Chapter 12

14. What is an ecological niche? What goes into determining this niche? Explain the example with Chthamalus and Balanus (barnacles).

• Ecological Niche is a range of abiotic and biotic conditions within which individuals of a species can survive, grow and reproduce. (what they eat, where they live, when they are active) • Chtamalus is desiccation tolerant and can occur in regions exposed from low tide until high tide. • Balanus is less tolerant to desiccation • Therefore, due to competition, Chthamalus is limited to areas where Balanus cannot occur.

5. What is a resource? Give some examples. What defines a limiting resource? How does this affect competition?

• A resource is something that is consumed and thus reduced. • A limited resource has higher demand than availability • Competition can increase in intensity when resources are limited

13. Is allelopathy an example of interference competition or exploitative competition? What are some features of allelopathy?

• Allelopathy is an example of interference competition. Allelopathy can cause organisms to produce biochemical that influence the growth, survival, and reproduction of other organisms. • For example, eucalyptus or Melaleuca trees can use allelopathy to increase fire frequency/intensity in order to reduce potential competitors.

19. Is behavioral differentiation due to adaptive evolution or a learned response? How is this different from morphological and physiological differentiation?

• Behavioral differentiation may be due to adaptive or learned responses. • It is different from morphological and physiological differentiation because morph/physio differentiation occurs via adaptive evolution, thus are relatively fixed (not easily reversed) • Behavioral differentiation may be due to adaptive evolution (fixed) or learned responses, (not fixed and can be changed).

18. How could two competing species live together? What is this called? In what ways could the organisms partition the resources? (3) How do populations adapt to follow these partitions? (3) Give an example of each.

• Coexistence via Resource (Niche) Partitioning - similar species can coexist if they share (partition) the resources such that their niches no longer completely overlap. • Natural selection drives competing species into different patterns of resource use and thus different niches. Partitioning allows each species to use a subset of the resource (organisms can specialize by physical attributes (color, shape, size), spatial attributes (resources in specific locations), and temporal attributes (acquiring resources in different times throughout the day.) • Adaptive evolution can result in unique changes in (1) Morphology, (2) Physiology, (3) Behavior which allows specialization and niche partitioning. • Morphology - Various shorebird species live in the same habitat (beaches) and eat similar foods (small insects and crustaceans) Different species specialize on: insects at different depths and different sized insects • Physiology - Adaptive evolution resulted in physiological and behavioral differentiation of reproduction allowing partitioning of the feeding aspect of the tadpole's niches. Adults reproduce in different months so that tadpoles hatch in different months and do not compete for food.

20. Character displacement is a type of resource partitioning that occurs ONLY when two species occur together. What is the defining characteristic of character displacement? If two species look very different where they overlap and also when they are apart, are they experiencing character displacement? Why or why not?

• Compare populations where 2 species occur together in the same location and where each species occurs alone in an area. • If 2 species differ morphologically, behaviorally, etc only when they are together vs when they are alone - then this is character displacement. • If 2 species have different morphologies, etc whether they are alone or together then it is not.

7. When it comes to competition affecting the survival or reproduction of another individual, how do we experimentally show there is competition? Does competition reduce the survival and reproduction in one or both individuals? Why?

• Competition usually reduces survival and reproduction in both individuals because both species cannot receive as much of the resource as they could if they were alone.

12. What is exploitative competition? Give some examples.

• Exploitative competition are indirect interactions. It affects others from accessing resources by consuming them first. • Bears finding and eating all the berries first - so that other bears do not get any at all. • Trees will extend their roots deeper or farther so that they gain water before other plants may get water. • Plants will also grow taller so that they receive more light than the plants below them.

Competition is an interaction between _________ individuals both requiring the same limited resource that when ___ ___ ________ by one individual reduces the survival or reproduction of another individual.

Competition is an interaction between two or more individuals both requiring the same limited resource that when used or defended by one individual reduces the survival or reproduction of another individual.

17. Describe Gause's lab experiment used to test the competitive exclusion principle. What did he use? What happened when the two species used the same resource? What happened when the two different species used slightly different resources but were in the same test tube?

• Gause used three species of a single-celled protest group, Paramecium. He constructed miniature aquatic ecosystems by growing Paramecium in tubes filled with a liquid medium that contained bacteria and yeast cells as a food supply. • Found that populations of each of the three Paramecium species reached a stable carrying capacity when grown alone. But when pairs of these species competed with each other, several different outcomes were obtained. • P. Aurelia drove P. caudatum to extinction because the two species were not able to coexist because they both fed primarily on bacteria floating in the medium. • P. caudatum and P. bursaria coexisted, it was clear that they competed for one or more resources because the carrying capacity of each was lowered by the presence of the other. • P. caudatum and P. bursaria could coexist because P. caudatum ate bacteria floating in the medium, while bursaria usually fed on yeast cells that settled to the bottom of the tubes.

11. What is interference competition? Is it only limited to interspecific competition?

• Interference competition are direct interactions - individuals "fight" for access to limiting resources. It is not only limited to interspecific competition. It can occur in both inter and intraspecific competition

4. Describe the difference between intraspecific and interspecific competition.

• Intraspecific Competition - members of the same species compete for the same limited resources • Interspecific Competition - members of different species compete for the same limited resources

16. Describe Tansley's 1917 test of the competitive exclusion principle. What was the observation, and why did it appear strange to researchers? What happened when species were planted in their less ideal soil type? What happened when the other species was added? Why?

• Observation: closely related species of Galium (a plant) generally do not occur together. • Each species could be grown alone on either soil. But, when the species were planted in their less ideal soil type - the survival and growth were limited. • When the species were grown together - species on the non preferred soil has reduced survival and growth. (Becoming locally extinct).

6. Other than consuming it, what is another method that individuals use to isolate resources during competition? What kinds of energy constraints must be balanced for this method to be effective?

• Other than consuming it, organisms can also defend the resource. • The energy required to defend it and the amount of energy they gain from the resource.

Define a community and explain how it relates to populations.

• Populations of different species living and potentially interacting in a certain "area" at a given time.

10. What does it mean when α>1 or β>1? What about when α<1 or β<1? When α=0 or β=0? When α=1 or β=1?

• Then adding an individual of the other species has a greater effect than adding an individual of your own species. Interspecific competition > intraspecific competition. • Then adding an individual of the other species has a less effect than adding an individual of your own species. Intraspecific competition is greater than interspecific competition. • If a or b is 0 - there is no competition and the equation reduces to the logistic equation • If a or b is 1 - adding an individual of species 1 or 2 has the same effect on the growth rate. Both intra and interspecific competition have the same effect.

15. When two species use the same limiting resource, what are the two possible evolutionary outcomes? Describe using the competitive exclusion principle.

• Two species cannot co-exist indefinitely on the same limiting resource (i.e. with substantial niche overlap) • Because of competitive exclusion principle, there are two possible outcomes; • Competitive exclusion of one species (the inferior competitor becomes locally extinct) • Coexistence via Resource (Niche) Partitioning - similar species can coexist if they share (partition) the resources such that their niches no longer completely overlap.

8. What is the general equation for the Lotka-Volterra competition model? Define each variable. Why do we need two equations to represent the interactions between two species?

• dN/dt = rN(1- N/K) • We need two equations to represent the growth rate of each of the 2 competing populations. • 1 = species 1 • 2 = species 2 • R - intrinsic rate of increase (how fast a population can grow) • N - population size • K - carrying capacity • T - time • Alpha - competitive effect of spp 2 on 1 - degree to which individual of spp 1 use the resources of individual of spp 2 • Beta - competitive effect of spp 1 on 2 - degree to which individuals of spp 2 use the resources of individual of spp 1.