The document discusses several topics related to biology: - Evolution occurs through natural selection acting on genetic variation over many generations, which can result in new species adapting to their environments. - Organisms are part of complex food webs, and removing a species can impact others who depend on it as a food source. - Human activity such as hunting and habitat destruction has caused some species to go extinct.

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©J.L.HOPTON2009
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OCR21stCenturyScience
Module
B3
THEBEGINNINGOFTHEEARTH
•lifebeganonearthabout3500millionyearsago
•newspeciesevolvedfromverysimplelivingthings
•evidenceforevolutionisprovidedby-fossils
-comparingDNA
•firstspeciesdevelopedfrommoleculeswhichself-copied
EVOLUTION
•happensduetonaturalselection
•ifspeciessurvivetheyreproduce
•tosurvivetheymustadaptto...
habitat,preyandpredators,competitionforfood&space
•variationinaspeciescanoccur;itcanbe
geneticenvironmental
•onlygeneticvariationcanbepassedon
•changescanoccuringenes-MUTATIONS
•mutatedgenesinsexcellscanbepassedontooffspring
•mutatedgenesoccasionallyproducenewcharacteristics
•acombinationofmutation,environmentalchangesand
naturalselectioncanproducenewspecies
•evolutioncouldhavebeendifferentiftheconditionson
earthhadchangedanytimeinthepast
CONFLICTINGTHEORIES
Whenprovidedwithinformationaboutalternativeviewson
theoriginoflifeonearthorevolutionoflifeyoushould...
•identifystatementsthataredata
•identifystatementsthatprovideanexplanation
•recognisedatawhichconflictwithanexplanation
•identifyimaginationandcreativity
•suggestwhysomescientistsmaydisagreewithnewdata
•suggestwhyscientistmightdisagreewitheachother
NERVOUSSYSTEM
•co-ordinatedinhumansbycentralnervoussystem
•centralnervoussystemincludesspinalcordandbrain
•useselectricalimpulses
•producesFASTresponses
•producesSHORT-LIVEDresponses
•nervecells(neurones)linkreceptortoeffectorcells
•receptorcellsarefoundin...eyes
skin
ears
•effectorcellsarefoundin...muscles
glands
•receptorcellsdetectstimuli
•effectorcellsrespondtostimuli
•examples...touchingahotplate
puttingyourhandonadrawingpin
lookingatabrightlight
COMMUNICATIONSYSTEMS
TheseareinvolvedinmaintainingaconstantinternalenvironmentorHOMEOSTASIS
HORMONALCOMMUNICATION
•involveschemicals(hormones)whichtravelintheblood
•producesSLOWandLONG-LASTINGresponses
THYROIDGLANDmakesahormonethatcontrols
chemicalreactionsinthebody
PANCREASmakesinsulinforcontrolling
blood-sugarlevels
ADRENALmakeadrenalinewhichspeedsup
GLANDSheartbeatandbreathingrate
TESTES(Male)maketestosteronewhichcauses
bodychangesatpuberty
OVARIES(Female)makeoestrogenand
progesteronewhichcausebody
changesatpubertyandcontrol
themenstrualcycle
•competitionbetweenspeciesexistsinthesamehabitat
•changesaffectingonespeciescanaffectanother
•rapidchangesintheenvironmentcancauseextinction
if...environmentalconditionschange
anewcompetitororanewpredatorarrives
anotherspeciesinthefoodwebbecomesextinct
anewdiseaseappears
•humanactivitycancauseaspeciestobecomeextinct...
DIRECTLY-beinghuntedtoextinction
(passengerpigeon,greatauk)
INDIRECTLY-havingtheirhabitatdestroyed
(treescutdownorhousesbuilt)
-bringingnewspeciesintoahabitat
(greysquirrels,mink)
AFOODWEB
Removingonespeciesfromthewebcanaffectothers
Ifthereisashortageofrabbits,hawkswillhuntthrushes
foxeswillhavetoeatmice
grasswillgrowbetter
SURVIVEORDIE!
Livingorganismsaredependantontheenvironmentandotherspeciesforsurvival
HAWKFOXOWL
THRUSH
WHEATGRASSLETTUCE
MOUSERABBITSLUGFINCH