Data was collected on rabbit red blood cells that were exposed to sodium chloride (NaCl) and scorpion venom. Under some osmotic conditions red blood cells swell and burst, releasing hemoglobin (hemolysis). The graph shows the response of red blood cells to different concentrations of sodium chloride, with and without scorpion venom. [Source: Adapted from Mirakabadi A Z, et al., (2006), J. Venom. Anim. Toxins incl. Trop. Dis., 12 (1), pages 67-77 (London: BioMed Central)]

a. in NaCl concentrations between 0.3 to $0.5 \%$ venom increases the percentage of hemolysis/more cells lyse $\checkmark$ b. venom has no effect below $0.3 \%$ and above $0.55 \% \mathrm{NaCl}$ OR Venom has no effect at very low or very high NaCl concentrations $\checkmark$

a. weigh all pieces to ensure same amount of plant material/allow comparisons $\checkmark$ b. control surface area by having same shape/ size $\checkmark$ c. carry out experiment at same temperature e.g. using a water bath or constant room temperature $\checkmark$ d. all samples in solution for same length of time $\checkmark$ e. all samples from same plant (to minimize variability) $\checkmark$ f. use a range of solutions of the same solute $\checkmark$ q. constant method of removing excess fluid before weiah tissue samples $\checkmark$