1.1. To present factors that determine population density, distribution and change
1.2. To describe how communities are organized and how they develop and diversify
 | Populations and Communities |
| Ecosystems |
| Biosphere |
| Human Impact on Biosphere |
2.2.1. Ecology - interaction of organisms and their environments
2.2.2. Population - several members of the same species within a defined geographic area
2.2.3. Community - several species that interact within a defined area
2.2.4. Ecosystem (27-1) - a system involving interactions of several communities
2.2.5. Biosphere - global ecosystem
3.2.1. Often the concentration is more important than numbers
3.2.2. Individuals are distributed uniformly, randomly, or in clumps (27-2)
| examples (27-3) (tussock grass, crocus, and flamingos) |
3.2.3. Clumping or aggregation is most common
| environmental conditions are seldom uniform |
| reproductive patters favor clumping (e.g. vegetative reproduction) |
| behavioral patterns often lead to groups (27-4) (e.g. gannet colony clumping favors protection and reproduction) |
3.3.1. Equation
I = rN
| I = population growth rate |
| r = intrinsic rate of increase = (births - deaths) per individual |
| N = population size (number of individuals) |
3.3.2. A housefly beginning to breed in April would increase to 2 X 1020 by August in an unlimited environment (would cover 10 cm of earth's land surface)
3.3.3. In the U.S. the birth rate is 16 per 1000 and death rate is 8.5 per 1000 so:
| r = 0.016 - 0.0085 = 0.0075 |
| growth rate is 0.75% per year or the population will double in 93 years |
3.4.1. Carrying capacity (K) - maximum number of population over a sustained period
3.4.2. Growth of sheep in South Australia (27-7)
3.5.1. boom and bust (27-8) (e.g. pea aphids in an alfalfa field, influenced by weather and season)
3.5.2. wild fluctuation independent of environmental conditions (27-9) (e.g., rmax >2, population overshoots k approaches 3 and is erratic)
3.5.1. Plot showing three types (27-10)
| low infant mortality (humans) |
| moderate infant mortality (hydra) |
| infant mortality high (oysters) |
3.6.1. Sweden (27-11) - birth rate = death rate; population is not growing
3.6.2. U.S. (27-12) - size of youngest group is equal to reproductive group; population will continue to increase until year 2000; note the baby boom bulge
3.6.3. India (27-13) - high birth rate; population will increase for next two generations
3.6.4. Growth of world population (27-14)
3.7.1. Predation, disease, and parasitism
| density dependent |
| example of predator prey (27-14) |
| moose/wolves (27-15) |
3.7.2. Competition
| intraspecific - same species - e.g. flowers planted too close |
| interspecific - different species - |
| principle of limiting similarity - no two species can occupy the same niche at the same time |
| niche - ecological role of a species in a community |
example - niches of three closely related warblers (27-16)
3.7.3. Behavioral and Physiological Changes
| cooperative hunting of dogs (27-17) |
| locusts migrate in phase (food depletion leads to swarming to find food) (27-18) |
| social behavior of ants and bees (27-19) |
3.7.4. Concept of limiting factors - only one factor can be limiting at time
4.1.1. Primary succession - communities established in newly formed habitats, e.g. sand dunes; bare rock
4.1.1.1. successions in ponds (Presque Isle, PA, a penisula in Lake Erie)
| newly formed pond (27-20) |
| 2-years low vegetation, cottonwood saplings (27-21) |
| 50-years, choked with weeds, cottonwoods (27-22) |
| 150-200 years, meadow (27-23) |
4.1.1.2. succesional stages at southern Lake Michigan (27-24)
4.1.2. Secondary succession - communities are reestablished where another community once existed
| e.g. abandoned railway (27-25) |
4.1.3. Bird Succession on abandoned farmland in Georgia (27-26)
4.1.4. Succession is characterized by a number of trends
| first species are rapid growers capable of surviving a harsh environment; later species are slower growing, more competitive |
| species composition changes regularly and more rapidly in early stages |
| number of species increases rapidly at first and then stabilizes (27-27) |
| successional species may alter environment and make it more favorable for competitors |
| gross primary productivity increases until it reaches a stable high (27-28) |
| store of inorganic nutrients in soil and organism of ecosystem increases and a larger proportion is held in tissues of plants |
| total biomass and non-living organic matter increase |
| size of plants increase |
| communities become more diverse and complex. |
4.1.5. Climax community (27-29) - when energy flow and biomass reach equilibrium, i.e. total respiration equals gross primary productivity, e.g. /sequoia forest (some trees are 2,000 years old)
8.1. Define population size, density, and distribution andage structure.
8.2. Why do populations not restricted in some way grow exponentially?
8.3. Define carrying capaacity and describe its effect as evidenced by a logistic growth pattern.
8.4. What are some limiting factors for growth of microbes, plants, and animals?
8.5. At the present growth rate, how long wil it take before the human population has another billion individuals added to it?
8.6. How did earlier human populations expand steadily into new environments? How did they increase the carrying capacity of their habitats? How have they avoided some of the limiting factors on population growth? Are their methods sustainable?
8.7. What is the difference between the habitat and nich of a species?
8.8. Why is it difficult to define "the human habitat?"
8.9. Describe competitive exclusion. How might two species that compete for the same resource coexist?
8.10. Define the difference between predator and parasite.
8.11. Define primary and secondary succession. Give specific examples of each.
8.12. What is a climax community? How does the climax-pattern model help explain its structure?
| biotic potential | carrying capacity | community |
| demographic transition model | ecology | life table |
| density-dependent controls | ecosystem | population |
| density-independent controls | habitat | limiting factor |
| exponential growth | J-shaped curve | logistic growth |
| zero population growth | survivorship curve | S-shaped curve |
| camouflage | climax community | coevolution |
| commensalism | community | habitat |
| competitive exclusion | interspecific competition | predator |
| mimicry | mutualism | niche |
| parasite | parasitism | predation |
| pioneer species | secondary succession | prey |
| primary succession | resource partitioning | symbiosis |
Microbial Ecology - Digital Learning Center for Microbial Ecology, Michigan State University
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