Invertebrates 1Invertebrates 1

Introduction, Porifera, CnidariaIntroduction, Porifera, Cnidaria

Lecture outlineLecture outline

1.1. Overview: Invertebrate lecturesOverview: Invertebrate lectures2.2. What is an animal?What is an animal?3.3. Introduction to major phyla in Introduction to major phyla in

Kingdom AnimaliaKingdom Animalia4.4. Basic phylogeny of Kingdom Basic phylogeny of Kingdom

AnimaliaAnimalia5.5. Phylum PoriferaPhylum Porifera6.6. Phylum CnidariaPhylum Cnidaria

1. Overview of Invertebrate 1. Overview of Invertebrate portion of courseportion of course

Evolutionary relationshipsEvolutionary relationships Body planBody plan

How animal meets its basic needsHow animal meets its basic needs Relationship of structure and functionRelationship of structure and function

Selected aspects of life-history and Selected aspects of life-history and ecologyecology

2. What is an animal?2. What is an animal? EukaryoticEukaryotic Multicellular: Multiple cell Multicellular: Multiple cell typestypes (Not just many (Not just many

cells)cells) HeterotrophicHeterotrophic No cell wallNo cell wall Characteristics of early development (unique!)Characteristics of early development (unique!)

Blastula and gastrula stages unique to animalsBlastula and gastrula stages unique to animals Sponges, have precursors to these stagesSponges, have precursors to these stages

Phylum Porifera: Phylum Porifera: spongessponges

Phylum Cnidaria: Phylum Cnidaria: Have CnidocytesHave Cnidocytes

Phylum Ctenophora:Phylum Ctenophora:The comb jelliesThe comb jellies

Phylum Platyhelminthes:Phylum Platyhelminthes:The flatwormsThe flatworms

Phylum Nematoda:Phylum Nematoda:The roundwormsThe roundworms

Phylum Annelida:Phylum Annelida:The segmented wormsThe segmented worms

Phylum Mollusca:Phylum Mollusca:The “soft-bodied” The “soft-bodied”

animalsanimals

Phylum Arthropoda:Phylum Arthropoda:Jointed appendagesJointed appendages

Phylum Echinodermata:Phylum Echinodermata:Spiny-skinnedSpiny-skinned

Phylum Chordata:Phylum Chordata:Animals with notochordsAnimals with notochords

4. Phylogenetic overview4. Phylogenetic overview Presumed to be monophyleticPresumed to be monophyletic

Hypothesis assumes all animals evolve from a Hypothesis assumes all animals evolve from a single common ancestorsingle common ancestor

That ancestor thought to be a sponge-like protist That ancestor thought to be a sponge-like protist called a called a choanoflagellatechoanoflagellate

Modern choanoflagellateModern choanoflagellate Found in aquatic habitatsFound in aquatic habitats

Some propose Some propose polyphyletic originspolyphyletic origins

Cite Cambrian explosionCite Cambrian explosion

Phylogenetic overview Phylogenetic overview (“traditional”)(“traditional”)

Multicellularity separates the Multicellularity separates the ancestral protists from all ancestral protists from all

animalsanimals

MulticellularityMulticellularity

Different Different typestypes of cells! of cells!

Development of two true Development of two true tissue layerstissue layers

Separates Phylum Porifera from all Separates Phylum Porifera from all othersothers Sponges All other groups (2-3 tissues)Sponges All other groups (2-3 tissues)

Development of a third Development of a third germ layer and bilateral germ layer and bilateral

symmetrysymmetry Cnidarians, Ctenophores All others Cnidarians, Ctenophores All others Radial symmetry, 2 layers Bilateral symmetry, 3 layers Radial symmetry, 2 layers Bilateral symmetry, 3 layers

(Porifera)(Porifera)

Further developments Further developments (briefly)(briefly)

Body cavitiesBody cavities

AcoelomateAcoelomate PseudocoelomatesPseudocoelomates CoelomatesCoelomates

Further developments Further developments (briefly)(briefly)

5. Phylum Porifera: The 5. Phylum Porifera: The spongessponges

Evolutionary Evolutionary relationshipsrelationships

Simplest multicellular animals Simplest multicellular animals Main cell type, choanocyte, resembles Main cell type, choanocyte, resembles

choanoflagellate cellchoanoflagellate cell Considered "multicellular" rather than Considered "multicellular" rather than

colonial, because there are different cell colonial, because there are different cell types.types.

Not much, if any cooperation between cellsNot much, if any cooperation between cells No real "tissues", no "systems" of any type (no No real "tissues", no "systems" of any type (no

nervous system, circulatory system, etc.)nervous system, circulatory system, etc.)

Sponge structureSponge structure

Review key parts…Review key parts…

Water movement and Water movement and feedingfeeding

Role of flagellumRole of flagellum Role of collarRole of collar Movement of Movement of

particlesparticles PhagocytosisPhagocytosis

ProtectionProtection

Sponges are sessile… Sponges are sessile… Toxins/warning coloration (this is why Toxins/warning coloration (this is why

many sponges are brightly colored)many sponges are brightly colored) Painful or sharp covering (spicules)Painful or sharp covering (spicules) Regenerative abilityRegenerative ability Camouflage (if not toxic)Camouflage (if not toxic) Bore into shells. Bore into shells. NOTE: Nudibranch predators co-opt NOTE: Nudibranch predators co-opt

sponge defenses (toxins, spicules)sponge defenses (toxins, spicules)

Phylum CnidariaPhylum Cnidaria

Evolutionary Evolutionary relationshipsrelationships

Diverge from the Porifera in the Diverge from the Porifera in the following ways:following ways:

DiploblastiDiploblastic: two true tissue layers c: two true tissue layers Ectoderm and endodermEctoderm and endoderm No mesodermNo mesoderm

RadiataRadiata: One of two phyla to exhibit radial : One of two phyla to exhibit radial symmetrysymmetry

Where Cnidarians fit in…Where Cnidarians fit in…

Cnidarians, Ctenophores All others Cnidarians, Ctenophores All others Radial symmetry, 2 layers Bilateral symmetry, 3 layers Radial symmetry, 2 layers Bilateral symmetry, 3 layers

(Porifera)(Porifera)

Body organizationBody organization Polyps and medusaePolyps and medusae

Key featuresKey features

Polyps and medusaePolyps and medusae Tissue layersTissue layers

Ectoderm, gastroderm (=endoderm)Ectoderm, gastroderm (=endoderm) MesogliaMesoglia

Secreted from the tissue layersSecreted from the tissue layers Gastrovascular cavityGastrovascular cavity

FunctionsFunctions Not a true body cavity!Not a true body cavity!

Nervous system: nerve netNervous system: nerve net No other major body systemsNo other major body systems

Tentacles with cnidocytes (stinging cells)Tentacles with cnidocytes (stinging cells)

Nervous system featuresNervous system features

True neurons Conduction can be unidirectional or

bidirectional along neurons Nerve net with no direct pathways Have simple sensory organs

Cnidocytes/nematocystsCnidocytes/nematocystsHow do they work?How do they work?

Life-history strategiesLife-history strategies