The Macroevolutionary Puzzle

Chapter 19

Macroevolution

The large-scale patterns, trends, and rates of change among

families and other more inclusive groups of species

19.1 Fossils

• Recognizable evidence of ancient life

• What do fossils tell us?– Each species is a mosaic of ancestral and

novel traits

– All species that ever evolved are related to one another by way of descent

Stratification

• Fossils are found in sedimentary

rock

• This type of rock is formed in layers

• In general, layers closest to the top

were formed most recently

Fossilization

• Organism becomes buried in ash or sediments

• Organic remains become infused with metal and mineral ions

• Carbon 14 dating

Figure 19.6Page 309

19.2 Geologic Time Scale

• Boundaries based on transitions in fossil record

Cambrian period

Proterozoic eon2,500myaArchean eon and earlier

Ordovician period

Silurian period

Devonian period

570

505

435

410

Carboniferous period

Permian period

Cretaceous period

Tertiary period

Quaternary period

370

290

210

205

138

65

1

Cambrian period

Jurassic period

Triassic period

Paleozoic era

Mesozoic era

Cenozoic era

Phanerozoic eon

Figure 19.4 (2)Page 308

19.3 Continental Drift

• Idea that the continents were once joined and have since “drifted” apart

• Initially based on the shapes

• Wegener refined the hypothesis and named the theoretical supercontinent Pangea

Changing Land Masses

10 mya65 mya260 mya420 mya

Figure 19.8cPage 311

Evidence of Movement

• Wegener cited evidence from glacial deposits and fossils

• Magnetic orientations in ancient rocks do not align with the magnetic poles

• Discovery of seafloor spreading provided a possible mechanism

Plate Tectonics

• Earth’s crust is fractured into plates

• Movement of plates driven by upwelling of molten rock

Pacific

plate

Nazca

plate

North

American

plate

South

American

plate

Eurasian

plate

African

plate

Somali

plate

Pacific

plate

Indo-

Australian

plate

Antarctic plate

Figure 19.8bPage 311

19.4 Comparative Morphology

• Comparing body forms and structures of

major lineages

• Guiding principle:

– When it comes to introducing change in

morphology, evolution tends to follow the

path of least resistance

Morphological Divergence

• Change from body form of a common ancestor

• Produces homologous structures

1

1

1

1

1

1

2

2

2

2

2

2

2

3

3

3

3

3

3

3

4

4

4

4

4

5

5

5

5

early reptile

pterosaur

chicken

bat

porpoise

penguin

human

Figure 19.10Page 312

Morphological Convergence

• Individuals of different lineages evolve in similar ways under similar environmental pressures

• Produces analogous structures that serve similar functions

19.5 Comparative Development

• Each animal or plant proceeds through a

series of changes in form

• Similarities in these stages may be clues

to evolutionary relationships

• Mutations that disrupt a key stage of

development are selected against

Altering Developmental Programs

• Some mutations shift a step in a

way that natural selection favors

• Small changes at key steps may

bring about major differences

• Insertion of transposons or gene

mutations

Development of Larkspurs

• Two closely related species have different petal morphology

• They attract different pollinators

front viewside view

D. decorum flower

front viewside view

D. nudicaule flower

Figure 19.12Page 314

Development of Larkspurs

• Petal difference arises from a change in the rate of petal development

00 10 20 40

2

4

6

Pet

al le

ng

th (

mill

imet

ers)

Days (after onset of meiosis)

D. decorum

D. nudicaule

Figure 19.12Page 314

Similar Vertebrate Embryos

• Alterations that disrupted early development have been selected against

FISH REPTILE BIRD MAMMAL

Figure 19.13aPage 315

Similar Vertebrate Embryos

Adult shark

Early human embryo

Two-chambered heart

Aortic arches

Certain veins

Figure 19.13bPage 315

Developmental Changes

• Changes in the onset, rate, or time of

completion of development steps can

cause allometric changes

• Adult forms that retain juvenile

features

Proportional Changes in Skull

Chimpanzee

Human

Figure 19.14bPage 315

19.6 Comparative Biochemistry

• Kinds and numbers of biochemical traits that species share is a clue to how closely they are related

• Can compare DNA, RNA, or proteins

• More similarity means species are more closely related

Comparing Proteins

• Compare amino acid sequence of proteins

produced by the same gene

• Human cytochrome c (a protein)

– Identical amino acids in chimpanzee protein

– Chicken protein differs by 18 amino acids

– Yeast protein differs by 56

Sequence Conservation

• Cytochrome c functions in electron

transport

• Deficits in this vital protein would be

lethal

• Long sequences are identical in wheat,

yeast, and a primate

Sequence Conservation

YeastWheatPrimate

Figure 19.15Page 316-317

Nucleic Acid Comparison

• Use single-stranded DNA or RNA

• Hybrid molecules are created, then heated

• The more heat required to break hybrid, the more closely related the species

Molecular Clock

• Assumption: “Ticks” (neutral mutations) occur at a constant rate

• Count the number of differences to estimate time of divergence

19.7 Taxonomy

• Field of biology concerned with

identifying, naming, and classifying

species

• Somewhat subjective

• Information about species can be

interpreted differently

Binomial System

• Devised by Carl von Linne

• Each species has a two-part

Latin name

• First part is generic

• Second part is specific name

Higher Taxa

• Kingdom

• Phylum

• Class

• Order

• Family

• Inclusive groupings meant to reflect relationships among species

Phylogeny

• The scientific study of evolutionary relationships among species

• Practical applications– Allows predictions about the needs or

weaknesses of one species on the basis of its known relationship to another

Examples of Classification

Kingdom

Genus

Species

Family

Order

Class

Phylum

Plantae

Zea

Z. mays

Poaceae

Poales

Monocotyledonae

Anthophyta

Plantae

Vanilla

V. planifolia

Orchidaceae

Asparagales

Monocotyledonae

Anthophyta

Animalia

Musca

M. domestica

Muscidae

Diptera

Insecta

Anthropoda

Animalia

Homo

H. sapiens

Hominidae

Primates

Mammalia

Chordata

corn vanilla orchid housefly human

Figure 19.17Page 318

A Cladogram

heart

lungs

feathersfur

shark mammal crocodile bird

Five-Kingdom Scheme

• Proposed in

1969 by Robert

Whittaker

Monera

Protista

Fungi

Plantae

Animalia

Three-Domain Classification

• Favored by microbiologists

EUBACTERIA ARCHAEBACTERIA EUKARYOTES

Six-Kingdom Scheme

EUBACTERIA ARCHAEBACTERIA PROTISTA FUNGI PLANTAE ANIMALIA