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CH. 25 Populations and Ecosystems (The Structure of Ecosystems (Trophic…
CH. 25 Populations and Ecosystems
Concepts
population
individuals of the same species in a habitat
plant never exists in isolation
carries out successful sexual reproduction
community
all populations together
population never exists in isolation
animals, fungi, protists, prokaryotes
ecosystem
community + physical, nonliving things
Plants in Relationship to Their Habitats
Abiotic Components of the Habitat
Climate
tolerabce range
between low and high extremes
Soil Factors
pioneers
first plant invades new soil
tolerate severe conditions
A horizon
#
uppermost layer of soil
litter and debris
zone of leaching
B horizon
second layer of soil
zone of deposition
humus and clay
C horizon
third layer of soil
parent rock and rock fragments
Latitude and Altitude
at equator 12 hr. days, no seasons
arctic, summer 24 hr. days
higher altitudes = poor soil no overhead sun
Disturbance
fires, landslides, avalanches, floods
Biotic Components of the Habitat
The Plant Itself
each plant modifies the habitat
Other Plant Species
mutualism
beneficial for both organisms
bee pollinating flower
competition
disadvantageous for both
plants not growing well together
competitive exclusion
one theory of competition
less adapted species dies
niche
adapted to particular set of conditions
ecotypes
specialized response to ecosystem
transplant experiments
test if ecotypes exists
common garden
where tested plants are grown together
Organisms Other Than Plants
Commensal relationships
one species benefits, other is unaffected
birds nest and trees
Predation
one species benefits, other is harmed
herbivors
herbivores
herbivory/browsing/grazing
animals that eat plants
pathogenic
fungi/bacteria affecting plant
other terms
habitat
set of conditions to complete life cycle
operational habitat
aspects of habitat that affect plant
The Structure of Populations
Geographic Distribution
Boundaries of the Geographic Range
limiting factor
determines the health of the plant
Local Geographic Distribution
random distribution
no obivious pattern position of individuals
clumped distributions
spacing between plants either small or large
never average
uniform distributions
evenly spaced from another
orchards, plantations
allelochemics
inhibition = allelopathy
chemicals released by plants
Age Distribution: Demography
affected by:
age distribution
demography
proportions of young, middle, old ages
two factors affect pop. growth:
Generation Time
length of time from birth of one to birth of its offspring
annuals have one year length
Intrinsic rate of natural increase
aka biotic potentiall
number of offspring produced by plant with ideal conditions
carrying capacity
limited number of population living in particular ecosystem
r- and K-Selection
r-Selection
r-selected species
annuals or small, shrubby perennials
bc environment gets too crowded
K-Selection
K-selected species
long-lived conifers
face intense competition
The Structure of Ecosystems
Physiognomic Structure
life forms
means of surviving stress
thermophytes
#
survive stress as seeds
geophytes
buds underground
hemicryptophytes
buds at surface of soil
chamaephytes
buds above ground
phanerophytes
buds are high
define:
physical size/shape of organism
distribution w/ each other and environment
Temporal Structure
define:
certain time span it takes for changes in an ecosystem
Species Composition
define:
number and diversity of species that coexists in ecosystem
Trophic Levels
define:
feeding levels
primary producers
autotrophs
primary consumers
herbivores
#
secondary consumers
carnivores
omnivores
decomposers
fungi and bacteria
process above:
energy flow
ATP, heat, CO2, and water
carbon flow
life span
rain washes a to b
more on herbivores
