Animal Evolution: Invertebrate Diversity (Learning Outline)

1. Characteristics of organisms of the Kingdom Animalia2. Evolution of animals: diploid multi-cellular aquatic organisms from a

colonial diploid protist. 3. Highlights of animal evolution.4. Order of appearance of animal groups. 5. Distinguishing features of the nine animal phyla and representative

organisms.6. Highlights of evolution of land animals from aquatic ancestors7. Order of appearance of land animals. 8. Parasitism as an integral part of animal evolution. 9. Common parasites causing common diseases and classification

groups10.For organisms covered in class or lab, place each in its classification

grouping , relation to others, and know their major evolutionary features.

Colonizationof land

Animals

Cenozoic

Origin of solarsystem andEarth

Humans

Single-celledeukaryotes Atmospheric

oxygen

Multicellulareukaryotes

Prokaryotes

Proterozoiceon

Archaeaneon

1

2 3

4

Last 0.5 bilion years

Evolution of Animals

Animals are eukaryotic, multi-cellular, heterotrophic organisms that ingest their

food

Diversity of animals

The ancestor of animals was probably a colonial, flagellated protist whose cells

gradually became more specialized and layered

Reproductivecells

Somaticcells

Digestivecavity

1 Colonial protist,an aggregateof identical cells

2 Hollow sphereof unspecializedcells (shown incross section)

3 Beginning of cellspecialization(cross section)

4 Infolding(cross section)

5 Gastrula-like“proto-animal”(cross section)

Species:Felis catus

Genus: Felis

Family: Felidae

Class: Mammalia

Order: Carnivora

Phylum: Chordata

Kingdom: Animalia

Bacteria Domain: Eukarya Archaea

• Species• Genus• Family • Order• Class• Phylum• Kingdom• Domain

Animal DiversityEukaryotic Kingdom: Animalia

– Body composition• Multi-cellular evolving from a colonial protist ancestor• Later forms developed tissues, organs, and organ systems

– Heterotrophic• Some free-living others parasitic

– Early forms are aquatic – Evolutionary adaptations led to evolution of land animals

Major steps of animal evolution

– Assembly of cells that work together– Formation of tissues: nerves and muscle– Movement followed by active predation– Body made of distinct layers of cells: 2 then 3– Body symmetry: radial and bilateral– Bilateral organisms:

• Mouth from second opening• Mouth from first opening

Two major animal forms: • Invertebrates 97% of all animals- evolved earlier• Vertebrates- later forms in one phylum only

Classification Criteria for Animals

• Level of OrganizationTissue, organ, organ systems

• Body SymmetryNone- asymmetricBilateralRadial

• Body PlanSac with one openingTube within a tube-two openings

• Segmentation (with and without appendages)

Phyla

Sac Body Plan

Tube within Tube

Organ Systems(Coelom)

Level of OrganizationColonial

Multicellular

Segmentation

Spon

ges

Cni

daria

ns

Flat

wor

ms

Rou

nd w

orm

s

Mol

lusc

s

Ann

elid

s

Radial Symmetry Bilateral Symmetry

No Body Cavity(No coelom)

Body Cavity(Pseudocoelom)

Mouth from First Embryonic

Opening

Mouth from Second Embryonic

Opening

Art

hrop

ods

Echi

node

rms

Cho

rdat

es

No true tissues

true tissues

*

Ancestralcolonial protist

No true tissuesTrue tissues

Bilateral symmetryRadial symmetry

Eumetazoans

Bilaterians

ProtostomesDeuterostomes

Spon

ges

Cni

daria

ns

Echi

node

rms

Cho

rdat

es

Flat

wor

ms

Mol

lusc

s

Ann

elid

s

Art

hrop

ods

Nem

atod

es

Phylogenetic Tree of Animals with

9 Phyla mostly

invertebrates

Invertebrates & Vertebrates

Phyla (by their common names)

Mouth from Second Embryonic

Opening

Mouth from First Embryonic

Opening

Animal development may include a blastula, gastrula, and larval stage

Key

Meiosis

Metamorphosis

Haploid (n)Diploid (2n) Sperm

EggZygote(fertilized egg)

Adult

Blastula(cross section)

Eight-cell stage

Digestive tract

EctodermLarva

Early gastrula(cross section)Future

mesodermLater gastrula(cross section)Internal sac

Endoderm

1

2

3

4

5

6

7

8

Diploid cells

Animals can be characterized by basic features of their “body plan”. They may vary in symmetry.

Top

Bottom

Dorsal surface

Anteriorend

Posterior end

Ventral surface

Animals and digestive cavities

Incomplete gut (sac-like)– radial symmetry– bilateral symmetry

Complete gut- type 1 – bodies without shells– bodies with shells– bodies with segments with exoskeleton

Complete gut- type 2– hydraulic tube feet– bodies with notochord (primitive backbone)

Sac Body Plan

Tube within Tube

Organ Systems(Coelom)

Level of OrganizationMulticellular

Segmentation

Spon

ges

Cni

daria

ns

Flat

wor

ms

Rou

nd w

orm

s

Mol

lusc

s

Ann

elid

s

Radial Symmetry Bilateral Symmetry

No Body Cavity(No coelom)

Body Cavity(Pseudocoelom)

Mouth from First Embryonic

Opening

Mouth from Second Embryonic

Opening

Art

hrop

ods

Echi

node

rms

Cho

rdat

es Phyla

*

INVERTEBRATESSponges have a relatively simple, porous body

Sponges are the simplest animals and have no true tissues- Loose assembly of cells that work together

Sponges filter food from the water passing through the porous bodyhttp://www.shapeoflife.org/video/sponges-origins (14 mins)

Cnidarians are radial animals with sensory tentacles and stinging cells, mouth and stomach, and true tissues of muscle and nerves (first predators). http://www.shapeoflife.org/video/cnidarians-life-move (14:45 mins)They have two body forms - Polyps, such as hydra - Medusae, the jellies

Hydra Jellyfish Sea anemone

Body covering(from ectoderm)

Tissue-filled region(from mesoderm)

Digestive tract(from endoderm)

Body covering(from ectoderm)

Muscle layer(from mesoderm)

Digestive tract(from endoderm)

Pseudocoelom

Body covering(from ectoderm)

Tissue layerlining coelomand suspendinginternal organs(from mesoderm)

Coelom

Digestive tract(from endoderm)

Animal body cavity-coelom

Flat worms- none

Round worms- pseudo coelom

Segmented worms-coelom

Flatworms are the first active hunters- found in the ocean, freshwater, on land, and even

inside other animals. (free living & parasitic)- a simple central nervous system and a head with a

brain - Mouth on the underside of the body not in the head

regionhttp://www.shapeoflife.org/flatworms (9:54 mins)https://www.youtube.com/watch?v=wZBPqITnyME (15 minutes)

Flatworms are the simplest bilateral animalsFlatworms are bilateral animals that have:- no body cavity - a sac-like gut- Hermaphrodites- internal delivery of sperm to egg

Bilateral symmetry

Gastrovascularcavity

Nerve cords

Mouth

Eyespots

Nervoustissueclusters

Parasitic flatworms e.g. Flukes and tapeworms

Flukes: liver diseases - sheep and cattle (fascioliasis) fas·ci·o·li·a·sis

- Human lung fluke disease (endemic hemoptysis): he·mop·ty·sis

Units withreproductivestructures

Scolex(anteriorend)

HooksSucker

Col

oriz

ed S

EM 8

0×

Tapeworms Cause diseasescommonly after eating raw or undercooked meat (beef and pork) or fish that contains the immature form of the tapewormhttp://www.shapeoflife.org/video/flatworm-animation-tapeworm (1:39 mins)

Molluscs- have a distinct body plan• bilaterally symmetrical • a muscular foot, visceral mass, and a mantle which may secrete a shell• well-defined organ systems: circulatory, respiratory, and digestive with a

rasping radulahttp://www.shapeoflife.org/video/molluscs-survival-game (15:08 mins)

Visceral mass

Mantle

Radula

Mouth

Nervecords

Foot

MouthRadula

Digestive tractShell

Digestive tract

ReproductiveorgansHeart

CoelomKidney

MantlecavityAnus

Gill

The largest group of molluscs includes the snails and slugs

Another group of molluscs are the bivalves have shells divided into two halves. This includes clams, oysters, mussels, and scallops

Another group are adapted to be agile predators such as squids and octopuses

Annelids (Segmented worms) –Segmentation provides added mobility for swimming and burrowing: earthworms, Leeches, marine wormsEarthworms eat their way through soil and have a closed circulatory systemhttp://www.shapeoflife.org/video/annelids-powerful-and-capable-worms(13:38 mins)

Marine worms

Excretoryorgan

GiantAustralianearthworm

Segment wall(partitionbetweensegments)

Mouth

Brain

Dorsalvessel

CoelomDigestivetract

Mucus-secretingorgan

Segmentwall

Anus

Bristles

Segmentwall

Blood vesselsNerve cord

Pumping segmental vessels

Nerve cordVentral vessel

Bristles

EpidermisCircularmuscle

LongitudinalmuscleDorsalvesselIntestine

Excretoryorgan

The largest group of segmented worms search for prey on the seafloor or live in tubes and filter food particles

Round worms (Nematodes)

• have a pseudocoelom and a • complete digestive tract and are • covered by a protective cuticle.• usually microscopic and colorless.• some live free in moist soil, water, or in decaying

matter.https://www.youtube.com/watch?v=dYPF5dmT__o

• Parasitic forms cause diseases of plants and animals. https://www.youtube.com/watch?v=fmOJ0bh8le4

Trichinella juvenile

LM 3

50×

Muscle tissue

Col

oriz

ed S

EM 4

00×

Free-livingNematode

Parasitic Nematode with complex life-

cycle

Undercooked pork or game (hunted wild animals)

Caenorhabditis elegans

Arthropods (Jointed legs) – segmented animals – jointed appendages– exoskeleton– Extremely diverse

Marine: http://www.shapeoflife.org/video/marine-arthropods-successful-design (9:28 mins)

Terrestrial: http://www.shapeoflife.org/video/terrestrial-arthropods-conquerors (13:41 mins)

Diverse arthropods include:

- Millipedes and Centipedes- Horseshoe crabs- Arachnids such as spiders, scorpions,

mites, and ticks- Crustaceans- aquatic. Include crabs,

shrimps, and barnacles- Insects

A dust mite (about 420 µm long)A scorpion (about 8 cm long)

A black widow spider (about1 cm wide)

Col

oriz

ed S

EM 9

00×

Crayfish External parts

Antennae(sensoryreception)

HeadThorax

Cephalothorax Abdomen

Swimmingappendages

Walking legs

Mouthparts (feeding)Pincer (defense)

CrayFish Dissection (Virtual)http://www.youtube.com/watch?v=2cBGuEDxvNo

Echinoderms- have spiny skin and a water vascular system for movement

- organisms such as sea stars and sea urchins- penta-radially symmetrical as adults-http://www.shapeoflife.org/video/echinoderms-ultimate-animal (13:54 mins)

Spine

Tube foot Tube foot

The water vascular system has suction cup–like tube feet used for locomotion and transport of substances including dissolved gases of respiration

Anus

Spines

Tube feet

Canals

StomachSea Star Dissectionhttp://www.youtube.com/watch?v=TioCree5axI