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Chapter 25 (the structure of ecosystems (Trophic levels (autotrophs…
Chapter 25
the structure of ecosystems
physiognomic Structure
physical size/shape of organism
their distribution in relation to each other
distribution in relation to physical environment
Life forms of Raunkiaer
Life form is means of surviving stress
therophytes
Annual life span
survives stress as seeds
geophytes
buds are underground
on rhizomes, bulbs, corms
Hemicryptophytes
buds are at surface of soil
protected by leaf ans stem base
many grasses and rosette plants
Chamaephytes
buds are above ground
low enough to not deal with winds
small shrubs
Phanerophytes
buds are located high
25-30cm high
trees and large shrubs
Temporal Structure
changes that an ecosystem undergoes
time is a constitute
could be as short as a day
could encompass seasons or decades
Animals is easy to observe
nocturnal cycle
active at night
sleep during the day
diurnal cycle
awake during the day
sleep at night
plants and some organisms change with the seasons
Spring
renewed activity
production of flowers and new leaves
summer
various species flower
take turns flowering
always at least something in bloom
spring bloomers make fruit
Autumn
flowers blooming late in summer start making fruit
leaves change color
most gardening happens in autumn
winter
leaves are gone
dormant plants
limited direct sunlight
Species Composition
number & diversity of coexisting species in ecosystem
depends on whether the climate is mild or stressful
poor or rich soil
stressful environ. w/poor soil wont have many species
rich soil in mild climate will
the more species there are, more niches created
#
broad or narrow species tolerance ranges
Trophic levels
basically feeding levels
autotrophs
lowest level
Primary Producer
brings energy into the system
photosynthesis is the most dominant method
primary consumers
herbivores
also called secondary producers
second step
preyed on by carnivores
Secondary consumer
Carnivores
omnivores exist both here and at primary consumer
third step
decomposer
fungi and bacteria
break down the remains of all organisms
including other decomposers
plants in relationship to their habitats
habitats
set of conditions
where organisns complete life cycles
migratory habitats?
animals that move have several
they have summer, winter, and route habitats
sort of life a vacation home
plants
plants dont migrate
parts of plants to though
seeds, pollen, spores, fruit
operational habitat
the aspects that directly affect a plant
doesnt include what we dont know
Abiotic components of the habitat
Climate
critically important to organisms
most species are restricted to regions
many components to climate
temperature
average temp not as important
the extreme temps are what really matters
rainfall
inches per year doesnt matter as much
you need to know how often it rains
need to know how hard it rains
if there is a flood season
relative humidity
winds, etc.
tolerance range
between low and high extremes
some species have broad tolerance ranges
other are super sensitive and dont
Soil factors
soil is broken down rock
all young soil is deficient in nitrogen
pioneers
first plants to invade new soil
tolerate severe conditions
sandy/rocky soil
harsh winds due to exposure
soil doesnt retain water
lack of nutrients in soil
pioneers change soil drastically
co2 from roots produce carbonic acid
accelerate chemical weathering
dead plant parts become substrate
decay creates humus
after many years, you get a thick soil layer
the thick layer has a soil profile
soil profiles have 3 horizon layers
A horizon
uppermost layer
sometimes called zone of leeching
consists of litter and debris
2 more items...
B horizon
Zone of deposition
rich in nutriets
contains both hummus and clay
C horizon
mostly parent rock
lots of rock fragments
no roots in this layer normally
latitude and altitude
latitude
contributes a lot to abiotic factors
at equator, days are 12 hours long
determines seasons
farther north or south latitudes have longer days/nights
intermediate latitude has distinct seasons
altitude
high altitudes
high winds
poor soil
much or all year is cold
short growing season
low altitudes
subject to flooding
standing water could stay year round
if isnt inland, then raising ocean levels
biotic components of the habitat
the plant itself
plants modify their habitats by existing
they can modify it to help, do nothing, or harn
other plant species
multiple species existing in the same area
creates possibility of interaction among species
types of interaction
mutualism
benificial for both animals
doesnt cause harm
competition
disadvantageius
fighting for the same resource
competitive exclusion
result of competition
whatever species is less adapted gets excluded from ecosystem
niche
space an organisms fills in the food web or ecosystem
set of conditions an organism adapts to
their habitat and food source is part of their niche
the structure of populations
Geographic Distribution
boundaries of the geographic range
limiting factor
one factor that determines the outcome
happens at any given time or locality
applies to all aspects of interaction
biotic factors
#
some plants dont thrive because of location, its due to competition
a cactus cant compete with other plants
some plants need animals to thrive
soil
#
soil factors produce abrupt boundaries
mineral composition and soil texture matter
local geographic distribution
individuals have 1-3 types of local distribution
random
no obvious, identifiable pattern
no predictive value
some may seem random, but may be too complex to see
clumped
spaces between plants are either small or large
rarely average though
birds can eat many seeds, and deposit them in same place
uniform
occur in orchards and tree plantations
evenly spaced from neighbors
not very common in natural populations
if it does occur, its due to intraspecies competition
roots of one individual could create a no-grow zone
zones could be created by chemicals
the chemicals are called allelochemics
the inhibition is called allelopathy
age distribution:demography
demography is just analysis of age distribution
mostly applied to animals, hard for plants
2-factors affecting rate of pop. growth
generation time
length of time from birth of 1 individual
to the birth of first offspring
intrinsic rate of natural increase
AKA biotic potential
number of offspring produced by an individual
but have to live long enough to reproduce
r- and K- Selection
r-Selection
disturbance usually produces r conditions
r is biotic potential
r-selected species
typically annuals
small or shrubby perennials
pioneer species
K- Selection
K is carrying capacity
species that live long to occupy a site longest
K-selected species
Redwoods
Douglas firs
bristle-cone pines
face severe competition
niches being created
Soil is a biotic factor
biotic components and factors go hand in hand