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Part 5: Evolution and biodiversity
Chapter 30: Evolving life
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Phylogeny
•
Evolutionary relationships depicted in a branching
diagram
– phylogenetic tree or cladogram
•
Pattern of relationships uncovered using cladistic
analysis
– relationships between taxa identified by shared derived
characters
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-2
Fig. 30.1: Phylogenetic tree
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PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Characters
•
Ancestral or primitive character
– plesiomorphic character or plesiomorphy
•
Shared plesiomorphies
– symplesiomorphies
•
Example
– platypus, koala, dingo

hair, internal fertilisation, suckle young
– these characters are symplesiomorphies

do not show the pattern of relationships between the taxa
(cont.)
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Characters (cont.)
•
Derived or advanced character
– apomorphy
•
Shared apomorphies
– synapomorphies
•
Example
– koala and dingo

anal and urogenital openings separate, mammary glands
with teats, egg shell absent
– these characters are synapomorphies

indicate that koala and dingo are more closely related to
each other than either is to platypus
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-5
Synapomorphies
•
•
Each branch of a cladogram is supported by one
or more synapomorphies
Each species has one or more unique characters
that distinguish it from other species
– autapomorphy
– contains no information about relationships
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PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-6
Types of characters
•
•
Range of character types used in exploring
evolutionary relationships
Morphology
– anatomy
– embryology
•
Molecules
– proteins (amino acid sequences)
– DNA and RNA (nucleotide sequences)
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Morphology
•
Anatomy
– comparison of body form

•
example: pentadactyl (five-digit) limb of vertebrates
Embryology
– comparison of developmental patterns

example: protostome vs. deuterostome
– comparison of embryonic form

example: notochord in chordates
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Comparative morphology
•
Vestigial organs
– rudimentary (poorly-developed) organs without functions
•
Evolutionary remnants of structures that were
functional in ancestral species
– indicate phylogeny
•
Example
– pythons possess cloacal spurs

vestigial hind limbs
– descended from limbed ancestors
(cont.)
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Comparative morphology (cont.)
•
Fossils
– preserved remains of organisms
•
Comparative morphology + geological time
– indicate minimum age of taxa
•
Reduced range of characters because of
fossilisation process
– usually bones, teeth, shells, wood
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PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Characters and information
•
•
All characters are not equally useful in
reconstructing phylogeny
Need to distinguish between
– characters that carry information
– characters that carry no information
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Divergent evolution
•
Pattern of evolution is divergence from a common
ancestral form
– example: crocodile, bird, bat and whale differ but are all
descended from a common ancestral form
•
Change in form
– example: crocodile, bird, bat and whale forelimbs differ in
external appearance but have same basic structure

•
pentadactyl limb
Homologous characters
– same plan, different function
– indicate common ancestry
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-12
Fig. 30.4: Forelimbs of vertebrates
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Convergent evolution
•
Convergence in form in unrelated organisms
– example: cacti, euphorbs, aloes and other succulent
plants are similar in form but are descended from
different ancestral forms
•
Similarity due to similar environments
– example: succulent plants inhabit arid areas
•
Analogous characters
– different plan, same function
– do not indicate common ancestry
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Fig. 30.5: Convergence in succulent plants
(a) cacti
(c) Aloe
Copyright © Dennis Stevenson, New York Botanic Garden
(b) euphorbs
Copyright © Professor Pauline Ladiges, University of Melbourne
Copyright © Professor Pauline Ladiges, University of Melbourne
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Reconstructing phylogenies
•
Homologous characters
– provide information for examining phylogeny
•
Analogous characters
– do not provide information for examining phylogeny
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Parallel evolution
•
Closely related organisms may evolve similar
features because they face similar environments
– features are analogous not homologous
– parallel evolution
•
Emphasises need to examine more than one set of
characters
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PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Molecules
•
Proteins
– comparison of amino acid sequences

•
example: chimpanzees and humans have identical
sequences in several important proteins
DNA
– comparison of nucleotide sequences

example: phylogeny of apes reconstructed using
mitochondrial DNA
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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DNA and RNA sequences
•
Rates of change differ between sequences
• Nuclear-encoded RNA
– ribosomal RNA (rRNA) genes
– highly conserved (slow to change)
– used to reconstruct phylogenies back to the origin of life
•
Mitochondrial DNA (mtDNA), chloroplast DNA
(cpDNA)
– variable rates of change
– can be used for more closely related taxa
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Fig. 30.8: Phylogeny of great apes and
humans
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-20
Classification
•
Grouping organisms with common characters
• Classification reflects phylogeny
– grouped according to pattern of common ancestry
•
Classification is dynamic
– changes as more information about relationships
becomes available
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Taxonomy
•
Methods and principles of classification
• Rules for naming organisms
– written codes for consistency
– International Codes of Nomenclature
•
Taxon = group of organisms, level (rank) of
classification
– kingdom (highest level, most inclusive)
– species (lowest level, least inclusive)
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Taxonomic hierarchy
kingdom
phylum
class
order
family
genus
species
intermediate ranks indicated by prefix sub- (e.g. subphylum,
subfamily, subspecies)
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Monophyly
•
Hierarchical classification reflects phylogeny
– expresses the branching pattern of cladograms
•
Each named group should be monophyletic
– containing all descendants of a common ancestor
– non-monophyletic groups: paraphyly, polyphyly
•
Traditional classifications often include nonmonophyletic groups
– changing as we uncover more data about morphological
and molecular characters
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Paraphyly
•
Paraphyletic group
– does not include all descendants of a common ancestor
– example: paraphyletic family Pongidae (great apes) does
not include humans (family Hominidae) although apes
and humans form a monophyletic group
•
Polyphyletic group
– includes descendants from unrelated groups
– based on convergent evolution
– example: kingdom Protista is composed of many
unrelated lineages
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Fig 30.13: Monophyletic, paraphyletic and
polyphyletic taxons
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-26
Binomial system
•
Codes of nomenclature set rules for naming ranks
of taxa
– example: animal families end in –idae, plant families end
in –aceae
•
All taxa except species have a single-word name
– example: Chordata (phylum), Mammalia (class), Felidae
(family)
•
Only species are identified by two words
– genus + specific epithet
– binomial system
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Species names
•
Species names composed of two parts
– genus name (capitalised)
– specific epithet (never capitalised)
•
Combination of genus + specific epithet are unique
for each species
– Tachyglossus aculeatus (echidna)
– Aquila audax (wedge-tailed eagle)
– Litoria nasuta (rocket frog)
(cont.)
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Species names (cont.)
•
May be more than one species in a genus
– Aquila audax (wedge-tailed eagle)
– Aquila chrysaetos (golden eagle)
– Aquila heliaca (imperial eagle)
•
Specific epithet may be used in several genera
– Litoria nasuta (rocket frog)
– Perameles nasuta (long-nosed bandicoot)
– Acropora nasuta (staghorn coral)
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-29
What is a species?
•
Basic unit of taxonomy
• Different concepts of how the species taxon is
defined
– biological species concept

based on reproductive isolation between species
– morphological species concept

based on phenotypic difference between species
– many other concepts

based on different aspects
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
30-30
Kingdoms
•
Highest (most inclusive) rank of classification
• Linnaeus classified all organisms into two
kingdoms
– plants and animals
•
Now six major lineages recognised
– Bacteria, Archaea, Protista, Plantae, Fungi and Animalia
•
Changing classification
Copyright  2005 McGraw-Hill Australia Pty Ltd
PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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Fig. 30.16: Schemes of classification
Bacteria: copyright © Kwangshin Kim/Photo Researchers,Inc.; Archaea: copyright © James King-Holmes/Science Photo Library/Photo Researchers, Inc.; Protista:
copyright © Professor Geoff McFadden, University of Melbourne; Plantae: copyright © K Thiele, University of Melbourne; Fungi: copyright © H Swart; Animalia:
copyright © Martin Harvey/ANT Photo Library
Copyright  2005 McGraw-Hill Australia Pty Ltd
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