BIOL 1209 Control Vs Blank

A scientist is doing research to understand how volatile hydrocarbons affect phytoplankton (algae) growth during oil spills. In the lab, he adds different levels of a volatile hydrocarbon (0- 50 μg/ml) to phytoplankton in distilled water with nutrients, and sodium carbonate buffer. The scientists uses a spectrometer to detect the level of algae in the tube. In this way he can see growth of algae. Independent factor: volatile hydrocarbons Dependent factor: Algae as detected by absorbance in a spectrometer What belongs in the control?

Algae Distilled water Sodium carbonate buffer Nutrients

Eliminates background noise from the instrument detecting the dependent variable

Blank

Is specific to the instrument and treatment used in the experiment.

Blank

Is specific to the sample being measured in the instrument

Blank

In setting up an experiment, a scientist keeps all components the same except the concentration of phosphate added. The scientists then measures if a microscopic cyanobacteria grows better with added phosphate by measuring how blue/green his samples are in the spectrometer. The blue/green absorbance is a measure of cyanobacteria levels. Sample that has everything except the cyanobacteria. Sample that contains everything except phosphate. Graph of known concentrations of cyanobacteria versus their Absorbance readings in a spectometer.

Blank Control Standard curve

A scientist wants to study Blue green algae growth in response to phosphate. The scientist sets up tubes with the following : Experiment for Graph of Phosphate versus Blue Green Algae Growth Condition 1 Water Blue Green algae No phosphate Condition 2 Water Blue Green Algae Low phosphate Condition 3 Water Blue Green Algae High Phosphate Which Condition is the control for this experiment?

Condition 1

Does not have the experimental component varied (independent) in the experiment.

Control

Series of experimental tubes. Green circles represent algae. Cat represents growth media. Alternative hypothesis: Changing the concentration of arsenic (As) will change the population size of the algae. Which tube(s) are the control for this experiment?

E

The pigment, fucoxanthin, gives brown algae its distinctive green-brown color. A scientists want to use a spectrophotometer to measure the level of fucoxanthin in the Giant Kelp algae. Kelp was washed to remove ocean organisms, and its pigment extracted using small a amount of water (dH2O) containing a mixture of methanol and salt. The mixture was filtered to remove debris. Select all components needed for an appropriate blank for the extracted pigment sample in the spectrophotometer.

Salt Methanol dH2O

A scientist is doing research to understand how microplastics affect daphnia (water fleas) growth in areas of copper pollution. In the lab, he adds different levels of a volatile microplastics (0- 50 μg/ml) to daphnia in fresh water with nutrients and sodium carbonate buffer. The scientists uses a spectrometer to detect the level of algae in the tube. In this way he can see growth of algae. Independent factor: microplastics Dependent factor: daphnia as detected by absorbance in a spectrometer What belongs in the blank for the spectrometer?

Sodium carbonate buffer Nutrients Fresh water

A scientist is monitoring the growth of a bacteria using a spectrophotometer. He has multiple bacterial samples with different growth solutions components. The scientist would change the blank for a spectophotometer for different samples..

True, the scientist would change the blank for different samples.

A scientist wants to study the growth of Blue Green algae in response to phosphate. In a tubes of Blue Green algae in water, the scientist sets up tubes with the following : Experiment for Graph of Phosphate versus Blue Green Algae Growth Condition 1 Water Blue Green algae No phosphate Condition 2 Water Blue Green Algae Low phosphate Condition 3 Water Blue Green Algae High Phosphate What would be in the blank tube for Condition 2 if the scientist is detecting the Blue Green Algae with their instrument?

Water Low Phosphate