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Extra Air for the Cucumbers: Photosynthesis on a Farm

Grade 7 life science: analyze a greenhouse carbon dioxide and light trial and an alpaca energy budget to explain how photosynthesis moves matter and energy.

Grade 7ScienceInteractive · Printable

Aligned toMS-LS1-6

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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 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Matching, Circle the answer, Short answer

About this worksheet

What students practice

Students use greenhouse data to explain that plants build new matter from carbon dioxide and water.
Students explain why light energy limits how much extra carbon dioxide a plant can use.
Students trace matter and energy from a crop into an animal and back out.

How to use

Have students mark which two bays differ in only one way before they answer the Table 1 questions; use the final question as a written claim, evidence and reasoning task.

Curriculum

NGSS standard covered

MS-LS1-6

Explain how photosynthesis cycles matter and moves energy into and out of organisms.

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Name Date

Extra Air for the Cucumbers: Photosynthesis on a Farm

Use greenhouse bay data and an alpaca's energy budget to trace matter and energy.

The greenhouse bays

Read the passage and study Table 1. Then answer the questions.

Winter Cucumbers and Clover-Fed Alpacas

1The Ferreira farm sits in a cold northern valley. In summer, its herd of 12 alpacas grazes clover pasture. In winter, the alpacas eat clover hay, and the family grows cucumbers in a heated greenhouse to sell at the town market. Seventh grader Linnea Ferreira helps her father, Gustavo, in the greenhouse after school, and this winter she used the farm's records for a science fair project.

2Linnea started with a model of photosynthesis. In the chloroplasts of a leaf, light energy is used to combine carbon dioxide (CO₂) and water into sugar, and oxygen is given off. A plant uses some of the sugar in cellular respiration to release energy for its cells. It builds the rest into larger molecules, such as starch and cellulose, that make up its roots, stems, leaves and fruit.

3On sunny winter days, the greenhouse vents stay closed to keep the heat in. Linnea's CO₂ sensor showed that on those days the air inside could drop from about 420 parts per million (ppm) at sunrise to about 260 ppm by noon, unless CO₂ was added from a tank. Many greenhouse growers add CO₂, so her father agreed to a trial.

4The greenhouse has four bays. Each bay held 50 cucumber plants of the same variety, planted on the same day in slabs of rock wool, a fiber made from melted rock. The slabs were fed with water and a small amount of dissolved fertilizer, and every bay was kept at 22 °C. Bays 1 and 3 were kept near 400 ppm of CO₂, close to the level in outdoor air. Bays 2 and 4 were kept near 800 ppm. Bays 3 and 4 also had shade cloth that blocked half of the light. After six weeks, Linnea recorded the cucumbers picked per plant. She and her father also pulled and dried sample plants, with their fruit, to find the dry mass each plant had gained (Table 1).

5When the cucumber harvest ends, the alpacas eat the leftover vines. To see what happens to the food after that, the farm's veterinarian, Dr. Oyelaran, shared an energy budget for a young, growing alpaca that ate 1 kg of dried clover hay (Table 2 in Section 2). Energy is measured in megajoules (MJ).