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Populations and Ecosystems Ch.25 (The Structure of Ecosystems…
Populations and Ecosystems Ch.25
Plants in Relationship to Their Habitats
Abiotic Components of the Habitat
Climate
organisms live with certain climatic conditions
many components
temperature
lowest winter
highest summer
rainfall
relative humidity
wind
moisture
occurs as rain or snow or hail
supplies water but damages leaves
growing season
determined by date of last severe killing frosst
length must be adequate
photosynthesis
development
reproduction
metabolic processes respond to abiotic factors
tolerance range
between low and high extremes
vary from species
Soil Factors
formed by break down of rocks
initial soil is this
varaible to
in amount of nutrients
pioneers
must tolerate severe conditions
associated w/nitrogen-fixing prokaryotes
change soil significantly
CO2 from respiration of root produces carbonic acid
accelerates chemical weathering
A horizon
uppermost/zone of leaching
litter
debris
B horizon
zone of deposition
materials from A deposit here
C horizon
composed mostly of parent rock & rock fragments
less diverse
Latitude and Altitude
equator days 12hrs long
no seasonal variation
cannot measure season w/photoperiod
higher latitudes to north or south
summer days become longer, as does winter
aboce Artic & Antartic Circles
mid summer days 24hrs and are mid winter nights
intermediate & higher latitudes
day length is excellent indicator of season
some species sensitive to photoperiod
light energy strikes vary w/latitude
Disturbance
phenomena
fires
natural/common
some plants fire resistant
landslides
snow avalanches
floods
produce significant/radical chance in environment quickly
may eliminate all individuals in area
alters soil
no impact on
climate
latitude
altitude
manmade
insecticides
herbicides
hunting
habitat destruction
Habitat: set of conditions in which an organism completes its life cycle
no plant migratory but parts are
spores
pollen
fruits
seeds
vegetative propagules
operational habitat
aspects of the habitat that definitely affect a plant
Biotic Components of the Habitat
The Plant Itself
modifies the habitat and is a part of it
may be beneficial, detrimental, or neutral to continued success of species
ex: pine trees shading forest floor
seedlings need light
other species flourish and crowd pine seeds
disturbance need for pines to grow
Other Plant Species
several individual or species create possibility of interaction
mutualism
beneficial for both
competition
disadvantageous
two populations do not grow well together
competitive exclusion
species less adapted is excluded from ecosystem by superior competitors
each species adapted to niche
particular set of condtions
ex: some plants grow in full sun, others in partial
geographic ranges
abiotic & biotic factors
ecosystem diversity creates subpopulations
specialize in certain featured
especially if gene flow is not rapids and through
ecotypes
specialized in response to particular ecosystem factors
same species enough differences
to test use transplant experiments
3 more items...
Organisms Other Than Plants
Animals, fungi, and prokaryotic important biotic aspects of habitat
interactions between plants and organisms
beneficial
pollinators
seed disperal
ex: ants & acacias
commensal relationships
one benefits, other unaffected
ex: nest in tree
detrimental for one or both partners
predation
one benefits, one harmed
herbivores
browsing
grazing
pathogenic
cause mild disease or virulent kill plant
mutualistic
ex; mycorrhizal funcas
The Structure of Populations
Geographic Distribution
Boundaries of the Geographic Range
limiting factor
applies to all aspects of plants interaction w/habitat
any factor can acts as limiting factor
ex: water
ex: extreme temp
ex: lack of warmth
plants that rely on animals for pollination & seed dispersal
soil factors
produce abrupt boundaries
ability of plant to spread through geographic area is a result of its adaptations to abiotic and biotic components
Local Geographic Distribution
3 types
random
no obvious indefinable pattern to the position of individuals
no predictive value
clumped
spacing between plants is large or small
rarely average
results from many factors
seeds fall near plant
animal eats it's deposited together
uniform
occur in orchards & tree plantations
individuals evenly spaced
not common in nature
those that do occur in nature result from competition
intraspecies roots release chemicals
allochemicals
Age Distribution:Demography
greater number of young than old
manner of which pop responds to various factors in habitat
retaliative proportions of young, middle aged, and old
Two factors affect possible rate of growth
generation time
length of time from birth to birth of its offspring
intrinsic rate of natural increase
number of offspring produced by an individual that live to reproduce under ideal conditions
large percentage does not germinate
biotic potential
r
carrying capacity
K
number of individuals in environment is limited
carrying capacity
r and K Selection
r Selection
a disturbance
ex: fire
ex: flood
destroys individuals in area
poulation density low
sread of preadators and pathogens slow
threats not high
antiherbivore and antifungal less important
two agents not limiting factor biotic potential limiting factor
mutations that increase r are advantageous
r related species
typically annuals or small shrubs
K Selection
almost every possible site is filled
advantageous to survive long time
K-selected species
growth & reproduction slower
ex: Douglas firs
ex: bristle-cones
ex: redwoods
adaptions beneficial
The Structure of Ecosystems
Physiognomic Structure
physical size & shape of organisms
distribution in relation to each other and to physical environment
trees, shrubs, and herbs most useful categories
system of life forms
means of surviving stress
therophytes
annual life span
survive stress as seeds
geophytes
buds underground on rhizomes, bulbs, corms
hemicryptophytes
buds located @ surface of soil
buds protected by leaf & stem base
chamephytes
buds located above ground, low enough to not be exposed to wind
small shrubs
phanerophytes
buds located high on shoots
25-30 cm above ground
large trees and large shrubs
Temporal Structure
changes in ecosystem with undergoes time constitute
time span
a day
seasons
dcades
plants change dramatically w/seasons
spring usually renewal
species bloom early spring
form fruits and mature seeds in summer
species flower later release seeds in autumn
over time ecosystems gradually change
Species Composition
number and diversity of species that coexist in ecosystem
depends on climate, soil, species tolerance ranges
Trophic Levels
feeding levels
autotrophs
bring energy into system
photosynthesis
energy & carbon compounds enter ecosystem
energy/carbon flow
energy moves from trophic levels
minerals flow through ecosystem
primary producers
first stem in food web
energy and nutrient supply
food for herbivores
primary consumers
preyed on by secondary consumers
decomposers break down remains of organisms
