3. Communities and Ecosystems Flashcards
Finishes the first set of slides, covers energy pyramaids and chi
What does each bar on a energy pyramid represent?
Whats on the bottom?
Width of the bar represents what?
-Trophic levels
-autrotrophs
-width represents energy stored
Energy is measured per…? and what 3 units
per unit area, (kJ/m2/y)
Pyramid of numbers, width represents what?
number of organisms
Biomass
What is it?
Whats it measured in?
2 ways to measure it?
-The total dry weight of organisms
-g/m2
1.gather a sample of the organisms,
dry them in an oven at 60-800C and then record their mass. Number per sample area will help determine the biomass
2.estimate by measuring size,
density of organisms and estimating biomass based on % that is water
Pyramaid of biomass
Width represents what?
Why do the ecosystems form this pyramid shape?
2 situations when it may not be a pyramaid?
-amount of dry matter
-Loss of carbon dioxide, water
and other waste products
-Fatty foods have twice as
much energy per gram (ie.
peanuts)
– Aquatic ecosystems
■ Producers are being eaten as
soon as they reproduce
species
groups of organisms that can potentially interbreed to produce
fertile offspring
Mesocosms are..?
Closed mesocosms
-models to help us investigate sustainability of ecosystems
-closed mesocosms allow energy in and out but have a fixed
supply of matter
Why are mesocosms easier to experiement with than natural ecosystems? What is the disadvantage?
-cheaper, smaller, less time
-able to control and manipulate without causing irreverisble change
-not as accurate and realistic and a natural ecosystem
The Chi test is used to determine..?
-whether there is a significant (ie. statistical) difference between the observed and expected frequencies
Null hypothesis
When is it rejected?
there is NO association between Species A & B (ie. if one species is present, we do not necessarily expect to
find the other species)
when the chi value is LARGER than the critical value
