Download Communities: Many Interacting Populations

Community Ecology
Many Different Interacting
Populations
The difference between a niche
and habitat
Habitat: The area where an organism lives.
• A habitat includes both biotic and abiotic factors.
Niche: the full range of physical and biological
conditions in which an organism lives and the
way in which the organism uses those
conditions.
• The combination of biotic and abiotic factors in
an ecosystem often determines the number of
different niches in that ecosystem
Habitat is the organisms address, the niche is its
occupation
Species Relationships: based on
how organisms obtain energy
(feeding relationships)
1) Autotrophs: Transform energy from inorganic
(nonliving) substances into organic substances.
- Photosynthetic = energy from the sun
- Chemosynthetic = energy from inorganic
chemicals and geothermal energy (sulfur, salt,
hydrogen sulfide, iron, methane, etc.)
e.g. Archaebacteria
2) Heterotrophs: Obtain their energy from
consuming organic (living) materials.
- Herbivore = consumption of plants
- Carnivore = consumption of flesh
- Omnivore = consumption of both plants
and flesh.
- Detritivore = consumption of detritus (dead
organic matter) i.e. decomposers.
All of these feeding relationships result in close
interactions between different populations.
Interaction
Effect on
1st Pop’n
Effect on
other
Pop’n
Examples
Predation
+
-
Lions/Zebras,
Snakes/mice
Interspecific
Competition
-
-
Elk/Mule Deer,
Coyotes/
Vultures
Study the graph
demonstrating hare and
lynx population growth.
Describe two patterns
demonstrated b/w
predator and prey
populations.
Competitive exclusion principle: no two species
can occupy the same niche in the same habitat at the
same time.
- results in resource partitioning
• Symbiotic Relationships= A type of interaction where
both populations live with each other at all times.
Interaction
Effect on
Effect on
1st
other
Population Population
Parasitism
+
-
Mutualism
+
+
Commensalism
+
0
(Not
Affected)
Examples
Tick/Deer,
Tapeworm/
Cow
Ants/aphids
Bee/Flower
Nested
Bird/Tree,
Pilot
Fish/Shark
Parasitism
Mutualisms =
Coevolution
Commensalisms
Community Structure
• Biodiversity: (species diversity) The variety
of different kinds of organisms that make
up a community.
• Two Components
Biodiversity
• Species Richness:
the total number of
different species that
occupy a community.
• Species Evenness:
the relative
abundance of
organisms of each
species.
Ecosystem Ecology
The interactions between the
communities and their abiotic
factors.
Trophic Structure
• The feeding
relationships, and
flow of energy
(abiotic) between
organisms in a
community.
• The energy stored
in producers can be
passed through an
ecosystem along a
food chain.
Food Chain: a series of
steps in which
organisms transfer
energy by eating or
being eaten.
- Simple; only show
individual feeding
relationships.
- In most ecosystems
feeding relationships
are more complex
Food Webs
• A graphic representation of the feeding
relationships among the various
organisms in an ecosystem.
• Links all the food chains in an ecosystem
together.
Trophic Levels
• Each step or level in a food chain or food
web
• Producers make up the first level, and
consumers make up the second-fourth.
10 producer 10 consumer
20consumer30 consumer40consumer
• Limits: Each food chain w/in a food web
usually only has a few links; why?
10% Rule
• Only about 1/10 (10%) of the energy
stored in the organic matter of each
trophic level is converted to organic matter
at the next level.
• What happens to the other 90% of the
energy
The 10% Rule applies to the overall number of
individual organisms (as well as overall
biomass) at each trophic level.
**this explains why there are always fewer large
predators than prey in ecosystems**