Study Guide

Ecology: Organisms and Their Environments Questions

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Ecology: Organisms and Their Environments Questions

  1. Some forms of bacteria, like multiple-resistance Staphylococcus aureus (MRSR), are resistant to many kinds of antibiotics. Explain how this type of resistance might occur.
  2. What method(s) of prey defense do you expect caribou to use against wolves?
  3. What types of events might lead to primary community succession?
  4. What is the difference between population ecology and community ecology?
  5. Why are there so few top carnivores, or tertiary and quaternary consumers, in ecosystems compared to producers?
  6. What does age structure information tell ecologists about a population?
  7. How is ecosystem ecology related to population ecology?
  8. What is the difference between density-dependent and density-independent factors? Give some examples of each type of factor.
  9. Why do some species have many offspring at different times over the course of their lives while others have numerous offspring once and then die shortly afterward?

Ecology Answers

  1. Answer: As bacteria like Staphylococcus aureus come in contact with antibiotic treatments from humans, some members of the bacterial population contribute more to the next generation because they are slightly more resistant to the antibiotic than other members. Through time, most of the members of the succeeding populations have the resistance. As humans continue to expose the bacteria to different antibiotics, the bacterial populations adapt through an evolutionary arms race with humans. This is a form of coevolution.
  2. Answer: Caribou likely use physical and behavioral defenses against wolves. Physical defenses include sheer population numbers and herding, making the individual probability of being eaten much lower. Behavioral defenses include running in a straight line for a long distance, as wolves are known to only be able to run at full speed for about a mile.
  3. Answer: Any event that eradicates all life in an area can lead to primary community succession. These types of events might include volcanic eruptions, the formation of new islands, extremely hot forest fires, human development, meteorite strikes, and other major catastrophes.
  4. Answer: Population ecology focuses on characteristics of whole populations of the same species, rather than just attributes of individual organisms. Community ecology focuses on interactions between members of populations of different species.
  5. Answer: Because energy is passed so inefficiently from one trophic group to the next—only 10% per level—it takes many producers to sustain a few top carnivores. In short, there is only so much energy to go around.
  6. Answer: Among other things, age structure data allow ecologists to predict future population growth patterns.
  7. Answer: Ecosystems are composed of communities and habitats. Communities are composed of populations. Therefore, the characteristics of populations determine the characteristics of communities, which determine, in part, the characteristics of ecosystems.
  8. Answer: Density-dependent factors affect population growth rates to a greater degree as the density of the population increases. Density-independent factors can affect population growth rates regardless of population size or density. Examples of density-dependent factors include disease and resource supply. Examples of density-independent factors include catastrophic events, like tsunamis, fires, and floods.
  9. Answer: Some species evolved in environments, where the risk of dying young or the risk of offspring mortality was low. These organisms were able to reproduce multiple times and live longer lives because of these decreased mortality risks. Other organisms evolved in environments, where the risk of dying young or the risk of offspring mortality was high. In these species, the individuals that passed the most genes onto the next generation were those that were earliest in investing the most energy into reproduction.

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