There is a large tree growing in the middle of the lawn. You notice that there are lots of daisies in the lawn, but none under the tree. Suggest two hypotheses to explain why there are no daisies under the tree. Choose one of your hypotheses and make a prediction from it which can be tested by an experiment. Describe an experiment which could be done to find out if the prediction is correct.

Answer and Explanation:

Hypothesis:

1- No daisies can grow under the tree because its canopy does not allow enough radiation to reach the ground under it.

2- No daisies can grow under the tree because it changes the soil composition and pH.

Prediction:

Daisies grow better and faster when they are completely exposed to solar radiation.  

Experiment:

30 daises young plants, grown under the same conditions, will be planted in three different parcels. Planting will take place during spring.The three parcels will have the same soil, with all the nutritional requirements that daisies need to grow properly. The three parcels will be watered every day to keep equal humidity conditions. The variable under study is the radiation, so this is the only factor that will differ between parcels. One of the parcels will be completely exposed to solar radiation. A second parcel will receive sunlight during half of the day, while the other half of the day will be under the shadow. The third parcel will be completely under the shadow (no radiation will reach this parcel).  Daisies will be grown for four months. Every fifteen days all the plants will be counted in each parcel to check their survival. Their length will be measured, and the presence of new leaves, floral buttons, and ramifications will be registered. The size of the leaves and flowers will also be registered. After four months, data will be analyzed to evaluate how does the radiation influence the plants' growth.