Activities in Eco 2

Activity # 7 1.) Do herbivores eat only specific portion of the leaves? Can this be used to classify herbivores? Are herbivores species-specific in their choices of food? 2.) What would be the ultimate fate of the energy contained in the uneaten part of the leaf? Does any of it ever flow again through larger animals such as carnivores? 3.) Do herbivores prefer young leaves than older ones? How might time of the year affect your calculations? What about time emergence of various species of leaf-eating animals? Do insects eat leaves as larvae or adults, or both? 4.) What percentage of plant production goes to animal consumption? What does this indicate of the value of the secondary production? How does your data compare with that of the other groups? Activity # 8 1.) Although the idea behind CMR method is simple and logical, the results in practice are often not very accurate. Cite possible reasons for this. 2.) Many modifications of the mark-and-recapture method have been devised to correct some of the limitations or deficiencies of the method. Examples are the Bailey and JollySeber methods. Discuss each of these. If the mark-recapture method were to be used in serious research, which of these modifications should probably be used. 3.) Were the assumptions for the CMR method met in this stimulated exercise? How likely is it that they will be fulfilled in a real sampling study such as sampling of a grasshopper population? 4.) What are some of the methods used for marking animals in population estimate studies? 5.) What is meant by “trap-shy” and “trap-prone” organisms? Will they affect your estimates to total population? Activity # 9 1.) Explain the mathematical models or equations for exponential and logistic growth patterns. 2.) What is meant by doubling time? How is it computed? 3.) Would you be able to compute the value of “r” from your obtained data? If yes, what is the computed value of “r” for the two selected populations ? 4.) What would be some advantages of having a high intrinsic growth rate value? Why don’t all organisms have a high “r” value? 5.) How is the concept of life history i.e. r- and K-selection related to the concept of population growth? 6.) What are the factors that limit population growth rate? Differentiate density-dependent factors with density-independent factors. Activity # 10 1.) What kind of life table was constructed in this exercise? Why? Describe the other types of life tables.

2.) What are the factors that influence mortality rate in a population? 3.) Outline and describe the different types of survivorship curves. Name specific populations that exhibit such types of survivorship curves. 4.) How will you compute for the mean life span value of a given population based from the life table data? 5.) How would you compare the mortality rate and life span of the male and female members of the population. Make critical comments. Activity #11 1.) Outline and describe some of the factors that influence age structure of a population. 2.) A population may pass through changes in age structure without changing in size. O you agree or disagree? Justify. 3.) Differentiate sex ratio from dependency ratio. What is the relation of these parameters to age distribution? 4.) What are the different types of age pyramids? Illustrate and describe each of these types? 5.) How does your age structure data and age pyramid compare with known data on Philippine population? World population? Activity # 12 1.) In this experiment, which plant is a stronger competitor? Justify. 2.) Do you think growing corn and mongo together has more effect on corn or on mongo? Or the effects equal? 3.) Enumerate the possible effects of competition on a weaker competitor. 4.) How would you detect the presence of competition in a community of plants? Or animals? Activity # 13 1.) Discuss the significance of competition as an agent of natural selection. 2.) What is meant by scramble and contest competition? Which of these types is more advantageous to any of the competing populations? Is this applicable to plant population? 3.) What is meant by self-thinning response in relation to crowding behaviour of trees in a woodland or forest? 4.) Based on the result of your investigation, which is more advantageous for a forest manager, single-species planting (monoculture) or mixed species planting? 5.) Define and discuss the concept of resource partitioning? Activity # 14 1.) Based on your graph, which exhibits an initial increase in the population size that of rats or snakes? 2.) By just looking at the graph, can you deduce which population is that of predator and which population is that of prey? Explain.

3.) If all the snakes were hunted to extinction, what do you think will surely happen to the prey population? Will this effect reversible? 4.) What is meant by a “key predator”? What is its ecological role in natural communities? 5.) How are predators classified? 6.) Why do predators do not overeat their prey? Activity # 15 1.) Does the curve generated from the regression equation fit the data reasonably? If yes, what assumed constants were actually held constant? If not what are some sources for observed deviation? 2.) In graph 2, does the functional response yield a density dependent mortality for the prey? Is the prey population regulated by this type of functional response? 3.) While the prey is being handled searching ceases, how does this affect the Hollings model? 4.) The prey is evenly distributed (see preparation). How would you aggregate prey distribution alter Hollings model? 5.) Give the probability (P+) at time (t) for a density (x). Removal of one prey alters the density and therefore the likelihood that the next tap will catch a prey is reduced. How does this affect the results observed? 6.) From related literature explain the mechanisms involve in type III functional response. Can this type of response be regulated? Begin the discussion with an operational definition of regulation. 7.) How can functional responses be incorporated with numerical responses?