Question

For a school science experiment, Sam took three jars of equal sizes and filled them with equal amounts of nutrient-rich soil. From a bag of mustard seeds, he sowed 10 seeds in Jar A, 20 seeds in Jar B, and 40 seeds in Jar C. All three jars were given the same amount of water and exposed to the same amount of sunlight daily.

The growth of the mustard plants was monitored for three weeks, and the following measurements show the average height of the seedlings and were recorded at the end of each week.

JAR A JAR B JAR C
Week 1 4 cm 3.2 cm 3 cm
Week 2 8.5 cm 6.6 cm 5.8 cm
Week 3 14 cm 10.2 cm 8.6 cm

What can Sam conclude from the recorded data?
A.
The growth rate of mustard plants is affected by the number of seeds planted in a particular area.
B.
The growth rate of mustard plants is controlled completely by the seeds' genes.
C.
The growth rate of mustard plants remains constant as the plants grow from seeds.
D.
The growth rate of mustard plants does not depend on the environment in which the seeds are grown.

Answer 1

A.

Because the jars were given the same soil, water, and light, the only intentional difference was the number of seeds. Jar A (fewest seeds) produced the tallest seedlings, Jar B intermediate, and Jar C (most seeds) the shortest. This pattern shows that seed density (competition for nutrients, water, light and space) affected the plants' growth rate.