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  • Animal Diversity - Invertebrates see the schedule for reading and watching assignments

    Bullet Points: • metazoa: sponges vs eumetazoa – cell junctions, tissues, muscle, nerve

    • some defining properties of animals • movement, symmetry & cephalization • body plans – symmetry • bilateria: charging ahead, with a head • multicellularity, tissues, immunity & cancer • development – a tube within a tube • which came 1st the mouth or the anus? • body cavities • segmentation • Turing: interacting morphogen gradients • HOX regulatory genes: paralogous sets

    & Whole Genome Duplications (WGD) • Evo-Devo: Variations on Ancestral Themes the homologous developmental genetic tool-kit

  • SpongeBob SquarePants

    a jellyfish (cnidara)

    Gary the Snail (mollusk)

    Mr. Krabs (arthropod)

    Patrick Star (echinoderm)

    Sandy Cheeks (chordate)

    Watch: Bozeman Science: AnimalsSquidward Tentacles (mollusk)

  • R ichter, D

    .J. and K ing, N

    . (2013) T he genom

    ic and cellular foundations of anim

    al origins. Annual Review

    of G enetics. 47: 509-537.

    You should be able to explain the classification, “body plans”, patterns of development and # of copies of the HOX gene cluster for the cast of -

    Learning Goals:

    Don’t panic! The next slide

    simplifies the picture.

  • Watch: Bozeman Science: Animals

    1 2


    Three important distinctions among the

    2 Whole Genome Duplications in ancestral tetrapod: 2x2=4 copies of HOX gene cluster

    Chordates = vert’s + a few odd species4

  • What is an Animal?

    (Metazoa). 1. Multicellular, heterotrophic, eukaryotes, w/o cell walls, that ingest food

    4. Life history (mostly): diploid dominates, sexual w/ small flagellated sperm & large immobile egg;

    cleavage, blastulation, gastrulation … ch 36.7:

    c) unique intercellular junctions: Fig 4.26 integrate tissues (except Porifera)

    2. Cells a) lack cell walls (ch 4) b) supported by extracellular matrix: (ch 4.7)

    proteoglycans, glycoproteins, integrin & collagen

    collagen ( gut ) is most abundant protein in vert. body

    3. Nervous tissue & muscle tissue (except Porifera)

    +. Glycogen: carbohydrate store (like fungi) Fig. 5.6:

  • A new paradigm for animal symmetry Gábor Holló Published 23 October 2015

    The symmetry of an animal body inherently characterizes the body plan.

    Sponges … comprise animals with asymmetrical bodies. All other animals are characterized by some kind of symmetry,

    these are of only a few types: radial, … and bilateral symmetry. True spherical symmetry is absent from animal body plans.

    Bilateral symmetry dominates the animal world

    with more than 99% of species showing this symmetry type. Radial symmetry is typically and widely found in [slow moving] cnidarians

    and the secondarily radialized echinoderms [echinoderms are in the Bilateria, active juveniles are bilaterally symmetrical, sedentary adults become radial ]

    absent from animal body plans

  • Body plans: Symmetry

    Most animals that move actively are bilateral.

    Bilateral symmetry is associated with

    cephalization, concentrating sensory equipment on the cephalic [head] end, that is usually first to encounter food, danger, and other stimuli.

    Cephalization also includes a central nervous system concentrated in the head …

    Many radial animals are sessile forms (attached to a substratum) or plankton (drifting or weakly swimming aquatic forms).

    They meet the environment equally well from all sides.

    adult echinoderms and some mollusks lose juvenile bilateral symmetry when they grow into sedentary adults. All bilateria share the same basic developmental genomic tool-kit.

    * *


    see text Fig 27.5

    [a protist]

    Aka “other bilaterians”

  • Watch: Why Are You Multicellular?

  • The [sponge] Amphimedon queenslandica genome and the evolution of animal complexity

    M Srivastava et al Nature 466, 720–726 (05 August 2010) The emergence of multicellular animals from single-celled ancestors

    over 600 million years ago required the evolution of mechanisms for coordinating cell division, growth, specialization, adhesion and death.

    Dysfunction of these mechanisms drives diseases such as cancers, in which social controls on multicellularity fail, and autoimmune disorders, in which

    distinctions between self and non-self are disrupted. Metazoan multicellularity [is] intimately related to cancer and immunity. Sponges [are] the oldest surviving metazoan phyletic lineage. Sponges share key adhesion and signalling genes with eumetazoans, …

    [ cellular communication that regulates development & maintenance of organization ] Comparison of the A. queenslandica draft genome with sequences from other species

    can provide [an] estimate of the genome of the common ancestor of all animals … The A. queenslandica genome allows us to assess the origin of

    the six hallmarks of metazoan multicellularity: (1) regulated cell cycling and growth; (2) programmed cell death; (3) cell–cell and cell–matrix adhesion; (4) developmental signalling and gene regulation; [HOX etc] (5) allorecognition and innate immunity; and (6) specialization of cell types. A recurring theme is the overlap [90%] of these core ‘multicellularity’ genes

    with genes perturbed in cancer, a disease of aberrant multicellularity.

  • Patterns of development in bilateria: other bilaterians vs Deuterostomes chordates & echinoderms

    Vertebrates are Chordates which are segmented, bilateral Deuterostomes, so you should understand basic deuterostome development & structure - more on development in a later lecture

    “identical twins” up to 16 cells

    coelom lined w/

    mesoderm is a

    body cavity

    gut is not a

    body cavity, it’s a tube

    “other bilaterians” = the group formerly known as Protostomes

  • Patterns of development in bilateria: Body Cavities - Coeloms

    The molecular-based phylogeny (Fig 27.5) suggests that the bilateral animals are a monophyletic group with true coeloms lined with mesoderm. {coelom is shared derived trait in bilateria clade}

    Bilaterians lacking coeloms (acoelomates - flatworms) & those w/ pseudocoeloms (not completely lined by mesoderm - roundworms) evolved secondarily from coelomates.

    Peritoneal dialysis

    phylogenetically, these are all in the B

    ilateria C oelom

    ate clade, but som

    e have lost the coelom &

    som e lose bilateral sym

    m etry

  • Segmentation, the [modular] repetition of anatomically similar units along the axis running from the front to the rear of their bodies, seems to be the secret behind the diversity of the largest and most common animal groups on Earth … annelids, arthropods and vertebrates

    These three groups are not closely related to one another. {and not all lineages of bilateria are visibly segmented}

    Is it possible that they all inherited this feature from a very distant common ancestor …? {and some lineages of bilateria lost segmentation?}

    Or has segmentation occurred several times during the history of evolution? The researchers found that the genes controlling segment formation

    during embryo development are almost the same in drosophila and in annelid worms. These similarities led them to conclude that [contrary to what is in our text]

    the genes had been inherited from a common ancestor …supports the idea that segmentation only appeared once in the history of evolution … {shared derived} Segmentation Is the Secret Behind the Extraordinary Diversification of Animals ScienceDaily (July 27, 2010)

    Hedgehog Signaling Regulates Segment Formation in the Annelid Platynereis N Dray et al. Science 16 July 2010: 339-342. Hedgehog proteins first arose in the common ancestor of Cnidarians and the bilateria

    more than 650 million years ago [orthologous across eumetazoa; with multiple paralogs evolved within lineages – includes HOX gene family: BMP, etc.]

  • Demystification of animal symmetry … Gábor Holló Biology Direct201712:11 The two main symmetries that can be observed in the animal body plan are


    and bilateral

    [Bilateria] It is now widely recognised that the evolution of animal form is mainly caused by

    the changes in gene regulatory networks (GRNs). A biological structure, such as body parts, as well as the whole body,

    is built thanks to the aligned action of gene regulatory networks (GRNs). They determine which protein-coding gene will be transcribed,

    and when, in which cells and how much protein will be produced. The transcription of protein-coding genes

    is directed by regulatory sequences of the DNA. The different types of regulatory regions

    (for example, enhancers, promoters, silencers, insulators and so on) are activated by the binding of specific proteins called transcription factors (TFs).

    The binding of a proper combination of the given TFs to the r