Homeostasis and thermoregulation help maintain internal stability and optimal body temperatures in organisms. Thermoregulation is critical for survival as biochemical and physiological processes are sensitive to temperature changes. Animals regulate temperature through balancing heat loss and gain. Osmoregulation balances water and solute levels in organisms through controlling movement between internal fluids and the external environment. Plants and animals have different adaptations for osmoregulation depending on their habitat. Excretion eliminates waste products of metabolic reactions through various processes depending on if the organism is a plant or animal. Control and coordination in animals is regulated by the nervous and endocrine systems, using electrical and chemical signals. Plants coordinate growth and movement through plant hormones. Support structures in animals include skeleton

1. Homeostasis
is the ability or tendency to maintain internal stability in an organism to compensate for
environmental changes.
Thermoregulation is the processbywhichanimalsmaintainaninternal temperature withina
tolerable range.Thermoregulationiscritical tosurvival because mostbiochemicalandphysiological
processesare verysensitive tochangesinbodytemperature.Forevery10°C(18°F) decrease in
temperature,the ratesof mostenzyme-mediatedreactionsdecrease two-tothreefold.Increasesin
temperature speedupreactionsbutcause some proteinstobecome lessactive.Forinstance,the
oxygencarriermolecule haemoglobinbecomeslesseffective atbindingoxygenastemperature
increases.Membranescanalsochange fluidity,becomingincreasinglyfluidorrigidastemperatures
rise or fall,respectively.Eachanimal specieshasanoptimal temperature range.Thermoregulation
helpsmaintainbodytemperature withinthatoptimal range,enablingcellstofunctioneffectively
evenasthe external temperaturefluctuates.
Osmoregulation balances the uptake and loss of water and solute
Justas thermoregulationdependsonbalancingheatlossand gain,regulatingthe chemical
compositionof bodyfluidsdependsonbalancingthe uptake andlossof waterandsolutes.This
processof osmoregulationisbasedlargelyonthe controlledmovementof solutesbetweeninternal
fluidsandthe external environment.Because solute movementresultsinthe movementof waterby
osmosis,the neteffectistoregulate bothsolutesandwater.
Osmoregulation in plants
Plantsare distributedindifferenthabitats.Thesehabitatsmaybe aquatic,moderate,severelydry or
terrestrial.Thusplantsare dividedintothreegroupsonthe basisof nature of habitat.These are:
Hydrophytes:
The aquatic plantsare calledhydrophytes.Theyhave the adaptationtosave themselvesfrom
excessivewaterinfreshwaterenvironment.Theseplantshave large surface area.So,transpiration
takesplace excessively.Theyhave alarge 'numberof stomataon theiruppersurface,these stomata
openinthe atmosphere.So,theypromote lossof waterortranspiration.
Mesophytes:
The plants,livinginthe moderate environmentare calledmesophytes.These plantshave moderate
wateravailability.Whenthere issufficientsupplyof water,the stomataare openedtopromote the
lossof excessive water.Whenthere islesssupplyof water,the stomata are closedto preventthe
lossof water eg.Brassica,rose,mangoetc.
Xerophytes:
The plantslivinginthe severelydryterrestrial environmentare calledxerophytes.Theyhave
followingadaptationtoreduce the rate of transpiration.
(i).Many xerophytespossessmallthickleavesItreducesthe surface are to volume of the plants.

2. Thus itreducesthe lossof waterby transpiration.
(ii).Theyhave thick,waxyandleatherycuticle.
(iii).Thestomataare onthe lowersurface of the leaves.These stomataare presentindepressions.
(iv).Some plantslike cacti shedtheirleavesduringthe dryseasons.Therefore,the transpirationis
stoppedcompletely,Theyhave stemastheirphotosyntheticorgan.Theirstemstore waterinthe
rainyseasonand use it in drycondition.
Osmoregulation in Animals
The animal cellsrequire more critical balance of waterandsolutesinthe body.Theycannotsurvive
withoutwatergainor waterloss.Watercontinuouslyenterorleave the cell.However,the quantity
of waterandthe solute iskeptinbalance.There are twoapproachesinmaintainingthisbalance:
1. Osmoconformers:
The animalswhichdonot require toactivelyadjustingtheirinternal osmoticstate are called
osmocoformers.These animalskeeptheirbodyfluid isotonictothe external environmentTheyeven
keeptheirbodyfluidisotonictomarine andsaltwaterenvironment
2. Osmoregulators:
The animalswhichactivelyadjusttheirinternal osmoticstate accordingtoexternal environmentare
calledosmoregulatory.Theirbodyfluidconcentrationdiffersgreatlywithoutside environment.They
discharge excesswaterinhypotonicenvironmentandexcrete saltinhypertonicenvironment.The
animalslivingindifferenthabitatshave distinctadaptationtoregulate balance.Thesehabitatsmay
be freshwaterandterrestrial environment.
Excretion
Livingorganismsare one giantchemical lab.Hundredsof chemical reactionshappeninourbodies
betweenvariousbiomolecules.Inplants,photosynthesisisbasicallyachemical reaction.All these
metabolicreactionshave byproductsthatare eliminatedthroughthe processof excretion.
Excretion in Plants
There isan immense difference inthe structure andcompositionof plantsandanimals.Didyou
knowthat whenchemical reactionsoccurinplants,oxygenisreleased?Thisoxygenissupposedlya
waste productthat the photosynthesisprocessgenerates.
Photosynthesisoccursinplants,inthe presence of sunlight.Thischemical reactiongivesrise to
oxygen,whichisagas. It diffusesthroughthe stomataorthe openingsinthe leaves.Anyexcess
waterthat ispresentinplantsgetsevaporatedthroughthe transpirationprocess.
Anotherinterestingfeature here inplantsisthatsome of the plantwastesare storedin cellular
vacuoles, inleavesthatfall off.Some otherwaste productsare storedinthe xylem, likeresinsand
gums.

3. Excretion in Animals
Thisis a well-developedandcomplex systemthattakescare of eliminatingthe wastesfromthe
humanbody.Thisis a vital functionthat helpsinthe smoothfunctioningof the humanbody.Kidneys
are the mainorgans of the excretorysysteminhumanbeings.Ureters,urinarybladder,andurethra
alongwithbloodvesselsare the othercomponentspresent.The urine thatisformedinthe kidneys
istransportedthroughthe uretersto the urinarybladder.Itisexpelledoutthroughthe urethra.
But, a pointto be notedisthat skinand lungs,alsohave arole to playin excretingoreliminating
waste substancesfromthe body.The sweatglandsinthe skinhelpinthe excretionof small amounts
of water,salts,andurea.Lungs helpingettingridof carbon dioxidethroughthe respirationprocess.
Let uslearnmore indetail aboutthe humanexcretorysystem.
Control and coordination
in animals
Whenlearningaboutthe control andcoordinationinanimalsandhumans,we have totake a lookat
the nervoussystemandthe hormonal systemandunderstandtheirrespective functions.
The nervous system
Neuronsformthe basisof the functional aswell asthe structural unitof the nervoussystem.The
mainjobof these neuronsistoreceive the external stimuli andthensendittothe brain,so that the
brainin turncan readthose signalsanddirectthemto the necessarypartsof the bodyto take
properaction.For example,whenyoutouchsomethingreallyhot,thenthe neuronswill transmit
thismessage tothe brain thatyou are touchingsomethingreallyhotandthe brainwill thensenda
message backto the handsthrough the neurons,due towhichyouwill immediatelymoveyourhand
fromthere.Thistransferof messagestakesplace throughelectrical impulseswhichmove
throughoutthe bodythroughnerve fibres.
The dendritesare nerve endingtipsthatare specialisedforreceivingthe outside stimuli andis
presentinoursense organs.The momentthese dendritesreceive astimuli achemical reactiongets
sparkedoff due to whichelectrical impulsesare generatedwhichinturnmovesfromthe dendrite to
the nucleusthentothe axon andthenfinallytothe nerve endings.There isagappresentin
betweentwonerve cellswhichisknownassynapse.Fromthe nerve endingsof one neurone,the
synapse takesinthe message andthentransmitsitto the consecutive neuronandthusthrough a
chainaction,these electrical impulsesare carriedfromone partof the bodyto anotherto reach the
brain.
The central nervous system
Anyunderstandingof the control andcoordinationwillbe incompletewithoutthe understandingof
the CNS or the Central NervousSystem.The brainandthe spinal chordtogetherformthe CNS.All
the electrical impulsesare interpretedinthe brainwhichthenpromptsactions.The humanbrainis
dividedmainlyintothree parts,dependingonthe type of functiontheyperform.While the forebrain
isconcernedwithactivitieslike thinking,the hindbrainandthe midbraintake care of the basic
involuntaryactions(actionswhichwe doinvoluntarily).The hindbrainisinturndividedintothe
medullaandthe cerebellum.Whenyoucoughorsneeze orthe beatingof yourheartetc is
controlledbythe medulla.The cerebellumisresponsible formaintainingbalance andthe proper
functioningof the muscles.

4. What is a reflex action?
The suddenandautomaticresponse thatwe have to an external stimulusisknownasa reflex action.
For example,ourimmediatemovingawayof the handwhenwe touch somethingtoohotisa reflex
action.Whenlearningaboutcontrol andcoordinationclass10, one needstounderstandthe reflex
arc or the pathwaythroughwhicha reflex actiontakesplace.
Whenyoutouch somethinghot,the receptorsreceive the signal andthenthe sensoryneuron
carriesthat message tothe CNS,whichtheninterpretsthe signal andsendsbacka reactionto the
affectedpartof the bodywiththe helpof motorneurons.Thenthe effectorsgive areactiontothe
stimuli,likeimmediatelymovingawaythe handfromthe hot object.
The hormone system
All the actionsof coordinationandcontrol cannotbe performedbythe nervoussystemalone.Thisis
because the electrical impulseswhichare usedbythe nervoussystemfortransmittinginformation
cannot be accessedbyall the cells,especiallythe oneswhichare notconnectedtothe nerve tissue.
Andon top of that cellsneedsome time togenerate impulsesandcarrythemfrom one place to
another.Thisiswhythe endocrine glandof ourbody,secreteshormoneswhichgetmixedintoour
bloodstreamandcanreach all the target cells.Hormonesperformthe functionof chemical
messengers.
Growth hormone
Secretedfromthe pituitarygland
Controlsandcoordinatesthe growthof an individual
Its deficiencycanleadtodwarfism
Insulin
Maintainsandcontrolsthe sugarlevel inbloodSecretedfromthe pancreasItsdeficiencymight
resultina rise inthe sugar level inblood
Sex hormones
Helpsto developthe sexual featuresof anindividualDifferentformales(testosterone) andfemales
(estrogen).Secretedfromthe reproductiveglandsof the body
Thyroxin
Thyroidglandsecretesthishormone withthe helpof iodine Controlsthe metabolismof fatWhen
presentinlesserquantity,mayresultingoitre whichischaracterised byaswollenneck
Plantscontrol and coordinate theirmovementwiththe helpof hormoneslike auxin,gibberellins,
abscisicacidand cytokinins.Theirmovementsmayormay notbe dependentontheirgrowth.
Coordination in Plants
You see plantsall aroundyou.But,are theyof the same size or height?Of course not!You see big
trees,medium-sizedshrubs,andevenplantsaplings. Thistellsusthatplantsexhibitsome growth
changesas well assome movements.Thiscoordinationinplantsisattributedto the presence of
planthormones.Unlike animals,plantsdonothave anymuscularsystemornervoussystem.But,

5. theyare still able toshowmovementandalsocoordination.These movementsare alwayscontrolled
and nothaphazard.Let us learnmore aboutcoordinationinplants.
What is coordination in plants?
Coordinationisthe abilitytouse differentpartsof the planttogether,smoothlyandefficiently.In
plants,coordinationisdue tothe resultof a chemical system, whereinplanthormonesor
phytohormoneshave amajorrole.
Movement in plants Plants exhibit two types of movements.
1. Growth-dependentmovementscalledthe TropicMovements.( towardsorawayfrom a stimulus)
2. Non-growthdependentmovementscalledthe NasticMovements.( independentof stimulus)
Tropic movementsThesecanbe classifiedagaininto5 types.Theyare:
• Phototropism(light)
• Geotropism(gravity)
• Hydrotropism(water)
• Chemotropism(chemicals)
• Thigmotropism(touch)
1. Phototropism –It is the movementof plantsinresponse tolight.The shootsystemof aplant
exhibitsthischaracteristic.The shootmovestowardsthe light.
2. Geotropism– It isthe movementof aplantpart towardsthe soil.Thisisa characteristic of the
root system.The rootsalwaysmove inthe directionof the earth’sgravity.
3. Hydrotropism–It isthe movementof a planttowardsthe water.The stimulushere iswater.
4. Chemotropism –It isthe movementof plantsinresponsetoa chemical stimulus.A classic
example of thistype of movementisthe growthof the pollentube towardsthe ovule,during
fertilization,inaflower.
5. Thigmotropism –It is a directional movementinplantsinresponse totouch.Fore.g.the plant
tendrilsclimbaroundanysupportwhichtheytouch.NasticMovementsNasticmovementsinplants
are notdirectional movements.Theyare notdependentonstimulusandare growthindependent.
For example,the leavesof atouchme not plant(Mimosapudica),foldup
immediately whentouched.These kindsof changesoccurdue tothe changesinthe amountof
waterin the leaves.Dependingonthe quantity,theyeitherswell uporshrink.
Plant hormones or phytohormones
Theyare responsible forthe control andcoordinationof plants.There are differenttypesof
hormones,whichaffectthe growthof a plant.Phytohormonesare chemical compoundswhichare
releasedbystimulatedcells.Thesehormonesare diffusedaroundthe plantcells.Theyhave arole to
playinthe cell division, cellenlargement,celldifferentiation,fruitgrowth,fallingof leaves,ripening
of fruits,ageingof plantsetc.
The differenttypesof phytohormonesare:

6. 1. Auxins2. Gibberellins3.Cytokinins4.AbscisicacidAuxins –Theyhelpinthe cell growthat the
shoottips.By elongatingthe cells,theyhelpinthe growthprocess.
Gibberellins –These hormonesare responsible forthe cell growthinthe stem, seedgermination,
and flowering.
Cytokinins –Theypromote cell divisioninplants.Theyalsopromote the openingof the stomataand
delayageinginleaves.
Abscisicacid – This hormone inhibitsthe growthof the plant.Andtherefore,itpromotesdormancy
inseedsandbuds.The detachmentof fruits,flowers,andfallingof leavesetc.are promotedbythis
hormone.
Support
Support in animals: Skeletons
The skeletonisthe supportingstructure of anorganism.There are three differenttypesof skeletons:
hydrostaticskeletons,endoskeletonsandexoskeletons.
1. Hydrostaticskeleton:Waterexertspressure onmuscularwalls,forexample,injellyfish.
2. Exoskeleton:The stable chitinousormineralisedoutershellof anorganism, forexample,the shell
of a grasshopperorprawn.
3. Endoskeleton:A cartilaginousormineralizedsupportstructure inside the body,forexample,in
humansand othervertebrates
Support in plants
The plant hasvariousmethodsandsystemsforsupportto maintainitsshape andforits protection,
these methodsmaybe physiological or structural.
The physiological support is a temporary support, because itdependsonthe presenceof the
waterin the plantcellsandthere isno support, if thiswateris lostThe physiological support
Physiological supporteffectsonthe cell itself asawhole
The structural support Structural supporteffectsonthe cell wall orsome parts of the cell