Question

3. After studying about recycling, members of John’s biology class investigated the effects of various recycled products on plant growth. John’s lab group compared the effect of different aged grass compost on bean plants. Because decomposition is necessary for the release of nutrients, the group hypothesized that older grass compost would produce taller bean plants. Three flats of bean plants (25 per flat) were grown for 5 days. The plants were then fertilized as follows: flat A = 450. g of 3 month old compost; flat B = 450. g of 6 month old compost; flat C = 0 g of compost. The plants received the same amount of sunlight and water each day. At the end of 30 days, the group recorded the height of the plants in cm.

Hypothesis:
Independent Variable:
Dependent Variable:
Constant (at least one):
Control:
Number of groups:
Number of trials per group:

Answer 1

In the biology experiment, the hypothesis predicted that older compost leads to taller bean plants, the independent variable was the age of the compost, the dependent variable was the plant height, and the control was the group with no compost.

Step-by-step explanation:

Identifying Variables and Structure in a Biology Experiment

In the described biology class experiment, the hypothesis is that older grass compost will produce taller bean plants due to the necessary decomposition for the release of nutrients. The independent variable is the age of the grass compost (3 month-old, 6 month-old, and no compost). The dependent variable is the height of the bean plants measured at the end of the experiment. Constants in the experiment include the amount of sunlight and water received by the plants daily, ensuring other factors do not influence the plant growth. The control in this experiment is flat C, which received no compost. The experiment had three groups (flat A with 3 month-old compost, flat B with 6 month-old compost, and flat C with no compost), and each group consisted of 25 bean plants, which implies that there were 25 trials per group.

To address the question directly, we can summarize:

• Hypothesis: Older compost produces taller bean plants.
• Independent Variable: Age of the grass compost.
• Dependent Variable: Height of bean plants.
• Constant: Amount of sunlight and water each day.
• Control: Flat with 0 g of compost.
• Number of groups: 3.
• Number of trials per group: 25.

Answer 2

The hypothesis may be,
"If the compost is older, then the height of the bean plants will be taller."
Because it relates the independent and dependent variables

The independent variable is the age of compost
Because it is the variable being changed

The dependent variable is the plant height of the bean plant
Because it is the variable on which the effect of the independent variable is being investigated

The constant are the sunlight and water provided.
Because they are the same for each group

Flat C is the control group
Because it is given no compost

There are 3 groups and each group has 25 trials.