26- biological diversity text

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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 26

The Tree of Life

An Introduction toBiological Diversity




• Overview: Changing Life on a Changing Earth

• Life is a continuum

– Extending from the earliest organisms to thegreat variety of species that exist today




• Geological events that alter environments

– Change the course of biological evolution

• Conversely, life changes the planet that itinhabits

Figure 26.1




• Geologic history and biological history have

been episodic – Marked by what were in essence revolutions

that opened many new ways of life




• Concept 26.1: Conditions on early Earth made

the origin of life possible• Most biologists now think that it is at least a

credible hypothesis

– That chemical and physical processes on earlyEarth produced very simple cells through asequence of stages

• According to one hypothetical scenario

– There were four main stages in this process




Synthesis of Organic Compounds on Early Earth

• Earth formed about 4.6 billion years ago

– Along with the rest of the solar system

• Earth’s early atmosphere

– Contained water vapor and many chemicalsreleased by volcanic eruptions


http://slidepdf.com/reader/full/26-biological-diversity-text 7/65Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

As material circulated through the apparatus,Miller and Urey periodically collected samples for analysis. Theyidentified a variety of organic molecules, including amino acids suchas alanine and glutamic acid that are common in the proteins of organisms. They also found many other amino acids and complex,oily hydrocarbons.

RESULTS

Figure 26.2

Miller and Urey set up a closed system in their laboratory to simulate conditions thought to have existed on earlyEarth. A warmed flask of water simulated the primeval sea. Thestrongly reducing “atmosphere” in the system consisted of H 2,methane (CH 4), ammonia (NH 3), and water vapor. Sparks weredischarged in the synthetic atmosphere to mimic lightning. Acondenser cooled the atmosphere, raining water and any dissolvedcompounds into the miniature sea.

EXPERIMENT Electrode

Condenser

Cooled water containingorganicmoleculesH2O

Sample for

chemical analysis

Coldwater

Water vapor CH 4

H 2N H 3

CONCLUSION Organic molecules, a first step in the origin of life, can form in a strongly reducing atmosphere.

• Laboratory experiments simulating an early

Earth atmosphere – Have produced organic molecules from

inorganic precursors, but the existence of such

an atmosphere on early Earth is unlikely



Extraterrestrial Sources of Organic Compounds

• Some of the organic compounds from which

the first life on Earth arose – May have come from space

• Carbon compounds

– Have been found in some of the meteoritesthat have landed on Earth



Looking Outside Earth for Clues About the Origin of Life

• The possibility that life is not restricted to Earth

– Is becoming more accessible to scientifictesting



Abiotic Synthesis of Polymers

• Small organic molecules

– Polymerize when they are concentrated on hotsand, clay, or rock



Protobionts

• Protobionts

– Are aggregates of abiotically producedmolecules surrounded by a membrane or membrane-like structure



• Laboratory experiments demonstrate that

protobionts – Could have formed spontaneously from

abiotically produced organic compounds

• For example, small membrane-boundeddroplets called liposomes

– Can form when lipids or other organicmolecules are added to water



20 µm

(a) Simple reproduction. This lipo-some is “giving birth” to smaller liposomes (LM).

(b) Simple metabolism. If enzymes—in this case,phosphorylase and amylase—are included in thesolution from which the droplets self-assemble,some liposomes can carry out simple metabolicreactions and export the products.

Glucose-phosphate

Glucose-phosphate

Phosphorylase

Starch

Amylase

Maltose

Maltose

Phosphate

Figure 26.4a, b




The “RNA World” and the Dawn of Natural Selection

• The first genetic material

– Was probably RNA, not DNA




• RNA molecules called ribozymes have been

found to catalyze many different reactions,including

– Self-splicing

– Making complementary copies of shortstretches of their own sequence or other shortpieces of RNA

Figure 26.5

Ribozyme(RNA molecule)

Template

Nucleotides

Complementary RNA copy

3′

5 ′ 5′




• Early protobionts with self-replicating, catalytic

RNA – Would have been more effective at using

resources and would have increased innumber through natural selection




• Concept 26.2: The fossil record chronicles life

on Earth• Careful study of fossils

– Opens a window into the lives of organismsthat existed long ago and provides informationabout the evolution of life over billions of years




How Rocks and Fossils Are Dated

• Sedimentary strata

– Reveal the relative ages of fossils




• Index fossils

– Are similar fossils found in the same strata indifferent locations

– Allow strata at one location to be correlatedwith strata at another location

Figure 26.6




• The absolute ages of fossils

– Can be determined by radiometric dating

Figure 26.7

1 2 3 4

Accumulating“daughter”

isotope

R a

t i o o f p a r e n

t i s o t o p e

t o d a u g

h t e r

i s o t o p e

Remaining“parent”isotope

1

1

11

Time (half-lives)

2

4

816




• The magnetism of rocks

– Can also provide dating information

• Magnetic reversals of the north and southmagnetic poles

– Have occurred repeatedly in the past

– Leave their record on rocks throughout the

world




• The geologic record is divided into

– Three eons: the Archaean, the Proterozoic,and the Phanerozoic

– Many eras and periods

• Many of these time periods

– Mark major changes in the composition of

fossil species




• The geologic record

Table 26.1




Mass Extinctions

• The fossil record chronicles a number of occasions

– When global environmental changes were sorapid and disruptive that a majority of specieswere swept away

Figure 26.8

C a m

b r i a n

P r o

t e r o z o

i c e o n

O r d o v i c i a n

S i l u r i a n

D e v o n

i a n

C a r b o n

i f e r o u s

P e r m

i a n

T r i a s s i c

J u r a s s i c

C r e

t a c e o u s

P a

l e o g e n e

N e o g e n e

N um

b er

of f ami l i e

s (

)

Number of taxonomic

familiesExtinction rate

Cretaceousmass extinction

Permian massextinction

Millions of years ago

E x t i n c t i o n r a

t e (

)

Paleozoic Mesozoic

0

20

60

40

80

100600 500 400 300 200 100 0

2,500

1,500

1,000

500

0

2,000

Ceno-zoic




• The Cretaceous extinction

– Doomed many marine and terrestrialorganisms, most notably the dinosaurs

– Is thought to have been caused by the impact

of a large meteor

Figure 26.9

NORTHAMERICA

Chicxulubcrater

Yucatán

Peninsula




• Much remains to be learned about the causesof mass extinctions

– But it is clear that they provided life withunparalleled opportunities for adaptiveradiations into newly vacated ecological niches




• The analogy of a clock

– Can be used to place major events in theEarth’s history in the context of the geologicalrecord

Figure 26.10

Land plants

Animals

Multicellular eukaryotes

Single-celledeukaryotes

Atmosphericoxygen

Prokaryotes

Origin of solar system andEarth

Humans

Ceno-zoic

M e s o -

z o i c

P a l e o z o

i c

ArchaeanEonBillions of years ago

ProterozoicEon

1

2 3

4




• Concept 26.3: As prokaryotes evolved, theyexploited and changed young Earth

• The oldest known fossils are stromatolites

– Rocklike structures composed of many layersof bacteria and sediment

– Which date back 3.5 billion years ago



h i k




The First Prokaryotes

• Prokaryotes were Earth’s sole inhabitants

– From 3.5 to about 2 billion years ago

El T S




Electron Transport Systems

• Electron transport systems of a variety of types

– Were essential to early life

– Have: some aspects that possibly precede lifeitself

Ph h i d h O R l i




Photosynthesis and the Oxygen Revolution

• The earliest types of photosynthesis

– Did not produce oxygen




• Oxygenic photosynthesis

– Probably evolved about 3.5 billion years ago incyanobacteria

Figure 26.12




• Concept 26.4: Eukaryotic cells arose fromsymbioses and genetic exchanges betweenprokaryotes

• Among the most fundamental questions in

biology – Is how complex eukaryotic cells evolved from

much simpler prokaryotic cells

Th Fi t E k t




The First Eukaryotes

• The oldest fossils of eukaryotic cells

– Date back 2.1 billion years

Endosymbiotic Origin of Mitochondria and Plastids




Endosymbiotic Origin of Mitochondria and Plastids

• The theory of endosymbiosis

– Proposes that mitochondria and plastids wereformerly small prokaryotes living within larger host cells




• The prokaryotic ancestors of mitochondria andplastids

– Probably gained entry to the host cell asundigested prey or internal parasites

Figure 26.13

CytoplasmDNA

Plasmamembrane

Ancestralprokaryote

Infolding of plasma membrane

Endoplasmicreticulum

Nuclear envelope

Nucleus

Engulfingof aerobic

heterotrophicprokaryote Cell with nucleus

and endomembranesystem

Mitochondrion

Ancestralheterotrophiceukaryote Plastid

Mitochondrion

Engulfing of photosyntheticprokaryote insome cells

AncestralPhotosyntheticeukaryote




• In the process of becoming moreinterdependent

– The host and endosymbionts would havebecome a single organism




• The evidence supporting an endosymbioticorigin of mitochondria and plastids includes

– Similarities in inner membrane structures andfunctions

– Both have their own circular DNA

Eukaryotic Cells as Genetic Chimeras




Eukaryotic Cells as Genetic Chimeras

• Additional endosymbiotic events and horizontalgene transfers

– May have contributed to the large genomesand complex cellular structures of eukaryoticcells




• Some investigators have speculated thateukaryotic flagella and cilia

– Evolved from symbiotic bacteria, based onsymbiotic relationships between some bacteriaand protozoans

Figure 26.14

50 µ m




• Concept 26.5: Multicellularity evolved severaltimes in eukaryotes

• After the first eukaryotes evolved

– A great range of unicellular forms evolved

– Multicellular forms evolved also

The Earliest Multicellular Eukaryotes




The Earliest Multicellular Eukaryotes

• Molecular clocks

– Date the common ancestor of multicellular eukaryotes to 1.5 billion years

• The oldest known fossils of eukaryotes

– Are of relatively small algae that lived about1.2 billion years ago




• Larger organisms do not appear in the fossilrecord

– Until several hundred million years later

• Chinese paleontologists recently described570-million-year-old fossils

– That are probably animal embryos

Figure 26.15a, b150 µm 200 µm

(a) Two-cell stage (b) Later stage

The Colonial Connection




The Colonial Connection

• The first multicellular organisms were colonies

– Collections of autonomously replicating cells

Figure 26.1610 µ m




• Phyla of two animal phyla, Cnidaria andPorifera

– Are somewhat older, dating from the lateProterozoic

Figure 26.17

EarlyPaleozoicera(Cambrianperiod)

M i l l i o n s o

f y e a r s a g o

500

542

LateProterozoiceon

S p o n g e s

C n

i d a r i a n s

E c h

i n o

d e r m s

C h o r d a

t e s

B r a c h

i o p o

d s

A n n e

l i d s

M o

l l u s c s

A r t h r o p o

d s




• Molecular evidence

– Suggests that many animal phyla originatedand began to diverge much earlier, between1 billion and 700 million years ago

Colonization of Land by Plants, Fungi, and Animals




Colonization of Land by Plants, Fungi, and Animals

• Plants, fungi, and animals

– Colonized land about 500 million years ago




• Symbiotic relationships between plants andfungi

– Are common today and date from this time

Continental Drift




Continental Drift

• Earth’s continents are not fixed

– They drift across our planet’s surface on greatplates of crust that float on the hot underlyingmantle




• Often, these plates slide along the boundary of other plates

– Pulling apart or pushing against each other

Figure 26.18

NorthAmericanPlate

CaribbeanPlate

Juan de FucaPlate

Cocos Plate

PacificPlateNazcaPlate

SouthAmericanPlate

AfricanPlate

Scotia Plate AntarcticPlate

ArabianPlate

Eurasian Plate

PhilippinePlate

IndianPlate

AustralianPlate




• Many important geological processes

– Occur at plate boundaries or at weak points inthe plates themselves

Volcanoes andvolcanic islands

TrenchOceanic ridge

O c e a n i c c r u s t

S e a f l o o r s p r e a d i n g

S u b d u c t i o n z o n e

Figure 26.19




• The formation of the supercontinent Pangaeaduring the late Paleozoic era

– And its breakup duringthe Mesozoic era explainmany biogeographic puzzles

Figure 26.20

India collided withEurasia just 10 millionyears ago, forming theHimalayas, the tallestand youngest of Earth’smajor mountainranges. The continentscontinue to drift.

By the end of theMesozoic, Laurasiaand Gondwanaseparated into thepresent-day continents.

By the mid-Mesozoic,Pangaea split intonorthern (Laurasia)and southern(Gondwana)landmasses.

C e n o z o i c

N o r t h A m e r i c a Eurasia

AfricaSouth

AmericaIndia

Madagascar

AntarcticaA u s

t r a l i a

Laurasia

M e s o z o i c

G o n d w a n a

At the end of thePaleozoic, all of Earth’s landmasseswere joined in thesupercontinentPangaea.

P a n g a e

a

P a l e o z o i c

251

135

65.5

0

M i l l i o n s o

f y e a r s a g o




• Concept 26.6: New information has revised our understanding of the tree of life

• Molecular Data

– Have provided new insights in recent decadesregarding the deepest branches of the tree of life




• Robert Whittaker proposed a system with fivekingdoms

– Monera, Protista, Plantae, Fungi, and Animalia

Figure 26.21

Plantae Fungi Animalia

Protista

Monera

E u k a r y o

t e s

P r o k a r

y o t e s



B r y o p

h y t e s

( m o s s e s ,

l i v e r w o r t s ,

h o r n w o r t s )

Plants

Fungi

Animals

S e e

d l e s s v a s c u

l a r p

l a n

t s ( f e r n s )

G y m n o s p e r m s

A n g

i o s p e r m s

A m o e

b o z o a n s

( a m o e

b a s , s l i m e m o

l d s )

C h y t r i d s

Z y g o

t e f u n g

i

A r b u s c u

l a r m y c o r r h

i z a l f u n g

i

S a c

f u n g

i

C l u b f u n g

i

C h o a n o

f l a g e

l l a t e s

S p o n g e s

C n

i d a r i a n s

( j e l l i e s , c o r a

l )

B i l a t e r a

l l y s y m m e

t r i c a l a n i m a

l s ( a n n e

l i d s ,

a r t h r o p o

d s , m o

l l u s c s , e c h

i n o

d e r m s ,

v e r t e

b r a

t e s )

Chapter 29 Chapter 30 Chapter 28 Chapter 31 Chapter 32 Chapters 33, 34

26- biological diversity text

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