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Chapter 25: Populations and Ecosystems (The Structure of Ecosystems…
Chapter 25: Populations and Ecosystems
Plants in Relationship to Their Habitats
abiotic components of the habitat
soil factors
soils formed by the breakdown of rock
pioneers
first plants that invade a soil
soil profiles
three layers
A horizon
zone of leaching
uppermost
B horizon
C horizon
composed of parent rock and rock fragments
zone of deposition
where materials from horizon A accumulate
contains hummus and clay
latitude and altitude
control day length
can indicate seasons and photoperiod
climate
critically important to all organisms
has many components
relative humidity
rainfall
temperature
winds
tolerance range
varies greatly from species to species
disturbance
produces significant change in an ecosystem
examples
natural
fires
landslides
floods
avalanches
man made
herbicides
hunting
insecticides
habitat destruction
affect biotic factors directly
little impact on abiotic factors
biotic components the habitats
other plant species
interaction
mutualism
competition
role of competition
competitive exclusion
niche
#
set of aspects that directly affect a species
different species occupy different niches
geographic range
ecotypes
beginning of divergent speciation
before subspecies
organisms other than plants
examples
animals
fungi
prokaryotes
relationships
mutualism
commensal
predation
pathogenic
add great complexity to a plant's habitat
the plant itself
modifies habitat just by existing there
The Structure of Populations
age distribution: demography
relative proportions of individuals
applied to animal populations
factors affecting growth
intrinsic rate of natural increase
AKA biotic potential
represented by letter "r"
generation time
carrying capacity
represented by letter "K"
r
-and
K
-Selection
r
-selection
r
conditions produced by disturbances
#
r
selected species
annuals
small shrubby perennials
K
-selection
K
-selected species
examples
Douglas firs
bristle-cone pines
face intense competition
increased adaptations
geographic distribution
boundaries of geographic range
limiting factor
applies to aspects of a plant's interaction with its habitat
can be any factor in an ecosystem
biotic factors
critical
soil factors
produce abrupt boundaries
include mineral composition and soil texture
local geographic distribution
types
clumped
uniform
random
allelochemics
chemicals that inhibit other plants
can establish zones
example
purple salvias;
Salvia leucophylla
The Structure of Ecosystems
temporal structure
changes that an ecosystem undergoes with time
organsims change dramatically with seasons
succession
species composition
depends on
climate
soil
species' tolerance ranges
large numbers of species create more niches
species that can coexist
physiognomic structure
physical shape and size of organism
organism's distribution
most useful categories
shrubs
herbs
tress
life forms
almost infinite number of combinations
tropic levels
feeding levels
classification
primary consumers/ secondary producers
herbivores
secondary consumers
carnivores
primary producers
autotrophs
decomposers
fungi and bacteria
vitally important role
movement of energy
energy flow
energy is lost as it is transferred through trophic level
carbon flow
mineral flow
represented as pyramid of energy
minerals flow through
