Animal Diversity - Invertebrates see the schedule for ... · Animal Diversity - Invertebrates see...

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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 1 st 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

Transcript of Animal Diversity - Invertebrates see the schedule for ... · Animal Diversity - Invertebrates see...

Page 1: Animal Diversity - Invertebrates see the schedule for ... · Animal Diversity - Invertebrates see the schedule for reading and watching assignments Bullet Points: • metazoa: sponges

Animal Diversity - Invertebratessee 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 Themesthe homologous developmental genetic tool-kit

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SpongeBob SquarePants

a jellyfish(cnidara)

Gary the Snail(mollusk)

Mr. Krabs(arthropod)

Patrick Star(echinoderm)

Sandy Cheeks(chordate)

Watch: Bozeman Science: AnimalsSquidward Tentacles(mollusk)

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Richter, D

.J. and King, N

. (2013) The genom

ic and cellular foundations of anim

al origins.Annual Review

of Genetics. 47: 509-537.

You should be able to explain theclassification,“body plans”,patterns of developmentand # of copiesof the HOX gene clusterfor the cast of -

Learning Goals:

Don’t panic!The next slide

simplifies the picture.

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Watch: Bozeman Science: Animals

12

3

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

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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 abundantprotein in vert. body

3. Nervous tissue & muscle tissue(except Porifera)

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

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A new paradigm for animal symmetryGábor Holló Published 23 October 2015http://rsfs.royalsocietypublishing.org/content/5/6/20150032

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

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Body plans: Symmetry

Most animals that move actively are bilateral.

Bilateral symmetryis 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 echinodermsand some molluskslose juvenilebilateral symmetrywhen they grow intosedentary adults.All bilateria sharethe same basic developmental genomic tool-kit.

* *

*

see text Fig 27.5

[a protist]

Aka “other bilaterians”

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Watch: Why Are You Multicellular?

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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.

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Patterns of development in bilateria: other bilaterians vs Deuterostomeschordates & 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

coelomlined w/

mesodermis a

body cavity

gutis not a

body cavity,it’s a tube

“other bilaterians” = the group formerly known as Protostomes

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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 allin the B

ilateria Coelom

ate clade,but som

e have lost the coelom&

some lose bilateral sym

metry

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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}

http://www.sciencedaily.com/releases/2010/07/100726222316.htmSegmentation Is the Secret Behindthe Extraordinary Diversification of AnimalsScienceDaily (July 27, 2010)

Hedgehog Signaling Regulates Segment Formation in the Annelid PlatynereisN 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.]

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Demystification of animal symmetry …Gábor Holló Biology Direct201712:11https://biologydirect.biomedcentral.com/articles/10.1186/s13062-017-0182-5The two main symmetries that can be observed in the animal body plan are

radial

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 regulatory regions can either activate, modulate or inhibit the transcription of the target gene.

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A morphogen is a substance whose non-uniform distribution governs the pattern of tissue development in the process of morphogenesis or pattern formation, one of the core processes of developmental biology, establishing positions of the various specialized cell types within a tissue.

More specifically, a morphogen is a signaling molecule that acts directly on cells to produce specific cellular responses depending on its local concentration.

Typically, morphogens are produced by source cells and diffuse through surrounding tissues in an embryo during early development, such that concentration gradients are set up.

These gradients [interact and] drive the process of differentiation of unspecialised stem cells into different cell types, ultimately forming all the tissues and organs of the body.

The control of morphogenesis is a central element in evolutionary developmental biology (evo-devo).

https://en.wikipedia.org/wiki/Morphogen

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Demystification of animal symmetry …Gábor Holló Biology Direct201712:11https://biologydirect.biomedcentral.com/articles/10.1186/s13062-017-0182-5Morphogens are diffusible molecules which

govern the pattern formation of tissues during morphogenesis. Several morphogens which are responsible for the formation of the symmetrical body –

such as Wnt and bone morphogenetic protein (BMP) –, have been characterized …

A new paradigm for animal symmetryGábor Holló Published 23 October 2015http://rsfs.royalsocietypublishing.org/content/5/6/20150032

The establishment of the AP (Anterior-Posterior) axis in most animals is guided by the Wnt signalling pathway.

In bilaterians, the Wnt signalling system controls the expression of Hox genes which direct the positioning of diverse structures along the AP axis.

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How to make a hand.The antero-posterior limb bud axis is specified early in development by graded Sonic HedgeHog (SHH) signaling [early, top panel]. A three-node Turing network [of interacting signal gradients] composed of the WNT and BMP signaling pathways and the Sox9 transcriptional regulatorinteract to determine the periodic digit pattern [later, lower right].

PERSPECTIVE DEVELOPMENTIn Turing's hands- the making of digits [by interacting gradients]Zuniga & Zeller Science1 August 2014: Vol. 345 pp. 516-517

Posthumously pardoned for being gay in 2013

http://ideas.ted.com/how-the-zebra-got-its-stripes-with-alan-turing/Where do a zebra’s stripes, a leopard’s spots and our fingers come from? The key was found years ago — by the man who cracked the German Enigma codein WWII.

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https://learn.genetics.utah.edu/content/basics/hoxgenes/

These all haveone set/cluster of multiple paralagous copiesof the HOX familyof regulatory genes

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Review Evo-Devo: Variations on Ancestral Themes

E.M.De Robertis

Hox Complexes and the A-P Axis

E.B. Lewis made the remarkable discovery that [Hox] genes that control the identity of

the abdominal segments of the fly

(by repressing formation of legs and wings)

were clustered in the genome and

occupied the same order along the DNA

as they were expressed along the A-P body axis.

He called this phenomenon colinearityand hypothesized that new genes had been recently duplicated in flies

[paralogous homologues]and added sequentially to repress more anterior segmental identities in a multiple-legged ancestor that looked like a centipede.

Aka “other bilaterians”

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Review Evo-Devo: Variations on Ancestral ThemesE.M.De Robertis

The cephalochordate amphioxus has a single Hox complex comprising 14 Hox genes.[as does the arthropod fruitfly]

In vertebrates, [a clade within chordates]the entire ancestral genome has been duplicated twice.

These whole-genome duplications may have been a key component in the evolutionary success of vertebrates.

Mammals [in the vertebrate clade of chordates]contain four [2x2] Hox complexes [per haploid set of chromosomes] … with 13 paralogous (duplicated) genes.

The complexes follow the rules of colinearity, with genes at one end being expressed earlier and more anteriorly than those at the other end.

A mouse or human has a total of 39 Hox genes, as some of the duplicated genes were lost

amphioxusvertebrates

Aka “other bilaterians”

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Review Evo-Devo: Variations on Ancestral ThemesE.M.De Robertis

Hox Complexes of Drosophila and MammalsThe Hox complex has been

duplicated twice in mammalian genomes and comprises 39 genes. [2x2x13=52, lost 13]

The degree of overall homology and the conservation of regulatory complexity between vertebrate and insect Hox complexesis simply amazing.

Aka “other bilaterians”

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Hox Genes: Master Regulators of the Animal BodyplanA.J. Durston

Note: in tetrapod vertebrates2x2 = 4 setsof 13 duplicated and differentiatedparalogous loci,but some redundant copies are lost

https://learn.genetics.utah.edu/content/basics/hoxgenes/

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ReviewEvo-Devo: Variations on Ancestral ThemesE.M.De Robertis

The creative power of natural selection working on random mutations over immense periods of geological time explaines the immense variety of life on earth.

What we are learning from Evo-Devo is that the source of variation of [greatest] importance for evolution resides in deeply homologous developmental gene networks shared by all animals.

A key question is to what extent these deep genetic homologies have channeled, or constrained, the outcomes of evolution

Aka “other bilaterians”