# Quiz 5: Temperature Relations

Ligia oceanica is an isopod belonging to phylum arthropoda living near the seashore. It is commonly found in rock crevices and under rocks. Conditions on the surface: - • The body temperature of Ligia oceanica is given as 26 °C on the surface, where the relative humidity is 70%. • Relative humidity gives an idea of the water vapor content of the atmosphere. The lower the relative humidity, the lower the water vapor content of the atmosphere. • When there is a difference between the actual vapor pressure and the saturation vapor pressure, the difference in the two pressures at a particular temperature is given by the vapor pressure deficit. • The low vapor content of the atmosphere indicates a high vapor pressure deficit and low relative humidity. Such conditions promote more loss of water by the evaporation from the terrestrial organisms. This evaporation also contributes to the evaporative cooling of the organism. • Hence, Ligia oceanica at the surface loses more, which leads to the evaporative cooling and lowering of its body temperature. Conditions under the rocks: • The relative humidity under the rocks is given as 100%, which indicates a saturated atmosphere. • The actual vapor pressure is equal to the saturation vapor pressure. Hence, it indicates a zero vapor pressure deficit. • Under these conditions, the loss of moisture from the body cannot occur, since the atmosphere is already saturated with moisture. The relationship between the evaporative cooling and the vapor status of the atmosphere in terms of the relative humidity and vapor pressure deficit is given as follows. Hence, there is no evaporative cooling, and the body temperature of the isopod is high under the stones. Thus, evaporative cooling is effective in open air, but nearly impossible under the stones.

Scientific research is a systematic and stepwise approach of solving a problem as per the set rules. It is a lengthy process requiring complete knowledge of research methodology, proper planning, and execution. There are a number of steps involved in a scientific study. These are listed below. After the identification of the research problem, a hypothesis is formulated. A hypothesis is a statement that gives the solution for the research problem. There are two types of hypothesis: A null hypothesis states that the observations in the data are due to chance and statiscally insignificant. An alternative hypothesis states that the observations in the data are not due to chance, but due to a definite cause. In a scientific study, the researcher tries to disprove the null hypothesis, which indirectly proves the alternative hypothesis. For evaluation of hypothesis, data is collected from a population. Since the population size is usually huge, it is not practicable to collect the data from the whole population. Hence, a sample that is representative of a population is collected. This process is called sampling. A small population, however, can be taken as the sample itself. Sampling is an important step that may lead to sampling errors if done improperly. The sample size is a critical factor. A large sample size makes the research expensive, time-consuming, and laborious. It makes the interpretation of results difficult. However, a large sample size increases the accuracy. The margin of error (the discrepancy between the sample parameter and population parameter) is decreased. For example, if the margin of error is ±1%, then the difference between the population parameter and the sample parameter is ±1%. Thus, the smaller the margin of error, the higher is the precision. High confidence levels (the percentage of samples, including the population parameter studied out of the total samples) can be set. Confidence levels of 90%, 95% or 99% can be set. A confidence level of 95% indicates that out of 100 samples, 95 samples will contain the population parameter and 5 will not represent the population. In the case of a population showing high variability, a large population is preferred to include the heterogeneity of the population. A small sample size may not be the true representative of the population. It may lead to accepting or rejecting the null hypothesis incorrectly. Thus, it may lead to inaccurate results. The level of precision of the study, the population variability, and the confidence levels set for the study determine the sample size. Hence, a researcher should try to collect a sufficient number of samples to test the hypothesis.

The distinguishing features among vapor pressure deficit, osmotic pressure, and water potential are as follows: Vapor pressure deficit, osmotic pressure and water potential are expressed in the same units of pressure, Pascal. Vapor pressure deficit: It gives a difference in two pressures, that is, actual vapor pressure and saturation vapor pressure. Hence, its unit is Pascals. Osmotic pressure: It is a type of pressure exerted by moving water across the semi-permeable membrane. Hence, it also has a unit of pressure: Pascals. Water potential: It shows the movement of water from one place to another. Water flows from an area of high concentration or high water potential to an area of low concentration or low water potential. Thus, water potential can be correlated with water concentration and, in turn, to pressure. High water potential indicates more water concentration and hence more pressure exerted. Hence, it also has a unit of pressure: Pascals.