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2nd Grade Science (Next Generation Science Standards) ā€¢ Interdependent Relationships in Ecosystems

Do Plants Need Water to Grow?

Let's plan an investigation to find out what happens to a plant when it does not get water!

Explore the lesson 4 min read
A microscope with leaf and experiment flask for elementary science discovery
Inside this lesson 9 sections 4 questions 6 figures

SECTION 1

What's Happening?

ā„¹
šŸ” LOOK AT THIS!
šŸ’§With WaterTall & Green!šŸš«No WaterDroopy & Brownā†”
Two bean plants: one healthy with water, one wilted without water
ā„¹
šŸ’­ Thinking Questions

SECTION 2

What Scientists Know

All living things have needs. That means there are things they must have to stay alive and grow. People need food, water, and air. Plants have needs too!

1

Plants Need Water

Water helps a plant take in food from the soil. Without water, a plant cannot eat or grow. It will get droopy and turn brown.
2

Plants Need Light

Plants use sunlight to make their own food inside their leaves. Light is like the plant's kitchen!
3

We Can Test Ideas

Scientists plan investigations (that means they set up a test) to find out if something is true. We can do the same thing!

SECTION 3

Let's Try It!

We are going to plan an investigation. That means we will make a step-by-step plan to test our idea. Our idea is: "Plants need water to grow."

Worked example

  1. 1

    Our question

    Do plants need water to grow?
  2. 2

    What we need

    šŸŒ± Two small plants that are the same kind and same size šŸŖ“ Two pots with soil šŸ’§ A cup of water ā˜€ļø A sunny spot (like a window) šŸ“ A ruler šŸ““ A notebook to write what we see
  3. 3

    Step 1 ā€” Set up

    Put both plants in the same sunny spot. They must get the same sunlight!
  4. 4

    Step 2 ā€” Water only one

    Give water to Plant A every day. Do not give any water to Plant B.
  5. 5

    Step 3 ā€” Watch and record

    Every day, look at both plants. Use the ruler to measure how tall they are. Write down what you see in your notebook.
  6. 6

    Step 4 ā€” Compare

    After 10 days, look at your notes. Which plant grew more? Which one looks healthier?
Our Investigation Planā˜€ļøSame sunlight for both!Plant AšŸ’§Gets water every day āœ“Plant BšŸš«šŸ’§No water āœ—vs.We only change ONE thing: the water! Everything else stays the same.
Diagram showing the investigation plan: Plant A gets water, Plant B does not, both get sunlight

This is called a fair test. We only change one thing ā€” the water. We keep everything else the same (the sunlight, the soil, and the pot). That way, we know that water is what made the difference!

SECTION 4

What We Found Out

After 10 days, here is what Marcos wrote in his notebook:

DayšŸŒ± Plant A (with water)šŸŒ± Plant B (no water)
Day 15 cm tall, green and straight5 cm tall, green and straight
Day 36 cm tall, new leaf growing5 cm tall, leaves look a little droopy
Day 57 cm tall, more leaves5 cm tall, leaves are brown at the edges
Day 79 cm tall, strong stem5 cm tall, very droopy, dry soil
Day 1012 cm tall, many green leaves4 cm (bent over), brown and dried up

The plant that got water grew from 5 cm to 12 cm. It got big and green! The plant with no water stopped growing. Its leaves turned brown and it bent over.

This tells us something important: water helped the plant grow. Without water, the plant could not stay healthy.

Plant Height on Day 100 cm4 cm8 cm12 cm12 cmPlant A(with water)4 cmPlant B(no water)
Bar chart comparing Plant A at 12 cm tall versus Plant B at 4 cm tall on Day 10

SECTION 5

Do You See the Pattern?

Scientists always look for cause and effect. That means they ask: "When I do THIS, what happens?"

In our investigation, the cause was giving water (or not giving water). The effect was what happened to the plant.

CAUSE (What we did)EFFECT (What happened)
We gave the plant water šŸ’§The plant grew tall and stayed green šŸŒæ
We did NOT give water šŸš«The plant stopped growing and turned brown šŸ‚

This same pattern happens everywhere! When something needs something to live, taking it away causes a change.

LIVING THINGWHAT IT NEEDSWHAT HAPPENS WITHOUT IT
šŸŒ± PlantWaterIt wilts and stops growing
šŸŸ FishClean waterIt cannot breathe or swim
šŸ§’ You!Food and waterYou feel tired and hungry

SECTION 6

Real-World Connections

People use science to help plants grow! Farmers water their crops every day. If it does not rain enough, farmers use sprinklers or hoses to bring water to their plants. Without water, there would be no food in the grocery store!

Gardeners plan how to take care of their flowers and vegetables. They think about how much water each plant needs. Some plants need a lot of water. Some need just a little. It is like planning an investigation ā€” they watch what happens and make changes!

ā„¹
šŸ› ļø Design Challenge: Be a Garden Planner!
  • šŸ’§ How often will you water?
  • šŸ“ How will you know if the plants are growing?
  • šŸ““ What will you write down to keep track?

SECTION 7

Key Vocabulary

  • Investigation ā€” A plan to test an idea and find out if it is true.
  • Needs ā€” Things a living thing must have to stay alive and grow (like water, food, and air).
  • Fair test ā€” A test where you only change one thing and keep everything else the same.
  • Observe ā€” To watch carefully and notice what is happening.
  • Cause and effect ā€” When one thing (the cause) makes another thing happen (the effect).

SECTION 8

Practice: Show What You Know!

Question 1: Warm-Up

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Question 2: Building Skills

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Question 3: Thinking Deeper

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Question 4: Challenge

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SECTION 9

What's Next?

ā„¹
šŸ”® WHAT'S NEXT?

Varsity Tutors ā€¢ 2nd Grade Science (NGSS) ā€¢ Do Plants Need Water to Grow?