Chapter 2
Ecology
2.1: Organisms and Their Environments
Ecology- the study of the interactions that
occur between organisms and their
environments
Types of Ecological Research
1. Descriptive (qualitative)- gathered by
observation
 Listing behaviors of an organism
2. Quantitative- taking measurements and
conducting experiments
 Counting the number of times an
organism does a particular behavior
Biosphere
The portion of the Earth that supports life
Abiotic
Nonliving factors in the biosphere
Determine which species survive in a
particular environment
Examples?
Biotic
Living things and materials once belonging
to living things
Examples?
Levels of Organization
Atom
Smallest unit of matter that still possesses
the properties of an element
Molecules
Composed of two or more atoms
Cell
smallest unit of a living thing that still
retains the characteristics of life
Functional unit of living things
Tissue
Composed of a group of cells of the same
type that perform the same function
Organ
Structure composed of several types of
tissue performing a specific functions
Organ system
Group of organs working together to
perform an specific body function
Organism
An individual living thing
Population
A group of organisms belonging to the
same species, which interbreed and live in
the same geographic area at the same
time
Community
All of the populations of different species
that live in the same geographic area at
the same time
Ecosystem
Interactions between populations in a
community and the abiotic factors in that
environment
Can be terrestrial or aquatic
Biosphere
Composed of all the ecosystems on the
planet
Organisms in Ecosystems
Habitat- geographic area in which an
organism lives
Niche- an organism’s role in its
environment, includes how it interacts with
the biotic and abiotic factors in that
environment
Symbiosis
The close and permanent relationship
between organisms of two different
species
Mutualism- an association which benefits
both species
Species 1 : Species 2
+:+
Commensalism- an association which
benefits one species and does not affect
the other
Species 1 : Species 2
+:=
Parasitism- a relationship in which one
species benefits and the other is harmed
Species 1 : Species 2
+:-
2.2: Nutrition and Energy Flow
How do organisms get energy?
Producer (autotroph)- an organism that
makes its own food for an ecosystem
Consumer (heterotroph)- an organism that
gets its food from other organisms
Types of Heterotrophs
A. Herbivores
B. Carnivores
C. Omnivores
D. Scavengers- physical
E. Decomposers- chemical
Flow of energy in ecosystems
In an ecosystem, matter is recycled
through the different biotic and abiotic
factors
Energy flows!
Food chains
Simple feeding relationship in which
energy moves from producers to
consumers to decomposers
Trophic Levels
Autotrophs- make their own food
1st-order heterotrophs- eat autotrophs
2nd-order heterotrophs- eat 1st-order
heterotrophs
3rd-order heterotrophs-eat 2nd-order
heterotrophs
Food Webs
Shows all of the feeding relationships in an
ecosystem
Organisms usually eat more than one
thing!
Ecological Pyramids
The shape of the pyramid represents
several decreasing factors:
1. Decreasing energy
With each transfer of energy from one
organism to another, some energy is lost
as heat
Only 10% of the available energy is
transferred to the next level
2. Decreasing biomass
Biomass- total weight of organisms at
each trophic level
3. Decreasing population size
Populations farther up on the food chain
are smaller
Cycles in Nature
Matter cycles, energy flows!
Water Cycle
Evaporation
Transpiration- evaporation of water from
the surfaces of plants
Condensation
Precipitation
How do humans influence the water
cycle?
Carbon Cycle
CO2 enters the atmosphere as a result of
respiration of animals
Plants use CO2 for photosynthesis
Animals eat plants and use carbon for
growth
When animals die, the carbon is returned
to the soil
How do humans influence the carbon
cycle?
Nitrogen Cycle
 Animal wastes and the actions of decomposers
put nitrogen into the atmosphere
 Bacteria convert nitrogen into a form plants can
use
 Plants use the nitrogen to make protein
 Animals eat plants and use the nitrogen to make
protein
 How do humans influence the nitrogen cycle?
Phosphorous Cycle
Plants get phosphorous from the soil
Animals get phosphorous from plants and
use it for growth
Decomposers return phosphorous to the
soil
How do humans influence the
phosphorous cycle?