Principles of
Ecology
Unit 2
Chapter 2
What is ecology?
 Ecology: study
of interactions
that take place
between
organisms and
their
environment
Biosphere
 the portion of the Earth that supports
living things
 Ex: ocean, forest, atmosphere.
Abiotic vs. Biotic factors
 Abiotic = nonliving parts of the
environment
 Ex: light, air, temperature, soil
 Biotic = living parts of the environment
 Ex: bacteria, protist, fungus, plant,
animal
Levels of organization
from smallest to largest




Individual
Population
Community
Ecosystem
Individual
 made of cells, uses energy, reproduces,
responds, grows, and develops
Population
 group of organisms all of the same
species, which interbreed and live in the
same area at the same time
Community
 interacting populations in a certain area
at a certain time
Ecosystem
 interacting communities and abiotic
factors
Habitat vs. Niche
 Habitat: place where organism lives
 Niche: role or position a species has in
its environment
Habitats are capable of
changing.
What can lead to changes in habitats?
Symbiosis: interactions
between two species
 Mutualism: both benefits
 Commensalism: one benefits, the other
unaffected
 Parasitism: one benefits, one is harmed
Mutualism
Clownfish is protected, while providing a lure for the anemone.
Some say that this relationship can be commensalistic.
Commensalism
Volcano sponge using the crinoid sponge as a “lift” for increased
filtration but the crinoid sponge is unaffected.
Parasitism
Head lice
How organisms obtain
energy
 Autotroph (producer): photosynthetic or
chemosynthetic, makes own food
 Heterotroph (consumer): “eat” other
organisms, cannot make own food
 Decomposer: breaks down dead or
decaying organisms, recycles matter
Autotroph
Heterotrophs - scavengers
 Scavengers: feed off of dead or
decaying living things but do not recycle
matter back into the ecosystem
Heterotrophs - herbivores
 consume only
vegetative matter
 mostly primary
consumers.
Heterotrophs - carnivores
 obtain energy from
eating other
consumers
 Secondary and
tertiary consumers
Decomposers
Typical examples: fungus and bacteria
Food chain
 shows how matter and energy move
through an ecosystem (one route)
berries → mice → black bear
Food web
 shows
interactions
between
organisms
(all possible
routes)
Energy pyramid Pyramid of Energy
Heat
 Shows how
much
energy is
available at
each
trophic
(energy)
level
Heat
0.1% Consumers
1% Consumers
10%
Consumers
Heat
Heat
Autotrophs
Third-order
heterotrophs
First-order
heterotrophs
Second-order
heterotrophs
Decomposers
Four cycles in nature




Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle