Assignment 1

1. (a) Consider the results of Activity 4 in which you used the biophysical frog model. Under the climate change scenario, were the green tree frogs exposed to lethal conditions for either water loss or body temperature?

Note: Body temperatures above the Critical Thermal Maximum are lethal in a matter of minutes. Water loss, however, needs to be considered over a daily cycle – you can assume that after 24 h the frogs will find some water and rehydrate.

(b) Consider the effects of the same climate change scenario (+3°C) for a small frog with high cutaneous resistance, Litoria bicolor and cane toads Rhinella marina. The characteristics of the 3 species are show in the table below. The main differences among these 3 spreadsheets are the body masses and cutaneous resistances. Another difference is that, unlike Litoria caerulea, the other two species are assumed to be outside during the day rather than in a tree hollow. The wind speed inside a hollow is very low, and the humidity is higher. But the air temperatures are the same for all 3 models. Under the climate change scenario, were these 2 species exposed to lethal conditions for either water loss or body temperature?

Note: For this part of the question, use a 50g toad – check the mass in the spreadsheet and change it to 50g if needed. We will explore the effects of body size in question 1(d) below.

Species Mass (g) Cutaneous resistance (s/cm) Critical Thermal Maximum Temperature (°C)
Litoria caerulea 50 14 37.5
Litoria bicolor 1 63 41.0
Rhinella marina 1, 50 or 500 1.7 37.5

(c) Change the mass in the spreadsheet for Rhinella marina so that it is set up for a toadlet with a mass of 1g. Thus, the only difference between the spreadsheet for Rhinella marina and the spreadsheet for Litoria bicolor is the cutaneous resistance -with L. bicolor having one of the highest cutaneous resistances of any Australian frog and toads having very low resistance to evaporative water loss. Briefly discuss the effect of cutaneous resistance on water loss and body temperature. Under these environmental conditions (use the original values, not the climate change air temperatures), are these species in danger of dying due to either excessive water loss or excessively high body temperatures?

(d) Using the toad spreadsheet, explore and discuss the effect of body size on body temperature and water loss by using the model for masses of 1g, 50g and 500g – all of which are realistic masses for this species. Under these environmental conditions (use the original values, not the climate change air temperatures), are any of these 3 toads in danger of dying due to either excessive water loss or excessively high body temperatures?

Note: Use no more than 700 words plus any tables or figures you want to use in your answer for Question 1.   (17 marks)

2. Read the short paper once published in Science entitled “Mate Selection and Behavioral Thermoregulation in Fowler’s Toads” by L. Fairchild (Science 212:950-951), keeping in mind what we have been studying with respect to the physical environment. There are some problems with the way the author accounted for the effects of the physical environment in this study. Discuss at least one of these problems.

Note: Use no more than 200 words in your answer for Question 2.  (6 marks)

3. List and discuss the characteristics of some animals that would make them more susceptible to global warming. Explain why those characteristics make animals more susceptible. List and discuss the characteristics of some animals that would make them less susceptible to global warming. Explain why those characteristics make animals less susceptible.

Note: Use no more than 300 words in your answer for Question 3. (6 marks)

Submit this assignment through Learnline by the end of week 5.