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Populations and Ecosystems (Structure of Ecosystems (Trophic Levels…
Populations and Ecosystems
Structure of Ecosystems
Temporal Structure
changes an ecosystem undergoes w time
span can be short as 1 day or long as seasons or decades
Physiognomic Structure
physical size/shape and their distribution in relation to each other and to the physical environment
life forms
a system of trees, shrubs, and herbs
means by which the plant survives stressful seasons
Trophic Levels
basically feeding levels
primary producers
autotrophs
first step of any food web
energy and nutrient supply for the herbivores
primary consumers
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herbivores
sometimes called secondary producers
prayed on by carnivores
secondary consumers
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carnivores
prey on primary consumers
decomposers
fungi and bacteria
break down the remains of organisms
even other decomposers
energy floow
the flow of energy through the levels
happens when one organisms eats another from a different level
carbon flow
movement of carbon compounds move through the levels
happens when one organisms eats another from a different level
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carbon dioxide is released back into the atmosphere
Species Composition
refers to the number and diversity of species that coexist in an ecosystem
depends on whether the climate is mild or stressful
or if the soil is rich or poor
and the species tolerance ranges are broad or narrow
Plants in Relationship to Their Habitats
Biotic Components of the Habitat
living factors
The Plant Itself
modifies the habitat and is a part of it
Other Plant Species
mutualism
interaction that's beneficial for both organisms
competition
interaction is disadvantageous for both organisms
competitive exclusion
species that is less adapted is excluded by superior competitors
niche
particular set of conditions
ecotypes
species specialized in response to particular ecosystem factors
Organisms Other Than Plants
animals, fungi, and prokaryotes
commensal relationships
one species benefits and other is unaffected
predation
one species benefits and other is harmed
herbivores
animals that eat plants
grazing and browsing
pathogenic
fungi that can cause mild disease or kill plant
Abiotic Components of the Habitat
nonliving and physical phenomena
climate
important to all organisms
temperature, rainfall, relative humidity, winds
tolerance range
between the low and high extremes
soil factors
soils are formed by breakdown of rock
pioneers
first plants that invade a new soil
must tolerate severe conditions
after many years, thick soil created to 3 layers
B horizon
aka zone of deposition
where materials from the A horizon accumulate
rich in nutrients
contains both humus and clay
C horizon
lowest layer
composed mostly of parent rock and rock fragments
A horizon
uppermost layer
aka zone of leaching
consists of litter and debris
latitude and altitude
latitude contributes many factors to the abiotic environment
high altitude is similar to that of high latitude
disturbances
phenomena
landslides
snow avalanches
fires
floods
produce significant, radical changes in an ecosystem quickly
affect biotic factors directly
operational habitat
aspects of the habitat that definitely affect a plant
The Structure of Populations
Age Distribution: Demography
relative proportions of young, middle-aged, and old individuals
biotic potential
number of offspring produced by an individual that actually live ling enough to reproduce
generation time
length of time from birth of one individual until the birth of its offspring
r and K selection
r-selection
typically are annuals or small shrubby perennials
disturbance usually produces r conditions
K selection
species face intense competition from other plant species
douglas firs and bristle cone pines
Geographic Distribution
limiting factor
one factor that determines the health of the plant
Local Geographic Distribution
random distribution
no identifiable pattern to the position of individuals
clumped distribution
spaces between plants is either small or large '
uniform distribution
all individuals are evenly spaced from their neighbors
Concepts
population definition:
individuals of the same species in a habitat
community definition:
all populations together in a habitat
ecosystem definition:
community considered w living and nonliving environment
habitat definition:
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set of conditions which an organisms completes its life cycle
