Nadalie Valdez
APES Blk B
November 18, 2013
Pre Lab
1. Tow habitat properties that facilitate population growth of Lemna Minor are
that they are found in still waters from temperate to tropical zones, though it
prefers temperatures around 25 degrees C. in order to survive, the duckweed
needs both light and water.
2. Three limiting factors that could affect carrying capacity of Lemna Minor are
resource limitations such as sunlight, water, and nutrients. The threat of
predation from fish and birds; and waste accumulation.
3. Exponential growth: dN/dt=rN
D means change-> the change in the number of individuals as time changes
equals a constant r, multiplied by the number of individuals.
Exponential growth happens when numbers increase by a certain factor in
each successive time period.
Logistic growth: dN/dt=rN[(k-N)/k]
The difference between exponential growth and logistic growth is the [(kN)/k], it decreases the value of the growth rate as the population increases.
Logistic growth is population growth that starts with a minimum number of
individuals and reaches a maximum depending on the carrying capacity of
that habitat.
Hypothesis:
I had a feeling that the Lemna Minor would grow in a controlled environment
as long as it had the light to help it grow. However, when placed in the shade, I did
not think the Lemna minor would grow.
Light Shade
Day
Daily
Count
New frond
growth
Days since
previous
count
Change in
the # of
fronds/day
0
1
2
3
4
5
6
0
0
0
0
0
0
0
0
1
1
1
1
1
1
0
0
0
0
0
0
0
3
3
3
3
3
3
3
Change in #
of
fronds/day/
frond
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Half Shade
Day
Daily
Count
New frond
growth
Days since
previous
count
Change in
the # of
fronds/day
0
1
2
3
4
5
6
0
0
0
1
0
0
0
0
1
1
1
1
1
1
0
0
0
1
0
0
0
Full Shade
Day
Daily
Count
New frond
growth
Days since
previous
count
Change in
the # of
fronds/day
0
1
2
3
4
5
6
0
0
0
0
1
0
0
0
1
1
1
1
1
1
0
0
0
0
1
0
0
3
3
3
4
4
4
4
3
3
3
3
4
4
4
Change in #
of
fronds/day/
frond
0.0
0.0
0.0
.25
0.0
0.0
0.0
Change in #
of
fronds/day/
frond
0.0
0.0
0.0
0.0
.25
0.0
0.0
Conclusion:
1. (A)The shade treatment did hot help the population growth rate. The
evidence I found concluded that the shade does not help the growth
rate. The light shade had no growth, the half shade had the most
growth, and the full shade had some growth.
(B)There was no exponential growth. The populations that grew only
had at the most 2 fronds grow. The populations did not increase or
decrease at a fast rate.
2. (A)According to the class data, the habitat treatment that is most
conductive to population growth is nitrate.
(B)The habitat treatment that is most conductive to high carrying
capacity is phosphate.
3. Based on the class results, the treatment levels for each environment
parameter that is optimal for Lemna minor are low salinity, medium
phosphate, light shade, pH5, and low nitrate. Although the pH5 level
and the medium phosphate have lower growth rates than the others
in their parameters, it still has the highest carrying capacity out of the
other levels in the pH parameter making it the most optimal.
4. The relationship between the number of screens on a test tube and
carrying capacity is that the fewer amounts of screens on the test tube
equals an increase in carrying capacity. The relationship of fewer
screens equals a larger carrying capacity also goes for the relationship
between the number of screens on a text tube and duckweed’s
intrinsic rate of increase. The fewer screens on a test tube there were
meant a higher intrinsic rate of increase for the duckweed.
5. A population intrinsic growth rate of increase does change with
habitat because every solution in this experiment used the same type
of spring water and had equal amounts of light available to them, but
when saturated in different treatments, the rates on increase varied.
For example, when concentrated in a solution of medium phosphate,
the duckweed had a higher intrinsic rate of increase than when
concentrated in a solution of high nitrate. This means that being
placed in different types of treatments does affect the growth rate of
the Lemna Minor.
6. There are many differences between the effects of nitrate and
phosphate on duckweed. Phosphate has a higher influence on the
growth rate and as a result has a greater carrying capacity. Nitrate on
the other hand has a low growth rate and an even lower carrying
capacity. However nigh levels of both nitrate and phosphate solutions
have lower growth rates than the others in their parameters.
7. Birth and death rates are accounted for in the exponential population
growth equation by having N represent the number of individuals that
the current time t. this means it takes into account how individuals in
a duckweed population increase or decrease over a period of time.
8. The assumptions made about the plants in this experiment are that
duckweed’s habitat takes a huge role in the survival of their
population. Small changes to this plant’s environment can alter the
population as a whole, but that the major components of a plants
survival are that it has water and sunlight to maintain its growth.
9. Some possible sources of error in this experiment are the amount of
treatment added to the duckweed. Another error that may occur is
mixing the wrong amount of treatment with the wrong amount of
water. Another error that could take place could be not taking note of
all the changes in the experiment; this would lead to incorrect results.