Question

You design an experiment to test the effects of pesticides on size of radishes. You expect pesticides to have negative impacts on growth. You have been provided with 200 radish seeds and 40 growth pots. You have two treatment groups (P = pesticides, NP = no pesticides). [10 pts]

a) Using the A to B relationship we have used since the start of class, what is your prediction? [2 pts]

b) What type of dependent variable do you have? (circle one) [2 pts]

Numerical                    Categorical

c) How many seeds will you have per pot? [2 pts]

d) How many replicates will you have per treatment group? [2 pts]

e) What decision about H₀ would you expect to make if your prediction is correct? [2 pts]

2. Evolution [10 pts]

Some people (group 1) say that animals typically engage in behaviors that are ‘good for the species’. Other people (group 2) would argue that animals typically engage in behaviors that are ‘good for themselves’.

a) Based only on what we have covered so far in this class, where do you think evolutionary biologists would fit? Circle your answer. [2 pts]

Group 1                       Group 2

b) Explain your decision [3 pts]

Prior to Darwin proposing the theory of natural selection, there was an alternative explanation for evolution proposed by Lamarck (often referred to as Lamarckism). Lamarck proposed that favorable traits could be acquired within a lifetime and passed on to the offspring. To demonstrate the problem with Lamarckism, you decide to run an experiment in which you provide rats with the opportunity to acquire big muscles by encouraging them to work out. You provide half of your rats (group A) with the opportunity to obtain a major reward if they pick up heavy objects numerous times every day. The other half of the rats (control group) are not provided with the same opportunity (group B). Over time, you see that the first group of rats become very muscular compared to the second group. You then breed the rats from the experiment with other rats that did not work out.

c) Match the mechanism shown on the right below with the scenario shown on the left. [3 pts]

Group A offspring more muscular than Group B offspring                              Lamarckism

Group B offspring more muscular than Group A offspring                              Natural selection

No difference in muscularity between offspring from groups A and B

d) Which of the scenarios shown on the left above would you to expect to occur in your experiment [2 pts]

3. A researcher examines the relationship between a herbal extract and weight loss in humans. To achieve this goal, she records the weight of each participant before and after administering the herbal extract. The results are shown below. You will need to use the t-table provided in lecture on April 29 to answer your questions. You do NOT need to submit the table with your worksheet. [20 pts]

Subject	Weight before	Weight after	d = Difference
1	128	120
2	131	123
3	165	163
4	140	141
5	178	170
6	121	118
7	190	188
8	135	136
9	118	121
10	146	140
11	212	207
12	135	126
Mean	-	-	3.8
Standard deviation	-	-	4.1

a) The analysis should be paired. Explain the reasoning. [2 pt]

b) Complete the missing cells in the table (lightly shaded) [1 pts]

c) What is your t-value. Show your calculations. [6 pts]

d) How many degrees of freedom do you have? [1 pt]:

e) What is your critical t-value [2 pt]:

f) What is your p-value? [2 pts]

g) What decision should you make about your H₀? [2 pts]

h) What is your conclusion? [2 pts]

i) What type of error could you be committing with your decision about H₀? [2 pts]

Answer 1

1. a. It can be predicted that with the increase of the amount of pesticide (A), the size of the radishes (B) will reduce.

b. The dependent variable being used in the experiment is the amount/concentration of the pesticide which is numerical.

c. Four seeds can be plotted in a single plot. One in each quadrant.

d. It is important to have 3 replicates per treatment group to get accurate results.

e. It can be predicted that Ho will negatively impact the growth of radish.