Question

research shows that, in general, lower incubation temperatures produce more males, and warmer temperatures produce more females. the exact temperature that creates 50% males and 50% females is called the pivotal temperature. temperatures above this will produce a higher ratio of females while temperatures below this will produce more males. that ratio increases until a certain temperature in which 100% of the hatchling will be female.

1. suggest two factors that might influence nest temperatures on a beach, resulting in two nests on the same beach having different temperatures.

research investigation
a laboratory investigation was carried out to determine the effect of nest (sand) temperatures on sea turtle sex ratio. sea turtle eggs were collected from a local beach the morning after a nesting event. the nest temperatures in which the eggs were collected from were measured and recorded to be 29°c, and this temperature was used as the median temperature in the experiment. these were placed into equally - sized groups and immediately buried in artificial sand nests set up in the lab. different groups were exposed to different temperatures, which remained constant for 67 days, until the hatchlings emerged. the ratio of female:male was determined for each
est.\ once all data was collected, all hatchlings were placed on the beach, where they were originally collected from. at that time, they made their way to the water and swam off.

1. in an experiment, the independent variable is the variable that is being manipulated, or changed. the dependent variable is the variable that is being measured. identify both variables.

independent variable: __________ dependent variable: __________

1. in order to have reliable results, you need to be certain that the independent variable is the only thing influencing any changes in your experiment. therefore, you will need to keep everything else consistent. these constants are your control variables. suggest 4 control variables for this experiment.

1 - __________ 3 - __________
2 - __________ 4 - __________

1. use the data set to graph a line graph. put temperature on the x - axis and % female on the y - axis.

temp °c % female hatchlings
26 0
26.5 0
27 7
27.5 23
28 33
28.5 43
29 49
29.5 58
30 63
30.5 71
31 78
31.5 87
32 100
32.5 100
33 100

Explanation:

Step1: Identify factors for nest - temperature variation

Factors like the depth of the nest in the sand (deeper nests may be cooler) and proximity to water (areas closer to water may have more stable and cooler temperatures) can influence nest temperatures on a beach.

Step2: Determine independent and dependent variables

The independent variable is the factor that is changed, which is the nest (sand) temperature. The dependent variable is what is measured, which is the sea - turtle sex ratio (specifically the percentage of female hatchlings).

Step3: Suggest control variables

1. Type of sand (as different sands may have different heat - retaining properties).
2. Size of the egg groups (to ensure similar starting conditions).
3. Time of incubation (kept at 67 days for all groups).
4. Location within the lab (to ensure uniform environmental conditions during incubation).

Step4: Graphing instructions

To graph, mark the temperature values on the x - axis (ranging from 26°C to 33°C) and the percentage of female hatchlings on the y - axis (ranging from 0% to 100%). Plot each data point (e.g., at 26°C, 0% female hatchlings; at 26.5°C, 0% female hatchlings etc.) and then connect the points with a line.

Answer:

1. Depth of the nest in the sand, proximity to water.
2. Independent variable: Nest (sand) temperature; Dependent variable: Sea - turtle sex ratio (percentage of female hatchlings).
3. 1 - Type of sand; 2 - Size of egg groups; 3 - Time of incubation; 4 - Location within the lab.
4. Graph with temperature on x - axis and % female on y - axis, plot points and connect them with a line.