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Populations and Ecosystems (Plants in relationship to their habitat…
Populations and Ecosystems
Plants in relationship to their habitat
Abiotic components of the habitat
Soil Factors
soil is breakdown of rock
first soil is thin and resemble the rock
pioneers
first plants to invade a new soil
soil is sandy
soil has a hard time holding water
must tolerate severe conditions
associated with N-fixing prokaryotes
The A Horizion
uppermost layer
consists of litter and diesease
rainwater washes nutrients downwards
"zone of leaching"
The B Horizion
where material from A horizon accumulate
"zone of deposition"
rich in nutrients
contains humus and clay
Below A horizion
C Horizon
parent rock and rock fragments
below B hrozion
Latitude and Altitude
Latitude
contributes many factors to abiotic environment
at the equator
all days are 12 hours long
no seasonal variation occurs
plants dont measure season by photoperiod
Arctic and Antarctic points
mid summer days
24 hours long
mid winter nights
amount of light energy striking a given area
varies with latitude
maximum radiation is at equator
sun is directly overhead
when the sun is low
less energy is recieved
Altitude
high altitudes
high winds
poor soil
much of the year is cold
short growing season
water is mostly snow and ice
Climate
most species only live in certain climates
restricts life outside of those regions
Average temp not that important
more important is the extremes
lowest winter and highest summer
Growing season is determined
Last spring killing frost
first autumn killing frost
Average moisture not very important
slow rain year round
produce different ecosystems
heavy rain/snow at certain times
moisture affects metabolism
Once there is sufficient water
Increased water increases growth and reproduction
too much water drowns roots
the roots cannot get soil oxygen
Disturbance
fires, landslides, avalanches, and floods
produce a radical change in an ecosystem quickly
man-made disturbances
insecticides, herbicides, hunting, and habitat destruction
fire is common in dry climates
many species have become fire resistant
happens through natural selection
many pines have thick bark
protects vascular cambium
many grasses benefit from fires
annuals and short live plants do not survive
underground seeds do
Biotic components of the habitat
The Plant itself
Any individual modifies the habitat
some trees create a dense canopy
this canopy blocks light
modifies the habitat
hinder light energy from reaching ground
Other plant species
several individuals can interact with one another
if it benefits both oragnisms
mutualism
If it is disadvantageous to both
competition
situation where two populations do not grow well together
use similar resources
competitive exclusion
#
less adapted species is excluded
Organisms other than plants
animals, fungi, and prokaryotes
plants and animals have many mutualistic realtionships
pollination
seed dispersal
ants-acacias
acacia thorns serve as homes for the ant
acacia leaflit tips are filled with glycogen
ants have food source
the ants attack animals that touch the plant
Comensal relationships
one species benefits and the other is unaffected
birds nest in trees
bird typically benefits
tree is unharmed
predation
one species benefits and the other is harmed
usually the species benefitting uses other for resources
animals eating plants
fungi and bactia
described as pathogenic rather than predatory
Habitat
Set of conditions in which an organism completes life cycle
migratory animals
winter area, summer area, and routes all habitiat
plants not migratory
parts of plants are
spores, pollen, fruits, seeds, and vegetative propagules
operational habitiat
all components are habitiat
whether effect or no effect
The Structure of populations
Geographic Distribution
Boundaries of the geographic range
limiting factor
determines the health of the plant
applies to everything within a plants interations
photosynthesis
In areas with high concentration of CO2
light is limiting factor
In areas of high light intensity
CO2 is limiting factor
any factor can act as limiting factor
Local geographic Distribution
random distribution
no obvious, identifiable pattern
no predictive value
clumped distribution
spacing between plants is small or large
seeds fall close to trees
Uniform distribution
orchards or plantations
all individuals evenly spaced from neighbors
not common in natural habitats
Age Distribution
an individual makes 4 offspring before death
The offspring than double
Than those offspring double
16 offspring
8 offspring
4 offspring
generation time
time from birth of individual to its birth off offspring
Biotic potential
number of offspring that can reproduce
represented as r
#
plants with many viable seeds have large r
measured under ideal conditions
many factors cause fluctuation between death and birth rate
r- and k- selection
r- selection
disturbances usually produce r- conditions
fire or flood kills many individuals
#
few survivors have plentiful resources
pioneers with many seeds have an advantage
predators/pathogens move slow
defenses aren't important
population growth limited by r potential
population growth limited by carrying capacity
K selection
in K habitats almost all sites are filled
population is close to max density
K selected species face intense competition
#
adaptions that increase use of a resource
The structure of ecosystems
Physiognomic structure
physical size and shape of organisms
distribution in the environment
means by how plant survives stressful seasons
regions of world
similar climate
similar physiognomic structures
Temporal structure
changes that an ecosystem undergoes with time
can be as short as a day
as long as a decade
plants change drastically during seasons
spring is renewed activity
late fall brings death to many plants
Species Composition
number and diversity of species in an ecosystem
depends on climate
depends on soil quality
depends on species tolerance range
competition can be intense
high number of species
creates more niches
Trophic levels
feeding levels
photosynthesis is most dominant method
accounts for almost all energy input
autotrophs are primary producers
first stem in food webs
herbivores eat the primary producers
secondary producer
decomposers
fungi, bacteria
breaks down remains
prevent plants from growing rapidly
release minerals into soil
energy flow and carbon flow
flow of energy through the food chain
starts with autotrophs
90% of an animals food is respired
10% is retained as growth
