Biology Experiments

Question 1

To investigate the action of amylase of starch

Answer 1

1. Put two test tubes (A: starch + amylase, B: starch + water) in water bath at 37 degrees celsius (body temperature) for 5 mins
2. Remove + pour half of A into new one (C), half of B into D
3. Test A for starch (iodine) and C for reducing sugars (Benedict’s)
   Results:
   A = no starch, has been broken down by amylase
   C = reducing sugar present, starch has been broken down to reducing sugar
   B = starch present, starch not broken down
   D = reducing sugar absent, starch not broken down

Question 2

To show that respiring animals produce carbon dioxide

Answer 2

1. Two test tubes capped with wooden stoppers, woodlice on metal gauze in one, limewater in both (other is control)
   Results: Limewater will turn milky in tube with woodlice
   Conclusion:
   Limewater has only turned milky in tube with wood lice, therefore they must be producing carbon dioxide

Question 3

To show that respiring plants produce carbon dioxide

Answer 3

Conical flask with sodium hydroxide solution (to remove carbon dioxide from air), conical flask (B) with limewater, bell jar containing plant covered by black cloth (plant would use up carbon dioxide it produced during photosynthesis), conical flask (C) containing limewater
Connected by tubing, pump at end to pull air through
Pump is turned on, air pulled through apparatus
Results: limewater in C turns milky, B stays clear
Conclusion: plant has produced carbon dioxide

Question 4

To show that respiring organisms produce heat energy

Answer 4

1. Put pea seeds that have been soaked overnight in water (germinating) in one thermos flask, and dead pea seeds in the other
2. Take temperature every day for three days
3. Plot graph of each (temperature on y-axis)
   Results:
   Temperature of flask with germinating pea seeds will increase, flask with dead pea seeds will stay the same
   Conclusion:
   Respiring seeds produce heat energy - only the living seeds produced it, the dead seeds don’t respire

Question 5

To show that respiring organisms produce water

Answer 5

1. Breathe in and out on cobalt chloride paper a number of times
2. Observe any colour changes
   Results: blue cobalt chloride paper turns pink
   Conclusion: living things produce water (a waste product of respiration)