Core Practical 1 - Daphnia Flashcards
What is the aim of this experiment (daphnia)
The aim of this experiment is to test and observe how the heart rate of Daphnia (Water fleas) is changed by making them absorb varying concentrations of a caffeine solution.
What are Daphnia and why are they used
Daphnia are water flees
-They are abundant so can be taken with little damage to biodiversity
-They are translucent so their heart rate can be observed easily
-They are invertebrates and have a less developed nervous system, so they feel less pain
What factors effect heart rate
Lowered by:
-sleeping
-stretching
Increased by:
exercise
Drinking alcohol
smoking
stress
caffeine
What is caffeine’s effect on heart rate
It causes heart rate to increase
Why were cavity slides and 2 strands of cotton wool used in our equipment
To immobilize and contain the Daphnia
The cavity slide also contained the solution (stopped it from spilling)
Why was a caffeine solution used in our equipment
The Daphnia would absorb the caffeine from our serial dilutions
Why were dropping pipettes used in our equipment
To transfer the daphnia to our cavity slides
To make serial dilutions
Why was distilled water used in our equipment
To make the serial dilutions (caffeine + distilled water)
Why were test tubes used in our equipment
To contain / make the serial dilutions
Why was a measuring cylinder used in our equipment
To measure out the correct volumes of caffeine solution and distilled water to make our serial dilutions
Why was a stop clock used in our equipment
To measure acclimation time and the heart rate
Why did we use paper towels / blotting paper
To remove excess solution
Why was a microscope used in our equipment
To clearly observe the Daphnia’s heart and count the heartrate
What was our counting method in this experiment
We used a pen and paper to make dots every heartbeat of the Daphnia’s in a 10s interval
What was the independent variable
Concentration of the caffeine solution
0% 0.2% 0.2 % and 0.3%
What was the dependent variable
The heart rate of the Daphnia in BPM
What were some control variable in the Daphnia experiment
Time - 5min acclimation time + waiting 1 min intervals after measuring heartrate for 10s
Size / species / age of Daphnia - using similar sized Daphnia that came from the same batch of eggs
temperature - solutions kept at room temperature + light turned off when not in use
What was our method in the Daphnia experiment
Create the serial dilutions of caffeine
Place 2 / 3 strands of cotton wool onto the cavity slide.
Take a daphnia using a dropping pipette
Place the daphnia and solution onto the cavity slide
Wait 5 min acclimation time
Turn on the microsoft light and dot on paper every time the heart beats (in 10s)
Turn of the light, dots×6 = bpm
Wait 1 min and repeat (twice) to find a mean
Place the daphnia into the used container
Repeat for each concentration
What ethical consideration did we have to make for this experiment
Daphnia cant consent - minimise the experiment time
Daphnia cant express pain - Excessive caffeine not used
Extreme conditions will be avoided (e.g high temperatures / pH - chlorine kills daphnia)
