Thursday, May 13, 2010
Thurs-Day 1
Bio - BRING IN your review books- starting on Friday, we will be using them throughout the rest of this Ecology/Human Impacts unit.
Today we reviewed the types of organisms in an ecosystem as classified by method of obtaining nutrients and then we listed more specific and descriptive synonyms.
For example, heterotrophs can be herbivores, omnivores, or carnivores. Carnivores can be further subdivided into predators (lions, bears, humans) and scavengers (vultures, hyenas).
Saprophytes are decomposers that obtain nutrients by digesting and absorbing the nutrients from dead organisms.
We looked at the pyramid of biomass in a stable ecosystem, explaining how each subsequent level has ONLY about 10% of the total mass of the lower level. This has to be so because 90% of the nutrients consumed are respired for energy, much of which is lost as waste heat and cannot be converted to the flesh of the organisms of the higher trophic level. For example, you weight a LOT LESS than all of the food that you've ever eaten because much of the energy and nutrients from that food was lost as waste CO2, H2O, and heat from you!
We then looked at the nutritional relationships and flow of energy/nutrients in an ecosystem as seen in a FOOD WEB (series of inter-related FOOD CHAINS). We saw how biodiversity can stabilize a food web by lowering the impact of the loss of one member of a food chain because a higher order consumer would have more choices/food sources in a higher biodiversity food web.
Finally, we predicted the various effects of losing/depleting one organism in a food web; the loss of an organism typically causes an INCREASE in the population of organisms that were previously being consumed by the now extinct/depleted organism. The loss of the one population may also caused increased competition among the species that used to eat the population of now depleted organisms. The increased competition usually results in a population decrease.
Today we reviewed the types of organisms in an ecosystem as classified by method of obtaining nutrients and then we listed more specific and descriptive synonyms.
For example, heterotrophs can be herbivores, omnivores, or carnivores. Carnivores can be further subdivided into predators (lions, bears, humans) and scavengers (vultures, hyenas).
Saprophytes are decomposers that obtain nutrients by digesting and absorbing the nutrients from dead organisms.
We looked at the pyramid of biomass in a stable ecosystem, explaining how each subsequent level has ONLY about 10% of the total mass of the lower level. This has to be so because 90% of the nutrients consumed are respired for energy, much of which is lost as waste heat and cannot be converted to the flesh of the organisms of the higher trophic level. For example, you weight a LOT LESS than all of the food that you've ever eaten because much of the energy and nutrients from that food was lost as waste CO2, H2O, and heat from you!
We then looked at the nutritional relationships and flow of energy/nutrients in an ecosystem as seen in a FOOD WEB (series of inter-related FOOD CHAINS). We saw how biodiversity can stabilize a food web by lowering the impact of the loss of one member of a food chain because a higher order consumer would have more choices/food sources in a higher biodiversity food web.
Finally, we predicted the various effects of losing/depleting one organism in a food web; the loss of an organism typically causes an INCREASE in the population of organisms that were previously being consumed by the now extinct/depleted organism. The loss of the one population may also caused increased competition among the species that used to eat the population of now depleted organisms. The increased competition usually results in a population decrease.
# posted by C @ 11:34 AM 
