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Populations and Ecosystems, image, image, image, image, image, fire is a…
Populations and Ecosystems
ecology
ecology is the study of how organisms relate to their surroundings
population is all of the individuals of a species that can interbreed
a community is all of the populations that interact in an area
an ecosystem is the physical nonliving environment a community exists in
habitats
the habitat is the set of conditions in which an organism completes its life cycle.
many components of a habitat impact others directly
pollinators are super important to plants they pollinate, thus disease to the pollinators greatly affects the plants
aspects that definitely affect an organism are part of its operational habitat
it was discovered that low burning fires were an important part of the redwood habitat causing seeds to sprout
abiotic factors
nonliving components of habitat, climate, soil , latitude, altitude and physical phenomena like flods fires avalanches
climate
temperature
the extremes are more important than the averages
some plants like orchids and bromeliads are restricted to frost free environments like the tropics
many temperate trees need a winter dormancy period to be vernalized and bloom
growing seasons are determined by the last and first frosts
moisture occurs as rain snow or hail, and habitats range from extremely dry like deserts to very wet like marshes lakes and rivers
humidity
winds
organisms have a tolerance range for these climate factors, temperate plants in the US and Canada tolerate around 100F to -40F
Soil Factors
soils are formed by the breakdown of rock
young soils are similar in makeup to the rock and lacking in nitrogen, they dont retain moisture well and are sandy
pioneers are hardy plants and are the first to invade a new soil, and change it over time
pioneers are usually associated with nitrogen fixing microbes
respiration in roots results in carbonic acid which further weathers rock
dead and decaying plants further enrich the soil becoming substrates for soil organisms becomes humus helping retain water
eventually three soil layers aka horizons arise
a layer has litter and debris which leaches nutrients into lower layers
b layer or zone of deposition accumulates nutrients, has humus and clay
c layer parent rock
essential elements are cycled between the soil, plants, decaying plants and then the soil again
latitude and altitude
latitude affects photoperiods
, along the equator there is no vatiation in daylight through the seasons,
while mid latitudes have distinct seasons with some variations in daylight in summer and winter
high latitudes have up to 24hrs of sunlight in the summer
the intensity of the light decreases as latitude goes up
areas of high altitude are similar to high latitude, they have poor soils but also high winds and less shielded from ozone oxygen co2 and water vapor
disturbances
physical phenomena like fires landslides avalanches and floods
can produce significant radical change
can eliminate all or most biotic factors
can alter the soil but little impact on climate latitude or altitude
man made disturbances have been caused by things like insecticides and pesticides
fire is a natural component of dry ecosystems and some species rely on it
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in some forests if regular small fires don't wipe out small plants they grow to a size that result in more devastating fires
biotic factors
living factors, plants and species of animals fungi protists and prokaryotes
an individual modifies the habitat and is a part of it, this can be beneficial, detrimental or neutral in a affect
in beech/oak forests the mature trees create a canopy that little can grow beneath except their own seedlings
while in pine forests, many things can grow under a pine well, except their own seedlings
pioneer species must colonize new soils after glaciers retreat
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other plants
mutualism - beneficial for both species
competition - disadvantageous, divide available resources
competitive exclusion - whichever species is less adapted is excluded from the ecosystem (theory)
each species is assumed to adapted to a certain set of conditions or niche
ex. some like full sunlight and other partial shade
a second theory suggest that species overlap in tolerance ranges
the long term result of competition is natural selection
organisms other than plants
mutualism
pollinators, spread pollen and receive nectar or pollen
frugivores eat fruit and spread seeds
one ant species lives inside acacia thorns and eats glycogen from leaftips, while defending the acacias from encroaching plants and animals.
this ex is obligate because the acacia and ants cannot survive without eachother
plant fungus mutualism - mycorrhizal fungus transports phosphate into the plant and receives carbohydrates
commensal relationships - one species benefits and the other is unaffected, like bird nests where the tree is unharmed but gains nothing
predation - one species benefits to the harm of the other
herbivory, process of plants being eaten by herbivores
eating twigs and leaves of shrubs - deer
grazing - eating herbs - sheep and cattle
fungi and bacteria are considered pathogenic rather than predatory
Populations
Geographic distribution
the ability of a plant to spread through an area is the result of its adaptations to abiotic and biotic factors
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usually though there is one Limiting Factor that determines the health of a plant and becomes more influential than other factors
light and water are common limiting factors
in a perfect environment, the plants innate capacity becomes its limiting factor
gardens and crops with pesticides and weed control are an example of this
Age Distribution - demography
the age of the different individuals has an affect on a species response to factors in its habitat
generation time - the length of time from the birth of one individual until the birth of its first offspring, affects population growth
annuals have a generation time of one year or less and can increase pop rapidly
intrinsic rate of natural increase or biotic potential is the number of offspring produced by an individual that live long enough to reproduce
in optimal conditions most seeds dont germinate and most seedlings dont survive
carrying capacity is the limited number of individuals of each population that can live in an ecosystem
carrying capacity is symbolized as K
individuals is represented by N
as N approaches K death rate begins to exceed birth rate
local distribution
random - no obvious pattern to the positions of individuals
clumped - spacing is small or large but rarely average
uniform - occur in orchards or plantations, rarely in nature although root systems can compete and result in uniform distribution
some plants release allelochemics which inhibit other plant growth
R and K
As a pop increases, it can go through a young phase with low N and plentiful resources
the population growth of this group would only be limited by its biotic potential or r
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later when conditions are more crowded population size is limited by K
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disturbances like fires and flood make prime r conditions
traits adaptive in r-sites
annual
early maturation
many small seeds
few defenses
ex. baileya radiata
traits adaptive in K-sites
perrenial
late maturity
fewer, larger seeds
many defenses
ex. douglas fir
the structure of ecosystems
physiognomic
the physical size and shape of organisms and their distribution
trees, shrubs and herbs are the three common categories
life forms is a different categorization
therophytes - annual life span, survive stress as seeds
geophytes - buds are underground on rhizomes, bulbs, corms
hemicryptophytes - buds are located at surface of soil, protected by leaf and stem bases - grasses and rosette plants
chamaephytes - buds are located above ground, bud low enough to not be exposed to strong winds: small shrubs
phanerophytes - buds are located high, on shoots at least 25 to 30 cm above ground; trees and large shrubs
temporal structure
the changes that an ecosystem undergoes with time are its temporal structure
many plants have daily rhythms like flower opening and closing
plants change dramatically with the seasons
spring produces new flower and leaves in coordination with warmer temps
early bloomers usually form fruits and mature seeds in summer
seeds can remain dormant until the following spring once dispersed
late summer and autumn herbs die out and trees begin to enter dormancy
some growing seasons occur in the fall in the southern US
species composition
the number and diversity of species that coexist in an ecosystem
stressful climates limit biotic and abiotic factors and result in lower numbers of species
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mild climates and rich soils support abundant numbers of species, with lots of competition
trophic levels
trophic levels are feeding levels
autotrophs bring in energy and are known as primary producers
primary consumers feed on primary producers
secondary consumers eat primary consumers
tertiary are the top carnivores that eat and are not preyed upon
decomposers break down the remains of the dead and return nutrients for the autotrophs
energy or carbon flow follows this path
fire is a necessary abiotic factor
pioneers are a biotic factor that influence an abiotic factor
species are limited by the biotic and abiotic factors on their habitat
intrinsic rate of increase limits young populations, carrying capacity limits crowded populations
