Lesson 4 Assignment 1
1) Cayuga Lake is a natural unit consisting of living and non-living parts which interact to form a stable
system. Examples of living and non-living parts include plants, animals, soil chemistry, temperature,
nutrient supply, etc. Cayuga Lake, in its natural state, is finely-tuned and well-balanced. It supports and
depends upon a tremendous diversity of plants and animals. In this ecosystem, Plants convert sunlight
to energy; insects convert plant matter to energy; fishes eat insects, fishes eat each other, and other
animals like humans catch and/or eat fishes. Most of these subcomponents depend on the water supply
from the lake. Decomposers, rippers and shredders tear everything down to make room and nutrients
for new plants and animals. Here is further break-down of how this ecosystem works:
The Sun provides energy to Producers
(green plants and algae, etc.).
Producers provide energy to Primary Consumers
(herbivores, or organisms that eat only
Primary Consumers provide energy to Secondary Consumers
(carnivores, animals that eat
herbivores, or omnivores, that eat both plants and animals).
Secondary Consumers provide energy to Tertiary Consumers
(carnivores and scavengers who
occupy the tops of their respective food chains, like eagles or humans).
Decomposers are microorganisms like bacteria and fungi which cause a breakdown of dead
(plants and animals)
, releasing their stored nutrients for re-use.
Nutrients released by decomposers are re-used by producers, starting the cycle over.
A certain amount of energy is lost in each stage of the food chain. This effectively limits the
overall length of any given food chain. In other words, at some point, the energy spent getting
food is greater than the energy gained from the food source, so an animal becomes weaker and
weaker as time goes on until death finally occurs
When humans interfere with delicate ecosystems, the most common result is severe disruption
of natural balances which, in turn, results in greatly reduced ecosystem function.
When agricultural runoff and sewer discharges (unnaturally high levels of fertilizer) are emptied
into Lake Pontchartrain, a dramatic increase in algal growth can be the result. This, in turn,
results in turbid or cloudy water; aquatic plants die because they can't get the same levels of
sunlight, and algae blooms deplete aquatic systems of necessary oxygen.
As aquatic plants die, small fish which depend upon these plants also begin to die. In turn,
larger fish which depend upon the smaller fish also die or leave. This represents the beginning
of ecosystem collapse.
Cayuga Lake contains three zones, each with its
characteristic communities of organisms.