BIOLOGY 111. CHAPTER 7: Darwinian Evolution

Transcription

1 BIOLOGY 111 CHAPTER 7: Darwinian Evlutin

2 BIOLOGY 101 CHAPTER 7a: Evlutin: Descent with Mdificatin

3 Evlutin: Descent with Mdificatin CONCEPTS: 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life. Descent with Mdificatin includes bth Micrevlutin and Macrevlutin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence

4 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species The times f Charles Darwin were steeped in the belief that Earth was a yung and unchanging planet The Greek philspher Aristtle ( A.D.) ppsed any cncept f evlutin and viewed species as fixed and unchanging. Aristtle believed that all living frms culd be arranged n a ladder f increasing cmplexity (scala naturae) with perfect, permanent species n every rung.

5 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species Darwin s revlutinary ideas had their rts in the wrk f many ther individuals, as well as events that shaped his life Darwin s views were influenced by fssils, remains r traces f rganisms frm the past mineralized in sedimentary rcks Fssils within layers f sedimentary rck shw that a successin f rganisms have ppulated Earth thrughut time

6 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species Palentlgy, the study f fssils, was largely develped by the French anatmist Gerges Cuvier ( ). In examining rck strata in the Paris Basin, Cuvier nted that the lder the strata, the mre dissimilar the fssils frm mdern life Cuvier recgnized that extinctin had been a cmmn ccurrence in the histry f life. Instead f evlutin, Cuvier advcated catastrphism, speculating that bundaries between strata were due t lcal flds r drughts that destryed the species then present. He suggested that the denuded areas were later reppulated by species immigrating frm unaffected areas

7 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species Later, gelgist Charles Lyell ( ) prpsed a thery f unifrmitarianism, which held that gelgic prcesses had nt changed, and cntinued thrughut Earth s histry. Als knwn as the Dctrine f Unifrmity, it is the assumptin that the same natural laws and prcesses that perate nw have always perated in the universe in the past and apply everywhere Lyell s bservatins and theries had a strng influence n Darwin. First, if gelgic changes result frm slw, cntinuus prcesses rather than sudden events, then the Earth must be far lder than the few thusand suggested by schlars f that time Secnd, slw and subtle prcesses persisting fr lng perids f time can als act n living rganisms, prducing substantial change ver a lng perid f time.

8 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species In 1809, French bilgist Jean-Baptiste de Lamarck ( ) published a thery f evlutin based n his bservatins f fssil invertebrates in the cllectins f the Natural Histry Museum f Paris. By cmparing fssils and current species, Lamarck fund what appeared t be several lines f descent

9 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species Lamarck explained his bservatins with tw principles: use and disuse f parts and the inheritance f acquired characteristics. Use and disuse was the cncept that bdy parts that are used extensively becme larger and strnger, while thse that are nt used deterirate The inheritance f acquired characteristics stated that mdificatins acquired during the life f an rganism can be passed n t ffspring. (n mechanism was prvided fr this)

10 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species Lamarck explained his bservatins with tw principles: use and disuse f parts and the inheritance f acquired characteristics. Use and disuse was the cncept that bdy parts that are used extensively becme larger and strnger, while thse that are nt used deterirate The inheritance f acquired characteristics stated that mdificatins acquired during the life f an rganism can be passed n t ffspring. A classic example is the lng neck f the giraffe. Lamarck reasned that the lng, muscular neck f the mdern giraffe evlved ver many generatins as the ancestrs f giraffes reached fr leaves n higher branches and passed this characteristic n t their ffspring.

11 Evlutin: Descent with Mdificatin 7.1 The Darwinian revlutin challenged traditinal views f a yung Earth inhabited by unchanging species Lamarck explained his bservatins with tw principles: use and disuse f parts and the inheritance f acquired characteristics. Lamarck believed that if simple rganisms did nt survive, they wuld simply reappear by spntaneus generatin. Lamarck saw spntaneus generatin as an nging prcess, with the simple rganisms being recreated as mre cmplex rganisms that pssessed characteristics respnsible fr the demise f their parents

12 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life Charles Darwin ( ) was brn in Shrewsbury in western England. When Darwin was 16, his father sent him t the University f Edinburgh t study medicine. Darwin left Edinburgh withut a degree and enrlled at Cambridge University with the intent f becming a clergyman. At that time, mst naturalists and scientists belnged t the clergy. After graduatin, Darwin jined the crew f the survey ship HMS Beagle as ship naturalist and cnversatin cmpanin t Captain Rbert FitzRy. FitzRy chse Darwin because he was educated, a skilled naturalist, and because his age and scial class were similar t thse f the captain.

13 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life The Vyage f the Beagle Darwin embarked frm England n the Beagle in December The primary missin f the five-year vyage f the Beagle was t chart prly knwn stretches f the Suth American castline Darwin cllected thusands f specimens f the extic and diverse flra and fauna f Suth America. He explred the Brazilian jungles, the grasslands f the Argentine pampas, the deslatin f Tierra del Fueg near Antarctica, and the heights f the Andes.

14 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life While n the Beagle, Darwin read Lyell s Principles f Gelgy. Darwin experienced gelgic change firsthand when a vilent earthquake rcked the cast f Chile, causing the castline t rise by several feet. He fund fssils f cean rganisms high in the Andes and inferred that the rcks cntaining the fssils had been raised there by a series f similar earthquakes These bservatins reinfrced Darwin s acceptance f Lyell s ideas and led him t dubt the traditinal view f a yung and static Earth.

15 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life Darwin s interest in the gegraphic distributin f species was further stimulated by the Beagle s visit t the Galápags Islands, a grup f yung vlcanic islands 900 km west f the Suth American cast. Darwin was fascinated by the unusual rganisms fund there. Darwin nted that while mst f the animal species n the Galápags lived nwhere else, they resembled species living n the Suth American mainland. He later hypthesized that the islands had been clnized by plants and animals frm the mainland that had subsequently diversified n the different islands

16 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life Darwin s Fcus n Adaptatin: During his travels, Darwin bserved many examples f adaptatins, characteristics f rganisms that enhance their survival and reprductin in specific envirnments. After his return t Great Britain in 1836, Darwin began t perceive that the rigin f new species and the adaptatin f species t their envirnment were clsely related prcesses.

17 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life Culd a new species arise frm an ancestral frm by the gradual accumulatin f adaptatins t a different envirnment? Fr example, clear differences in the beaks amng the 13 species f finches that Darwin cllected in the Galápags are adaptatins t the specific fds available n their hme islands. Darwin explained that adaptatins arise by natural selectin, a prcess in which individuals with favrable inherited characteristics leave mre ffspring than individuals with ther characteristics.

18 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life By the early 1840s, Darwin had develped the majr features f his thery f natural selectin as the mechanism fr evlutin. He based this idea n the principles f artificial selectin, specifically, the selective breeding f dgs Artificial Selectin is when desired alleles are increased in a ppulatin thrugh selective breeding

19 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life By the early 1840s, Darwin had develped the majr features f his thery f natural selectin as the mechanism fr evlutin. In 1844, Darwin wrte a lng essay n the rigin f species and natural selectin, but he was reluctant t publish and cntinued t cmpile evidence t supprt his thery.

20 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life In June 1858, Alfred Russel Wallace ( ), a yung naturalist wrking in the Suth Pacific islands f the Malay Archipelag, sent Darwin a manuscript cntaining a hypthesis f natural selectin essentially identical t Darwin s. Later that year, bth Wallace s paper and extracts f Darwin s essay were presented t the Linnaean Sciety f Lndn.

21 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life Darwin quickly finished The Origin f Species and published it the next year. Althugh bth Darwin and Wallace develped similar ideas independently, the Thery f Evlutin by Natural Selectin is attributed t Darwin because he develped his ideas earlier and supprted the thery much mre extensively. Wallace s wrk lacked the depth f Darwin s wrk The thery f evlutin by natural selectin was presented in The Origin f Species with immaculate lgic and an avalanche f supprting evidence.

22 Evlutin: Descent with Mdificatin 7.2 Descent with mdificatin by natural selectin explains the adaptatins f rganisms and the unity and diversity f life The Origin f Species Darwin never used the wrd evlutin in the first editin f The Origin f Species, althugh the final wrd f the bk is evlved. Instead Darwin used the phrase descent with mdificatin. All rganisms are related thrugh descent frm a cmmn ancestr that lived in the remte past. As a result, rganisms share many characteristics, explaining the unity f life. Over evlutinary time, the descendants f that cmmn ancestr have accumulated diverse mdificatins, r adaptatins, that allw them t survive and reprduce in specific habitats. Over lng perids f time, descent with mdificatin has led t the rich diversity f life we see tday.

23 Evlutin f Ppulatins: Alleles Change 7.4 Genetic Variatin Makes Evlutin Pssible The cmbined cncepts f Cmmn Descent with Mdificatin and Natural Selectin led t Darwin s Thery f Evlutin by Natural Selectin Cre Principles f the Thery f Evlutin by Natural Selectin: 1. Cmmn Descent with Mdificatin 2. Natural Selectin

24 Evlutin f Ppulatins: Alleles Change 7.4 Genetic Variatin Makes Evlutin Pssible Cmmn Descent With Mdificatin states that ppulatins change ver time, and that these changes are inherited Micrevlutin is defined as a change in allele frequencies in a ppulatin ver time.

25 Evlutin f Ppulatins: Alleles Change 7.4 Genetic Variatin Makes Evlutin Pssible Cmmn Descent With Mdificatin states that ppulatins change ver time, and that these changes are inherited and smetimes lead t the frmatin f new species Micrevlutin is defined as a change in allele frequencies in a ppulatin ver time. Macrevlutin is when these changes lead t frmatin f a new species Natural Selectin is the frce that acts upn these changes (variatin) and favrs traits that give a reprductive advantage

26 Evlutin: Descent with Mdificatin Timeline:

27 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence In The Origin f Species, Darwin presented a brad range f evidence t supprt the cncept f descent with mdificatin. Fur types f data dcument the pattern f evlutin and tell us abut the prcesses by which it ccurs: direct bservatins f evlutin, hmlgy, the fssil recrd and bigegraphy The strngest evidence cmes frm genetic research. This evidence demnstrates hw single genetic mutatins have led t the adaptatins leading t rganismal success They als clearly demnstrate the evlutinary mechanisms that drive the transitins f ne structure int anther like the transitins f fish fins int the legs f tetrapds

28 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence Direct Observatins f Evlutinary Change: Bilgists have dcumented evlutinary change in thusands f scientific studies We will cnsider tw examples f natural selectin as a mechanism f evlutin in ppulatins. What happens when a ppulatin f herbivrus insects feeds n plants with different defenses frm their preferred fd surce? Sapberry bugs use their beak, a hllw, needle-like muthpart, t feed n seeds lcated within the fruits f varius plants.

29 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence In Suthern Flrida, ne type f sapberry bug feeds n the seeds f a native plant, the balln vine In Central Flrida, balln vines are rare. Instead, sapberry bugs feed n gldenrain tree, an intrduced species frm Asia. Sapberry bugs feed mst effectively when their beak length clsely matches the size f the seed-cntaining fruit. (lnger beaks fr larger seeds) Gldenrain tree fruits are smaller than the native balln vine fruits, leading Sctt Carrll and clleagues t predict that in ppulatins that feed n gldenrain tree, natural selectin wuld result in beaks that are shrter than thse in ppulatins that feed n balln vine. Indeed, beak lengths are shrter in the ppulatins that feed n gldenrain tree.

30 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence Researchers have als studied beak length evlutin in sapberry bug ppulatins that feed n plants intrduced t Luisiana, Oklahma, and Australia. In each lcatin, the fruits f the intrduced plants were larger than the fruits f the native plants. Researchers predicted that natural selectin wuld result in the evlutin f lnger beak lengths in these sapberry bug ppulatins. Data cllected in field studies upheld this predictin. In Australia, the increase in beak length nearly dubled the success with which sapberry bugs culd eat the seeds f the intrduced species. Since the gldenrain tree reached central Flrida just 35 years befre the scientific studies were initiated, natural selectin caused rapid evlutin in a wild ppulatin.

31 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence A secnd example f nging natural selectin is the evlutin f drug-resistant pathgens (disease-causing rganisms). The evlutin f drug resistance is a particular prblem in bacteria and viruses, which exhibit rapid rates f reprductin. Many peple harbr the bacterium Staphylcccus aureus n their skin r in their nasal passages with n negative effects. Sme genetic strains f this species, knwn as methicillin-resistant S. aureus (MRSA), are frmidable pathgens. Virulent frms f MRSA such as clne USA300 can cause flesh-eating disease and ptentially fatal infectins. Hw did clne USA300 and ther strains f MRSA becme s dangerus?

32 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence In 1943, penicillin became the first widely used antibitic. By 1945, mre than 20% f S. aureus in hspitals were already resistant t penicillin These bacteria had an enzyme, penicillinase, which culd destry penicillin. Researchers develped antibitics that were nt destryed by penicillinase, but sme S. aureus ppulatins develped resistance t each new drug within a few years. In 1959, dctrs began using the pwerful antibitic methicillin, but within tw years, methicillin-resistant strains f S. aureus appeared.

33 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence Hw did these resistant strains emerge? Methicillin wrks by deactivating a prtein that bacteria use t synthesize their cell walls. Sme individual bacteria were able t synthesize their cell walls using a different prtein that was nt affected by methicillin. These individuals survived the methicillin treatments and reprduced at higher rates than did ther individuals. Over time, these resistant individuals became increasingly cmmn, leading t the spread f MRSA. Sme MRSA strains are resistant t multiple antibitics, due in part t the fact that bacteria can exchange genes with members f their wn and ther species

34 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence The examples f the sapberry bug and drug-resistant S. aureus highlight tw imprtant pints abut natural selectin. 1. Natural selectin is an editing mechanism, nt a creative frce.

35 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence The examples f the sapberry bug and drug-resistant S. aureus highlight tw imprtant pints abut natural selectin. 1. Natural selectin is an editing mechanism, nt a creative frce. It can act nly n existing variatin in the ppulatin; it cannt create favrable traits, it selects fr favrable traits that are already present in the ppulatin. 2. Natural selectin favrs traits that increase fitness in the current, lcal envirnment. What is adaptive in ne situatin is nt adaptive in anther. Beak lengths evlve that match the size f the typical fruit eaten by a particular sapberry bug ppulatin. But beak lengths suitable fr fruits f ne size can be disadvantageus when feeding n fruits f anther size.

36 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence Hmlgy: Mre evidence fr evlutin cmes frm similarities in the characteristics f different rganisms. Descent with mdificatin can explain why certain traits in related species have an underlying similarity even if they have very different functins. Characteristics present in an ancestral rganism are altered (by natural selectin) in its descendants ver time as they face different envirnmental cnditins.

37 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence Hmlgy: Similarity in characteristic traits frm cmmn ancestry is knwn as hmlgy. Fr example, the frelimbs f human, cats, whales, and bats share the same skeletal elements, even thugh the appendages have very different functins. These frelimbs are hmlgus structures that represent variatins n the ancestral tetrapd frelimb.

38 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence Hmlgies that are nt bvius in adult rganisms may becme evident when we lk at embrynic develpment. Fr example, at sme stage in their develpment, all vertebrate embrys have a tail psterir t their anus, as well as structures called pharyngeal puches in their thrat. The hmlgus thrat puches develp int very different adult structures, such as the gills f fish r parts f the ears and thrat in humans and ther mammals.

39 Evlutin: Descent with Mdificatin 7.3 Evlutin is supprted by an verwhelming amunt f scientific evidence The Fssil Recrd and Bigegraphy: The fssil recrd dcuments the pattern f evlutin, shwing that past rganisms differed frm present-day rganisms and that many species have becme extinct. Over lnger time scales, fssils dcument the rigin f majr grups f rganisms and the evlutinary changes within these grups. Bigegraphy is the gegraphic distributin f species. Frm ur understanding f evlutin and cntinental drift, we can predict where fssils f varius types f rganisms might be fund There is a tremendus amunt f evidence in bth areas in supprt f Darwin s theries and what we understand as evlutin