Chordates

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Chordates Tunicates Hemichordates Echinoderms Arth
ropods Tardigrades Nematodes Loricifera Priapulida
Rotifers Cycliophora Annelids Molluscs Bryozoa Br
achiopods Phoronids Platyhelminthes
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Biological diversity

• How many species are there?
• What is the taxonomic and geographical
  distribution of species number?
• Why do some groups have more species than others?
• Why are some parts of the world more species rich
  than others?
• What are the major divisions and characteristics
  of biological diversity?
• Bacteria v Eukaryotes
• Archae v Eubacteria
• Unicellular v multicellular
• Producers v consumers
• What is the time-scale of evolution?

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Species richness distribution
Purvis and Hector (2000)
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Species richness distributions
Purvis and Hector (2000)
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Species-number models in ecology and systematics

• Species number reflects random process of
  speciation and extinction
• Branching process
• Distribution of population sizes likewise is a
  random process
• Innovations
• Factors such as phytophagy (insects),
  warm-blooded nature (mammals, birds), flight
  (insects, etc.) enable new niches to be occupied
• Distinguishing hypotheses is made difficult by
  the fact that life has only evolved once
• Though comparing analogous structures (wings,
  phytophagy) is possible

All partitions are equally likely
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Linnaean taxonomic hierarchy

• Carl Linnaeus Swedish naturalist published
  Systema Naturae in 1735.

Domain Eukaryota All nucleated
organisms Kingdom Metazoa All
animals Phylum Chordata All animals with
backbone Class Mammalia Warm-blooded
milk-producing vertebrates Order Primates Monkey
s and apes (Super)Family Hominoidea Great
apes Genus Homo Species sapiens Other spp.
(e.g. habilis, erectus, extinct)
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Taxonomic difficulties

• Assignment of a taxonomic level really reflects
  the systematists bias
• There is no biological meaning to the taxonomic
  scheme
• The mammalian order primates (including families,
  subfamilies and many genii and species) is
  younger than the genus Drosophila
• Cladistic nomenclature represents each node of
  the phylogenetic tree
• BUT there are a lot of internal nodes

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Features common to all life

• Replication of DNA/RNA
• Exchange of genetic material
• Cells and cytoplasm (lipid bilayer membrane)
• Gene expression and RNA translation machinery
  (ribosomes)
• Energy converter (takes in energy and uses it to
  make order)

Excludes viruses
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The deep splits
Largely unresolved probably many
horizontal transfer events. Archaea may be
polyphyletic
Prokaryota
Archaea
Eubacteria
Eukaryota
Kingdoms Metazoa Plantae Protista Fungi
Euryarhcaeota Crenarchaeota
Proteobacteria Chlamydias Spirochaetes Gram-positi
ve Cyanobacteria
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Prokaryote v Eukaryote
Prokaryote No nucleus Single coiled chromosome
with few associated proteins Bacterial cell
wall No organelles 17s RNA
Eukaryote DNA in nucleus Chromosomes with many
proteins (histones) No cell wall Organelles
(mitochondria, chloroplasts) 18s RNA
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Archaea v Eubacteria
Eubacteria Archaea Eukaryota No
histones Histones associated Histones with
DNA One RNA polymerase Several Several Formyl
-methionine as Methionine Methionine start
codon Rare and unusal introns Some splicing
introns Spliceosomal introns
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The eukaryotes

• Protists
• Unicellular, enormously diverse
• Many important human pathogens (Plasmodium,
  Giardia)
• Fungi
• Networks of hyphae, saprophytes
• Many important agricultural pests (rusts, smuts,
  mildew)
• Plants and green algae
• Generate energy through photosynthesis
  (chlorophyll)
• Animals
• Consumers

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Chlorarachniophyte
Red alga
Euglena
ciliate
dinoflagellate
diatom
Green alga
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Endosymbiosis

• Mitochondria and chloroplasts are descendants of
  bacteria that lived within the cells of early
  eukaryotes
• Have their own genomes (circular)
• Have prokaryote-like ribosome subunits and
  membrane proteins
• No histones
• Most genes lost or migrated to the nucleus
• Other symbioses at earlier stages
• Tryptophan producing Buchnera in aphids
• Rhizobium nitrogen fixing in legumes
• Wolbachia

Chloroplasts from cyanobacteria
Mitochondria from proteobacteria
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Specialisations of multicellular life

• Differentiation of cell types
• Coordinated development
• Self / non-self recognition

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Platyhelminthes (flatworms, tapeworms, flukes)
Mollusca (snails, clams, squid)
Annelida (worms, leeches)
Echinodermata (starfish, sea-urchins,
sea-cucumbers)
Chordata (fish, amphibians, reptiles, birds,
mammals)
Arthropoda (insects, crustaceans, millipedes)
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Tardigrade
Bryozoa
Loricifera
Nemertea
Micrognathozoa
Brachiopods
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Colonial life
Sponge
Siphonophore
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Grades of body plan
Cell layer
Non-living tissue/space
Two-layer Cnidaria Ctenophores Platyhelmintes
Pseudo-coelomates Nematodes Rotifers
Coelomates Molluscs Annelids Echinoderms Chord
ates
Third layer can differentiate to provide internal
organs
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Specialisations of animals

• Specialised cell types (nerves, muscles)
• Motility (as oppose to mobility)
• Self / non-self cell recognition
• Immune systems
• Individual-individual communication
• Chemical, visual, olfactory, auditory
• Social organisation

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Polyploidy of early vertebrates
Ancestral vertebrate and all invertebrates
First round of polyploidisation (Amphioxus?)
Second round of polyploidisation
Differentiation, loss and rearrangement of genes
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Plant groups
Liverworts Mosses Club-mosses Ferns Cycads Conifer
s Ginkgos Welwitschia Flowering plants
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Relative genome size prokaryotes
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Relative genome sizes eukaryotes
source euGenes
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The C value paradox

• Haploid DNA content in a cell can be measured by
  flow cytometry
• In multicellular eukaryotes, there is no
  correlation between gene number and DNA content
  of cells
• Drosophila 0.18
• Human 3.19
• Grasshopper 13.4
• Lungfish 140
• What is the value of the extra DNA?
• Nuclear volume more DNA correlates strongly with
  larger cells
• None DNA is a self-promoting opportunist which
  naturally increases unless checked by the time
  and energy demands of replication and
  transcription
• (transposons, introns, LINES, SINES)

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Geological eras and epochs
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Time-line of life on earth
First land plants
Multicellular life
Cambrian explosion
Origin of life
Oxygen appears
First insects
First vertebrates
3800MY
1000MY
530MY
2500MY
410MY
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Time-line of life on earth II
First tetrapods
First Primates
First birds
Age of the dinosaurs
Modern humans
Chimp/ Human split
K/T extinction
First Mammals
5MY
0.1MY
360MY
60MY
170MY
100MY
210MY
65MY