Botulism is a rare disease caused by the botulinum toxin produced and secreted by Clostridium botulinum. Botulism causes muscle weakness and in severe cases can inhibit the muscles of respiration and lead to respiratory failure and even death. The exotoxin produced by Clostridium botulinum causes damage to its host by inhibiting of the release of the chemical messenger acetylcholine. Acetylcholine is a neurotransmitter, meaning it is responsible for enabling communication between a nerve cell and other cells. 

Experiment A

Scientists conducting a study on the lethality of the botulinum toxin are looking at the effect of acidification on the toxin’s potency. They design a study in mice to identify the minimal lethal dose of botulinum toxin. The scientists believe acidification will reduce the minimal lethal dose. The findings from their study are below:

Experiment B

Scientists also assessed the relationship between acidification and the incubation period. The incubation period was defined as the time between exposure to the toxin and the onset of symptoms. 

Data and concepts from: Bronfenbrenner, J. & Schlesinger M.J. (1922). Some of the factors contributing to toxicity of botulinus toxin by mouth. JAMA, 78(20), 1519-1521.

If a minimal lethal dose was , what would be the expect pH?

The cells of multicellular organisms must be linked to each other through special structures called cellular junctions. A gap junction is a type of cellular junction, which allows for the passage of small molecules for fast coordination between cells. For example, cardiac cells in the heart and neurons in the brain rely on gap junctions. However, gap junctions are small and there is a limit to how large a molecule can be in order for it to pass through the gap junction.    

An experiment is designed to see how large molecules can be to pass through a gap junction. A single layer of cells is grown in a petri dish. A single cell is then injected with a dye labeled with a fluorescent molecule. Researchers observe the following:

Based on the experiment’s data, which of the following is the best conclusion?

Poisons dart frogs earned their name because of a deadly neurotoxin they produce and secrete. To synthesize this neurotoxin, the frogs must consume termites which contain the necessary precursors that the frog processes into their poison. Frogs consuming more of these termites will be more poisonous than frogs consuming smaller amounts. Previous experiments have also shown that neurotoxin production is highest at low temperatures and decreases as temperatures increase. 

A team of researchers is curious about when these frogs are most toxic. They record average monthly temperatures for a year and count the number of termites found within a 5,000 square foot area as a measure of termite density in the environment. Results are shown below.

During what month would you expect the frogs to have the highest levels of neurotoxin?

A mycologist, a scientist specializing in the study of mushrooms, wants to compare the growth of three types of mushroom (A, B, and C) on varying growth substrates. He is also curious how light will affect the growth of each of the samples. He designs an experiment where each variety of mushroom will be grown on manure, wood chips, or rice flour and includes identical trials with and without light. He records the mass of the mushrooms produced after 14 days of fruiting and finds the following results:

Mushroom strain B produced the largest mushrooms when grown on which growth substrate?

A mycologist, a scientist specializing in the study of mushrooms, wants to compare the growth of three types of mushroom (A, B, and C) on varying growth substrates. He is also curious how light will affect the growth of each of the samples. He designs an experiment where each variety of mushroom will be grown on manure, wood chips, or rice flour and includes identical trials with and without light. He records the mass of the mushrooms produced after 14 days of fruiting and finds the following results:

What statement best describes the effect of light exposure on the mass of mushrooms that strain A produces?

Researchers at a biotechnology company have just developed a new immortal line of mammalian cells derived from raccoon hair follicles. They dub these cells RHF and note that they appear particularly resistant to environmental stressors in initial experiments. They design a set of experiments to test the limits of the RHF cell line.

Experiment 1: The scientists inoculate 5 identical flasks containing growth media with samples of the RHF cells. The flasks are then incubated in separate incubators at varying temperatures. The flasks are sampled daily for cell density to analyze growth of the cells, yielding these results:

Experiment 2: The scientists produce 5 separate batches of cell growth media containing various amounts of salt to raise the osmolality of the solution. They inoculate 5 flasks, each with various osmolalities, then incubate the flasks at 37 °C for seven days. The flasks are sampled daily for cell density, yielding these results: 

Describe the pattern of cell density over time of RHF cells grown at  in Experiment 1.

A sports physician is conducting an experiment in which a competitive bicycle rider has her heart rate, oxygen content in blood, and blood lactate measured. The measurements are taken at resting, during easy, moderate, difficult, and very difficult exercise. The results are summarized in the table below. Please note that the oxygen content was normalized to the resting oxygen content. 

If the cyclist was to exert herself even more to a heart rate of 160 bpm, what would be the expected oxygen percentage? 

Three different species of bacteria were grown in the laboratory. The experiment measured the effect of pH on the concentration of the three species of bacteria. The graphs below show the concentration of bacteria at different pH levels. Figure 2 shows the effect of pH on the concentration of a third bacterial strain, bacteria C.

Which of the following is not an accurate conclusion that can be drawn from the graph in Figure 1?

Three different species of bacteria were grown in the laboratory. The experiment measured the effect of pH on the concentration of the three species of bacteria. The graphs below show the concentration of bacteria at different pH levels. Figure 2 shows the effect of pH on the concentration of a third bacterial strain, bacteria C.

Which species of bacteria would be seen in concentrations over 0 on a medium with neutral pH?

The population of two different sparrow varieties were recorded from spring 1992 to fall 1996 and displayed below in the form of a graph. 

Upon studying the graph provided, which of these is a plausible conclusion?