Chapter 43: Ecological and Evolutionary Consequences of Interactions within and among Species

Modified from Principles of Life Study Guide: Hillis, Sadava, Hill and Price

43.1 Interactions between Species May Increase, Decrease, or Have No Effect on Fitness

1. Two of the main characters in the animated film Finding Nemo are anemone fish (clown fish) which live inside of sea anemones and are unaffected by their stings. How is this relationship an example of the ways in which interactions between species are not always easy to classify?

2. You have discovered two individuals of different species living in close association. Design an experiment to determine if the relationship is mutualistic.

43.2 Interactions within and among Species Affect Population Dynamics and Species Distributions

3. How might the rarity advantage apply to a consumer-resource interaction, such as that between predators and their prey?

43.3 Species Are Embedded in Complex Interaction Webs

4. After the European rabbit (an herbivore) was introduced into Australia in 1859, it quickly became a devastating invasive species, causing the extinction or decline of many native plants, major damage to crops and soil erosion. Rabbits also had a negative impact on some of Australia’s native mammals, such as bettongs, because the rabbits competed with them for food. Is it likely that the impacts of the rabbits would be confined to native herbivores? To control the growth of the rabbit population, biologists infected rabbits with the myxoma virus in 1950. It is estimated that in the first years after the introduction of the virus, as many as 99 percent of infected rabbits died. Over a period of years, however, biologists observed an increase both in the average life span of infected rabbits and in the percentage of rabbits surviving infection. How would you explain these later changes, and what do they suggest about the effectiveness of this control measure?

5. The Great Lakes of North America have been subjected to many waves of introduced species as a result of canal construction in the eighteenth and nineteenth centuries. This led to colonization by species from eastern North America, such as the sea lamprey. Subsequently, increases in international shipping traffic to the Great Lakes introduced species from other continents via discharge of ballast water, including the zebra mussel from Europe. Other species, such as coho salmon, a species native to the Pacific coast of North America, were deliberately introduced to enhance recreational fishing. Most recently, species of carp native to Asia have escaped from fish farms and now threaten to invade the Great Lakes via canals in the Chicago area that connect rivers of the Mississippi system to Lake Michigan. Draw a diagram indicating these four invasive pathways to the Great Lakes, specifying whether the species introductions were accidental or intentional. Since there are different sources and pathways for these invasive species and many invasive species now are well established in the Great Lakes, can you envision any way that the negative impacts of such species can be minimized without altering current Great Lakes ecosystems or the human infrastructure of canals, shipping pathways, or fish farms?

43.4 Interactions within and among Species Can Result in Evolution

6. Many bats prey on moths. Foraging bats use echolocation to detect moths; the bats emit calls and then listen to the echoes of calls returning from objects in the environment. Moths, in turn, have evolved ears capable of detecting bat echolocation calls; this allows the moths to avoid foraging bats. In response, some bats emit calls outside the hearing range of moths. Evaluate the statement. “Bats have clearly won the evolutionary arms race with moths.”

7. Interspecific cleaning interactions occur in many natural systems. In a familiar example, large predatory fish come to cleaning stations because their gill cavities are infested with crustacean ectoparasites that interfere with respiration. Small cleaner fish remove the ectoparasites. Evaluate the statement, “The cleaning behavior of the small fish evolved to help the larger fish.”

Additional Resources: use the web address listed

  • Animated Tutorial 43.1 Species Interactions and Population Dynamics ( PoL2e.com/at43.1)
  • Animated Tutorial 43.2 An Ant-Plant Mutualism (PoL2e.com/at43.2)
  • Activity 43.1 Ecological Interactions (PoL2e.com/ac43.2)
  • Activity 43.2 The Major Trophic Levels (PoL2e.com/ac43.2)