Energiedynamik
At the end of this lab, students should know...
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Q1: How do you calculate the percent biomass of a cabbage sample?
To calculate percent biomass, divide the final dry mass of the cabbage by its initial wet mass, then multiply by 100. First, wash and pat dry the cabbage's inner leaves, weigh it in a pre-weighed Petri dish to obtain wet mass, then incubate at 37°C for 48 hours. Reweigh the cabbage and dish after incubation to get dry mass, then apply the formula to determine the percentage.
Q2: What is the purpose of pre-weighing cabbage before an energy dynamics experiment?
Pre-weighing cabbage establishes a baseline measurement of biomass to track energy transfer through the food chain. By measuring both wet and dry mass, you quantify the water content and actual organic matter in the plant tissue. This data is essential for studying energy dynamics and productivity in ecological systems, allowing you to calculate energy available to herbivores like caterpillars.
Q3: Why is the cabbage incubated at 37°C for 48 hours during biomass measurement?
The 37°C incubation removes water from the cabbage tissue, allowing you to measure dry mass—the actual organic matter content. This two-day heating period ensures complete moisture removal, which is necessary to calculate the true biomass and water content percentage of the sample accurately.
Q4: How long does it take for Pieris rapae eggs to hatch under lab conditions?
Pieris rapae eggs hatch in approximately 48 to 72 hours under indirect sunlight or indoor light conditions. Once the eggs arrive, place them egg-side down on radish leaves that have been grown from seeds sown one week prior. The timing allows caterpillars to emerge and begin feeding on the host plant.
Q5: What preparation is needed before Pieris rapae eggs arrive?
One week before egg acquisition, sow radish seeds in pots containing fresh potting soil and place them in a sunny lab location. Water the soil daily until it is just damp to establish healthy radish plants. This timing ensures mature radish leaves are ready to receive the egg strips when they arrive, providing an immediate food source for newly hatched caterpillars.
Q6: When should caterpillars be transferred to cabbage during rearing?
Transfer caterpillars to cabbage when they reach their fourth instar growth stage, keeping them on the cabbage for three days. During this period, mist the caterpillars occasionally with water to prevent drying. This timing and care protocol ensures proper development and nutrition as the caterpillars progress through their larval stages.
Q7: What environmental conditions support successful Pieris rapae egg hatching?
Pieris rapae eggs hatch successfully under indirect sunlight or indoor light in a lab setting. Maintain radish plants by watering soil daily until it is just damp, creating a moist but not waterlogged environment. These moderate light and moisture conditions optimize hatching rates and support caterpillar survival on the host plant.