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Chapter 25: Populations & Ecosystems (Structure of Ecosystems (tropic…
Chapter 25: Populations & Ecosystems
Structure of Ecosystems
species composition
number of diversity of species that coexist in an ecosystem
physiognomic structure
trees, shrubs, and herbs
temporal structure
time span can be as short a a day or as long as season or decades
tropic levels
feeding levels
primary producers
first step in food chain
primary consumers
herbivores
decomposers
bacteria and fungi
Plants & Relationship to Their Habitats
habitat
set conditions where an organism lives its life cycle
operational habitat
aspects of the habitat that effect a plant
biotic components of the habitat
the plant
modifies habitat
other plant species
competitive exclusion
whichever species is less adapted for the habitat
mutualism
a relationship between organism that benefit both
competition
two species fight over limited resources in ecosystem
niche
where a species can live within an ecosytem
other organisms
commensal relationship
one species benefits and the other is unharmed
pathogenic
harmful bacteria/fungi attacks plant
predation
one species benefits and the other is harmed
abiotic components of the habitat
climate
critically important to all organisms
tolerance range
low and high extremes
soil factors
A horizon
uppermost layer
consists of contaminants
rainwater washes nutrients into deeper layers
B horizon
zone of deposition
rich in nutrients
contains clay and humus
C horizon
composed mostly of parent rock and rock fragment
disturbance
pollution
natural disaster
avalanches
wildfire
floods
landslides
tropical storms
Structure of Populations
geographical distribution
boundaries of geographic range
ability of a species to spread throughout a geographic range
limiting factor
one factor determining the health of the plant
local geographic distribution
random distribution
used whenever there is no obvious, identifiable pattern to the distribution of individuals
uniform distribution
evenly spread from neighbors
clumped distribution
spacing between organisms is small
r- and K- selection
r- selection
resources are plentiful for the few that remain
distributions usually produce r conditions
fire or flood destroys many individuals in the area
K- selection
population is close to its carrying capacity
conditions in a crowded habitat
