Zusammenfassung der Ressource
C1-Species and Communities-
Ecology
- Survival Factors
- Limiting Factors: component of an
ecosystem which limits the distribution or
numbers of a population
- Biotic or Abiotic
- Biotic factors: interactions
between organisms – either
intraspecific (within species) or
interspecific (between species)
- Abiotic factors include environmental
conditions – such as light, temperature,
salinity, rainfall, wind velocity, soil pH, etc.
- Law of Tolerance
- Optimal zone– Central portion of curve which has
conditions that favour maximal reproductive success
and survivability
- Zones of stress– Regions flanking the optimal zone,
where organisms can survive but with reduced
reproductive success
- Zones of intolerance– Outermost regions in which
organisms cannot survive (represents extremes of the
limiting factor)
- Definition: populations have optimal survival
conditions within critical minimal and maximal
thresholds. As a population is exposed to the extremes
of a particular limiting factor, the rates of survival begin
to drop
- Species Distribution
- Quadrats: rectangular frames of known dimensions that can be
used to establish population densities
- Transects: a straight line along an abiotic gradient from which
population data can be recorded to determine a pattern
- Ecological Niche
- The habitat in which an organism
lives
- The activity patterns of the organism (e.g. periods of time during which it is active)
- The resources it obtains from the environment (e.g. food sources, territorial boundaries, etc.)
- The interactions that occur with other species in the community (e.g. predator prey relationships,
competition, etc.)
- Interspecific competition
- Competitive exclusion – One species uses the resources more
efficiently, driving the other species to local extinction
- Resource partitioning – Both species alter their use of the habitat
to divide resources between them (i.e. niche separation)
- Species Interactions
- Herbivory
- eating only plant matter
which can be either harmful
or beneficial to the plant
species as a whole
- leaves / foliage
of crop plants
(folivores),
causing crop
failure
- Fruit-eating animals
spread the seeds from
a fruit in their feces,
promoting overall
seed dispersal
- Predation
- one organism
(predator) hunts
and feeds on
another organism
(prey)
- prey population
drops (e.g. due
to
over-feeding),
predator
numbers will
dwindle as
intra-specific
competition
increases
- If the prey
population rises,
predator numbers
will increase as a
result of the
over-abundance of
a food source
- Symbiosis
- Mutualism
- Both species benefit from
the interaction (anemone
protects clownfish, clownfish
provides fecal matter for
food)
- Commensalism
- One species benefits, the other is
unaffected (barnacles transported to
plankton-rich waters by whales)
- Parasitism
- One species benefits to the
detriment of the other
species (ticks or fleas feed on
the blood of their canine
host)
- Keystone Species
- Definition: a species that has a disproportionately large
impact on the environment relative to its abundance
- Predators – they can exert pressure on
lower trophic levels to prevent them
from monopolising certain resources
- Sea stars (predator) prey on
urchins and mussels,
preventing mussel
overpopulation and coral
reef destruction by urchins
- Mutualism – they can support the life
cycle of a variety of species within a
community (e.g. pollinators / seed
dispersal)
- Honey bees (mutualist) pollinate a
wide variety of plant species,
ensuring the continuation of the
plant life cycle
- Engineers – they can refashion the
environment in a manner that
promotes the survival of other species
- Beavers (engineer) build dams
that transform the environment
in a manner that allows certain
other species to survive
- Plant Survival
- Temperature
- Water Availability
- Salinity
- Light Availability
- Animal Survival
- Temperature
- Territory
- Food Availability