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Ch. 25 Populations and ecosystems (The structure of ecosystems (trophic…
Ch. 25 Populations and ecosystems
Ecosystem
Consists of communities and their physical environments
Populations
a group of individuals of the same species
Are rarely stable
Communities
Different populations existing together
Plants
Animals
Fungi
Plants and their habitats
Habitat
the set of conditions in which a plant completes its life cycle
includes migratory situations
spores
pollen
seeds
Exact area is highly debated
operational habitat
aspects that DIRECTLY impact the plant
pollinators
disease
Abiotic Componets
Climate
often restricts plants to certain regions
mainly reliant on extreme temperatures, not average
moisture
Tolerance range
area between highs and lows of climate factors
Soil factors
soil formed by breakdown of rock
new soil is a tough environment
sandy
low water holding
low nitrogen
as plants die, soil increasingly gets better
pioneers
first plants that invade a new soil
must tolerate severe conditions
Horizons
different soil levels
A horizon
zone of leaching
litter and debris
water transports nutrients down from here
B horizon
Zone of deposition
Materials from A horizon accumulate here
Contains humus and clay
C Horizon
mostly parent rock and rock fragments
Latitude and Altitude
Latitude
Closer to equator
no seasonal change
12 hour days
higer radiation
Higher latitudes
Summer days longer
winter nights longer
species can be sensitive to photoperiod
less radiation
disturbance
phenomena such as:
fire
can lead to fresh growth
Landslides
Avalanches
Floods
Produces radical change
Can eliminate many individuals
Can change soil composition
little or no impact on abiotic factors
lat + long
climate
Can be man made
hunting
herbicides
insecticides
habitat destruction
Biotic commonest
plants
Can be beneficial or detrimental
E,g, canopy trees prevent growth underneath
Other plants species
can coexist in different relationships
Mutualism
beneficial for both organisms
competitions
disadvantageous for both
competition for same resources
Competitive exclusion theory
better adapted plants use out the less adapted
May be minimal
each individual has its own niche
Theory 2
plants have an exclusive range to themselves, which is not used by other plants
long term results:
should be species modification
natural selection
Species may also modify across geographic ranges
ecotypes
4 more items...
organisms other than plants
Fungi
pathenogenic
spread disease to the plant
mutualism
mychorizae
receives carbs
gives plants phosphates
Animls
mutualism
pollenators
seed dispersal by fruit eating animals
frugivores
Commensal relationships
One species benefits, the other is unaffected
e.g. birds nesting in trees
predation
one species benefits, the other is harmed
animals eating plants
herbivores
e.g. insects laying eggs in plants
larvae feed on plant
prokaryotes
Structure of populations
Geographic distribution
Dependent on the plants:
adaptations
abiotic and biotic components of the area
One factor may limit the plants health
this is called the limiting factor
can be any factor in an ecosystem
e.g. excess water
does not= excess plant growth
may be biotic factors
e.g. plants can't exist where their pollinators do not exist
may be soil factors
may produce abrupt boundaries
e.g. beaches, limestone
local geographic distribution
small scale, local distribution of individuals
random distribution
no pattern to the position of individuals
has no predictive value
clumped distributions
plants distances from each other are either close or distant, not average
e.g. seeds fall close to parents
e.g. birds take seeds far away from the plants
uniform distribution
e.g. orchards and tree plantations
all individuals are evenly spaced from the others
not very common in natural populations
those that do occur naturally:
establish zones
can be established by roots
can be established by chemicals
allelochemicals
age distribution: demography
the relative proportions of young, middle-aged, and old individuals
may be measured in exponential numbers
generation time
the length of time from the birth of one individual to the birth of its first offspring
annuals- generation time of 1 year or less
conifers+ angiosperms= several years
intrinsic rate of natural increase
aka biotic potential
number of offspring produced by an individual that live ling enough to reproduce
is generally a large number
measured under ideal conditions
carrying capacity
the number of individuals that can live in a specific ecosystem
symbolized by K
r and k selections
r selections
produced by a disturbance
e.g. fire or flood
leaves plentiful resources
r selected species
typically annuals or small shrubby perennials
K selections
conditions in a crowded habitat
population is close to its carrying capacity
The structure of ecosystems
physiognomic structure
physical size and shape of organisms and their distribution to each other and the physical environment
trees
shrubs
herbs
temporal structure
the changes an ecosystem undergoes with time constitute
can be as short as a day
more useful for animas
can encompass seasons or decades
seasons more useful for plants
spring= renewed activity
Species compositions
number of diversity of species that coexist in an ecosystem
depends on climate
mild
intense competition
stressful
low number of species
depends on soil
rich
intense competition
poor
low number of species
depends on species tolerance range
broad
narrow
trophic levels
basically= feeding levels
autotrophs
bring energy into the ecosystem
mainly by photosynthesis
chemosynthetic bacteria
bring in chemical energy
known as primary producers
primary consumers
herbivores
consume autotrophs
secondary consumers
consume primary consumers
carnivores
decomposers
fungi and bacteria
break down remains of all types of organisms
energy flow
movement of energy throughout the ecosystem