Library

APES Chapter 5.3: Population Dynamics

By Sue O'Bannon
Last updated over 2 years ago
12 Questions

What limits the size of populations?

What do you think is one reason that elephants live in clumps?

Biotic potential is defined as the maximum number of individuals a species can produce. Under natural conditions, animals that overproduce have their population reduced by inadequate food supplies, parasitism, and predation.
Environmental Resistance is defined as the sum of the environmental factors (such as drought, mineral deficiencies, and competition) that tend to restrict the biotic potential of an organism or kind of organism and impose a limit on numerical increase.

Categorize each of the following into either "contributes to biotic potential" or "creates enviromental resistance".

  • limited space
  • food deprivation
  • high rate of reproduction
  • low infant mortality
  • large litter size
  • no predators
  • disease
  • sufficient food supply
  • predation
  • parasitism
  • high infant mortality
  • limited water availability
  • lack of disease
  • contributes to biotic potential
  • creates enviromental resistance

Which of these do you lead toward as your belief in what will happen to the human population? Link this back to your Environmental Worldview.

Think back to the Tragedy of the Commons. What did Garrett Harding say about the freedom to breed?

Categorize the following limiting factors as density-dependent or density-independent.

  • Usually Abiotic
  • habitat degradation
  • Flood
  • Forest fire
  • Disease
  • Access to water
  • Food availability
  • Space
  • Competition for Mates
  • pH (aquatic systems)
  • Usually Biotic
  • Predation
  • Extreme Temperatures
  • Drought
  • Density-Dependent
  • Density-Independent

Explain the pattern seen here and in other closely-linked predator/prey relationships.

Why is the NJ deer population so high? Which limiting factor is missing?

What are two reasons that the numbers of deer are problematic for humans?

What are some possible solutions to this deer population problem?

All organisms allocate energy to growth, reproduction, maintenance, and storage.
No choice is involved; this allocation comes as part of the genetic package from the parents. Maintenance for a given body design of an organism is relatively constant. Storage is important, but ultimately that energy will be used for maintenance, reproduction, or growth. Therefore the principal differences in energy allocation are likely to be between growth and reproduction. Almost all of an organism’s energy can be diverted to reproduction, with very little allocated to building the body. Organisms at this extreme are “opportunists.” At the other extreme are “competitors,” almost all of whose resources are invested in building a huge body, with a bare minimum allocated to reproduction.

Opportunistic species of animals or plants are adapted to exploit newly available habitats or resources and are typically found in unpredictable, transient, and variable environments. For example, clear-cut forests create well-lit open areas which are colonized rapidly by the windbone seeds of opportunistic species of plants, many of which are regarded as weeds by farmers and gardeners. Besides producing easily dispersed seeds, opportunistic species characteristically have a rapid growth rate, quickly establishing themselves in the new environment. Opportunistic species also have other characteristics: they reproduce early, have a small body size, and produce large numbers of seeds or offspring, a strategy known to ecologists as r-selection. Opportunistic species are most prominent during the early stages of ecological succession, when species that are more competitive in the long run are not very abundant. Opportunistic species have a great ability to alter their growth rate, physiology, or behavior to better suit the environmental conditions with which they are faced. Usually, this opportunistic response is accomplished without changes in the genotype, in which case it is known as phenotypic plasticity.

The opposite of an opportunist is a competitor. These organisms tend to have big bodies, are longlived, and spend relatively little effort each year on reproduction. An oak tree is a good example of a competitor. A massive oak claims its ground for 200 years or more, outcompeting all other would-be canopy trees by casting a dense shade and drawing up any free water in the soil. The leaves of an oak tree taste foul because they are rich in tannins, a chemical that renders them distasteful or indigestible to many organisms. The tannins are part of the defense mechanism that is essential to longevity. Although oaks produce thousands of acorns, the investment in a crop of acorns is small compared with the energy spent on building leaves, trunk, and roots. Once an oak tree becomes established, it is likely to survive minor cycles of drought and even fire. A population of oaks is likely to be relatively stable through time, and its survival is likely to depend more on its ability to withstand the pressures of competition or predation than on its ability to take advantage of chance events. It should be noted, however, that the pure opportunist or pure competitor is rare in nature, as most species fall between the extremes of a continuum, exhibiting a blend of some opportunistic and some competitive characteristics.

Research Type I survivorship species and insert a photo of one here. (Don't choose one that is listed here)

Research Type II survivorship species and insert a photo of one here. (Don't choose one that is listed here)

Research Type III survivorship species and insert a photo of one here. (Don't choose one that is listed here)