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Chapter 25: Populations & Ecosystems (Plants & Relationship to…
Chapter 25: Populations & Ecosystems
Plants & Relationship to Their Habitats
habitat
set of conditions in which an organism completes its life cycle
operational habitat
aspects of the habitat that affect a plant
abiotic components of the habitat
climate
critically important to all organisms
tolerance range
low and high extremes
soil factors
pioneers
first plants that invade a new soil
B horizon
zone of deposition
rich in nutrients
contains humus and clay
A horizon
uppermost
zone of leaching
consists of litter and debris
rainwater washes nutrients downward into the B horizon
C horizon
composed mostly of parent rock and rock fragment
latitude and altitude
no seasonal variation at the equator
disturbance
wildfires
landslides
snow avalanches
floods
biotic components of the habitat
the plant itself
modifies the habitat
other plant species
mutualism
interaction is beneficial for both organisms
competition
integration is harmful for both organisms
competitive exclusion
whichever species is less adapted is excluded from the ecosystem
niche
each species is assumed to be adapted to a particular set of conditions
transplant experiments
plants from each site ares transplanted to the alternate side
common garden
plants from both sites may be grown together
organisms other than plants
commensal relationships
one species benefits and the other is unaffected
predation
one species benefits and the other is harmed
herbivores/herbivory
animals that eat plants
browsing
eating twigs and leaves of shrubs
deer and giraffes
grazing
eating herbs
sheep and cattle
pathogenic
harmful bacteria/fungi attack plant
Structure of Populations
geographic distribution
boundaries of the geographic range
ability of a plant species to spread throughout a geographic area
limiting factor
one factor determining the health of the plant
local geographical distribution
random distribution
used whenever there is no obvious, identifiable pattern to the position of individuals
clumped distribution
spacing between plants is either small or large
uniform distribution
occurs in orchards and trees plantations
evenly spaced from their neighbors
age distribution: demography
the relative proportions of young, middle aged, and old individuals
generation time
length of tie from the birth of one individual until the birth of its first offspring
intrinsic rate of natural increase/biotic potential
number of offspring produced by an individual that actually live long enough to reproduce under ideal conditions
carrying capacity
number of individuals in a population that can live in a particular ecosystem
symbolized by K
r- and K- selection
r- selection
disturbance usually produces r conditions
fire or flood destroys many individuals in the area
resources are plentiful for the few that remain
K- selection
population is close to its carrying capacity
conditions in a crowded habitat
Structure of Ecosystems
physiognomic structure
trees, shrubs, and herbs
temporal structure
time span can be as short as a day or encompass seasons or decades
species composition
numbers of diversity of species that coexist in an ecosystem
trophic levels
feeding levels
primary producers
frist step of any food web
primary consumers
herbivores
secondary producers
decomposers
fungi and bacteria
