Mr. Himel
a grouping of plants, animals, and microbes interacting with each other and their enviornment
Plant Community
all the species of plants growing together in an area
How are plant communities generally characterized?
by certain dominant species
What are the 3 main components of an ecosystem?
1. A distinct plant community
2. a more or less distinct array of animal species
3. a large biomass of microbes made mostly of bacteria and fungi
Out of the three main components of an ecosystem, which has the greatest biomass?
The plant community followed by microbes
Which ecosystem community determines the animals found there? Why?
The plant community because they provide available energy to the ecosystem and are the base of the ecosystem's structure
the total array of plants, animals, and microbes
Do ecosystems have distinct boundaries?
No because one ecosystem grades into the next through a transitional region that shares many of the species and environmental characteristics of the two adjacent systems
What 2 kinds of observations give a general answer to why different ecosystems are found in different regions?
1. Different regions of the world have very different climatic conditions
2. plants and animals are usually specifically adapted to particular conditions
Abiotic Factors
all of the chemical-physical factors of the enviornment(non-living)
What are the two more obvious abiotic factors in an ecosystem?
precipitation and temperature
Why are annual averages for precipitation not specific enough information for ecologists?
Because rain is distributed evenly throughout the year and creates a different environmental effect from the same amount of rainfall coming almost exclusively during 6 months of the year.
What measurement of temperature is more significant that average temperatures? Why?
The cold temperature extreme proves to be more significant biologically that the average temperature. Whether freezing temperatures occur and the length of time of freezes have a much greater effect on what organisms are found in a region than the average temperature.
Law of Limiting Factors
Either too much or too little of any single abiotic factor may limit or prevent growth( and survival) despite all other factors being at or near their optimum levels.
Illustrate what is meant by abiotic factors interacting to create a matric of an infinite numer of environmental conditions by giving two examples or these interactions
A sandy soil or a lot of wind have a similar effect to less rainfall(drier conditions). These and other abiotic factors can interact to create a nearly infinite number of possibilities
condition at which maximum growth occurs for an organisms
Range of Tolerance
total range of a condition that will support growth of an organism
Limits of Tolerance
conditions below and above which an organism cannot survive and reproduce
What fundamental biological principle comes from observations of the above phenomena?
Each species has an optimum, a range of tolerance, and a limit of tolerance for every environmental factor
Explain why an organism from one ecosystem may be absent from adjacent (adjoining) ecosystems using the Law of Limiting Factors
The reason a species in one ecosystem does not penetrate indefinitely into an adjacent system is often because it confronts one or more abiotic (or biotic) factors which are limiting
Which abiotic factor most often limits plants in terrestrial ecosystems? Explain using the example of forests
Precipitation is most often the limiting factor for plants. Forests generally cannot be found in areas that receive less than 75 cm (30 in.) of rain per year
What 2 abiotic factors determine the distribution of plants of terrestrial biomes?
Precipitation and temperature usually determine the distribution of biomes
Why are variations of plant communities found within each biome?
Variations occur within biomes due to differences in other abiotic factors within the biome (such as soil or topography).
Abiotic factors other than the 2 in question 18 are sometimes more important in transition (edge) areas. What factor is used to explain why 2 areas which both receive 25cm of rainfall may support 2 different plant communities?
Other abiotic factors, such as soil, can influence the plant communities found in a transitional area. For example, the poor water-holding capacity of sandy soil would cause an area of 25cm of annual rainfall to only support desert plants. A clay or loam soil might support grassland in a different area with the same amount of precipitation
the particular abiotic conditions from the ground up to a height of 2 meters (about 6 feet)