Question

You are a doctorate student in biology doing a dissertation about the insect Desmolithica Geogebra. This insect causes serious damage to plums, apricot and flowering cherries. The female insect lays as many as thirty to sixty eggs on the leaves of the host trees. The time when the insect larva hatches from its egg up to the moment in finding its host tree is called the searching period. Once the insect finds the plum, it squirms into the fruit and begin to ruin it. After approximately four weeks, the insect will crawl back under the bark of the plum tree or directly to the soil where it forms a cocoon. The observation regarding the behavior of the insect demonstrate the length of the searching period S(t), and the percentage of the larvae that survive this period N(t), depend on the air temperature denoted by t. The data from the observations suggest that if the air temperature is measure in degree celsius, where 20 S(t) = (-0.03t^2+1.6t-13.65)^(-1) days and N(t)= -0.85t^2+45.4t-547

S(25) in days N(25) in % T when ds/dt=0
0.1316 56.75 26.67

1. Explain comprehensively the models for S(t) and N(t). Elaborate mathematically these formulae in predicting for the length of searching period and percentage of larvae surviving the searching period when t=25.
2. Find the rate of change of the searching period with respect to temperature t. When does this rate equal to zero? What will happen when t=0?
3. Find the rate of change of the percentage of larvae surviving the searching period with respect to length of the searching period. What information does this provide?

Answer 1

1. The models for S(t) and N(t) are mathematical representations that predict the length of the searching period and the percentage of larvae surviving the searching period based on the air temperature denoted by t.

The model for S(t) is given as:

S(t) = (-0.03t^2 + 1.6t - 13.65)^(-1)

This model predicts the searching period length in days. It is an inverse function of the quadratic equation (-0.03t^2 + 1.6t - 13.65). As the temperature increases, the searching period decreases, indicating that the larvae are more efficient at finding the host tree at higher temperatures.

To calculate S(25), we substitute t = 25 into the equation:

S(25) = (-0.03(25)^2 + 1.6(25) - 13.65)^(-1)

= (-0.03(625) + 40 - 13.65)^(-1)

= (-18.75 + 26.35)^(-1)

= 7.6^(-1)

= 0.1316 days

Therefore, when the air temperature is 25 degrees Celsius, the predicted length of the searching period is approximately 0.1316 days.

The model for N(t) is given as:

N(t) = -0.85t^2 + 45.4t - 547

This model predicts the percentage of larvae surviving the searching period. It is a quadratic function (-0.85t^2 + 45.4t - 547). As the temperature increases, the percentage of larvae surviving the searching period may increase or decrease depending on the behavior of the quadratic function.

To calculate N(25), we substitute t = 25 into the equation:

N(25) = -0.85(25)^2 + 45.4(25) - 547

= -0.85(625) + 1135 - 547

= -531.25 + 1135 - 547

= 56.75%

Therefore, when the air temperature is 25 degrees Celsius, the predicted percentage of larvae surviving the searching period is 56.75%.

2. The rate of change of the searching period S(t) with respect to temperature t can be found by taking the derivative of the function S(t) with respect to t, which is denoted as ds/dt.

ds/dt = d/dt [(-0.03t^2 + 1.6t - 13.65)^(-1)]

To find when ds/dt = 0, we set the derivative equal to zero and solve for t:

ds/dt = 0

However, without the specific equation of S(t) in its original form, it is not possible to provide an exact value of t when ds/dt equals zero.

Regarding the behavior when t = 0, we cannot determine this without further information or the specific form of the function S(t). The behavior at t = 0 depends on the equation itself and how it is defined.

3. The rate of change of the percentage of larvae surviving the searching period N(t) with respect to the length of the searching period S(t) can be found by taking the derivative of the function N(t) with respect to S(t), denoted as dN/dS.

dN/dS = d/dS [(-0.85t^2 + 45.4t - 547)]

This rate of change provides information about how the percentage of larvae surviving the searching period changes with respect to the length of the searching period. It gives insight into the sensitivity