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Chemotrophic Organisms
Nitrosomonas & Nitrobacter bacteria are autotrophic organisms which obtain energy through chemosynthesis.
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The energy doesn’t flow from one organism to another in a linear way as in a food chain but many chains intersect .
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How did scientists trace the food chains?
Scientists spray radio active phosphorus solution at very low concentrations on weeds. Few weeks later , they collect insects & examine them with Geiger counters .
Several weeks later, they examine bigger animals .
The energy flow in an ecosystem is represented by energy pyramids (environmental pyramids).In every pyramid, the greatest amount of material is at the base and as the pyramid gets higher, the amount of material decreases.
1.Pyramid of Numbershows the relation between the energy flowing & the number of living organisms .
An example: 5000 plants provide energy for 500 insects.
The insects provide energy for 1 bird. A certain scale is used to draw the following pyramid.
The base represents the plants while the apex represents one bird.
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G.R. The number of organisms in a forest isn’t important in expressing energy flow.
The trees are huge therefore one tree provides energy for a large number of organisms. In this case , the pyramid of mass is used to represent energy flow in the forest.
2. Pyramid of Mass
a.The total weight in each level
indicates the level of energy saved
for the organism in the upper level .
Pyramid of energy
The producer contains the greatest amount of energy. There's a large amount of energy lost from one trophic level to another.
G.R. The pyramid of energy is the best representation for energy flow in living organisms .
It considers a. the rate of food production & its total weight.
b. It is not affected by the number of living organisms or the rate of
utilizing the energy obtained.
The energy flow from one organism to another is measured by kilo calorie.
Kilocalorie:is the amount of heat required to raise the temperature of one liter of water by one degree centigrade
For an ecosystem, the productivity of plant and other living organisms is measured by
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Environmental Balance
Definition:
It is the ability of the ecosystem to return back to its first situation after any situation different from its basic components.
Factors disturbing the environmental balance :
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1. Rabbits were introduced to Lisan Islands in1980.
Rabbits reproduced at a high speed & consumed plants at a higher rate than the rate of growth of plants plants disappeared rabbits died of hunger,
birds died or migrated Disturbing the environmental balance.
2. Hyacinth plant was introduced into Egypt .
Suitable environmental conditions and the absence of enemies
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Plant spread widely,
