Question

exploring ecosystems: brine shrimp and environmental changes
step 1: your groups choice of environmental change:
step 2: hypothesis (use the iv affects dv formula) and include a reason for your choice.
step 3: identify your variables
independent variable:
dependent variable:
controlled variables (constants):
step 4: set up experiment
picture with labels of experimental setup
description of experimental procedure (steps)

Explanation:

This is an experimental design task focused on brine shrimp and environmental change. Below is a complete, structured experimental plan aligned with the steps provided:

1. Step 1: Water salinity is a critical environmental factor for brine shrimp, making it a clear, testable variable.
2. Step 2: The hypothesis follows the "IV affects DV" structure, with a biological rationale: brine shrimp osmoregulate to match water salinity, so extreme levels disrupt this process.
3. Step 3: Variables are defined to isolate the effect of salinity: the independent variable is the factor being tested, the dependent variable is the measured outcome, and controlled variables ensure no other factors skew results.
4. Step 4: The setup and procedure are standardized to ensure consistency and replicability, with clear steps to test each salinity condition.

Answer:

Step 1: Your Group's Choice of Environmental Change:

Water salinity level (measured in parts per thousand, ppt)

Step 2: Hypothesis (Use the IV affects DV formula) and include a reason for your choice.

Increasing water salinity beyond the optimal range for brine shrimp will decrease brine shrimp survival rate.
Reason: Brine shrimp rely on osmoregulation to maintain internal water balance; extreme salinity disrupts this essential physiological process.

Step 3: Identify your Variables

Independent Variable:

Water salinity level (tested at 10 ppt, 30 ppt, 50 ppt, 70 ppt)

Dependent Variable:

Brine shrimp survival rate (percentage of shrimp alive after 48 hours)

Controlled Variables (constants):

• Initial number of brine shrimp per container (10 shrimp)
• Volume of water per container (500 mL)
• Water temperature (25°C)
• Light exposure (12 hours light/12 hours dark cycle)
• Type of water (dechlorinated tap water + marine salt mix)

Step 4: Set up experiment

Picture with labels of experimental setup:

(Diagram description: 4 identical clear plastic containers labeled "10 ppt", "30 ppt", "50 ppt", "70 ppt". Each has a lid with small air holes, holds 500 mL of saltwater, and contains 10 brine shrimp. All containers sit on a tray under a timed grow light, with a thermometer placed next to the tray.)

Description of experimental procedure (steps):

1. Prepare 4 saltwater solutions: 10 ppt, 30 ppt, 50 ppt, 70 ppt by mixing marine salt with dechlorinated tap water.
2. Pour 500 mL of each solution into a labeled, separate container.
3. Add 10 healthy, adult brine shrimp to each container.
4. Place all containers in a location with a constant 25°C temperature and 12-hour light/dark cycle.
5. Check and count the number of live shrimp in each container at 24 hours and 48 hours.
6. Calculate the survival rate for each container using:

$$\text{Survival Rate (\%)} = \frac{\text{Number of Live Shrimp}}{\text{Initial Number of Shrimp}} \times 100$$

1. Repeat the entire experiment 3 times to ensure results are consistent.