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Populations and Ecosystems (Plants in relationship to Their Habitats…
Populations and Ecosystems
Plants in relationship to Their Habitats
the habitat is the set of conditions in which an organism completes its life cycle
abiotic components of the Habitat
climate is critically important to all organisms
the most important is the hottest and the lowest a climate gets
soil factors
soils are formed by breakdown of rock
the first plant to invade the soil was called pioneers
soil around this time was very sandy, had large particles and the important minerals were still inside the rocks
after several years the soil starts to change
it has a thick soil layer with three horizons underneath
A horizon is the uppermost layer and is sometimes called the zone of leaching
consists of litter debris as it breakdowns rainwater moves nutrient to next layer
B horizon is known for as zone of deposition
minerals from A horizon accumulate, reich in nutrients, humus and clay
C horizon is composed mostly of parent rock and rock fragments
latitude/longitude and disturbance
latitude contributes to many factors to abiotic environment
some ares days are longer same with nights
disturbances "phenomena" often have a radical effect in the ecosystems
Biotic Components of the Habitat
the plant itself
just the plant being in the environment effects the habitat
can be beneficial, detrimental or neutral
other plant species
when several individuals occur together the possibility of interaction occurs
if an interaction is beneficial for both organisms its called mutualism
however if it is disadvantageous its a competition
before subpopulation could be called subspecies they were called ecotypes
to test if ecotypes are true they used transplant experiments
took plants from each site and transplanted them in other sites
discovered that plants can be grown together in common ground
The Structure of populations
Geographic Distribution
a plants ability to spread throughout a geographic area is a result of adaptations
a limiting factor determines the health of the plant
so many things can act as a limiting factor: water, sun, wind, shade
local geographic distribution
local distribution of individuals living locally is also important
random distribution is used when there is no obvious, identifiable pattern to the position of individuals
clumped distributions: when the space between plants is to small or large
can be caused by to many seeds
uniform distributions typically happens in orchards and tree plantations
ideal because there is even space between individuals
Age Distribution:Demography
how a population responds to various factors in its habitat
demography is the relative proportions on young, middle-aged and old individuals
however this technique is mostly used with animals and will be difficult for plants
two factors affect the possible rate of population growth : generation time and intrinsic rate
generation time is the length of time from birth of one individual until the birth of an offspring
generation time is used to measure population instead of years
intrinsic rate of natural increase "biotic potential" is the number of offspring produced by an individual
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even with optimal conditions the individual has a large percentage of seeds that don't germinate
r-andK- selection
r-Selection is usually produced when there is a disturbance
ex. fire or flood are common in destroying many individuals
pioneers that replicate quickly have the advantage, this process helps get ride of certain species
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r-selected species are typically annuals or small shrubby perennials because the habitat quickly changes back to overcrowded and they can't survive
K-selection are conditions in a crowded habitat
typically when a perennial dies its spot is taken by a new species
K-selected species also face intense competition , good example Douglas firs and bristle-cone pine
The Structure of Ecosystems
many concepts can be considered in the structure of an ecosystem: common 4; physiognomic structure, temporal structure, species diversity and tropic level
Physiognomic Stucture
the physical size and shape of the organisms and their distribution
trees, shrubs and herbs are the three most useful categories and life forms
the classification was the means by which the plant survives stressful seasons
Temporal Structure
changes that an ecosystem undergoes with time
the time can be as short as a day or can encompass seasons and decades
we know that plants change dramatically with the seasons
spring is typically a time for renewed activity with production
late summer and autumn brings changes that depends on the ecosystem
in northern US, herbs die but shrubs and trees develop resting buds
Species Composition
refers to the number and diversity of species that coexist in an ecosystem
depends on whether the climate is mild or stressful , soil is rich or poor, and if the species tolerance is broad or narrow
stressful climates with poor soil only support a low amount of species
mild climates with rich soil supports an abundance of plant life
competition is intense, natural selection has resulted in habitat partitioning
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Trophic Levels
basically its feeding levels
each ecosystem contains some members, autotrophs, that bring energy into the system
autotrophs are known as primary producers
there the first step of any food web
herbivores "primary consumers" because they eat the primary producers
carnivores are secondary consumers because they eat herbivores
decomposers are fungi and bacteria break down the remains of all types of organisms
this whole process is referred to as the energy flow and carbon flow of the ecosystem
at each step most of the food is used in respiration which results in the production of ATP
