Starr & Taggart – 11th Edition

Evolutionary Patterns, Rates, and Trends

AP Biology: Chapter 19

Chapter 19

Key Concepts:

All species that have ever lived are related

Macroevolution refers to patterns, trends, and rates of change among lineages over geologic time

Fossil and geologic records and radiometric dating of rocks provide evidence of macroevolution

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Key Concepts: Anatomical comparisons help

reconstruct patterns of change through time

Biochemical comparisons also provide evidence of macroevolution

Diversity characterizes the distribution of species through time

Taxonomy is concerned with identifying and naming new species

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Macroevolution Large scale patterns,

trends and rates of change among families and other more inclusive groups of species.

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What is a Species?

A mixed herd of zebroids & horses. Zebroids – are interspecies hybrids (horses & zebras)

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What is a Species?

Morphological Species Concept Based on appearance alone

Biological Species Concept A species is one or more

populations of individuals that are interbreeding under natural conditions and producing fertile offspring, and are reproductively isolated from other such populations

Two plants of the same species

♂ & ♀ fish

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Species Example

Lions and tigers do not meet in the wild, so don’t interbreed; in captivity can mate to produce a liger (sterile)

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Reproductive Isolation Cornerstone of the biological species

concept Speciation is the attainment of

reproductive isolation Reproductive isolation arises as a

by-product of genetic change

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Reproductive Isolating Mechanisms

Any heritable feature of body, form, functioning, or behavior that prevents breeding between one or more genetically divergent populations

Prezygotic or Postzygotic

Prezygotic-Mechanical isolation

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Types of Isolation

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Isolating Mechanisms

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Pre-Zygotic Isolation

Mating or zygote formation is blocked Temporal Isolation

Behavioral Isolation

Mechanical Isolation

Ecological Isolation

Gamete Mortality

Behavioral - albatross

Temporal-cicada

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Post-Zygotic Isolation

Takes effect after hybrid zygotes form Zygotic mortality - Egg is fertilized but

zygote or embryo dies

Hybrid inviability - First generation hybrid forms but shows low fitness

Hybrid infertility - Hybrid is fully or partially sterile

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Genetic Divergence

Gradual accumulation of differences in the gene pools of genetically separated populations

Natural selection, genetic drift and mutation can contribute to divergence

Gene flow counters genetic divergence

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Mechanisms of Speciation

Allopatric speciation

Sympatric speciation

Parapatric speciation

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Allopatric Speciation

Physical barrier prevents gene flow between populations of a species Effectiveness of

barrier varies with species

Archipelago hotbed of speciation

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Allopatric Speciation on Archipelagos (Island Chain)

Hawaiian Honeycreepers

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Hawaiian Honeycreepers

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Allopatric Speciation

Physical separation between populations promotes genetic changes that eventually lead to speciation.

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Speciation without a Barrier Sympatric speciation

Species form within the home range of the parent species

Parapatric speciation Neighboring populations become

distinct species while maintaining contact along a common barrier

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Sympatric Speciation

New species forms within home range Polyploidy leads to speciation in plants Self-fertilization and asexual reproduction

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Sympatric Speciation

A species forms within the home range of an existing species, in the absence of a physical barrier.

A lake in West Africa in which 9 species of cichlids (a small fish)evolved.

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Speciation by Polyploidy

Change in chromosome number

(3n, 4n, etc.) Offspring with altered

chromosome number cannot breed with parent population

Common mechanism of speciation in flowering plants Polyploidy cotton

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Allopatric vs. SympatricSpeciation

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Parapatric Speciation Neighboring

populations become distinct species while maintaining contact along a common border, the hybrid zone.

Bullock’s oriole

Baltimore oriole

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Models of speciation

Models of Speciation

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Patterns of Change in a Lineage

Cladogenesis Branching pattern Lineage splits, isolated populations

diverge

Anagenesis No branching Changes occur within single lineage Gene flow throughout process

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Evolutionary Trees

new species

branch point (a time of divergence, speciation)

a single lineage

branch point (a time of divergence, speciation)

a new species

a single lineage

extinction (branch ended before present)

dashed line (only sketchy evidence of presumed evolutionary relationship)

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Gradual Model Speciation model

in which species emerge through many small morphological changes that accumulate over a long time period

Fits well with evidence from certain lineages in fossil record

Punctuated equilibrium

Gradualism

Tim

e

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Punctuation Model Speciation model

in which most changes in morphology are compressed into brief period near onset of divergence

Supported by fossil evidence in some lineages

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Adaptive Radiation Burst of

divergence Single lineage

gives rise to many new species

New species fill vacant adaptive zone

Adaptive zone is “way of life”

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Extinction Irrevocable loss of a species Mass extinctions have played a major

role in evolutionary history Fossil record shows 20 or more large-

scale extinctions Reduced diversity is followed by

adaptive radiation

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Who Survives? Species survival is to some extent random Asteroids have repeatedly struck Earth,

destroying many lineages Changes in global temperature favor

lineages that are widely distributed

Mass extinctions

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Identifying SpeciesPast and Present

Taxonomy – field of biology concerned with identifying, naming and classifying species

Somewhat subjective

Devised by Carl von Linne

Assigning species names

Binomial nomenclature system

Genus (generic) and Species (specific)

Higher Taxa Family, Order, Class, Phylum, and Kingdom

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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

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Examples of Classification

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How Many Kingdoms?

Whittaker’s Five-Kingdom Scheme (1969) Monera Protista Fungi Plantae Animalia

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Six Kingdom Scheme

Carl Woese Includes the Archaebacteria

Eubacteria Archaebacteria Protista Fungi Plantae Animalia

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Three Domain Scheme Favored by microbiologists

Eubacteria Archaebacteria Eukaryotes

EUBACTERIA(Bacteria)

ARCHAEBACTERIA(Archaea)

EUKARYOTES(Eukarya)

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ConstructingACladogram

Jaws Limbs Hair Lungs Tail Shell

- - - - + -

+ + - + + +

+ + + + + -+ + + + - -+ - - + + -+ - - - + -+ + + + - -

Lamprey

Turtle

CatGorillaLungfishTroutHuman

Taxon Traits (Characters)

Jaws Limbs Hair Lungs Tail Shell

0 0 0 0 1 0

1 1 0 1 1 1

1 1 1 1 1 01 1 1 1 0 01 0 0 1 1 01 0 0 0 1 01 1 1 1 0 0

Lamprey

Turtle

CatGorillaLungfishTroutHuman

Taxon Traits (Characters)

Please note: the tail column was changed as it was incorrect in the text.

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jaws

lampreyturtle, gorilla, trout, cat,

lungfish, human

Constructing a Cladogram

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trout

Constructing a Cladogram

jaws

lampreyturtle, gorilla, cat, lungfish, human

lungs

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lungfish

Constructing a Cladogram

trout

jaws

lamprey turtle, gorilla, cat, human

lungs

limbs

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gorilla, cat, humanturtle

Constructing a Cladogram

lungfishtrout

jaws

lamprey

lungs

limbs

hair

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gorilla

Constructing a Cladogram

humanturtlelungfishtrout

jaws

lamprey

lungs

limbs

hair

tail loss

cat

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Constructing a Cladogram

A Cladogram

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Evolutionary Tree

extreme

thermophiles

halophilesmethanogens cyanobacteria

ARCHAEBACTERIA

PROTISTANS

FUNGIPLANTS

ANIMALS

clubfungi

sacfungi

zygospore-forming

fungi

echino-derms

chordatesannelids

mollusks

flatworms

sponges

cnidarians

flowering plants conifers

horsetails

lycophytes

ferns

bryophytes

sporozoans

green algae amoeboidprotozoans

slime molds

ciliatesredalgae

brown algaechrysophytes

cycads

ginkgos

rotifers

arthropodsround-worms

chytrids

oomycotes

euglenoids

dinoflagellates

Gram-positive bacteria

spirochetes

chlamydias

proteobacteria

? crown of eukaryotes

(rapid divergences)

molecular origin of life

EUBACTERIAparabasalids

diplomonads(e.g., Giardia)

(alveolates)

(stramenopiles)

chlorophytes

kinetoplastids

extreme

(e.g., Trichomonas)

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In Conclusion

Macroevolution is the study of patterns, trends, or rates of change among groups of species over long periods of time

There is extensive evidence of evolution based on similarities and differences in body form, function, behavior, and biochemistry

Completeness of fossil records are variable

Fossil and geologic record show that such changes have influenced evolution

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In Conclusion

Comparative morphology reveals similarities in embryonic development and identified homologous structures

Comparative biochemistry has identified similarities and differences among species

Taxonomists identify, name, and classify species