More Related Content Similar to 14 lecture presentation0 Similar to 14 lecture presentation0 (20) More from Uconn Stamford (20) 14 lecture presentation01. © 2010 Pearson Education, Inc.
MACROEVOLUTION AND THE DIVERSITY
OF LIFE
• Macroevolution:
– Encompasses the major biological changes evident in the fossil record
– Includes the formation of new species
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• Speciation:
– Is the focal point of macroevolution
– May occur based on two contrasting patterns
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• In nonbranching evolution:
– A population transforms but
– Does not create a new species
Video: Galápagos Islands Overview
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• In branching evolution, one or more new species branch from a
parent species that may:
– Continue to exist in much the same form or
– Change considerably
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THE ORIGIN OF SPECIES
• Species is a Latin word meaning:
– “Kind” or
– “Appearance.”
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What Is a Species?
• The biological species concept defines a species as
– “A group of populations whose members have the potential to interbreed
and produce fertile offspring”
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Reproductive Barriers between Species
• Prezygotic barriers prevent mating or fertilization between
species.
Video: Blue-footed Boobies Courtship Ritual
Video: Albatross Courtship Ritual
Video: Giraffe Courtship Ritual
11. VIABLE, FERTILE
OFFSPRING
Hybrid breakdown
FERTILIZATION
(ZYGOTE FORMS)
INDIVIDUALS OF
DIFFERENT SPECIES
MATING ATTEMPT
Reduced hybrid fertility
Reduced hybrid viability
Temporal isolation
Habitat isolation
Behavioral isolation
Mechanical isolation
Gametic isolation
Prezygotic Barriers
Postzygotic Barriers
Figure 14.3
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• Prezygotic barriers include:
– Temporal isolation
– Habitat isolation
– Behavioral isolation
– Mechanical isolation
– Gametic isolation
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• Postzygotic barriers operate if:
– Interspecies mating occurs and
– Hybrid zygotes form
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VIABLE, FERTILE
OFFSPRING
Hybrid breakdown
FERTILIZATION
(ZYGOTE FORMS)
INDIVIDUALS OF
DIFFERENT SPECIES
MATING ATTEMPT
Reduced hybrid fertility
Reduced hybrid viability
Temporal isolation
Habitat isolation
Behavioral isolation
Mechanical isolation
Gametic isolation
Prezygotic Barriers
Postzygotic Barriers
Figure 14.3
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• Postzygotic barriers include:
– Reduced hybrid viability
– Reduced hybrid fertility
– Hybrid breakdown
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Mechanisms of Speciation
• A key event in the potential origin of a species occurs when a
population is severed from other populations of the parent
species.
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• Species can form by:
– Allopatric speciation, due to geographic isolation
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Video: Grand Canyon
Allopatric Speciation
• Geologic processes can:
– Fragment a population into two or more isolated populations
– Contribute to allopatric speciation
Video: Volcanic Eruption
Video: Lava Flow
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• Speciation occurs only with the evolution of reproductive barriers
between the isolated population and its parent population.
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What Is the Tempo of Speciation?
• There are two contrasting models of the pace of evolution:
– The gradual model, in which big changes (speciations) occur by the
steady accumulation of many small changes
– The punctuated equilibria model, in which there are
– Long periods of little change, equilibrium, punctuated by
– Abrupt episodes of speciation
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EARTH HISTORY AND MACROEVOLUTION
• Macroevolution is closely tied to the history of the Earth.
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Geologic Time and the Fossil Record
• The fossil record is:
– The sequence in which fossils appear in rock strata
– An archive of macroevolution
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• Geologists have established a geologic time scale reflecting a
consistent sequence of geologic periods.
Animation: Macroevolution
Animation: The Geologic Record
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• Fossils are reliable chronological records only if we can
determine their ages, using:
– The relative age of fossils, revealing the sequence in which groups of
species evolved, or
– The absolute age of fossils, requiring other methods such as radiometric
dating
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• Radiometric dating:
– Is the most common method for dating fossils
– Is based on the decay of radioactive isotopes
– Helped establish the geologic time scale
41. Carbon-14 in shell
Time (thousands of years)
Radioactive decay
of carbon-14
How
carbon-14
dating is
used to
determine
the vintage
of a
fossilized
clam shell
Carbon-14radioactivity
(as%oflivingorganism’s
C-14toC-12ratio)
100
75
0
50
25
0 5.6 50.411.2 16.8 22.4 28.0 33.6 39.2 44.8
Figure 14.15
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Plate Tectonics and Macroevolution
• The continents are not locked in place. Continents drift about the
Earth’s surface on plates of crust floating on a flexible layer
called the mantle.
• The San Andreas fault is:
– In California
– At a border where two plates slide past each other
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• About 250 million years ago:
– Plate movements formed the supercontinent Pangaea
– The total amount of shoreline was reduced
– Sea levels dropped
– The dry continental interior increased in size
– Many extinctions occurred
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• About 180 million years ago:
– Pangaea began to break up
– Large continents drifted increasingly apart
– Climates changed
– The organisms of the different biogeographic realms diverged
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• Plate tectonics explains:
– Why Mesozoic reptiles in Ghana (West Africa) and Brazil look so similar
– How marsupials were free to evolve in isolation in Australia
48. Mass Extinctions and Explosive Diversifications
of Life
• The fossil record reveals that five mass extinctions have occurred
over the last 600 million years.
• The Permian mass extinction:
– Occurred at about 250 million years ago
– Claimed about 96% of marine species
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• The Cretaceous extinction:
– Occurred at the end of the Cretaceous period, about 65 million years ago
– Included the extinction of all the dinosaurs except birds
– Permitted the rise of mammals
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CLASSIFYING THE DIVERSITY OF LIFE
• Systematics focuses on:
– Classifying organisms
– Determining their evolutionary relationships
• Taxonomy is the:
– Identification of species
– Naming of species
– Classification of species
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Some Basics of Taxonomy
• Scientific names ease communication by:
– Unambiguously identifying organisms
– Making it easier to recognize the discovery of a new species
• Carolus Linnaeus (1707–1778) proposed the current taxonomic
system based upon:
– A two-part name for each species
– A hierarchical classification of species into broader groups of organisms
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Naming Species
• Each species is assigned a two-part name or binomial, consisting
of:
– The genus
– A name unique for each species
• The scientific name for humans is Homo sapiens, a two part
name, italicized and latinized, and with the first letter of the
genus capitalized.
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Hierarchical Classification
• Species that are closely related are placed into the same genus.
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• The taxonomic hierarchy extends to progressively broader
categories of classification, from genus to:
– Family
– Order
– Class
– Phylum
– Kingdom
– Domain
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Classification and Phylogeny
• The goal of systematics is to reflect evolutionary relationships.
• Biologists use phylogenetic trees to:
– Depict hypotheses about the evolutionary history of species
– Reflect the hierarchical classification of groups nested within more
inclusive groups
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Cladistics
• Cladistics is the scientific search for clades.
• A clade:
– Consists of an ancestral species and all its descendants
– Forms a distinct branch in the tree of life
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Classification: A Work in Progress
• Linnaeus:
– Divided all known forms of life between the plant and animal kingdoms
– Prevailed with his two-kingdom system for over 200 years
• In the mid-1900s, the two-kingdom system was replaced by a
five-kingdom system that:
– Placed all prokaryotes in one kingdom
– Divided the eukaryotes among four other kingdoms
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• In the late 20th century, molecular studies and cladistics led to the
development of a three-domain system, recognizing:
– Two domains of prokaryotes (Bacteria and Archaea)
– One domain of eukaryotes (Eukarya)
Animation: Classification Schemes
67. Evolution Connection:
Rise of the Mammals
• Mass extinctions:
– Have repeatedly occurred throughout Earth’s history
– Were followed by a period of great evolutionary change
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• Fossil evidence indicates that:
– Mammals first appeared about 180 million years ago
– The number of mammalian species
– Remained steady and low in number until about 65 million years
ago and then
– Greatly increased after most of the dinosaurs became extinct
69. American black bear
Eutherians
(5,010 species)
Millions of years ago
Monotremes
(5 species)
Marsupials
(324 species)
Ancestral
mammal
Reptilian
ancestor
Extinction of
dinosaurs
250 200 150 100 5065 0
Figure 14.26
Editor's Notes Figure 14.1 Two patterns of evolution
Figure 14.2a Similarity between different species
Figure 14.2b Diversity within one specie
Figure 14.3 Reproductive barriers between closely related species
Figure 14.4a Temporal isolation
Figure 14.4b Habitat isolation
Figure 14.4c Behavioral isolation
Figure 14.4d Mechanical isolation
Figure 14.4e Gametic isolation
Figure 14.3 Reproductive barriers between closely related species
Figure 14.5a Reduced hybrid viability
Figure 14.5b Reduced hybrid fertility
Figure 14.5c Hybrid breakdown
Figure 14.7 Allopatric speciation of antelope squirrels on opposite rims of the Grand Canyon
Figure 14.10 Two models for the tempo of evolution
Figure 14.14a Petrified wood
Figure 14.14b Insect fossil in amber
Figure 14.14c Dinosaur bone
Figure 14.14d Dinosaur footprints
Table 14.1 The Geologic Time Scale
Figure 14.15 Radiometric dating
Figure 14.16 California's San Andreas fault
Figure 14.17 The history of plate tectonics
Figure 14.19a Leopard (Panthera pardus)
Figure 14.19b Tiger (Panthera tigris)
Figure 14.19c Lion (Panthera leo)
Figure 14.19d Jaguar (Panthera onca)
Figure 14.20 Hierarchical classification
Figure 14.21 The relationship of classification and phylogeny for some members of the order Carnivora
Figure 14.23 A simplified example of cladistics
Figure 14.25 The three-domain classification system
Figure 14.26 The increase in mammalian diversity after the extinction of dinosaurs