1. 7.2 Communities & Ecosystems
Living Organisms Interacting with Each Other & Their Environments

2. Main Ideas
Organisms both cooperate and compete to increase the chances of survival and reproduction.
The Earth “system” has experienced disruptions by natural and artificial causes. Long-term survival depends on this ability to regain its balance.
The Earth’s biosphere is broken down into nine diverse biomes; these are the habitats for terrestrial animals. These are dominated by access to water, energy, and nutrients.

3. 3A. Two key processes of ecosystems: Energy flows & chemicals cycle
Energy flows within food chains from the sun, through plants, animals and decomposers; most is lost as heat (calories).
Chemicals are recycled among air, water, soil and organisms.
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4. 3B. Trophic structure determines how ecosystems work.
A food chain is the stepwise flow of energy and nutrients:
Plants: producers
Herbivores: primary consumers
Carnivores: secondary & tertiary consumers
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5. PIP # 2

6. 3B. Trophic structure determines how ecosystems work.
The break down of organic compounds to inorganic compounds is called “decomposition”.
“Detritivores” or “Recyclers” (animal scavengers, fungi and bacteria) decompose waste matter and recycle nutrients.

8. 3C. Energy supply limits the length of food chains.
Productivity: what organisms
do with the energy they get.
Secondary
Primary

9. 3C. Energy supply limits the length of food chains.
Fate of energy from food:
cellular respiration
heat
Only 10% or less of the energy in food is stored at each trophic level and available to the next level.
This stepwise energy loss limits most food chain to three to five levels.

10. 3D. An energy pyramid explains why meat is a luxury for humans.
Because the energy pyramid tapers so sharply, a field of corn or other plant crops can support many more vegetarians than meat-eaters. 1%
10%
10%
100%
100%
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11. Main Ideas: Recap
Organisms both cooperate and compete to increase the chances of survival and reproduction.
The Earth “system” has experienced disruptions by natural and artificial causes. Long-term survival depends on this ability to regain its balance.
The Earth’s biosphere is broken down into nine diverse biomes; these are the habitats for terrestrial animals. These are dominated by access to water, energy, and nutrients.

12. Works Cited
Biology: Concepts and Connections. Third Edition (2000) Campbell, et al., Benjamin Cummings San Francisco