1.5.4 Abiotic Factors

8/11/2019 1.5.4 Abiotic Factors

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1.5.4 INVESTIGATEANY THREEABIOTIC FACTORSPRESENT IN THE SELECTED ECOSYSTEM, AS LISTEDRELATE RESULTS TO CHOICE OF HABITAT SELECTED

BY EACH ORGANISM IDENTIFIED IN THIS STUDY

Abiotic !cto"# !# $i#t%& i' t(%#)$$!b*#+

pH, temperature (air and ground oraquatic), light intensity, water current,air current, dissolved oxygen, mineralcontent, percentage air in soil,

percentage water in soil, percentagehumus, salinity, degree of exposure andslope.

M!t%"i!$#E-*i/%'t E ui ment to measure the chosen


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+rom ,Syllabus Clarifications

1.5.4 Keep it simple-presence or absenceof the abiotic factor will suffice.

Measure simply-e.g. temperature. Relatethe abiotic factor to the ecosystem beingstudied.

Three (3) suitable factors that are relevant/present in the habitat from the list above.Investigate these factors in the investigation.Suitability to habitat. (Syllabus P13, Teacher

Guidelines P23).


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P"oc%&*"%

1. hoose any three abiotic factors present in theselected ecosystem from the list above.

!. "easure the abiotic factors for the habitat of eachof the identi#ed organisms by using theappropriate equipment and following the relevantinstructions.

$. %ecord results.

&. 'amiliarise yourself with all procedures beforestarting.

. %elate results to the choice of habitat bycommenting on the suitability of each habitat for

the organism.


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R%#*$t'biotic factors and measurements

0rganism ame Habitat


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Co'c$*#io'Co//%'t


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C$ic0 o' t(% $i'0 o"b!c0"o*'&

i'o"/!tio' o'+ pH

temperature (airand ground oraquatic)

light intensity

water current

air current

dissolved oxygen

mineral content

air in soil

water in soil humus in soil

salinity

degree ofexposure

slope

*dvance

preparation


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pH

+oth in soil and water, pH aects plantgrowth. Each species grows best at a

certain pH. *ny departure from theoptimum pH will have an adverse eectand may -ill the plant. lants such asbrac-en, gorse, heather, a/alea,rhododendron, camellia, and oa- onlygrow on acid soils (pH range &.0 2.).

3hese plants are now -nown to beintolerant of calcium ions in the soil andmay be -nown as c!$ci*%# (4lime

haters5). lants that live in limestone


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pH

ertain aquatic animals, such as the freshwatershrimp, can tolerate a wide range of pH.8thers, such as planarian 9atworms, caddis 9y

larvae and some damsel9y nymphs are moreabundant in al-aline, calciumrich waters.Earthworms also prefer al-aline soils.

"ar-ed changes in pH are ecological features insome areas e.g. woodland in :illarney ;ationalar-. 3he pH over the limestone areas isal-aline and one #nds beech and ash. *s thesoil becomes acidic over the sandstone areasthe 9ora changes and oa- becomes thepredominant tree species.


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pH


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"easuring pH>

3he pH of water samples can bemeasured directly using pH paper or a

pH meter and a probe. 3o measure thepH of soil, ta-e a sample of soil, place itin a measuring cylinder and add anequal volume of distilled water. ?ha-e

vigorously for about 10 minutes andthen #lter. (=f clay particles are present,they can be 9occulated by using bariumsulphate solution instead of distilled

water.) 3he pH of the #ltrate is then

7ac8 to Select from 'biotic %ist


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Temperature (air and ground or

aquatic)

3hroughout northern Europe there is aseasonal variation in temperature

closely lin-ed to light intensity. 3hereare also daily temperature and lightcycles. =n ecological studies, the precisetemperature at any one moment is of

little value.8f much greater signi#cance are the

diurnal (daily) and seasonal variations.@iurnal temperature is best measuredwith a maxmin thermometer.


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aquatic)

3emperatures at dierent heights ofvegetation above ground level are also

of considerable practical importance.=nvestigations have shown that atmidday the foliage, together with thebare soil between plants, are the

warmest places. *t night the bare soilcools more rapidly. 3herefore ifvegetation is removed ground leveltemperature shows mar-ed 9uctuations,

a factor that aects the rate of


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aquatic)

"ost plants photosynthesise between*pril and ?eptember, when the mean air

temperature is above A o. 'or the restof the year they undergo changes thatassist survival at low temperatures.*nnual plants produce coldresistant

seeds, perennials shed their leaves andform buds or dormant undergroundstorage organs.


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aquatic)3he winter survival tactics shown by animals

include cold avoidance and cold tolerance.old avoidance is shown by migratory birds

and butter9ies, whose annual migration towarmer climates ensure they neverexperience adverse weather conditions. oldtolerance is shown by insects many insectsenter a nonfeeding stage to overwinter.

Hedgehogs hibernate for the winter.3emperature gradients are an important feature

of ponds and la-es especially in summer. ?ucha gradient exists because warm water rises tothe surface and cold water falls.


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Measuring Temperature>

3emperature can be measured using a standardmercuryin glass or alcohol thermometer.?uch a thermometer with a thic-ened bulband in a protective case can be used in air,

soil and water. @igital thermometers could beused to measure habitat temperaturesinstead of standard thermometers. ?tandardmaxBmin thermometers can be used tomeasure the temperature range over aperiod of time which, for many investigations,is more important than a reading at anyparticular moment.



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Light intensity

?unlight is the source of energy thatdrives all ecosystems. ?easonalvariation in light intensity aects plantproductivity. Cess than 0.! of thetotal incident radiation on the earth isused by plants in the process ofphotosynthesis.

"any plants grow in direct sunlight, butmost plants show some degree of shadetolerance.

*nimals respond to changes in lightintensity by modifying their behaviour,


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Light intensity

3wo aspects of light, its duration and itsintensity, are generally important to

ecological studies. 3he duration ofdaylight hours can be determinedastronomically and is predictable forany location. hotoperiodism is a

biological response to the changes inthe ratio of light and dar- in a !& hourperiod. 'lowering plants may be dividedinto three categories>


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Light intensity

a) ?hort day plants. 3hese plants 9ower inearly spring or autumn and require adar- period exceeding a certain criticallength.

b) Cong day plants. 3hese plants require aperiod less than the critical period. 3hey9ower in summer.

c) @ayneutral plants. 3hese plants areunaected by photoperiod.

?ome plants require only a single

exposure to the critical daynight cyclein order to 9ower.


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Light intensity

Examples of photoperiodic responses inanimals are

a) "any small birds and mammals matein spring and early summer due toincreasing daylight.

b) onversely, sheep and goats respond

to shortening day length as they matein late summerBearly autumn.


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Measuring light intensity>

Cight intensity can be measured at anyparticular time using $i(t /%t%"#,

such as those used by photographers.However, the readings may not be veryuseful because light levels 9uctuatecontinuously. =n addition, if light

intensity is being studied in relation tothe distribution of plants, it is moreimportant to measure the light receivedover a relatively long period of time,

because it is this which most aects

7 8 S l f 'bi i %i


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Measuring light intensity>

Li(t "ob%# connected to a computeror datalogger can be used to ta-e

continuous measurements of light.*lternatively, it is possible to comparethe amount of light received over a longperiod of time by using $i(t#%'#iti2%

!%", such as o/alid paper used byprinters. 3his gradually dar-ens onexposure.



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Water current

* still body of water will inevitably bedisturbed by various factors, which will

aect the distribution of organisms inthe water.


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Water current

?till water communities can vary greatlyin appearance, anything from a small

temporary puddle to a large la-e iscapable of supporting life to someextent. 3he si/e and depth of a stillbody of water are maDor factors in

determining the characteristics of thatecosystem.


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Water current

8ne of the main dierences betweenstill water and running water

communities is the fact that the water ismoving at a particular velocity inrunning water communities.

3his can have great bearing on what

organisms occupy the ecosystem andwhat particular ecological niches theycan exist in.

%unning water can bring many factorsinto play aecting the lives of the


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Water current

"ovement of minerals and stones causedby the velocity and volume of the water

means the water bed is constantlychanging. 3he faster and higher volume ofwater present will result in a directincrease in amount and si/e of particles

shifted downstream. ?tanding waves are used by salmon at the

bottom of waterfalls to spur themupstream. *t the same time, they cause

small air poc-ets, which results in a small


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Water current

Erosion is caused by the running waterbrea-ing down the river ban- and beds,

causing the geography of the river tochange over a long period of time. 3hismeans, for example, that hydroserespreviously occupying the river ban-

may #nd themselves distanced from therunning water and over time this wouldmean the overall ecosystem wouldchange.


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Water current

=n general the diversity of plant species in a runningwater community is small compared to that of astill water community. "ost plants have gonethrough evolutionary adaptations to cope with the

force and dierent conditions that running waterbrings. *s these conditions are more harsh for atypical species of plant, more notably larger plants,smaller species have found the conditions of thecommunity more favourable. 3his is due to the fact

that they are more 9exible in regards to thephysical conditions of the water. *lgae can grow inall sorts of dierent places and surfaces, andtherefore are a successful constituent of therunning water ecosystem.


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Water current

"ost of these algae have developedevolutionary adaptations over time that

prevent the water current sweepingthem away.

8ther animals have developed some ofthe following adaptations over time that

help them cope with the conditions inhand>


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Water current

?uc-ers 3hese suc-ers attach themselves to asurface and can also assist movement in anydirection.

Hoo-sBlaws 3hese sharp obDects can dig intoany given obDect and allow the animal to cling toa position or claw their way around the surface.

+ody 9attening 3his adaptation can allow theanimal in the water bear less of the brunt of the

force of water moving downstream, thereforereducing it as an inhibitor of their movement.

3his also allows these animals to enter con#nedareas (such as under stones) that may present auseful environment for them to live in.


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Water current

?treamlining 3his reduces the frictionalforces between the 9owing water and

the streamlined animal.'light ?ome animals have adaptations

allowing them to 9y, removingthemselves from the force of the current

at ground level and enabling them tomove upstream more easily if needs be.



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Water current

3he simplest procedure to measurewater current is to record the time ta-en

for a 9oating obDect to travel a -nowndistance. =t is preferable to use anobDect which is mainly submerged toeliminate any wind eects.

'ormula>urrent (mBsec) F distance travelled by

the obDect

time ta-en to travel thatdistance



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Air current

*ir movements may aect organisms indirectly,by evaporative cooling or by a change inhumidity. =t may also aect them by

determining their shapeG the development ofbranches and roots of trees in exposed areas.


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Measuring air current>

* 3i'& 2!'%measures direction and an!'%/o/%t%"measures wind speed.



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Dissolved oxygen

8xygen concentration in water is a limitingfactor for most aquatic organisms.


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Dissolved oxygen

8xygen gradients exist in large ponds andla-es most of the year. ?urface water,

100 saturated, may contrast greatlywith the water at the bottom of thepond, which may be only !saturated.


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Dissolved oxygen

8xygen depletion may occur for any ofthe following reasons

a) =n winter when the water is coveredwith ice.

b) =n late summer when plants die bac-and microorganisms decompose dead

leaves.c) *t any time if sewage or other organic

eJuents enter the water.



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Measuring dissolved

oxygen>a dissolved oxygen probe and meter

or the


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Mineral content

=norganic ions constitute approximately1 of an organism by weight, but they

are essential for its health.


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Mineral content

?oil is tested by farmers and gardenersfor the presence or absence of certain

essential minerals, using soil test -its.:its are available from garden centres."inerals in soil become used up orleached away and may have to be

replaced using fertilisers or by leavingthe ground fallow for a season.

@ierent plant species have dierentmineral requirements and the

distribution therefore depends on the




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Percentage air in soil

3he amount of air present in the soildepends on the structure of the soil and

its water content.


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Percentage water in soil

3he water content of soils varies greatly. *ny freelydrained soil, which holds as much water as possibleis said to be at #eld capacity. *ddition of any more

water which cannot drain away causes water loggingand anaerobic conditions.

?ome plants can tolerate waterlogged conditions."any headed bogcotton which inhabits bog poolshas aerenchyma tissue which channels oxygen to

the roots of the plant which allows it to penetrate todepths of 20cm into the waterlogged peat.

Karrow, which lives in drier soil, is a hemi parasitewhich lives o minerals and water from roots ofother plants.



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Percentage humus

* maDor component of soil is dead organicmatter e.g. leaf litter. *s it decomposes

it forms a gelatinous brownblac-material called humus. Humus is acolloidal acid substance, an immediateproduct in the decomposition of dead

plants and animals.3he presence of humus encourages plant

growth for a number of reasons.



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Percentage humus

1. 3he moist stic-y substance binds mineralstogether forming a crumbly, less compacted soil.

3his increases the air content of the soil andimproves drainage.

!. Humus provides food for many invertebrates e.g.earthworms.

$. Humus and clay particles carry negative charges,which prevent positively charged ions from being

washed out of the soil by rain (leaching).&. Humus absorbs solar radiation because of its

dar- colour. Humus rich soils heat up quic-ly,promoting the germination of seeds and thegrowth of seedlings.


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Salinity

3he salt content (salinity) of a water body is one of themain factors determining what organisms will befound there. 3hus fresh waters and saline waters are

inhabited by quite dierent organisms. lants andanimals that live in or use freshwater generally have asalt content inside their cells that is greater than thewater they inhabit or use.

3hey tend to give o salts as waste products. ?altwater

plants and animals have a salt content equal to or lessthan the salinity of the surrounding water, and thushave dierent mechanisms for maintaining their saltbalance. =n brac-ish waters we #nd plants andanimals that can tolerate changes in salinity.


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Salinity

=ntertidal organisms tolerate abruptchanges in salinity.


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To measure salinity>

?alinity can be measured using aconductivity probe and meter.

*lternatively, since the density of water isrelated to the amount of salt dissolvedin it, the salinity of the water can bedetermined from the density and water

temperature. * hydrometer can be usedto measure density. Lsing density andwater temperature values the salinitycan be read from a salinity table.


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Degree o e!posure

(a) *ir


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Degree o e!posure

3he splash /one is exposed to oceanspray, but is covered completely only

during the highest of high tides. 3heplants and animals e.g. lichens, snails,sand hoppers that live here cannot livesubmerged in sea water but may

bene#t from salt water spray.3he upper shore is out of the water most

of the timeG it is completely coveredonly during high tides. lants and

animals e.g. barnacles, snails, spiral


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Degree o e!posure

3he mid shore is exposed to the air twicea day and it supports a great variety of

plants and animals e.g. bladder wrac-,-notted wrac-, sea anemones, limpets.

3he lower shore is exposed to air onlyduring the lowest tides. 3he plant and

animal life e.g. sea urchins, star#sh, andserrated wrac- found here is abundantand varied.


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Degree o e!posure

?ome organisms have adapted to preventdrying out in the following ways>

3hey have protective body structures.

"olluscs have shellsG -elps have strong,smooth blades (fronds)G chitons have 9atbodies.

?nails withdraw into their shellsG some snailsthen secrete a mucus seal.

*nemones gather in large masses to reducethe body surface area exposed to the air.

Cimpets #t themselves into small depressionsthat they ma-e in roc-s.


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Degree o e!posure

(b)


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Degree o e!posure

?ome animals hide from the waves bycrawling under or between roc-s orplants. rabs crawl into crevices inroc-s, and small animals hide in theholdfasts of -elp. Encrusting algae growunder roc- ledges.

?ome burrow into the sand e.g.lugworm.


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Slope

?lope usually in9uences runo, nutrientaccumulation, soil and organic matteraccumulation.

?lopes are important when considering thetemperature of the soil surface.

?outhfacing slopes receive more sunlight,

and are therefore warmer than north facingslopes (in the northern hemisphere). =n=reland, the southwestern slopes face therain bearing winds.



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Slope

?lopes with a steep gradient are generallydrier than those with a shallowergradient as water drains more readily

from a steep slope. *s a result they aremore nutrient poor, have shallower soiland are more subDect to erosion andhigher winds. Cess steep slopes can

accumulate soil, nutrients etc. and maybe subDect to less erosion.

=f a slope is convex, erosion, winds andruno are enhanced. =f a slope is

concave, accumulation of water and



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Ad"ance preparation

%efer to'ieldwor- hec-list *ppendix 1
http://var/www/apps/conversion/1.5.3%20Organism%20Distribution/6%20Mandatory%20Activity/1.5.3%20Checklist%20of%20Resources%20(nbss).dochttp://var/www/apps/conversion/1.5.3%20Organism%20Distribution/6%20Mandatory%20Activity/1.5.3%20Checklist%20of%20Resources%20(nbss).doc


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1.5.4 Abiotic Factors