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Ch 25: Populations and Ecosystems (Structure of Ecosystems (Physiognomic…
Ch 25: Populations and Ecosystems
Plants in relationship to their habitats
Habitat
conditions where organism completes life cycle
Abiotic Components
Climate
temperature
can be restricting
rainfall
can be damaging
timing is key to certain plants
humidity
wind
Soil Factors
Pioneers
first plant that invade a new soil
A horizon
uppermost layer of soil
consists of litter and debris
zone of leaching
B horizon
zone of deposition
2nd layer of soil
material from A accumulate here
mostly clay and humus
C horizon
3rd layer
Latitude and Altitude
high latitude and altitude
high winds
poor soil
short growing season
Disturbance
include
fires
landslides
snow avalanches
floods
produce radical change in environment
can completely eliminate individuals
disrupt/alter soil
man-made disturbances
insecticides
herbicides
hunting
habitat distruction
Biotic Components
The Plant itself
modifies the habitat
Ex: beech/oak forrests
produces dense canopy
heavily shaded forest floor
beech/oak seedling grow well
Other Plant species
mutualism
interaction of 2 species where both benefit
Competition
interaction of 2 species which is disadvantageous to one or both
competitive exclusion
the inability of species to grow due to competition
one specie is more adapted
niche
conditions exploited best by one species
Ecotypes
races of species adapted to certain environmental factors
Transplant experiments
species are transplanted to alternate sites
Organisms other than plants
commensal relationships
one species benefits and other is unaffected
frugivores
seed dispersal by fruit eating animals
Predation
one species benefits, other is harmed
Herbivores
animals that eat plants
Structure of Populations
Geographic Distribution
Boundaries
limiting factor
water
light
other nutrients
growth of organism is dependenr on these
Local Geographic Distribution
Random Distribution
no pattern of animal position
Clumped distributions
spacing between plants
small
large
rarely average
Uniform distributions
plants are evenly spaced from neighbors
allelopathy
allelochemics
growth of species by chemicals
Age Distribution: Demography
population growth
generation time
time from birth-birth of first offspring
intrinsic rate of natural increase
number of offspring produced by individul
depending on certain conditions
also known biotic potential
r- and k- selection
r- selection
disturbances produce r- conditions
EX: fire
few individuals remain
have plentiful resources
r- selected species
have high growth rates
exploit less crowded niches
K- selection
k-selected species
crowded area/population
low growth rates
few resources
leads to high competition
Structure of Ecosystems
Physiognomic Structure
physical size and shape
distribution in relation to each other
physical enviroment
Temporal Structure
change an ecosystem undergoes with time constitute
Ex; plants changing with season
time can be short or very long
Species Composition
number of species & diversity
depends on certain economical conditions
