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Chapter 25 (the structure of ecosystems (trophic levels (feeding levels,…
Chapter 25
the structure of ecosystems
physiognomic structure
the physical size and shape of the organisms and their distribution in relation to each other and the physical environment
temporal structure
the changes that an ecosystem undergoes with time constitute
plants change dramatically throughout the season
species composition
refers to the number and diversity of a species that coexist in an ecosystem
depends on whether the climate is mild or stressful
trophic levels
feeding levels
primary producers- autotrophs
primary consumers- herbivores and some omnivores
secondary consumers- carnivores and some omnivores
decomposers- fungi and bacteria that break down remains
energy flow= carbon flow
plants in relations to their habitats
abiotic components of the habitats
nonliving and physical phenomena
Climate
most species are restricted to certain regions
the average temperature is not as important as the extremes
growing seasons are usually determined by the last, severe killing frost in the spring and the first killing frost of autumn
moisture occurs as rain or snow or as hail
this supplies water but also damages the plant
between the high and low extremes is the tolerance range
ranges vary greatly from species to species
Soil Factors
the first plants that invade new soil are called pioneers
after many years, a thick soil may result in a distinct profile with 3 layers or horizons
a
uppermost
consist of litter and debris
called the zone of leeching
rainwater washes nutrients from it downward into the next layer
c
composed mostly of parent rock or rock fragments
b
the zone of deposition
area where materials from a accumulate
rich in nutrients and contains both humus and clay
young soil are less diverse than more mature soils
as plants die, they decompose and release nutrients back into the soil
latitude and altitude
latitude
at the equator plants cannot measure season by photoperiod
altitude
high altitude is similar to those at a high latitude
disturbances
examples- fires, landslides, avalanches, and floods
fire is easily started by the plant debris on the ground and how plants are easily flammable
the soil is enriched by the ash in fire
biotic components of the habitat
the plant itself
by the plant just being in the habitat, it modifies its environment
habitat modification may be beneficial, but it can be detrimental or neutral
other plant species
mutualism- beneficial for both
competition- two organisms do not grow as well together as they do seperately
competitive exclusion
species is less adapted is excluded from ecosystem by superior competitors
niche- adapted to a particular set of conditions
transplant experiments are conducted to see what living condition is better for a plant
commensal relationship- one benefits and the other one is unaffected
organisms other than plants
frugivores- fruit eating animals that aide in seed dispersal
fungi and bacteria are pathogenic rather than predatory
introduction
habitat is a set of conditions in which an organism completes its life cycle
parts of the plant can become migratory, but no whole plant can
seeds, pollen, fruit, spores, and vegetative propagules can move
operational habitat
aspects of the habitat that definitely affect a plant
the structure of populations
geographic distributions
limiting factor- how the habitat limits the plant from developing and overpopulating
random distribution- no uniform or obvious pattern in the individuals
clumped distributions- where the space is too small or large and rarely average
uniform distributions- type that occurs in orchards or farms
zones can be established by using chemicals called allelochemics
age distribution (demography)
generation time- the length of time from the birth of one to the birth of its offspring
instrinsic rate of natural increase/ biotic potential- number of offspring produced by an individual in ideal conditions
r- and K- Section
carrying capacity is symbolized by K
r is the biomic potential