Trophic levels: the flow of energy through an ecosystem. Energy is always lost from one trophic level to the next.

• Producers - autotrophic organisms using solar or chemical energy to produce all the organic nutrients for an ecosystem.
• Consumers - heterotrophic organisms that cannot make their own food. They get energy from the chemical bonds in the nutrients they eat.
  • Primary consumers (herbivores) - eat primary producers (plants).
    • Conversion efficiency: only 10 to 20 percent of the available energy passes from producers to primary consumers.
  • Secondary consumers (carnivores) - eat primary consumers (herbivores).
    • Conversion efficiency: only 5 to 10 percent of the available energy passes from primary consumers to secondary consumers.
  • Tertiary consumers (carnivores) - eat secondary consumers (carnivores).
    • The conversion efficiency for tertiary consumers may be as low as 1%.
  • Omnivores - eat both plants and animals.
  • Decomposers - break down dead tissues and wastes.

• Gross primary productivity - the total amount of energy produced, including the energy used by the plants for their own respiration.
• Net primary productivity - the rate at which plants store energy that is not used in plant respiration.

                                                                                                                                           

Conservation Scientist

Food chain the specific sequence in which organisms obtain energy within an ecosystem.  Food web interrelated food chains within an ecosystem. As the diagram indicates, a food web may have many linked food chains and be very complex.

Competition - within any ecosystem, some organisms utilize resources and reduce the availability of those resources to other organisms.

• Intraspecies competition - between organisms of the same species.
• Interspecies competition - between organisms of different species.

Predation - refers to the relationship between a predator and its prey.

Have you ever seen a rabbit run onto the road in front of a car and suddenly stop? While this is not a good reaction at the time, it is the behavior that will most often save the rabbit from being caught by a predator. How?

Even predator and prey populations are related. If the predator population is low, the numbers of the prey species will increase. Most predator species will reproduce in larger numbers if food is abundant. As the numbers of the predator species increase, the prey population begins to decline.

Use this computer simulation to explore predator/prey populations.

Symbiosis the close association between two dissimilar organisms.

• Parasitism - one organism obtains its nutrition from another organism to the harm of the host.
• Commensalism - one organism benefits from another organism while that organism neither benefits nor is harmed.
• Mutualism - the relationship benefits both organisms equally.

Ecological pyramid - a graph representing trophic level numbers within an ecosystem. The primary producer level is at the base of the pyramid with the consumer levels above.

• Numbers pyramid - compares the number of individuals in each trophic level.
• Biomass pyramid - compares the the total dry weight of the organisms in each trophic level.
• Energy pyramid - compares the total amount of energy available in each trophic level. This energy is usually measured in kilocalories.

Most ecological pyramids would be like the one on the left. The pyramid on the right is "inverted". Give an example of an ecosystem that would produce an inverted numbers pyramid. Why would an energy pyramid never be inverted?

Population a group of individuals of the same species living in the same area.                      World population information

Population density - the number of individuals in a population in a given area at a given time. Carrying capacity - the maximum number of individuals that an ecosystem is capable of supporting. As population numbers increase, certain factors in the environment become limits to growth. All living things need a certain amount of space in which to live, food, water, and oxygen. Biotic potential - the rate at which a population will grow if all individuals survive and reproduce at their maximum capacity. This is a theoretical number that is never realized in nature. While the term is not usually applied to human populations, health and census data are available for such calculations. Realized intrinsic rate of growth - a measure of the difference between natality (birth rate) and mortality (death rate). r = n - m 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.

Use this computer simulation to explore human population dynamics.

• U.S. Census Bureau
• State & County Quick Facts
• Human population Growth  

Day 2 Assignment - Biotic Relationships
This assignment must be turned in by the beginning of class tomorrow to receive credit.
Scoring criteria

1. Describe and give an example of the difference between a habitat and a niche.

2. List two example of primary producers.

3. Which of the trophic levels produces the most biomass? Which level the least?

4. Visit this site   and play the "Food Chain Survival Game". Practice by doing the easy and moderate levels. Record your answers here for the hard level.

5. Visit this site    "Webbing It" and see how long it take you to put together the food web puzzle.

   1. Record your time here. (include the number of times you cheated)

   2. List the names of the producers in the food web.

   3. List the names of the secondary consumers.

   4. List the names of the tertiary consumers.

   5. Are there any omnivores in the food web?

6. Describe an example of each type of symbiosis?

7. Using this predator  prey data construct a graph showing the relationship between the two populations and place it here. Describe and support any comparison patterns you can see developing on the graph.

8. Find or draw an example of each type of ecological pyramid and place it here (or one that contains all). Label each pyramid.

   1. What patterns do you see in each of the pyramids?

   2. How would the reduction on the bottom of the pyramid effect the top?

   3. What might cause a reduction on the bottom?

9. What is the current human population density for earth?

10. Calculate the realized intrinsic rate of growth for humans in the United States.

11. What is the estimated carrying capacity for humans on earth?

    1. What will ultimately limit there growth?

12. What is the estimated population of humans by the year 2050?

Honors biology: Complete the above questions along with these

1. Read the information about shrews below and do the calculations:

   Shrew Mathematics Exercise:

   The short-tailed shrew is a ravenous predator that is found throughout the plains states. Although it is seldom seen, it is common. There can be as many as 50 shrews living on one acre of land, with 10 to 20 shrews per acre common. Few animals are as hungry as a shrew. It must eat 1¹/₂ times its own body weight in insects and other small animals in a single day. Solve the following problems so you can picture how much a shrew really eats.

   You must clearly show where the numbers come from and what the calculations represent.

   1. The short-tailed shrew must eat 1¹/₂ times its own body weight in insects each day. If a shrew weighs 18 grams and a grasshopper weighs 3 grams, how many grasshoppers must a shrew kill and eat in one day? (Count each grasshopper killed in a day. If only part of a grasshopper needs to be eaten, count the whole grasshopper. For instance, 2¹/₂ grasshoppers needed in a day would be three grasshoppers killed and eaten).
   2. How many grasshoppers must it eat in one week?
   3. If three shrews live in your garden, how many grasshoppers can they eat in one growing season? (Consider June, July, August, and September as the growing season).
   4. If you had to eat as much as a shrew (1¹/₂ times your body weight), how many quarter pound hamburgers would you have to eat in one day?

    

2. Use this information about prairie dogs to answer the questions below:

   In January of 2000, all members of a population of black-tailed prairie dogs in a field of native short-grass prairie north of Red Rock were counted. The population contained 50 prairie dogs. This population is isolated from other prairie dog populations and cannot expand far due to the fact that there are irrigation systems in the adjacent fields and wheat is grown there. Since the black-tailed prairie dog is now considered an endangered species, a wildlife biologist is monitoring this population. During 1999, 5 prairie dogs died and 10 were born. The field containing the prairie dog town measures 250 square meters.

   Prairie dogs are herbivores, feeding on several types of small plants found around their burrows. They are preyed upon by small carnivores as well as hawks and falcons. These same hawks and falcons feed on other small rodents round in the prairie dog town.

   1. What is the intrinsic growth rate, r, for this population in 2000?

      a. 0.01 prairie dogs per     prairie dog per year

      b. 0.05 prairie dogs per     prairie dog per year

      c. 0.10 prairie dogs per     prairie dog per year

   2. If there are no predators or diseases in the area, what would you expect the population of prairie dogs to be at the end of December 2001?

      a. 56 prairie dogs

      b. 61 prairie dogs

      c. 67 prairie dogs

   3. What was the initial density of the prairie dog population?

      a. 0.2 prairie dogs     per square meter

      b. 2.5 prairie dogs     per square meter

      c. 5 prairie dogs     per square meter

   4. What is the source of the energy that keeps prairie dogs alive?

      a. prairie grass

      b. glucose

      c. sunlight

   5. The wildlife biologist monitoring the prairie dogs suspects that the prairie dog town has been polluted with heavy metals, that cannot be excreted or metabolized by plants and animals. In which of the following organisms would you expect the biologist to find the highest concentration of heavy metals?

      a. small plants

      b. prairie dogs

      c. hawks & falcons

Research Links:

• Planet Earth Information - The Nine Planets by William A. Arnett
• Math Equations & Tables - Math2.org
• Astronomical Constants and Equations - NASA Kennedy Space Center

Biomass is the weight of all the living matter in a particular area.