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NOTES- Chapter 20 : Interactions of Life
I. Living Earth
A. __Biosphere___________ - the part of Earth that supports life.
“Bio” = ___life___
1. The biosphere includes the top of the Earth’s _____crust______, all the __waters_______ on the
Earth’s surface, and the surrounding _____atmosphere______.
B. ____Ecosystem_____ - All the organisms living in an area and the nonliving features in their
environment. (______biotic______ = living factors ; _____abiotic_____ = nonliving factors)
1. _____Ecology_____ is the study of the interactions that occur among organisms and their environment.
2. A _____population_______ is made up of all the organisms in an ecosystem that belong to the
same species.
Ex. All the bison in a prairie ecosystem or coyotes in an area
3. A ______community_______ is all the populations in an ecosystem. Ex. Bison, grasshopper, cowbirds
C. ______Habitat__________ - the place in which an organism lives. (Ex. trees for woodpeckers etc.)
1. Must provide the kinds of ______food_________, ____shelter_______, _temperature___,
and __moisture_____ the organism needs to survive.
D. ______Niche________ - the role of a species in an ecosystem. IT’S JOB
1. Includes the organisms _______food______, _____shelter_____, how it avoids __danger______,
finds _____a mate_________, and ____cares for its young___.
2. All members of a species occupy ______The same Niche________.
II. Interactions Within Communities
A. Transfer of energy
1. ______Sun________ - main source of energy for most life on earth
2. __________Autotrophs_________ (producers) - organisms that produce their own food
Most are _green_plants_or green algae____ that get energy through _photosynthesis__.
3. ___Heterotrophs___________ (consumers) - organisms that cannot make their own
food but obtain energy by eating other organisms (get energy indirectly from the sun.)
a. __Herbivores____________ eat plants and are called __primary_________
consumers (Ex. rabbit eating grass)
b. __Carnivores____________ eat animals. (ex. frog eats bug, lion eats
zebra)
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those that eat herbivores are __secondary____ consumers.
(Ex. snake eating rabbit that ate the grass)

those that eat secondary consumers are __tertiary______ consumers.
(Ex. hawk eating a snake that ate the rabbit that ate the grass)
c. _Omnivores________ eat plants and animals. (Ex. us)
d. _Decomposers_____ consume dead plant and animal matter, so the nutrients
contained within them can be reused (break them down/rot)
(ex. earthworms, fungi, or bacteria)
****Each level (step) in the transfer of energy through an ecosystem is called a ___trophic level_______.
(At each level _____less___ energy is made available (about ___90____ % lost at each level.)
heat
Food (chemical energy)
Available energy (@ 10%)
waste
4. ____Food Chain____ - a series of organisms that transfer energy through an
ecosystem.

Plant
All begin with a _______Producer_________________________.
---- herbivore ---- carnivore ---- another carnivore ---- decomposer
(producer)
( primary consumer) (secondary consumer) (tertiary consumer)
*ARROWS indicate _flow of energy____________.
5. A network of food chains in an ecosystem make up a
__________Food Web__________________.
( Most consumers eat more then one type of food)
*Changes in the population of one organism affect
All other populations in a community ___________
_______________________________________
Ex. If mouse population disappears then: populations that it ate would increase –> plants, hawks would
have less to eat, snakes would eat more grass hoppers, coyotes would eat more deer
6. * __Compost_________________ - a pile of organic matter such as leaves, grass clippings, plant
clippings, newspapers, kitchen scraps, and soil etc. allowed to decay naturally.
Benefits: less stuff in landfills, good fertilizer, holds moisture, prevents disease
* ___Biomass_____________ - the total mass of living and formerly-living material within a given area
*___Decay___________________ - the breakdown of organic matter from larger to smaller molecules
Heat Energy
Big
Molecules
Decomp
Small
Molecules
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


Big molecules
Small molecules
Decomposition
Heat energy