Week 1 · Theme 1 Systems, Unit 1 Interactions of Organisms: Get Started, Concept 1.1 Plant Needs (A) · 3 lessons
3
Seeds in a towel, seeds in soil
Discovery Education Science P5: Term 1, Unit 1, pp. 11–14
GoalPredict, test and explain whether a seed needs soil to sprout.
New words
germinate · to begin to grow: a seed sproutsseedling · a young plant that has just sproutedprediction · a statement of what you think will happen, with a reason
Explanation
A seed holds a tiny new plant and a store of food. When it gets water and some warmth, it germinates: first a root pushes out, then a shoot. A seed can sprout in a wet paper towel with no soil at all, because the food stored inside it feeds the young plant. So soil is not a need for sprouting. Later the seedling uses up that store. Then it needs light and minerals, and the usual place where roots find water, minerals and a firm hold is soil. Soil is very useful, but it is not a basic need by itself. To test an idea fairly, we change only one thing, here towel or soil, and keep everything else the same.
Example results from one class
Day
Seedling in towel (cm)
Seedling in soil (cm)
4
2
1
8
4
5
12
5
9
Worked examples
Hana puts three bean seeds in a damp towel inside a clear bag and three seeds in a cup of soil. Both go on the same warm windowsill and get the same amount of water. Only one thing is different: towel or soil.
On day 4 Hana sees roots on the towel seeds, but nothing above the soil. Did the soil seeds fail? No. Roots and shoots grow out of sight underground, so later she lifts one gently to look.
Part
What it says
Claim
A seed can sprout without soil.
Evidence
The towel beans grew roots within 4 days.
Reasoning
A seed stores food, and water wakes it up.
A scientist answers with claim, evidence and reasoning, as in the table.
Class activity
Towel and soil test (one to two weeks, a grown-up helps). You need six bean seeds, two cups, potting soil, a paper towel, a clear bag, water and a ruler. Wet the towel, fold three seeds inside it and seal it in the bag. Plant three seeds 2 cm deep in a cup of soil. Keep both in the same warm, bright place and keep them damp. Write a prediction first, then measure every two days in a table. Wash your hands afterwards. Do not eat the seeds.
Practice
1
What feeds a seed while it sprouts in a wet towel?
The food stored inside the seed.
2
Look at the table. By how many cm did the soil seedling grow between day 5 and day 10?
Day
Towel (cm)
Soil (cm)
5
3
2
10
4
7
7 − 2 = 5 cm.
3
Marwan says, “Soil is a basic need for every plant.” Give one piece of evidence against this.
Seeds sprouted in a wet towel with no soil.
4
Name two things you keep the same to make the bean test fair, and the one thing you change.
Same: any two of the kind of seed, the water, the warmth, the light. Change: towel or soil.
