Daphnia practical Flashcards
what is the independent variable
caffeine concentrations
how do you vary the independent variable
change the caffeine concentration 0.1 + 0.5%
what are the control variables
pond water and distilled water
what is the dependant variable
heart beat of the daphnia
how do you measure the dependant variable
count heart beats under a microscope
draw lines for each heartbeat on a piece of paper
15 seconds x 4
what daphnia variables should be controlled
use same daphnia
age
size
gender
what environmental variables should be controlled
take sample from same pond
keep in pond water when not using
similar temperatures
what procedural variables should be controlled
volume of solution used
acclimatisation time (2 minutes)
what repeats should be carried out
repeat 3-5x with caffeine solution
how is the investigation made reliable
use the mean results
make sure results can be repeated
how is the investigation made valid
make sure conclusions measure what is supposed to
use control variables
reliable results are obtained
what are the ethical issues
daphnia may die or be injured
temperature change is different from there environment
unethical to use living organisms
why is it good to use daphnia in this experiment
transparent so it is easy to count heartbeat
do not have a fully developed central nervous system so are not susceptible to pain
what is the method
calculate resting heart rate in pond water
put daphnia in caffeine solution on slide an let acclimatise for 2 minutes
place cotton wool strands so daphnia does not move then place slide under microscope
count heart beats in 15 seconds then times by 4 to get bpm
carry out for different caffeine concentrations
repeat 5x for each caffeine concentration
