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Populations and Ecosystems (Structure of ecosystems (trophic levels…
Populations and Ecosystems
Structure of populations
geographic distribution
boundaries
limiting factor=determines health of the plant at any given time/locality
local geographic distribution
individuals have 1 of 3 types
clumped
spacing between plants is either small or large; not average
uniform
all individuals are evenly spaced from their neighbors
occur in orchards and tree plantations
not very common in natural populations
random
no obvious, identifiable pattern to position of individuals
no predictive value
allelochemics (chemicals) released by one plant to inhibit another (allelopathy)
age distribution/demography
factors that affect rate of population growth
generation time
length of time from birth of one individual until birth of its offspring
annuals have generation time of 1 year or less
conifer and angiosperms have longer gen. time
intrinsic rate of natural increase
AKA biotic potential
number of offspring produced by an individual that live long enough to reproduce under ideal conditions
measured under ideal conditions
carrying capacity
r- and K- selection
r = species own biotic potential ; young phase
K = carrying capacity
r- seletion
disturbance usually produces r conditions
r-selected species
typically annuals or small shrubby perennials
ideally suited for temp. disturbances
little defense against predators
K- selection
#
select for different phenotypes than in disturbed habitat
advantageous to live for a long time, holding on to a site
many long-lived conifers= K-selected species
conditions in a crowded habitat; close to carrying capacity
Structure of ecosystems
physiognomic structure
physical size and shape of organisms and their distribution in relation to each other and to the physical environment
categories: trees, shrubs and herbs
life forms
other possible classification system
criterion= means by which plant survives stressful seasons
temporal structure
changes and ecosystem undergoes with time
time span can range from a day to seasons and decades
species composition
number and diversity of species that coexist in and ecosystem
depends on climate, soil, and species' tolerance ranges
trophic levels
feeding levels
primary producers=autotrophs; energy and nutrient supply for herbivores
primary consumers= herbivores (AKA secondary producers)
secondary consumers= eat herbivores
decomposers= break down remains of all kinds of organisms; fungi and bacteria
energy flow/carbon flow
passed along trophic levels
a lot of energy lost as heat
Plants in relationship to their habitats
habitat
set of conditions in which organism completes its life cycle
all components, whether with known effect or not
operational habitat=aspects of the habitat that definitively affect a plant
components
abiotic
nonliving factors and physical phenomena
includes..
climate
species/organism has tolerance range
soil factors
pioneers=first plants that invade a new soil; must tolerate severe conditions :warning:
new soils are low in nitrogen
horizons
after many years, soil may have 3 distinct horizons (layers)
A horizon
3 more items...
B horizon
3 more items...
C horizon
1 more item...
latitude and altitude
amount of sun changes with latitude
high altitude-> high winds, poor soils, cold
disturbance
fires, landslides, snow avalanches, floods
quick, radical changes in ecosystem
biotic
=living factors
Inlcudes...
the plant itself
modifies the habitat and is part of it
other plant species
interations
mutualism=beneficial for both organisms
competition
disadventageous
results in competitive exclusion
niche=particular set of conditions each species is adapted to
ecotypes
subpopulations of species each specialized in response to particular ecosystem factors at its locality
transplant experiments determine if ecotypes exist
organisms other than plants
animals, fungi, prokaryotes
commensal relationships=one species benefits and other is unaffected
predation
#
one species benefits and other is harmed
herbivores; herbivory; browsing; grazing
="pathogenic" in relation to fungi and bacteria
#
portions of plants are migratory (ex. pollen)
