Intensity of sunlight changes as the day goes by, so therefore if the independent variable is Sun exposure, it means that the variable is also time as well. So therefore the experiment will be conducted over a period of time where the Sun’s intensity changes as time goes by.
Throughout the year, the amount of sunlight (and essentially UV radiation) fluctuates according to the seasons and the Earth’s orientation to the Sun. Furthermore, cloud cover as well as weather conditions on the rocky shore may influence an organism’s inclination to be exposed to sunlight.
During summer, sunlight and UV radiation are at their highest, which also increases the rate of photosynthesis in plants and phytoplankton. These organisms are also potential food sources for organisms that inhabit the rocky shores, so food availability is also a factor which may influence any organism’s inclination to reveal itself to open areas.
This design describes the method to use to determine the effect of sunlight intensity on the amount of organisms that are stuck to rocks on a low energy rocky shore in the lower intertidal zone.
VARIABLES
(Data is not needed for a full 24 hours as amount of sunlight generally doesn’t change after the Sun has set, unless conducting experiment at one of the poles of the Earth, when times of sunrise and sunset should regularly be checked)
*Sunrise and sunset are defined by the point at where the Sun has just touched the horizon prior to rising or setting
Control of Constant Variables
(Experiment is to be repeated 5 times so as to reduce random error)
MATERIALS
Experiment
- 1 x 1m quadrat
- Clock (Analogue or digital) displaying the correct time according to the time-zone of the site (±0.5sec [analogue] ±0.5min [digital])
- 1 metre ruler (increments of 1 cm) (±0.5cm)
Controlling of Variables
- Xplorer GLX
- Salinity meter attachment to Xplorer GLX
- pH meter attachment to Xplorer GLX
- Thermometer
METHOD
Prior to recording of data (Approx. 5:30am, however must be before sunrise)
- The area within the rocky shore in the lower intertidal zone was determined and the 1 x 1m quadrat was placed on the area to be studied
- The temperature of the environment, tide height, water salinity, pH of the water and the weather of the site were all measured and recorded using the thermometer, tide recordings for that specific day, the Xplorer GLX as well as the salinity meter attachment and the pH meter attachment, respectively.
Recording of data
- At sunrise, the number of gastropod organisms that were adhered to the rocky shore were counted and recorded
- Step 1 was repeated at: (The clock was used to determine the times to count)
- 0800 hours
- 0900 hours
- 1000 hours
- 1100 hours
- 1200 hours
- 1300 hours
- 1400 hours
- 1500 hours
- 1600 hours
- 1700 hours
- 1800 hours
- Sunset
- 1900 hours (or when sun has completely gone over horizon and no natural light is available)
- Conduct steps 1 and 2 on a day with similar temperature of the environment, tide height, water salinity, pH of the water and the weather of the site, however at the same site
RISK ASSESSMENT
POSSIBLE METHODS OF STATISTICAL ANALYSIS
Due to the data being continuous, a trend according to the number of gastropods counted verses the time of day may be presented. Due to conducting the experiment five times, an average for each time may be found. As well as providing a trend on how many gastropods are found, this also gives an indication as to if gastropods prefer sunlight to shade, which immediately gives indications of their adaptations to that environment.
RAW DATA TABLE
BIBLIOGRAPHY
Epiphragm (2010) (Internet)Wikipedia (Accessed 7/03/2011) Available from:
Epiphragm – Definition (2011) (Internet) Mariam-Webster Dictionary (Accessed 7/03/2010) Available from: