Question

Caroline Strömberg is a paleobotanist, studying of fossil plants. She hypothesized that some species of grass have evolved to accumulate silica in their tissues as a defense against herbivory.

1a. Describe how a species of grass "evolved to accumulate silica in their tissues," using Darwin's four postulates of natural selection (individual variation, heritability, over reproduction, the difference between generations).

1b. Describe the relative abundance and the relative position (in the sediment) of plant and animal fossils Dr. Strömberg is likely to observe if her observations support her hypothesis that "some species of grasses accumulate silica in their tissues as a defense against herbivory."

1c. Despite not being able to conduct experiments with fossils, many paleontologists conduct experiments using modern plant and animal species. Design an experiment (that you could conduct in modern-day) to test the hypothesis that the silica in some grass species is a defense against herbivory.

• Be sure to include a description of your variables (independent and dependent variables and which additional variables you will control for and why). In addition, justify your sample size and defend why you think your experiment is generalizable.

1d. Draw graphs showing the data you expect to see from your experiment. Label the axes, and include standard error bars.

Answer 1

1. a) Whenever the growth of the grasses takes place they acquire the nutrient from the soil and in some cases, it can be the possibility that the grasses must have used the silica as a nutrient and then it must have been transferred from the one generation to the other. Based on the darwin's four postulates 1. Individual species are variable and thus it can be the possibility that this evolution of species needs such kind of the mineral for their survival. 2. And this version must have passed on or inherited in the offspring produced by the parental generation. 3. Whenever the more offsprings are produced then there is a higher probability that it will contain that evolved gene. 4. The offspring will further mate and pass on the gene. Thus this study can be correlated with these postulates.

b) It can be a case that this evolved species of the grass which is accumulating the silica content in it is showing the herbivory phenomenon. Because whenever the silica accumulation has been taken place in the grasses it has been seen that the grasses lead to leaf abrasiveness, act as a feeding deterrent, reduce growth performance by changing the cell division status and change feeding preferences of folivorous insects, small herbivorous mammals (voles) and sheep as the mammals can feed them and evade from the microorganism infection. In case of increasing consumption, this type of grass can help in the deterioration of the mandible organisms and increase its own benefits.

c) If we have to plan the experiment to check for the similar effect we can, first of all, use the tissue culture technique in which the mesenchymal stem cell allows to grow under the media containing the different silica content based on the optimized silica level and the optimized growth we will study and observe the accumulation of the silica inside the tissue. Thus it will further when divide transfers the amount of the silica content in the offspring and silica accumulating gene. Thus, whenever the offspring will show the silica accumulation at the same level then the generation wise the silica level will increase and thus the experiment will succeed in interpreting that the silica accumulating gene has transferred inside the offspring and the fittest species has survived in the changing environment which is the concentration of silica in this case.

d) Graph for the above-mentioned experiment will be as follows: (It is not possible for placing the SD as this is the hypothetical experiment and the solid results are required when the error bars has to place)