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Arthropods, from lasttime…Diversity of Arthropoda

Crustacea are the dominant marinearthropods

any terrestrial crustaceans?

sowbugs 2

Diversity of ArthropodaCrustacea are the dominant marine

arthropods

Should we call them shellfish?

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Diversity of ArthropodaCrustacea Morphology

- each segment of thorax andabdomen usually has anappendage

- appendages may be branched

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Diversity of ArthropodaUniramia - “one branch”(unbranched appendages)

Includes insects, millipedes,centipedes

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Diversity of ArthropodaThe insects in particular...

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Diversity of ArthropodaThe insects in particular…

- three body sections

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- three body sectionshead, thorax, abdomen

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- six legs

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- six legs- comprise most of the animal species

on the planet

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Diversity of all described species ofanimals

FLIESB’FLIES& MOTHS

ANTS,BEES &WASPS

BEETLES

TRUEBUGS

OTHERARTHROPODS

OTHERPHYLA

CHORDATA

OTHERINSECTS

73 % INSECTS

12 % OTHERARTHROPODS

4 %CHORDATES

11 % ALLOTHERPHYLA

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Diversity of ArthropodaInsect speciesDescribed species of vertebrates -

38,000Described species of insects - 875,00And the rate of discoveries of new

insect species suggests that thereare many undescribed - estimates of2 million to 30 million

Even the most conservative estimatesuggests that most insect species havenot been described!

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Why have insects been so evolutionarilysuccessful?i. Small size - habitat becomes more

complex as you become smaller,allows more subdivision

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ii. Flight - more movement and rapidcolonization of plants

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Diversity of all described species ofanimals

FLIESB’FLIES& MOTHS

ANTS,BEES &WASPS

BEETLES

BUGS

OTHERARTHROPODS

OTHERPHYLA

CHORDATA

OTHERINSECTS

What do theseinsect groupshave incommon?

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iii. Complete metamorphosis - change inbody plan

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iii. Completemetamorphosis -change in bodyplanallowsspecialization ofimmatures forfeeding andgrowth, of adultsfor dispersal andreproduction

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Why have insects been so evolutionarilysuccessful?i. Small size - habitat becomes more complex

as you become smaller, allows moresubdivision


iii. Complete metamorphosis - change in bodyplan

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Animal diversity 4 - TheDeuterostomes (Echinodermata,Chordata)Key concepts• Key morphological characters of the

Echinodermata, Chordata• Distinguish lineages of vertebrates:

Three lineages of fishes (jawless fishes,cartilaginous fishes, bony fishes) and threelineages of terrestrial vertebrates (amphibians,reptiles [including birds] and mammals)

• Distinguish three groups of mammals• Secondary evolution of ocean dwelling for

terrestrial animals: the marine mammals

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The EchinodermataExamples?Sea stars, sea urchins, sea cucumbers,

sand dollars

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The Echinodermata: Sea stars, seaurchins,

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The Echinodermata: Sea cucumbers

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The Echinodermata: Sand dollars, brittlestars

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The EchinodermataMorphology“Pentameric” symmetry as

adults - rays or armsarranged in groups of 5(but planktonic larvaebilaterally symmetrical)

Endoskeleton ofinterlocking calciumcarbonate plates coveredby epidermis

Water-filled canal system leads to “tube feet”for moving or manipulating things - feet can beextended or retracted with water pressure

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The Echinodermata FeedingPredacious (sea stars) or

grazers (sea urchins) or filterfeeders (sea cucumbers,others)

Favorite foodof sea stars isbivalves likeclams andmussels - howdo they eatthem?

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The Echinodermata FeedingHow do sea stars eat

bivalves?Anchor themselves,

both sides of shellwith tube feet, exertconstant pressure,wear out themuscles of thebivalve. Then...

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The Echinodermata FeedingHow do sea stars

eat bivalves?Then, the seastar everts itsmouthparts andstomach into thecrack,consumes thecontents!

After dinner - everted stomach,and empty shell

Tubefeet

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Last, but hardly least, the Chordata

Chordates = Vertebrates + two smallgroups

- the Tunicates and the Lancelates

Lancelate

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The ChordataTunicatesAs adults look like sponges! But larvae have

all the defining features of chordates

What featurein particular?

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The Chordata Morphology- dorsal hollow nerve cord- notochord (a flexible rod, supporting

the nerve cord) for at least part of life

Lancelet

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In vertebratesthe notochord disappears early in

development, and is replaced by thevertebral column that surrounds thenerve cord

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The general vertebrate body plan

Dorsal nervoussystem

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Internal skeleton

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Internal skeletonOrgans suspended

in coelom

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Internal skeletonOrgans suspended

in coelomWell developed

circulatory systemwith heart

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Evolution of vertebrates• First vertebrates were likely mud-suckers• similar in morphology to modern jawless

fishes• ingested mud, removed organic material• osmoregulatory* abilities allowed fishes

to exploit estuaries**

*osmoregulatory: control of levels of solutes incells (in this case salts)

**estuaries: where salty ocean water and freshwater mix

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Modern jawless fishes - Lampreys andhagfish

Mouth of alamprey

Lampreyfeeding

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Second group of fishes - thecartilaginous fishes

Examples?

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Second (?) group of fishes - thecartilaginous fishes

So named because skeleton madefrom cartilage

First real jaws? (some have JAWS)

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Third group of fishes - the bonyfishesCartilage replaced by bony skeleton

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Third group of fishes - the bony fishesMost fish are bony fish

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Third group of fishes - the bonyfishes

evolved lunglike sacs for respiration,became modified into swim bladders

What are swim bladders used for?

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Amphibians - the first vertebrates onland

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Amphibians - the first vertebrateson landBut - confined to moist habitats:1) Respire with lungs and across

moist skin2) Reproduce in the water, have

external fertilization3) Eggs not waterproof - generally

have to be laid in water (videosegment showing exceptions!)

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Reptiles - better adapted to dryland1) skin

covered withscales

3) Egg with waterproof shell - the Amniotes

2) Internalfertilization

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One hypothesis for terrestrialvertebrate phylogeny

REPTILES

MAMMALSTURTLESTUATARASLIZARDS &SNAKESCROCODILIANSDINOSAURS ANDBIRDS

AMPHIBIANS

AMNIOTES

A tuatara - singlespecies remainingof this reptilelineage 45

The reptiles

REPTILES

MAMMALSTURTLESTUATARASLIZARDS &SNAKESCROCODILIANSDINOSAURS (INCL.BIRDS)

AMPHIBIANS

AMNIOTES

Birds are reptiles and closely relatedto dinosaurs: scales have beenmodified into feathers

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REPTILES

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Mammalia

I. What unites us? Hair, milkproducing glands

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Mammalia

i. What unites us? Hair, milkproducing (mammary) glands

ii. Not many species (4,500 comparedto 875,000 species of insects)

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Mammaliai. What unites us? Hair, milk producing

glandsii. Not many species (4,500 compared to

875,000 species of insects)Iii. But very diverse morphologically,

ecologically

2 g160,000 kg

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Mammaliai. What unites us? Hair, milk producing

glandsii. Not many species (4,500 compared to

875,000 species of insects)iii. But very diverse morphologically,

ecologicallyiii. And our species has the greatest

impact of any animal on life on thisplanet

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MammaliaThree commonly distinguished groups of

mammalsMonotremes - egg laying mammals with

reptilian-like splayed legs. Only 3 spp.:the Australian platypus and 2 spp. ofechidna

Marsupials - give birth to tiny young,nursed in ventral pouch - most of 240spp. in Australia

Eutherian mammals - (= “placentalmammals”) by far the most diverse -over 4,000 spp.

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Monotremes - egg laying mammals

Echidna

Platypus

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Marsupials - mammals with pouches

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Eutherian mammals - the rest of us

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Evolution of Cetacea (whales,porpoises and dolphins)

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Evolution of Cetacea (whales, porpoisesand dolphins)How did land mammals adapt to the sea?

Entire transition from land mammal tomarine whale - only 8 million years.

Secondary evolution of ocean dwelling inanimals

Secondary evolution - reacquisition of alost trait

New fossils show the closest land-livingrelatives to whales are the artiodactyls(includes hippos, pigs, camels giraffes,deer, sheep and cattle)

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Evolution of Cetacea (whales, porpoisesand dolphins) Likely evolutionarysequence

Lived onland - fedwhilewading

Reconstruction of the first cetaceanA later groupwere morelikecrocodiles -ambushedprey inshallow water 58


A later marine group had a very longsnake-like body, a tail-fluke andcomplete, tiny hind-limbs with mobileknee and toes

Hind limb

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Modern Cetacea - nearly 80 species

Forelimbs modified to form flippersNostrils on top of the head - blowholeHind limbs do not extend out of body

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