Population Growth in Lemna
minor
Pre-Lab: Important Notes &
Homework
• Safety: goggles, aprons, gloves
• Data collection: EVERY DAY for 1st week
• HW:
– Become familiar with background info &
procedures (S-1 – S-3 & S-5 – S-9). If anything is
unclear, write it down for discussion on 10/28.
– Copy Data tables, pre-lab questions (S-4) and post
lab questions (S-10) into your notebook
– Draw proper measuring technique for pipette,
beaker, graduated cylinder
Pre-Lab: Class work
• Lecture / discussion
• Each person will complete the following tasks
in their own notebook. Feel free to discuss
with group mates.
– Answer the Pre-lab questions found on S-4 (you
should have already copied the questions.)
– Draw pictures of the three sets of test tubes you
are establishing. Make sure to label contents of
each set.
– Draw figure 3
Lecture / Discussion
• Several Objectives
– How L. minor population growth rate reacts in
differing environments (pollution issues)
– Determining r and K (biotic potential and its
relationship to population growth )
– Practice with designing / running an experiment
(practice for Paper 3)
Lecture / Discussion
• Why need a control?
• Why have replicates?
• What is carrying capacity?
– What part of the curve shows carrying capacity?
– Is that in a logistic growth curve or exponential
growth curve?
• What is biotic potential?
Determining Population Size
• Where,
– d means change
– N means Number of individuals
• Nt is N at any given time (t)
• N0 is N at time = zero
– r is a constant: population’s intrinsic rate of
increase
• rm = biotic potential
– K is carrying capacity
– e is Euler’s constant (number) = 2.72
• Exponential population
growth equation:
–
–
dN/dt=rN
Nt = N0ert
• Logistic population
growth equation:
–
dN/dt = rN [(K-N)/K]
Drawings
• Test tubes
– the water?
– L. minor?
– Any treatments:pH
buffer, solutions, screens
& rubberbands?
– Plastic wrap with holes &
rubberbands?
• Beaker, graduated
cylinder, pipette
– The meniscus?
– Pipette at 90° angle to
tabletop?
Data Tables
• Three different tests x three replicates = 9 test
tubes
• Need a data table / each test tube