groups, compared with each other, best show that pollen has to reach the silks for kernels to form, with the bag ruled out as a cause?

A. Groups A and D
B. Groups A and B
C. Groups B and C
D. Groups A and C

The Group D silks were uncovered 10 days after the pollen rows stopped shedding, yet their ears had only about 6 kernels. Which explanation fits the passage and Table 1 best?

A. The bags trapped pollen from each plant's own tassel, and that pollen harmed the silks.
B. By the time the bags came off, almost no pollen was left in the air to reach the silks.
C. The long time in a bag blocked sunlight, so the ears made too little sugar for kernels.
D. The silks turned into tassels inside the bags and shed their own pollen instead.

Corn flowers have no petals, no nectar and no scent. How do these features fit the way corn is pollinated?

A. Corn pollen is too heavy to blow away, so petals would not help move it.
B. Bees visit corn at night, when bright petals and scent would not be noticed.
C. The silks hide nectar inside the husk, and bees reach it through the tip.
D. Wind carries corn pollen, so the plant spends no energy on parts that draw in animals.

Table 2. Ears at Different Distances From the Last Pollen Row (20 ears each)
Distance (m)	Kernels per ear (avg.)
1	530
10	470
30	330
60	180

Use Table 2.

From 1 m to 60 m away from the pollen row, the average number of kernels per ear fell by kernels.

Use paragraph 3 and Table 2. Why does the field have a pollen row after every four seed rows?

A. Every seed row stays within a few meters of pollen, where Table 2 shows ears fill well.
B. Bees can fly the short distance between rows and carry pollen from tassels to silks.
C. The roots of the pollen rows share water with the seed rows, which helps the kernels grow.
D. The pollen rows block the wind, so pollen falls straight down onto the silks below.

Use paragraph 3. Lorenzo misses one tassel in a seed row, and it sheds pollen. Which result is most likely?

A. Some ears near that plant may catch its pollen, so some of their seeds are not the planned cross.
B. The ear on that plant turns into a second tassel and sheds even more pollen into the field.
C. The pollen rows stop shedding pollen, because the extra tassel blocks the wind from them.
D. The silks on that plant grow pollen of their own and fill the ear with it in a few days.

Monarch eggs on the field edge

Use paragraph 5 and Table 3.

Table 3. Monarch Eggs Found in July (40 plants of each kind)
Plant	Plants with eggs	Eggs found
Young milkweed, under 50 cm	27	32
Tall milkweed in flower	7	8
Goldenrod	0	0
Corn, edge row	0	0

Use Table 3.

The young milkweed had times as many eggs as the tall milkweed in flower.

How does laying eggs on young milkweed most likely help a female monarch reproduce successfully?

A. Eggs on young milkweed blow on the wind to new fields more easily than others.
B. Caterpillars that hatch on young plants can feed on the goldenrod next to them.
C. Caterpillars that hatch there find soft young leaves that are easy to chew.
D. She drinks nectar from the flowers of young milkweed while she lays her eggs.

10.

Before laying, a female drums on a leaf with her feet, which have taste receptors. Which result in Table 3 does this behavior help explain best?

A. Seven of the tall milkweed plants had eggs on them.
B. No eggs were found on the goldenrod or the corn.
C. Lorenzo and Dr. Mwale searched 40 plants of each kind.
D. The young milkweed plants were under 50 cm tall.

11.

Sort each structure or behavior by how it most likely helps reproduction.

The tassel sits at the very top of the corn plant.A female monarch tastes a leaf with her feet before laying.Each tassel sheds millions of tiny, light grains.A female monarch picks young milkweed with soft leaves.Silks are covered with fine, sticky hairs.

Helps pollen reach silks	Helps eggs and young caterpillars

12.

Lorenzo's friend says, "A corn tassel wastes millions of pollen grains, so making that much pollen is pointless." Do you agree? Write a claim, give evidence from Tables 1 and 2, and explain how the tassel, the pollen and the silks help corn reproduce by wind.