Analyzing Activity Budgets and Energy Expenditure in Birds
School
City University of Hong Kong**We aren't endorsed by this school
Course
CHEM 3068
Subject
Biology
Date
Dec 12, 2024
Pages
7
Uploaded by sanafatima543a
CHEM3068/3068A General Ecology Tutorial 41.Activity budgets measure how much time an animal spends performing a particularbehaviour. Since energy cost per unit time varies among different behaviours, how animalsallocate their time to various behaviours has important consequences for their overall energybudget. Three behaviours are identified in the adult of a bird species. They are flight, beingon water, and attending the nest. To forage, the birds would fly from the land, spend time onwater, and then return to the land. Attending the nest involves either incubating the eggs orrearing the chicks, depending on whether the eggs have hatched. Results obtained are shownin Figures 1 – 3. Fig. 1. Mean daily percentage of time spent undertaking three recorded behaviours for incubatingand chick-rearing birds.
Fig. 2. The daily energy expenditure of the birds, dependent on allocation of time in nestattendance, being on the water, and flying. Percentage of time spent in each activity should beread parallel to the direction of the tick marks for each axis respectively.Fig. 3. Total energy cost (KJ) of foraging trips dependent on percentage of trip spent flying inrelation to duration of foraging trip. Black dots indicate values from individual foraging tripsfrom 21 birds.
a)Based on the results shown in Fig. 1, compare the activity budgets between theincubating birds and chick-rearing birds. Give explanations for their differences.(5 marks)b)What is the major factor responsible for the difference in daily energy expenditure amongthe birds as shown in Fig. 2? Explain your answer.(2 marks)c)Based on your understanding of the daily energy expenditure (Fig. 2) and the distributionof data points in Fig. 3, what is the foraging strategy of the birds in relationship to theduration of foraging trip and the adaptive value of this strategy?(3marks)
2.Many ecologists have suggested that mechanical defenses (e.g., thorns in plants) againstherbivores are costly to produce and their production requires the diversion of valuable plantresources. Therefore, defenses should be switched on, or induced, by the presence ofherbivores. A study was undertaken to test this hypothesis using a long-lived thorny shrubwhich is eaten by the sheep.In Experiment 1, thorns are removed from half the surface area using scissors, just as theyare beginning to form. The results on the fruit set (i.e., ratio of fruit to flowers produced) areshown in Figure 1.In Experiment 2, herbivores are either allowed to feed on the plants freely or excluded byfences. The density of thorns on the plants is monitored and the results are shown in Figure2. Percent fruit set is also recorded and the results are shown in Figure 3.Figure 1. The effect of removing thorns from plants on the fruit set.
Figure 2. Between-year differences in thorn density (number of thorns / 25 cm2) for plants excluded andnonexcluded from herbivores from 1998 to 2000.Figure 3. Differences in percent fruit set for plants excluded and nonexcluded from herbivores from 1998 to 2000a.What is the effect of removing thorns from plants on the fruit set? Explain your answer.(3 marks)When thorns are removed, there is higher fruit sets produced as more energy is channeled tomake fruits rather then making thorns. And in the presence of thorns, there are less fruit sets.
b.Comment on the effect of herbivore exclusion on the production of thorn. Explain whythere is such a difference between the two treatments. (5 marks)In the absence of herbivores, plants are not in constant attack of herbivores so there is no risk and they will channel their energy to fruit production.In the presence of herbivores, they can sense the risk/danger so they react accordingly by producing more thorns. c.What is the effect of excluding herbivores on the fruit set shown in Fig. 3? Explain youranswer with reference to Fig. 1 and Fig. 2.(3 marks)In the absence of herbivore, fruit set is much higher.Explain more… as plants will use the energy which produces thorn into producing more fruits. In3.The seven-spot ladybird beetle defends itself against predator by possessing a toxin,precoccinelline. To advertise its unprofitability to predators, the forewings of the beetlecontain a pigment carotenoid that produces warning colours of the wings. A “resourcecompetition model” hypothesized that warning colouration and chemical defence competefor a shared resource within individuals. The model predicts that at low resource states, thereshould be a positive correlation between warning colouration and chemical defence, i.e.,when resource availability increases, prey is predicted to invest increasingly in both thewarning colouration and chemical defence. To investigate if food availability affected theproduction of these two chemicals in adult beetles, the larvae were reared on either a Low-diet or High-diet, and the concentration of carotenoid and precoccinelline in the adult wasmeasured. The results are shown in the figure below:a.Explain why the “resource competition model” predicts a positive correlation betweenwarning colouration and chemical defence when food availability is low. (Hint: What
will happen if most of the resource is used for either warning colouration or chemicaldefence when resource is limiting?)(5 marks)b.Describe the effect of diet level on the production of carotenoid and precoccinelline. Isthe “resource competition model” supported by the experimental results? Explain youranswer.(4marks)c.The “resource competition model” also predicts that when resources are very abundant,individuals are predicted to invest disproportionately higher in toxins and to reduceinvestment in warning colouration. Explain the rationale behind.(2 marks)d.An experiment was undertaken to test if the starling, a predatory bird of the beetle, is ableto discriminate the warning colour of beetles reared on low- and high-diet. What is thepurpose of this experiment?(1mark)