Mr. Bouyer
Day 1 - 2 | Day 3 - 4 | Lab | Reading Assignment

Use natural available resources to describe animal distribution patterns. Use natality and mortality to describe the growth of animal populations. Classify animals as either "r-selected species" or "K-selected species". Describe the predator-prey relationship between selected animals. Construct a population profile.

Animal Identification Assignment.

What is meant by the equation r = n - m?

Basic terms:

• Ecology - the study of relationships between organisms and their environment.
• Population - a group of interacting individuals of the same species.
• Community - a group of interacting populations.
• Ecosystem - a functional environmental unit, consisting of a biotic community and the abiotic (nonliving) factors on which the organisms depend.
• Biosphere - the total of all ecosystems. In other words, all the inhabited area on earth.

Population size and density:

• To begin to study a population, the size of the population (number of individuals) is determined.
• For the size of a population to have meaning, the area covered by the population must be known.
• Density - the number of individuals per area unit.

• To give a better picture of population density, distribution within the area needs to be known.
• Random distribution - each individual has an equal chance of being found at any place in a given area. This is a hypothetical condition that might never occur in nature because resources are not randomly distributed.
• Uniform distribution - animals are evenly spaced throughout the habitat. This can at least be approached in nature.
• Clumped distribution - animals are found in areas where resources are found. This is by far the most common distribution pattern in nature.
• Many animal populations will have different distribution patterns at different times.

• The age structure can tell more about population dynamics than either density or distribution.
• Functional age classes: because of the difference in lifespans, the ages of these groups can be very different from one group of animals to another.
  • Prereproductive - too young to reproduce.
  • Reproductive - able to reproduce.
  • Postreproductive - too old to reproduce.
• Population age profile - an estimation of the number of individuals in each age class.
  • When the number of prereproductive individuals forms a high percentage of the population, the population is likely to be increasing in size.
  • A stable population has a fairly even number of individuals in each age class.
  • When the number of postreproductive individuals is large, the population is declining. There are too few individuals maturing to provide population replacement.
  • A species with a short life span will show all three types of age profiles during one seasonal cycle.
• Natality - the ratio of the number of births in a given time to the total population.
• Mortality - the ratio of the number of deaths in a given time to the total population.

1. Exponential growth model:
• A population could reach its biotic potential, the maximum growth rate of which a population is physiologically capable, if these conditions are met:
  • environmental conditions are ideal
  • there are no restrictions on reproduction
  • mortality rate is kept extremely low
• Realized intrinsic rate of growth is measured by the difference between natality (birth rate) and mortality (death rate).
  • r = n - m (rate = natality - mortality)
  • Since environmental conditions are rarely ideal, the maximum growth rate is almost never achieved in nature. For this reason, the realized intrinsic rate of growth more closely represents the actual growth of organisms in nature than does the biotic potential.
• Zero population growth is reached when r = 0, natality equals mortality, and population size remains constant, even though individuals are being born and are dying.

2. Logistic growth model:

• Environmental resistance - the combination of many factors that tend to prevent exponential growth.
• Exponential growth begins to slow because of a combination of declining birthrate and increasing death rate. Eventually, the population stops growing as it fluctuates around zero population growth at the habitat's carrying capacity - the maximum population density that the environment can support for an extended time.
• Restricted or logistic population growth can be expressed by the equation
  d N / d t = r N x (K - N) / K
  • d - means an instantaneous change in
  • N - the number of individuals already in a population
  • t - a unit of time
  • r - realized intrinsic rate of population growth
  • K - carrying capacity
• r-selected species - capable of very rapid population growth, approximating an exponential growth pattern followed by a crash in the adult population .
• K-selected species - have more or less stable populations adapted to exist at or near carrying capacity in relatively stable habitats.

These mathematical models help us understand, but not necessarily precisely describe, how populations actually grow. Both models make important simplifying assumptions that do not actually relate to nature.

• The exponential model assumes that populations grow without being influenced by environmental resistance.
• While the logistic model may seem more realistic, it makes several assumptions:
  • Assume the carrying capacity is constant.
  • Assume each individual affects the growth of the entire population by increasing environmental resistance as soon as it is born.
  • Assume the number of offspring produced by an individual relates directly to the resources available at the time of birth.

• Two things can be said about populations:
  1. Population density varies from habitat to habitat.
  2. No population increases indefinitely.

• Law of the minimum - the essential material available in amounts most closely approaching the minimum needed by an organism will tend to limit the organism's growth and development.
• Limits of tolerance - an organism can only tolerate certain extremes in environmental factors. Populations cannot exist outside the tolerance limits of its individuals.
  • Euryecious species have a high tolerance for many environmental factors and are widely distributed.
  • Stenoecious species have a low tolerance for many environmental factors and therefore have a narrow distribution.
  • Density-independent controls are forces whose effect on a population is not influenced by the density of the population. These include severe storms, droughts, and volcanic eruptions.
  • Density-dependent controls decrease population growth most effectively when the population density is high, and have less influence when the density is low. These include competition, emigration, and stress.
  • Competitive exclusion principle - the competition between populations of two species for the same limiting resource eventually leads to the elimination of one of the species populations.

• There can be many ecological niches in one geographical area. An animal's niche is determined by all the ways the animal interacts with its environment, including what it eats, how it obtains its food, what physical and chemical conditions it will tolerate, what conditions are optimal for its well-being, and how it interacts with its predators and parasites.

• Predation - the feeding of free-living organisms on other organisms.
• Predator-prey relationships:
  • Some species appear to be linked, with population numbers fluctuating together. But do the predators control prey populations, or do prey populations control predators?
  • Optimal foraging brings a predator the maximum net food energy gain. Predators do not normally spend great effort pursuing rare, energy-poor, or hard to handle prey.
  • Prey availablility is a key factor in the foraging behavior of predators. Increasing numbers of prey elicit two types of responses from predators:
    1. Functional response - There is a relationship between prey density and the number of prey consumed per predator per unit of time. The predator seems to focus its attention on the shape and general appearance of the abundant prey, filtering out other potentially distracting stimuli. The abundant prey makes up an increasing percentage of the predator's diet.
    2. Numerical response - There is a relationship between prey density and predator density. Predator numbers increase as a prey population increases.

Portfolio Assignment 032:
Scoring criteria

1. Explain how the percentage of each functional age class found in a population determines the health of most populations.
2. In a population of 100,000, there are 900 deaths and 2,000 births in a particular length of time. Calculate the natality and the mortality in this population.
3. What is the realized intrinsic rate of growth in the population in question #2?
4. What is the best example of a euryecious species you can think of?
5. (statement 1) Predators control prey populations.
   (statement 2) Prey populations control predators.
   Choose the statement above that you believe is most accurate. Write a paragraph giving a compelling argument to support your choice.
6. Use the following information to answer the final multiple choice questions.

   Susan got a two cubic foot aquarium for her birthday. With the help of a pet store, Susan set up the aquarium complete with 4 female guppies, 1 male guppy, and 10 snails. She provided pleanty of food and kept the aquarium clean and supplied with air. After 6 months, she took inventory and found 50 guppies and 150 snails.

   1. Snail population density in the aquarium at the end of 6 months was
      1. 150 snails/cubic foot
      2. 25 snails/cubic foot
      3. 75 snails/cubic foot
      4. 150 snails
   2. The population growth rate for snails during the 6 months was
      1. 150 snails
      2. 140 snails
      3. 25 snails/month
      4. 14 snails/snail/6 months
   3. In the 7^th month, Susan noticed that 40 guppies were born and 30 died. The guppy population size at the end of the 7^th month was
      1. 10 guppies
      2. 30 guppies
      3. 40 guppies
      4. 60 guppies
   4. Susan will know that her guppy population has reached the carrying capacity of her tank when
      1. guppies are no longer born
      2. guppies no longer die
      3. the guppy birth rate equals the death rate
      4. there is no longer room for guppies to swim
   5. The snails may start getting sick and some may die. Disease is an example of a (an) ___ population control.
      1. fatal attraction
      2. exponential
      3. density-independent
      4. density-dependent

Day 3 - 4

Would you say that humans are more like a K-selected species or an r-selected species?

While zoologists are usually concerned with the population ecology of "animals", the population ecology of humans is important at times. Over the next two days, you are to build a population profile of the State of Oklahoma. To do this, you will need the most current population information available for Oklahoma. While your research might not be limited to these, the following links may be helpful:

U.S. Census Bureau
Oklahoma State Department of Health
Oklahoma Center for Health Statistics

In-class Assignment 034:
This assignment must be turned in by the end of class tomorrow to receive credit.
Scoring criteria

1. Complete this population profile worksheet.

Zoology Class

Realized intrinsic rate of growth is calculated using the equation rate = natality - mortality.

While humans do not fit into either of these catagories, they most closely fit with K-selected species.
The long period of time between birth and sexual maturity in humans does not allow them to react like an r-selected species.