Diversity of Life II

Lecture 6

Copyright © 2012 Joe Marx.

Diversity of Life II Page 2

Topics for This Lecture• What is an animal?• What are the major types

of animal?• When did each type of

animal first appear in the fossil record?

TAXONOMIC CATEGORIES—

KingdomPhylum

SubphylumClassOrderFamilyGenus

Species

Image courtesy of Wikimedia Commons.Diversity of Life II Page 3

Animals• The biological kingdom comprising multicellular

eukaryotes whose members digest food outside their cells and then absorb the products.– Unlike other eukaryotes, lack rigid cell walls.

• Definite fossils date from the Cambrian.– Possible fossils appear about 610 mya, in the

Ediacaran.

White's Tree Frog (Litoria caerulea), Australia.

Animal Taxonomic Overview1. Asymmetric animals.

2. Radially symmetric animals.

3. Bilaterally symmetric animals.(More or less correspond to coelomates, which have a body cavity—the coelum—filled with fluid and containing organs attached to each other.)

a) Protostomes, in which the first opening that forms in the embryo becomes the mouth.I. Lophotrochozoa, which have a distinctive larval

form or a distinctive feeding apparatus.

II. Ecdysozoa, which shed their exoskeletons.

b) Deuterostomes, in which the second opening that forms in the embryo becomes the mouth.

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Both images courtesy of Wikimedia Commons.Diversity of Life II Page 5

• Phylum of asymmetric filter feeders without nerves, muscles or internal organs.– Cells are differentiated but do not

form tissues, which are cellular assemblages that perform a specific function.

• Oldest fossils are from the Ediacaran.

Porifera (Sponges)

Basic spongebody plan.

◄ Raphidonema farringdonense from the Cretaceous Faringdon Sponge

Gravels, Oxfordshire, England. About one inch across.

Diversity of Life IIImage courtesy of UC Museum of Paleontology,

www.ucmp.berkeley.edu. Page 6

Cnidaria• Phylum of radially symmetric animals that

includes jellyfish, sea anemones and corals.– Cells are organized into tissues.– Body is essentially a bag or “stomach” with one

opening.– Stinging cells help catch prey.

• Oldest fossils are from the Ediacaran.

◄ Basic Cnidarian body plan. Cnidarians are constructed of two

cell layers.Mesoglea is a non-living jellylike

substance.

Diversity of Life II Images courtesy of U.S. Geological Survey. Page 7

Corals• Class of cnidarians that secrete calcium

carbonate skeletons.– Some form large colonies of interconnected

individuals, which may build organic reefs.• Have left an excellent fossil record.

Coral fossil from a 500-million year old reef in Tennessee.Modern staghorn coral.

Diversity of Life IILeft-hand image courtesy of NASA.

Right-hand image courtesy of Wikimedia Commons. Page 8

Annelids (Segmented Worms)• Phylum of lophotrochozoan protostomes that

includes earthworms, leeches and marine worms.– Have fluid-filled coelum divided into segments, which

expand and contract independently.• Rarely fossilize, except for trace fossils.

– Oldest accepted fossils are of Cambrian age.

Leech in water. ►

◄ Annelid body plan.

Image courtesy of Wikipedia.Diversity of Life II Page 9

Mollusks• Phylum of lophotrochozoan

protostomes that includes snails, clams and octopuses.– Have a coelum with no

segmentation.– Often have a radula, a filelike

structure for obtaining food.– Usually have a CaCO3 shell,

Inside of a Californian red abalone shell.

secreted by a fold of the outer skin called the mantle, and a gill for extracting oxygen from water and emitting waste.

• Have left a rich fossil record, first appearing in the Lower Cambrian.

Image courtesy of Wikimedia Commons.Diversity of Life II Page 10

• Class of mostly marine mollusks that includes clams, mussels, scallops and oysters.– Have shells in two, more or less symmetrical parts,

known as valves.– Have no head—feed by using gills to filter large

particles from water.• Fossils first appear in the Lower Cambrian.

Bivalves

◄ Bivalve shells.

Image courtesy of Wikipedia.Diversity of Life II Page 11

Gastropods• Class of mostly marine mollusks that includes

snails, slugs, abalones and conches.– Usually have a one-piece shell, generally coiled or

spiraled, though it may be reduced or lacking.– Typically have a head, with a mouth and one or

more sensory tentacles, and a flattened foot.– Have U-shaped body plans with the anus above

and to the side of the head.• Fossils first appear in the Upper Cambrian.

Arion ater, the black slug. The large opening behind the head is

used for breathing. ►

Images courtesy of Wikipedia.Diversity of Life II Page 12

Cephalopods• Class of marine mollusks that includes squids,

octopuses and chambered nautiluses.– Except for nautiloids, have an internalized or

absent shell.– Characterized by a bilateral body symmetry, a

prominent head, and a modification of the mollusk foot into arms or tentacles.

• Fossils first appear in the Upper Cambrian.

Chambered Nautilus (Nautilus pompilius)

Image courtesy of Wikipedia.Diversity of Life II Page 13

Lophophore• A characteristic feeding organ possessed by

several phyla of lophotrochozoans. • Consists of a ring of tentacles around the mouth.

– The hollow tentacles—often arranged in a coil or horseshoe shape—bear cilia, fine mobile hairs.

– The cilia create water currents that enable filter feeding.

Freshwater bryozoan, with extended lophophore, from a lake

in North Carolina. ►

Diversity of Life IILeft-hand image courtesy of Ohio Dept. of Natural Resources.

Right-hand image courtesy of Wikipedia. Page 14

Brachiopods (Lamp Shells)• Phylum of lophotrochozoan protostomes that

superficially resemble bivalve mollusks.– Have two mutually nonsymmetrical shells, each of

which has its own bilateral symmetry.• Most conspicuous of Paleozoic fossils, first

appearing in the Lower Cambrian.

Ordovician brachiopods from Ohio.

Lingula anatina, showing the fleshy stalk by which most brachiopods attach

themselves to the substrate.

Image courtesy of Wikimedia Commons.Diversity of Life II Page 15

Bryozoans (“Moss Animals”)• Phylum of tiny lophotrochozoan protostomes that

usually live in colonies.– Have minimal coelomate bodies with a looped

alimentary canal.– Typically build CaCO3 skeletons that superficially

resemble coral.• Fossils first appear in the Early Ordovician.

◄ Bryozoan skeleton in Ordovician limestone from Batavia, Ohio.

Image courtesy of Thomas Stromberg.Diversity of Life II Page 16

Arthropods• Phylum of ecdysozoan protostomes that includes

insects, spiders, crabs and lobsters.– Comprise about 80% of described animal species.– Have a stiff external skeleton protecting a coelum

that is divided into segments, to each of which is attached jointed appendages.

• Earliest certain fossils are of Lower Cambrian age.

Velvet Worm (Onychophora) from the Amazon rain forest in Peru. Onychophorans

are a minor ecdysozoan phylum closely related to arthropods. They are not related, as

formerly thought, to annelid worms.►

Image courtesy of National Science Foundation Multimedia Gallery.

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Trilobites• Extinct subphylum of

marine arthropods with a body divided into three lobes.

• Fossils first appear in the Cambrian.– Most diverse group of

animals preserved in the fossil record.

Olenellus getzi,Cambrian Kinzers formation, eastern

Pennsylvania, 515 mya. ►

Image from plate 19 of Prof. Albert Oppel's "Über jurassische Crustaceen" (1860-2).

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Crustaceans• Subphylum of mostly marine arthropods

including lobsters, shrimps, crabs and barnacles.– Characterized by a head formed of five fused

segments, behind which additional segments comprise a thorax and an abdomen.

• Fossils first appear in the Cambrian.– Their fossil record is uneven due to a lack of hard

parts.

Glyphea pseudastacus, a fossil lobster from the Jurassic of Bavaria. ►

Image courtesy of Wikimedia Commons.Diversity of Life II Page 19

Insects• Class of six-legged, mostly terrestrial, arthropods

including about a third of known animal species.– Though similar in body plan to crustaceans,

insects differ from other arthropods by having exposed mouthparts and one or two pairs of wings.

• Fossils first appear in the Lower Devonian.– Their fossil record is uneven due to the lack of

hard parts.

◄ Convolvulus Hawk-moth (Agrius convolvuli).

Diversity of Life IIImage courtesy of National Oceanic and Atmospheric

Administration. Page 20

Echinoderms• Phylum of marine deuterostomes without

backbones, including starfishes and sea urchins.– Have fivefold radial symmetry.– Usually have an internal skeleton of calcite plates

that readily fossilize.• Fossils first appear in the Lower Cambrian.

Sand dollar, Gray’s Reef National Marine Sanctuary, Georgia. ►

Image courtesy of National Oceanic and Atmospheric Administration.

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Asteroidea (Starfishes)• Class of echinoderms that have five or more arms

radiating from an indistinct disk.– Lack a rigid skeleton.– Use a water vascular system featuring tube feet,

projections located on the bottom of the arms, to move and grasp prey.

– Extrude stomach around captured food.• Scanty fossil record, first appearing in the Lower

Ordovician.

Redbanded Sea Star, Orthasterias koehleri (foreground), and

Blood Star, Henricia leviuscula, in Pacific Ocean off Alaska. ►

Diversity of Life IIImage copyright © 2003 by Daniel P.B. Smith,

courtesy of Wikipedia. Page 22

Echinoidea (Sea Urchins)• Class of globe or disc-shaped echinoderms that

includes sea urchins and sand dollars.– Have rigid skeleton composed of interlocked plates

to which spines attach.– Divided into regular sea urchins, which have radial

symmetry, and irregular sea urchins, like sand dollars, which have bilateral symmetry.

• Fossils first appear in the Upper Ordovician.

◄ A group of Diadema antillarium, the long-spined sea urchin.

Image courtesy of National Oceanic and Atmospheric Administration.

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Crinoids (Sea Lilies)• Class of echinoderms that sieve water-borne food

with featherlike arms and use tube feet to pass the food to a centrally-located mouth.– Most swim by waving their arms but some attach to

the seafloor with a long, flexible stalk.• Fossils first appear in the Ordovician.

Top view of a stalked crinoid, about five

inches across, southern Marianas. ►

◄ Fossil crinoids from Germany.

Image by Ivy Livingstone, copyright © BIODIDAC.Diversity of Life II Page 24

Chordates• Phylum of deuterostomes that includes the

vertebrates—animals with backbones—as well as a few closely related invertebrates.

• Have• Have, at some point in life:– A notochord (a flexible rod extending

the length of the body).– A hollow nerve cord along the back.– Pharyngeal slits (“gills”).– A muscular tail.

• Include lancelets, primitive chordates with no backbone.

• Fossils first appear in the Lower Cambrian.

The lancelet Branchiostoma lanceolatus.

Diversity of Life IIUpper image courtesy of Mateus Zica.

Lower image courtesy of U.S. Geological Survey. Page 25

Conodonts (“Cone Teeth”)• Class of extinct, eel-like, marine vertebrates.

– Produced abundant, tiny fossils called conodont elements:• Probably used for filter feeding.• Made of calcium phosphate that darkens with heat.• Found from the Cambrian to the Upper Triassic.

◄ Scanning electron microscope photomicrograph of conodont elements from the Jonesboro Limestone in Cades Cove, Great Smoky Mountains National Park,

Tennessee.

▲ Reconstruction of a conodont.

Image courtesy of Wikimedia Commons.Diversity of Life II Page 26

Fishes• Vertebrates with neither four limbs nor four-

limbed ancestors.– Skeletons are either cartilaginous or bony.

• Bony fishes are either ray-finned or lobe-finned.

• Fossils first appear in the Lower Cambrian, but are scarce until hinged jaws appear in the Silurian.

Latimeria chalumnae, one of two living species of a lobe-finned fish called a coelocanth.

Image courtesy of Wikipedia.Diversity of Life II Page 27

Amphibians• Vertebrates that have either four limbs or four-

limbed ancestors and that lay eggs that are not enclosed in a protective membrane.– Include frogs, toads and salamanders.– Typically lay eggs in fresh water.– Larvae live in water and gradually metamorphose

into terrestrial adults.• Fossils first appear in the Devonian.

◄ Tadpole of Littlejohn's Tree Frog (Litoria littlejohni), southeastern

Australia.

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Reptiles• Vertebrates that have either four limbs or four-

limbed ancestors, that lay eggs protected by membranes, and that are not mammals.– Include crocodiles, lizards, snakes and turtles.– Similar to fish and amphibians in ectothermic

temperature regulation:• Behaviors serve to gain or lose environmental heat.• Blood circulation distributes heat among body regions.

– Differ from fish and amphibians in their complete adaptation to life on land.• Eggs survive out of water.

• Fossils first appear in the

Upper Carboniferous.Hylonomus lyelli, Late

Carboniferous, Nova Scotia, Canada.

Image courtesy of Nobu Tamura.

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Dinosaurs• Terrestrial crocodilian

reptiles with limbs held erect beneath the body.– Share a common

ancestor with birds.– Probably endothermic,

like birds and mammals, with an internally controlled body temperature.

• Fossils found from the Upper Triassic to the end of the Cretaceous.

Struthiomimus altus, a long-legged, ostrich-like dinosaur, probably

feathered, from Alberta, Canada.

Image courtesy of Wikimedia Commons.

Birds• The sole surviving dinosaur clade.

– Defined as all descendants of the most recent common ancestor of modern birds and Archaeopteryx.• Evolved from theropod dinosaurs during the Jurassic.

– Characterized by:• Feathers.• A beak with no teeth.• Hard-shelled eggs.• A high metabolic rate.• A lightweight but strong skeleton.• Bipedalism (Two hind limbs used for locomotion).

– With about 10,000 living species, the most diverse group of four-limbed vertebrates.

Diversity of Life II Page 30Image courtesy of Raimond Spekking

and Wikimedia Commons.

Archaeopteryx lithographica. ►

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Mammals• Class of endothermic vertebrates typified by:

– Presence of sweat glands for heat dissipation.– Female production of milk for infants.– Presence of hair for insulation.– Teeth highly differentiated by form and function.– Three minute ear bones that are not part of the jaw.– Presence of a neocortex region in the brain.

• Fossils first appear in the Upper Triassic.– Evolved from reptiles by way of the therapsids.

Image courtesy of Nobu Tamura.

◄ Cynognathus, a cynodont therapsid, about 3 ½ feet long, from

the Triassic of South Africa