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ECOLOGY

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Title: ECOLOGY


1
ECOLOGY
  • A study of the interactions of living organisms
    and the environment in which they live

2
A. Introduction
  • Ecology is the scientific study of the
    interactions between organisms and their
    environment.

3
  • The environment of any organism includes the
    following components
  • Abiotic factors non-living chemical and physical
    factors such as temperature, light, water, and
    nutrients
  • Biotic factors the living components

4
B. Abiotic factors affect the distribution of
organisms
  • Temperature some organisms can only tolerate
    specific ranges of temperature.
  • Water some organisms can only tolerate either
    fresh or salt water.
  • Sunlight provides energy that drives nearly all
    ecosystems.
  • The intensity and quality of light, and
    photoperiod can be important to the development
    and behavior of many organisms.

5
  • Wind amplifies the effects of temperature by
    increasing heat and water loss (wind-chill
    factor).
  • Rocks and soil the physical structure and
    mineral composition of soils and rocks limit
    distribution of plants and the animals that feed
    upon them.

6
C. Approaches to studying ecology
  • Organismal ecology is concerned with the
    behavioral, physiological, and morphologicalways
    individualsinteract with theenvironment.

Fig. 50.2a
7
  • Population ecology a population is a group of
    individuals of the same species living in a
    particular geographic area.
  • An example of a population could be gray
    squirrels living in Sea Cliff.
  • Population ecology examines factors that affect
    population size and composition.

8
  • Community ecologya community consists of all
    the organisms ofall the species thatinhabit a
    particulararea. (all biotic)
  • An example of a community could be gray
    squirrels, raccoons, cardinals, chipmunks, and
    black crows living in Glen Head.

Fig. 50.2c
9
  • Ecosystem ecology an ecosystem consists of all
    the abiotic factors in addition to the entire
    community of species that exist in a certain
    area.
  • Example? All bullfrogs, minnows, snails,
    snapping turtles, algae in a pond and how ph,
    temperature, sunlight impact this life

10
D.Biomes can be aquatic or terrestrial
  • Marine biomes have a salt concentration of
    approximately 3 and cover approximately 75 of
    the earths surface.
  • Freshwater biomes are usually characterized by
    salt concentration of less than 1 and are
    closely linked to the soils and biotic components
    of the terrestrial biomes through which they pass.

11
  • Freshwater biomes (ponds and lakes, small and
    large freshwater).
  • The littoral zone is shallow and close to shore.
  • The limnetic zone is the open surface water.
  • The profundalzone consistsof the deep,aphotic
    regions.

12
  • Lakes
  • Oligotrophic lakes are deep, nutrient-poor and do
    not contain much life.

13
  • Eutrophic lakes are shallower and have increased
    nutrients.

14
  • Mesotrophic have a moderate amount of nutrients
    and phytoplankton productivity.
  • Over long periods of time, oligotrophic lakes may
    become mesotrophic as runoff brings in nutrients.
  • Pollution from fertilizers can cause explosions
    in algae population and cause a decrease in
    oxygen content.

15
  • Streams and rivers are bodies of water moving
    continuously in one direction.

16
  • Wetlands are areas covered with water that
    supports many types of plants.
  • They can be saturated or flooded and include
    areas known as marshes, bogs, and swamps.
  • They are home tomany differenttypes of
    organisms,from herbivoresto crustaceans.
  • Unfortunately,humans havedestroyed them,but
    many are nowprotected inmany places.

Fig. 50.21a
17
  • Estuaries are areas where freshwater and salt
    water meet.
  • The salinity of these areas can vary greatly.
  • They are crucial feeding areas for many types of
    water fowl.

18
  • Zonation in Marine communities.
  • The intertidal zone is where the land meets the
    water.
  • The neritic zone includes the shallow regions
    over the continental shelves.
  • The oceanic zone extends past the continental
    shelves, and can be very deep.
  • The pelagic zone is the open water.
  • The benthic zone is the seafloor.

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  • Coral reefs exist in the neritic zone.
  • They constitute aconspicuous anddistinctive
    biome.
  • They are dominatedby coral and includea very
    diverseassortment ofvertebrates
    andinvertebrates.

21
E.The geographic distribution of terrestrial
biomes is based mainly on regional variations in
climate
22
  • Vertical stratification is also important in
    these biomes.
  • The canopy of the tropical rain forest is the top
    layer, covering the layers below.
  • The permafrost in the tundra is a permanently
    frozen stratum that lies under ground.
  • Human activity has radically altered the natural
    patterns of many biomes.

23
  • Tropical forests are close to the equator,
    receive high amounts of rainfall (although this
    can vary from region to region), and contain a
    great variety of plants and animals.
  • The vegetation is layered, with the canopy
    being one of the top layers.

24
  • Savannas are grasslands with scattered trees,
    that show distinct seasons, particularly wet and
    dry.
  • Fire is an important abiotic factor.

25
  • Deserts have low rainfall, and are generally hot.
  • Vegetation is usually sparse, and includes cacti
    and succulents.
  • Many animalsare nocturnal,so they canavoid the
    heat.

Fig. 50.25c
26
  • Chaparrals have mild wet winters and dry hot
    summers.
  • They containdense spiny,evergreenshrubs
    andhave periodicfires.
  • Some plantsproduce seedsthat will
    onlygerminateafter a fire.

Fig. 50.25d
27
  • Temperate grasslands exhibit seasonal drought,
    occasional fires, and are usually used for
    grazing and agriculture.

28
  • Temperate deciduous forests contain dense stands
    of trees and have very cold winters and hot
    summers.
  • The trees loseleaves and godormant in winter.
  • This biomeincludes a largevariety of plantsand
    animals.
  • Humans havelogged many ofthese forestsaround
    the world.

Fig. 50.25f
29
  • Coniferous forests (taigas) are the largest
    terrestrial biome on earth.
  • They exhibit long cold winters and short wet
    summers.

30
  • Tundra contains low growing plants.
  • The climate is windy and cold which
  • causes a short growing season.
  • A layer of permafrost is found below 1 meter and
    does not thaw, which prevents root growth not
    many animals live in tundra biomes.
  • There are two types, arctic, which is found in
    areas of Alaska and the Arctic circle, and
    alpine, which is found on very high mountaintops.

31
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32
F. Population ecology
  • Populations have size and geographical
    boundaries.
  • The density of a population is measured as the
    number of individuals per unit area.
  • The dispersion of a population is the pattern of
    spacing among individuals within the geographic
    boundaries.

33
  • Measuring density of populations is a difficult
    task.
  • We can count individuals we can estimate
    population numbers.

34
  • One sampling technique that researchers use is
    known as the mark-recapture method.
  • Individuals are trapped in an area and captured,
    marked with a tag, recorded, and then released.
  • After a period of time has elapsed, traps are set
    again, and individuals are captured and
    identified.
  • This information allows estimates of population
    changes to be made.

35
  • Patterns of dispersion vary
  • Clumped xxx
  • xxx
  • This dispersion pattern is mostly due to
    resource distribution.
  • Uniform x x x
  • x x x
  • This dispersion pattern is due to direct
    interactions between individuals such as
    competition for resources.
  • Random xx x xxx
  • x xxxx
  • This pattern is due to the absence of
    interactions within a population.

36
  • Clumped dispersion is when individuals aggregate
    in patches.

37
  • By contrast, uniform dispersion is when
    individuals are evenly spaced.

38
  • In random dispersion, the position of each
    individual is independent of the others.

39
Click here- how to study biodiversity
40
G. Demography is the study of factors that affect
the growth and decline of populations
  • Additions occur through birth, and subtractions
    occur through death.
  • Demography studies the vital statistics that
    affect population size.
  • Life tables and survivorship curves.
  • A life table is an age-specific summary of the
    survival pattern of a population.

41
  • A graphic way of representing the data is a
    survivorship curve.
  • This is a plot of the number of individuals in a
    cohort still alive at each age.
  • A Type I curve shows a low death rate early in
    life (humans).
  • The Type II curve shows constant mortality
    (squirrels).
  • Type III curve shows a high death rate early in
    life (oysters).

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  • Reproductive rates.
  • Demographers that study populations usually
    ignore males, and focus on females because only
    females give birth to offspring.
  • A reproductive table is an age-specific summary
    of the reproductive rates in a population.
  • For sexual species, the table tallies the number
    of female offspring produced by each age group.

44
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45
H. Population Growth
  • To understand how much a populations growth may
    be changing, birth and death rates must be
    considered.

46
  • Using mathematical notation we can express this
    relationship as follows
  • If N represents population size, and t represents
    time, then ?N is the change is population size
    and ?t represents the change in time, then
  • ?N/?t B-D
  • Where B is the number of births and D is the
    number of deaths

47
  • If B D then there is zero population growth
  • Under ideal conditions, a population grows
    rapidly.
  • Exponential population growth is said to be
    happening
  • Under these conditions, we may assume the maximum
    growth rate for the population (rmax) to give us
    the following exponential growth
  • dN/dt rmaxN

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49
I. The logistic model of population growth
incorporates the concept of carrying capacity
  • Typically, unlimited resources are rare.
  • Population growth is therefore regulated by
    carrying capacity (K), which is the maximum
    stable population size a particular environment
    can support.

50
  • The logistic growth equation
  • We can modify our model of population growth to
    incorporate changes in growth rate as population
    size reaches a carrying capacity.
  • The logistic population growth model incorporates
    the effect of population density on the rate of
    increase.

51
  • The graph of this equation shows an S-shaped
    curve.

52
  • How well does the logistic model fit the growth
    of real populations?
  • The growth of laboratory populations of some
    animals fits the S-shaped curves fairly well.

53
  • Different types of populations may show different
    life history strategies relative to their
    population growth.
  • In K-selection, organisms live and reproduce
    around K, and are sensitive to population
    density- they follow the logistic growth curve.
  • In r-selection, organisms exhibit high rates of
    reproduction and occur in variable environments
    in which population densities fluctuate- they
    follow an exponential growth curve for a period
    of time.

54
Who are r-selected and k-selected populations?
  • An example of an r-selected population is a group
    of mosquitoes in the spring.
  • An example of a k-selected population is a group
    of giraffes living on a savanna.

55
r-selected K-selected
Homeostatic capability Limited Extensive
Maturation time Short Long
Lifespan Short Long
Mortality rate High Low
56
r-selected K-selected
offspring and size/ reproductive episode Many, small Few, large
reproductions/lifetime 1 Several
Age at 1st reproduction Early (young) Late (older)
Parental care None Often extensive
57
J. How does density impact population growth?
  • Why do all populations eventually stop growing?
  • What environmental factors stop a population from
    growing?
  • The first step to answering these questions is to
    examine the effects of increased population
    density.

58
  • Density-dependent factors increase their effect
    on apopulation as populationdensity increases.
  • This is a type of negativefeedback.
  • Density-independent factorsare unrelated to
    populationdensity, and there is nofeedback to
    slow populationgrowth.

Examples of density dependent factors include
disease, available food or territory, health,
predation, pollution Examples of density
independent factors include hurricanes, tsunami,
fires, earthquakes
59
  • Some populations have regular boom-and-bust
    cycles.
  • The populations of predators and their prey can
    fluctuate greatly.

60
K. The human population has been growing almost
exponentially for three centuries but cannot do
so indefinitely
  • The human population increased relatively slowly
    until about 1650 when the Plague took an untold
    number of lives.
  • Ever since, human population numbers have doubled
    twice
  • How might this population growth ever stop?

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62
  • Age structure.
  • Age structure is the relative number of
    individuals of each age.
  • Age structure diagrams can reveal a populations
    growth trends, and can point to future social
    conditions.

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64
What can we learn from these graphs?
  • Kenyas population ? Bulge in the young
    population means that most of these individual
    can reproduce in the future, although there is a
    high mortality rate at old age.
  • US population ?shows a bulge in the baby
    boomers and more of the population survives into
    old age.

65
L. Estimating Earths carrying capacity for
humans is a complex problem
  • Predictions of the human population vary from 7.3
    to 10.7 billion people by the year 2050.
  • Will the earth be overpopulated by this time?

66
  • Wide range of estimates for carrying capacity.
  • What is the carrying capacity of Earth for
    humans?
  • This question is difficult to answer.
  • Estimates are usually based on food, but human
    agriculture limits assumptions on available
    amounts.

67
  • We may never know Earths carrying capacity for
    humans, but we have the unique responsibility to
    decide our fate and the fate of the rest of the
    biosphere.

68
M. Community Ecology
  • Possible interspecific interactions exist in a
    community and can have positive or negative
    effects.

69
  • Competition.
  • Interspecific competition for resources can occur
    when resources are in short supply.
  • There is potential for competition between any
    two species that need the same limited resource.
  • The competitive exclusion principle two species
    with similar needs for same limiting resources
    cannot coexist in the same place.

70
  • The ecological niche is the role an organism
    plays in an environment.
  • For example, a squirrels niche would include
    where it lives, the territory it covers, the
    other squirrels or other species it encounters,
    its mate, etc..
  • The competitive exclusion principle can be
    restated to say that two species cannot coexist
    in a community if their niches are identical.

71
  • Classic experiments confirm this.

72
  • Predation.
  • A predator eats prey.
  • Predator adaptations many important feeding
    adaptations of predators are both obvious and
    familiar.
  • Claws, teeth, fangs, poison, heat-sensing organs,
    speed, and agility.

73
  • Plant defenses against herbivores include
    chemical compounds that are toxic.
  • Animal defenses against predators.
  • Behavioral defenses include fleeing, hiding,
    self-defense, noises, and mobbing.
  • Camouflage includes cryptic coloration, deceptive
    markings.

74
  • Chemical defenses include odors and toxins
  • Aposematic coloration is indicated by warning
    colors, and is sometimes associated with other
    defenses (toxins).

75
  • Mimicry is when organisms resemble other species.
  • Batesian mimicry is where a harmless species
    mimics a harmful one.

Fig. 53.7
76
  • Müllerian mimicry is where two or more
    unpalatable or harmful species resemble each
    other.

Fig. 53.8
77
  • Mutualism is where two species benefit from their
    interaction. (ie ants and the Acacia tree)
  • Commensalism iswhere one speciesbenefits from
    theinteraction, but otheris not affected.
  • An example wouldbe barnacles thatattach to a
    whale.

78
  • In parasitism, predators
  • live on/in a host and depend
  • on the host for nutrition.
  • Example a tick is a parasite to
  • a dog or human

79
  • Coevolution refers to reciprocal evolutionary
    adaptations of two interacting species.
  • When one species evolves, it exerts selective
    pressure on the other to evolve to continue the
    interaction.
  • Example many flowers have coevolved with the
    pollinators that are attracted to them.

80
N. Trophic structure is a key factor in community
dynamics
  • The trophic structure of a community is
    determined by the feeding relationships between
    organisms.
  • The transfer of food energy from its source in
    photosynthetic organisms through herbivores and
    carnivores is called the food chain.

Click animation
81
  • Charles Elton firstpointed out that the length
    of a food chain is usually four or five links,
    called trophic levels.
  • He also recognizedthat food chains are not
    isolated units butare hooked togetherinto food
    webs.

82
  • Food webs.
  • Who eats whom in a community?
  • A given species may weave into the web at more
    than one trophic level.

Fig. 53.11
83
  • The autotrophs are the
  • primary producers, and are usually
    photosynthetic (plants or algae).
  • They use light energy to synthesize sugars and
    other organic compounds.

84
  • Heterotrophs areat trophic levelsabove the
    primaryproducers anddepend on
    theirphotosyntheticoutput.

85
  • Herbivores that eat primary producers are called
    primary consumers.
  • Carnivores that eat herbivores are called
    secondary consumers.
  • Carnivores that eat secondary consumers are
    called tertiary consumers.
  • Another important group of heterotrophs is the
    detritivores, or decomposers.
  • They get energy from detritus, nonliving organic
    material and play an important role in material
    cycling.

86
Food chains can be represented as food pyramids
  • The pyramid of energy
  • Energy is transferred from the sun to producers
    to primary, secondary and then tertiary
    consumers.
  • There is a 10 transfer of energy from on level
    to the next.
  • Most energy is used for metabolism or lost as
    heat at each level.

87
Fig. 54.11
88
  • The dynamics of energy through ecosystems have
    important implications for the human population.

89
  • Pyramid of biomass Producers are greatest in
    biomass at the bottom of the pyramid.As you go
    up the food chain, biomass decreases
  • Most biomass pyramids narrow sharply from primary
    producers to top-level carnivores because energy
    transfers are inefficient.

90
  • Pyramids of numbers show how the number of
    individuals present in each trophic level
    decreases from producer to each level of consumer.

91
O. Decomposition connects all trophic levels
  • The organisms that feed as detritivores often
    form a major link between the primary producers
    and the consumers in an ecosystem.
  • The organic material that makes up the living
    organisms in an ecosystem gets recycled.

92
  • An ecosystems main decomposers are fungi and
    prokaryotes (bacteria), which secrete enzymes
    that digest organic material and then absorb the
    breakdown products.

93
P. Ecological succession is the sequence of
community changes until a stable climax community
is formed.
  • Ecological succession is the transition in
    species composition over ecological time.
  • Primary succession begins in a lifeless area
    where soil has not yet formed.
  • Example?
  • lichen ?moss? grass?shrubs?trees

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  • Mosses and lichens colonize first and cause the
    development of soil.
  • They are called the pioneer species
  • The climax community is the last stable stage to
    appear.
  • In NY state, the climax community consists of
    oak, maple and beach trees.

96
  • Secondary succession occurs where an existing
    community has been cleared by some event (ie
    fire,earthquake, volcanic eruption, hurricane),
    but the soil is left intact.
  • Grasses grow first, then trees and other
    organisms.

animation
97
Q. Ecosystems rely on cycles
  • Cycles include
  • The water cycle
  • The carbon cycle
  • The nitrogen cycle
  • The phosphorus cycle

98
  • The water cycle

99
  • The carbon cycle also includes hydrogen and
    oxygen.

100
animation
101
  • The nitrogen cycle.
  • Nitrogen enters ecosystems through two natural
    pathways.
  • Nitrogen from the atmosphere can enter the soil
    by rain and dust.
  • Nitrogen fixation, where certain bacteria convert
    N2 to compounds in the soil that can be used to
    synthesize nitrogenous organic compounds like
    amino acids.
  • These archeabacteria are found on the root
    nodules of legumes like clover and represent a
    mutualism.

102
  • The direct product of nitrogen fixation is
    ammonia, which picks up H and becomes ammonium
    in the soil (ammonification), which plants can
    use.
  • Certain aerobic bacteria oxidize ammonium into
    nitrate, a process called nitrification.
  • Nitrate can also be used by plants.
  • Some bacteria get oxygen from the nitrate and
    release N2 back into the atmosphere
    (denitrification).

103
  • The phosphorous cycle.
  • Organisms require phosphorous for many things.
  • This cycle is simpler than the others because
    phosphorous does not come from the atmosphere.

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105
R. The human population is disrupting chemical
cycles throughout the biosphere
  • The growing human population size coupled with
    technology that is not environmentally friendly
    leads to great disruptions in our ecosystems.

106
  • In agricultural ecosystems, a large amount of
    nutrients are removed from the area in the crop
    biomass.
  • After awhile, the natural store of nutrients can
    become exhausted.

107
  • Recent studies indicate that human activities
    have approximately doubled the worldwide supply
    of fixed nitrogen, due to the use of fertilizers,
    cultivation of legumes, and burning.
  • This may increase the amount of nitrogen oxides
    in the atmosphere and contribute to atmospheric
    warming, depletion of ozone and possibly acid
    rain.

108
  • Excess nitrogen can runoff into water systems,
    which leads to algae blooms, which ultimately
    leads to oxygen depletion after aerobic bacteria
    consume the dead algae.
  • This process is calledeutrophication

109
  • Controlling pollution may help control
    eutrophication.

110
S. Combustion of fossil fuels is the main cause
of acid precipitation
  • The burning offossil fuelsreleases
    sulfuroxides and nitrogen thatreact with
    waterin the atmosphereto produce sulfuric and
    nitric acids.

111
  • These acids fall back to earth as acid
    precipitation, and can damage ecosystems greatly.
  • The acids can kill plants, and can kill aquatic
    organisms by changing the pH of the soil and
    water.

112
T. Toxins can become concentrated in successive
trophic levels of food webs
  • Humans produce many toxic chemicals that are
    dumped into ecosystems.
  • These substances are ingested and metabolized by
    the organisms in the ecosystems and can
    accumulate in the fatty tissues of animals.
  • These toxins become more concentrated in
    successive trophic levels of a food web, a
    process called biological magnification.

113
  • The pesticide DDT, before it was banned, showed
    this affect.

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115
U. Human activities may be causing climate change
by increasing carbon dioxide concentration in the
atmosphere
  • Rising atmospheric CO2.
  • Since the Industrial Revolution, the
    concentration of CO2 in the atmosphere has
    increased greatly as a result of burning fossil
    fuels.

116
  • Measurements in 1958 read 316 ppm and increased
    to 370 ppm today

117
  • The greenhouse effect.
  • Rising levels of atmospheric CO2 may have an
    impact on Earths heat budget.
  • When light energy hits the Earth, much of it is
    reflected off the surface.
  • CO2 causes the Earth to retain some of the energy
    that would ordinarily escape the atmosphere.
  • This phenomenon is called the greenhouse effect.

118
  • Global warming.
  • Several studies predict a doubling of CO2 in the
    atmosphere will cause a 2º C increase in the
    average temperature of Earth.
  • Rising temperatures could cause polar ice cap
    melting, which could flood coastal areas.
  • It is important that humans attempt to stabilize
    their use of fossil fuels.

119
V. Human activities are depleting the atmospheric
ozone
  • Life on earth is protected from the damaging
    affects of ultraviolet radiation (UV) by a layer
    of O3,or ozone.
  • Studies suggest thatthe ozone layer hasbeen
    graduallythinning since 1975.

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121
  • The destruction of ozone probably results from
    the accumulation of chlorofluorocarbons,
    chemicals used in refrigeration and aerosol cans,
    and in certain manufacturing processes.
  • The result of a reduction in the ozone layer may
    be increased levels of UV radiation that reach
    the surface of the Earth.
  • This radiation has been linked to skin cancer and
    cataracts.

122
W. Biodiversity is vital to human welfare
  • Why should we care about biodiversity?
  • How does it benefit us to maintain species
    diversity and genetic diversity?

123
  • Biodiversity is acrucial naturalresource,
    andspecies that arethreatened couldprovide
    crops, fibers, and medicines forhuman use.
  • The loss of species also means the loss of genes.
  • Biodiversity represents the sum of all the
    genomes on Earth.

Fig. 55.3
124
X. The four major threats to biodiversity are
habitat destruction, introduced species,
overexploitation and food chain disruption
  • Habitat destruction
  • Human alteration of habitat is the single
    greatest cause of habitat destruction.
  • Destruction of physical habitat is responsible
    for the 73 of species designated extinct,
    endangered, vulnerable, or rare.
  • About 93 of the worlds coral reefs have been
    damaged by humans.

125
  • Introduced species
  • Introduced species are those that humans move
    from native locations to new geographic regions.
  • The Nile perch wasintroduced into LakeVictoria
    as a food fish,but led to the extinctionof
    several native species.

126
  • There are manyexamples of howexotic
    specieshave disruptedecosystems.

127
  • Overexploitation
  • This refers to the human harvesting of wild
    plants and animals at rates that exceed the
    ability of those populations to rebound.
  • The great auk was overhunted and became extinct.

128
  • The African elephant has been overhunted and the
    populations have declined dramatically.
  • The bluefin tuna is another example of an
    over-harvested species.
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