Introduction to Invertebrates Chapter 29. Introduction to Invertebrates Animals What makes an animal? How can you tell if something is an animal or not?

Introduction to Introduction to InvertebratesInvertebrates

Introduction to Invertebrates

Chapter 29


AnimalsAnimals

What makes an animal?What makes an animal?

How can you tell if something is an How can you tell if something is an animal or not?animal or not?

What are some examples of animals?What are some examples of animals?

2

Introduction to Introduction to InvertebratesInvertebrates 3

Evolution of Animals (intro)Evolution of Animals (intro)

All animals are multicellular All animals are multicellular heterotrophic organisms that must heterotrophic organisms that must take in preformed food.take in preformed food.

mulitcellular:mulitcellular: made of more than one cell

heterotrophic:heterotrophic: take in preformed food from other organisms

food:food: complex organic molecules; often glucose related compounds


OutlineOutline

Criteria for the Evolution of Criteria for the Evolution of AnimalsAnimals

1. Multicellularity1. Multicellularity2. True Tissues2. True Tissues3. Bilateral Symmetry3. Bilateral Symmetry4. Body Cavities4. Body Cavities5. The Coelom5. The Coelom6. Segmentation6. Segmentation7. Development7. Development


Evolution of Animals (intro)Evolution of Animals (intro)All animals are multicellular All animals are multicellular heterotrophic organisms that must heterotrophic organisms that must take in preformed foodtake in preformed food

Classification CriteriaClassification Criteria

Level of organizationLevel of organization

Cellular, tissue, organ Cellular, tissue, organ

Body PlanBody Plan

Sac, tube-within-a-tubeSac, tube-within-a-tube

SegmentationSegmentation

Segmentation leads to specializationSegmentation leads to specialization


Evolution of Animals (intro)Evolution of Animals (intro)

Classification Criteria, contClassification Criteria, contSymmetrySymmetry

Radial - Two identical halvesRadial - Two identical halves Bilateral - Definite right and left halvesBilateral - Definite right and left halves

Type of CoelomType of Coelom Acoelomate Acoelomate PseudocoelomPseudocoelom CoelomCoelom

Early Developmental PatternEarly Developmental Pattern Protostome - First embryonic opening Protostome - First embryonic opening becomes the mouth becomes the mouth

Dueterostome - Second embryonic Dueterostome - Second embryonic opening becomes the mouthopening becomes the mouth

7Animals:How does this picture demonstrate that an animal is involved?

8 Traditiona

l Phylogene

tic Tree of Animals


AnimaAnimal?l?

In order to be In order to be considered an considered an animal, what must animal, what must be true about this be true about this organism?organism?

9


MulticellularityMulticellularitySpongesSponges

Only level of animal to have cellular Only level of animal to have cellular organizationorganization

Saclike bodies perforated by many poresSaclike bodies perforated by many pores

Beating of flagella produces water Beating of flagella produces water currents that flow through pores into currents that flow through pores into central cavity and out osculumcentral cavity and out osculum

Sessile filter feedersSessile filter feeders

Asexual reproduction by fragmentation or Asexual reproduction by fragmentation or buddingbudding

11 Simple Sponge Anatomy


Porifera in the Animal CladogramPorifera in the Animal Cladogram

SpongesSponges

sitting at the sitting at the bottom of the bottom of the animal phylogenyanimal phylogeny

simplest of the simplest of the existing animals existing animals and possibly one and possibly one of the simplest of of the simplest of all timeall time

12

Introduction to Introduction to InvertebratesInvertebrates 13True Tissue Layers True Tissue Layers – Ctenophora & – Ctenophora &

CnidariansCnidarians

Many animals have a total of three Many animals have a total of three possible germ layerspossible germ layers Ectoderm – outside layer; skin or outer covering , brain and Ectoderm – outside layer; skin or outer covering , brain and

peripheral nervesperipheral nerves

Endoderm – inside layer; gut track and some digestive tissuesEndoderm – inside layer; gut track and some digestive tissues

Mesoderm – inner layer; muscles Mesoderm – inner layer; muscles

phlya Ctenophora and Cnidaria phlya Ctenophora and Cnidaria develop only develop only ectodermectoderm and and endodermendoderm

DiploblastsDiploblasts – animals derived from only 2 – animals derived from only 2 embryonic layersembryonic layers

Radially symmetricalRadially symmetrical


True Tissue LayersTrue Tissue Layers

phlya Ctenophora and Cnidaria phlya Ctenophora and Cnidaria develop only develop only ectodermectoderm and and endodermendoderm

So what is in the middle if these organisms (the first with true tissue layers) ?

What are Ctenophora called again?


Types of SymmetryTypes of Symmetry

15


Comb Jellies - CtenophoraComb Jellies - Ctenophora

Characteristics:Characteristics:

•Small, transparent, and often Small, transparent, and often luminescentluminescent

•Most of body composed of mesogleaMost of body composed of mesoglea

•Largest animals propelled by beating Largest animals propelled by beating of ciliaof cilia

•Capture prey with tentaclesCapture prey with tentacles

17

Comb Jelly Compared to Cnidarian


CnidariansCnidarians

Tubular animals that most often Tubular animals that most often reside in shallow marine watersreside in shallow marine waters

Polyp and medusa body formsPolyp and medusa body forms

Specialized stinging cells (cnidocytes)Specialized stinging cells (cnidocytes)

Fluid-filled capsule, nematocystFluid-filled capsule, nematocyst

Two-layered body sacTwo-layered body sac

Outer layer - Protective epidermisOuter layer - Protective epidermis

Inner layer - Gastrovascular cavityInner layer - Gastrovascular cavity

Nerve net found throughout body Nerve net found throughout body

19 Cnidarian Diversity


HydraHydra

Freshwater cnidarianFreshwater cnidarian

Small tubular poly body about one-Small tubular poly body about one-quarter inch in lengthquarter inch in length

Gastrovascular cavity is central cavityGastrovascular cavity is central cavity

Tentacles can respond to stimuliTentacles can respond to stimuli

Can reproduce sexually and asexuallyCan reproduce sexually and asexually

21 Anatomy of

Hydra


ObeliaObeliaA colony of polyps enclosed by a hard, A colony of polyps enclosed by a hard, chitinous covering. chitinous covering. Chitin?Chitin?

Feeding polypsFeeding polyps

Extend beyond coveringExtend beyond covering

Have nematocyst-bearing tentaclesHave nematocyst-bearing tentacles

Reproductive polypsReproductive polyps

Budding of new polypsBudding of new polyps

Also has sexual reproduction Also has sexual reproduction (medusae) stage(medusae) stage

23 Obelia Life Cycle

Ctenophora and Cnidarians

Where are we now?

How are cnidarians and ctenophora different from sponges?

What new “feature” do they posses that sponges did not have?

http://www.youtube.com/watch?v=bcmLxsJ5SAg&feature=related

24






25


Bilateral SymmetryBilateral SymmetryNew CharacteristicsNew Characteristics

Bilateral Symmetry Bilateral Symmetry

animals have a “left and right”animals have a “left and right”

one plane of symmetryone plane of symmetry

CephalizationCephalization

identifiable or obvious “head” end of the identifiable or obvious “head” end of the animalanimal

having mouth and/or sensory organs at having mouth and/or sensory organs at one endone end


Bilateral SymmetryBilateral Symmetry

PseudocoelomatesPseudocoelomates

Both phyla today will be considered Both phyla today will be considered pseudocoelomatespseudocoelomates

What is the difference between What is the difference between acoelomates, pseudocoelomates and acoelomates, pseudocoelomates and coelomates (or eucoelomates?) coelomates (or eucoelomates?)



Coelomates (also known as eucoelomates — "true coelom") have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm (one of the three primary tissue layers).

Pseudocoelomate have a pseudocoel (literally “false cavity”), which is a fully functional body cavity. Tissue derived from mesoderm only partly lines the fluid filled body cavity of these animals. Thus, although organs are held in place loosely, they are not as well organized as in a coelomate.

Acoelomate animals, like flatworms, have no body cavity at all. Organs have direct contact with the epithelium. Semi-solid mesodermal tissues between the gut and body wall hold their organs in place.



Flatworms (phylum Platyhelminthes)Flatworms (phylum Platyhelminthes)

Majority are parasiticMajority are parasitic

Organ-level organizationOrgan-level organization

No specialized circulatory or respiratory structuresNo specialized circulatory or respiratory structures

Have undergone cephalizationHave undergone cephalization

Ladder-type nervous systemLadder-type nervous system

Ribbon worms (phylum Nemertea)Ribbon worms (phylum Nemertea)

Have distinctive proboscisHave distinctive proboscis

Have a complete gut trackHave a complete gut track

Flatworms

Belong to the phylum platyhelminthes. (Plat = flat)

There are three classes:Turbellaria TrematodaCestoda

Characteristics of Flatworms

They are acoelomates (they don’t have body cavities)

They have bilateral symmetryShow cephalizationRespiration through skinSingle opening to digestive tract (pharynx)


Free-living FlatwormsFree-living Flatworms

Planarians (genus Dugesia)Planarians (genus Dugesia)

Live in freshwater habitatsLive in freshwater habitats

Head is bluntly arrow shapedHead is bluntly arrow shaped

Auricles function as sense organsAuricles function as sense organs

Two light-sensitive eye spotsTwo light-sensitive eye spots

Three kinds of muscle layers:Three kinds of muscle layers:

Outer circular layerOuter circular layer

Inner longitudinal layerInner longitudinal layer

Diagonal layerDiagonal layer

33Planarian Anatomy


PlanariansPlanarians

Planarians, cont.Planarians, cont.

Excretory organ functions in osmotic Excretory organ functions in osmotic regulation and water excretionregulation and water excretion

Can reproduce asexuallyCan reproduce asexually

HermaphroditicHermaphroditic

Practice cross-fertilizationPractice cross-fertilization


Parasitic FlatwormsParasitic Flatworms

Parasitic flatworms are flukes Parasitic flatworms are flukes (trematodes) and tapeworms (trematodes) and tapeworms (cestodes)(cestodes)

Well-developed nerves and Well-developed nerves and gastrovascular cavity are unnecessarygastrovascular cavity are unnecessary

FlukesFlukes

Reproductive system well developedReproductive system well developed

Usually hermaphroditicUsually hermaphroditic

38Life Cycle of Schistosomiasis


Parasitic FlatwormsParasitic Flatworms

TapewormsTapeworms

Have anterior region with Have anterior region with modifications for attachment to modifications for attachment to intestinal wall of hostintestinal wall of host

Behind head region, scolex, a long Behind head region, scolex, a long series of proglottids are foundseries of proglottids are found

Segments each containing a full set of Segments each containing a full set of both male and female sex organsboth male and female sex organs

Complicated life cyclesComplicated life cycles

40Life Cycle of a Tapeworm, Taenia

Class Trematoda

Are parasitic flukes

Have suckers on both ends of the body

Can live inside or outside of host

Not much cephalization

Class Trematoda

Nervous and Nervous and excretory excretory systems like systems like turbellariansturbellarians

HermaphroditesHermaphroditesHave complex life Have complex life cyclescycles

Class Cestoda

ParasiticTapewormsLong, ribbon-like bodies

Absorbs nutrients from host

Hermaphrodites

http://www.britishbeef.co.uk/scolex.html

Tapeworm Anatomy

48 Ribbon Worm, Lineus

Phylum Nemertea (Rhynchocoela) RibbonwormsThe nemerteans (ribbon worms)

are long, marine predatory worms and there are about 1000 species known.

Unlike members of the Platyhelminthes nemerteans have a complete gut with a mouth and anus and a true circulatory system

Phylum Nemertea (Rhynchocoela) Ribbonworms

Prey is captured using a long muscular proboscis armed with a barb called a stylet..

The proboscis lies in an interior cavity called the rhynchocoel and muscular pressure on fluid in the rhynchocoel causes the proboscis to be quickly everted.

The prey is wrapped in the sticky, slime-covered, proboscis and stabbed repeatedly with the stylet. Neurotoxins in the slime incapacitate the prey.

8.18

Figure 14.24b

Figure 14.24a

Internal structure of female ribbon worm

(left).

Nemertean with proboscis extended

(below)

8.19

Figure 14.25

Baseodiscus mexicanus a nemertean fromthe Galapagos Islands


PseudocoelomPseudocoelomWhat is different What is different about the animals about the animals we discussed we discussed today?today?

How are flatworms How are flatworms (Platyhelminthes) (Platyhelminthes) different from different from cnidarians?cnidarians?

How are nemertea How are nemertea (ribbon worms) (ribbon worms) different from different from flatworms?flatworms?


PseudocoelomPseudocoelom

Pseudocoelom:Pseudocoelom:

A “false” body cavity that is A “false” body cavity that is incompletely lined by mesodermincompletely lined by mesoderm

Provides a space for internal organs Provides a space for internal organs and can serve as hydrostatic skeletonand can serve as hydrostatic skeleton

Both phyla today are animals with a Both phyla today are animals with a complete body gut track and pseudo complete body gut track and pseudo coelomcoelom

phylum Nematoda and Rotiferaphylum Nematoda and Rotifera


Types of Body Cavities

3 types of body cavities



acoelomate



pseudocoelomate



Coelomates – not

there yet


PseudocoelomPseudocoelom

Roundworms (phylum Nematoda)Roundworms (phylum Nematoda)

Non-segmented, generally colorless Non-segmented, generally colorless wormsworms

Several parasitic roundworms infect Several parasitic roundworms infect humanshumans

60Roundworm Anatomy


Parasitic RoundwormsParasitic Roundworms

Ascaris Ascaris – Intestinal roundworm– Intestinal roundworm

Trachinella Trachinella - Trichinosis- Trichinosis

Dirofilaria Dirofilaria - Heartworms- Heartworms

Wuchereria Wuchereria - Elephantiasis- Elephantiasis

62Filarial Worm


RotifersRotifersRotifers (phylum Rotifera)Rotifers (phylum Rotifera)

Named for crown of cilia resembling a Named for crown of cilia resembling a rotating wheelrotating wheel

Serves as both as an organ of Serves as both as an organ of locomotion and aids direction of food locomotion and aids direction of food to mouthto mouth

Important base of many ecosystemsImportant base of many ecosystems

PlanktonicPlanktonic

Transparent organismsTransparent organisms

Can survive dessicationCan survive dessication

64Rotifer

Rotifers on youtube.com

25X Magnificat

ion

http://www.youtube.com/watch?v=wDyKhhqP0Xc&safety_mode=true&persist_safety_mode=1&safe=active

http://www.youtube.com/watch?v=wDyKhhqP0Xc&safety_mode=true&persist_safety_mode=1&safe=active


Pseudocoelomates

How are nematoda and rotifera different from platyhelminthes and nemertea (flatworms and ribbon worms?)

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Introduction to Invertebrates Chapter 29. Introduction to Invertebrates Animals What makes an animal? How can you tell if something is an animal or not?