What's Happening?
Cup A was put near a sunny window and got water every day. Cup B was put inside a dark closet and never got water.
After two weeks, your teacher took both cups out. Cup A had a tall, green plant growing! But Cup B had… nothing. The seed just sat in the dry dirt.
Why did the plant in Cup A grow, but the seed in Cup B did not?
- What was different about Cup A and Cup B?
- What do you think plants need to grow big and strong?
What Scientists Know
Plants are living things. Just like you need food, water, and a place to sleep, plants need certain things to grow. Scientists call these things needs.
When we observe (that means watch carefully) plants growing, we can figure out exactly what they need. Let's look at the most important things.
Water 💧
Light ☀️
The Right Space 🌍
Let's Try It!
You will need: 4 small cups, soil, bean seeds, water, a sunny window, a dark closet.
When you compare your cups, you are doing what real scientists do! Scientists collect observations (notes and drawings about what they see) and then compare them to figure out answers.
What We Discovered
When we compare all four cups, we can see something important. The plant that got water AND light grew the best. It was tall and green!
The cups that were missing something did not grow well. Cup 2 had light but no water. It barely grew. Cup 3 had water but no light. It grew a little, but it was pale and weak. Cup 4 had nothing — and it did not grow at all.
This tells us that plants need both water and light. Not just one — both! When we collect our observations (our drawings and notes) and compare them, we can see what made the difference.
| CUP | WHAT IT GOT | WHAT HAPPENED |
|---|---|---|
| Cup 1 | ☀️ Light + 💧 Water | Grew tall and green! |
| Cup 2 | ☀️ Light only | Barely grew, dried out |
| Cup 3 | 💧 Water only | Weak and pale |
| Cup 4 | Nothing | Did not grow |
See the Pattern!
Did you notice something? Every time a plant had what it needed, it grew. Every time it was missing something, it did not grow well. That is a pattern!
A pattern means something happens the same way again and again. Scientists love to find patterns because patterns help us understand the world.
This pattern is about cause and effect. A cause is what makes something happen. An effect is what happens because of it.
| CAUSE (WHAT WE DO) | EFFECT (WHAT HAPPENS) |
|---|---|
| Give a plant water and light | The plant grows tall and green 🌱 |
| Do NOT give a plant water | The plant dries up and does not grow 😟 |
| Water a flower garden | The flowers bloom and grow pretty 🌸 |
| Forget to water a flower garden | The flowers droop and turn brown 🥀 |
See? The same pattern shows up everywhere! When living things get what they need, they grow. When they do not, they struggle. This pattern works for plants in a cup, plants in a garden, and even plants in a big forest!
Plants in the Real World
People use what we know about plants every day! Farmers grow food for us. They make sure their plants get plenty of water and sunlight.
Have you ever seen a greenhouse? A greenhouse is a big glass building where people grow plants. The glass lets sunlight in. People also make sure the plants get water. Greenhouses help people grow plants even in the winter!
At home, if you have a plant on a windowsill, you are using the same science. You put it near the window for light and give it water so it stays healthy.
Key Vocabulary
- Observe — To watch something very carefully and notice details.
- Compare — To look at two or more things and find what is the same and what is different.
- Growth — When a living thing gets bigger and taller over time.
- Needs — Things a living thing must have to survive and grow, like water and light.
- Pattern — Something that happens the same way again and again.