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Populations and Ecosystems (The Structure of Ecosystems (trophic levels…
Populations and
Ecosystems
Plants & their Habitats
Habitat Components
Abiotic
Climate
Critically important to all organisms
Components
Temperature
rainfall
relative humidity
winds
Soil Factor
Formed by breakdown of rock
Pioneers:1st plants to invade new soil
Initially thin & identical to parent rock
Layers of thick soil
A horizon: uppermost
B Horizon: 2nd layer; zone of deposition
C horizon: 3rd layer;
composed mostly of parent rock and rock fragment
Latitude and
Altitude
Latitude contributions
At equator
Days are 12 hrs long
no seasonal variations
plants cannot measure season by photoperiod
Higher Latitudes
Summer days longer
Winter nights longer
Above Arctic and Antarctic Circles
mid-summer & mid-winter nights days 24 hours long
Intermediate & Higher Latitudes
day length=excellent indicator of season
Some species sensitive to photoperiod
Amount of light energy that strikes varies w/ this
Altitude
High altitudes
High winds
Poor soil
Much/all year is cold
Short growing season
Varying
day lengths
Dependent on latitude
Above much of Earth's atmosphere
not fully shielded by
Ozone
carbon dioxide
Oxygen
water vapor
Disturbance
Little/no impact
Examples
Fires
landslides
Snow avalanches
Floods
Biotic
The plant itself
Habitat Modification
Modifies habitat just by being in one
May be
Beneficial
Detrimental
Neutral
Other plant species
Interaction bt species
Mutualism: beneficial for both organisms
Competition: Disadvantageous for one species
Competitive Exclusion: Theory that less adapted species is excluded
Niche: species adapted to particular set of conditions
Organisms other than plants
Frugivores: fruit-eating animals
Seed dispersal(pollination): mutualism
Relationships
Commensal
One species benefits
Other unaffected
Predation
One species benefits
Other is harmed
Herbivory
Browsing
1 more item...
Grazing
1 more item...
Pathogenic
Between plants, fungi, and bacteria
The structure of Populations
Geographic distributions
Boundaries of geo range
Limiting Factor: determines plant's health
Local Geo Distribution
Random: no identifiable pattern
Uniform: evenly spaced from neighbor
clumped: space is small/large; rarely average
Age distribution
Affects the manner in which a pop. responds to various factors in its habitat
demography: # of middle aged, young, & old people there are
Factors that affect this
generation time
length of time from birth of individual until birth of its offspring
Biotic potential
intrinsic rate of natural inrease
number of offspring that can live to reproduce
does not = # of seeds produced
r & k selection
r-selected species
produced by disturbance
pop. growth is limited by species own biotic potential
annual, early maturity, many small seeds, few chemical defenses
k-selected species
perennial, late maturity, few large seeds, many deffenses
pop. growth is governed by carrying capacity of ecosystem
deals with crowded environment, limited sources, and competition
The Structure of Ecosystems
Physiognomic structure
physical size, shape, & distribution of organisms in relation to
each other
physical environment
means by which plant survives stressful seasons
system of life forms
defined by C. Raunkiaer in 1934
temporal structure
changes to an ecosystem over time
time span can be short or long
species composition
trophic levels
feeding levels
primary producers
Autotrophs
1st step in food web
energy & nutrient supply for
HERBIVORES
constitute primary consumers
Secondary Consumers
carnivores
prey on herbivores
omnivores exist at both levels
decomposers
fungi & bacteria
break down remains of
all types of organisms
even organisms of other decomposers
vitally important in an ecosystem
Energy in ecosystem
Plants are eaten
energy and carbon compounds move to herbivore
then to carnivore
then to decomposers
energy flow
carbon flow
