CH35 Coelomates Raven Biology

7/29/2019 CH35 Coelomates Raven Biology

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VertebratesChapter 35


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The Chordates (phylum Chordata)

deuterostome coelomates

nearest relatives are echinoderms

(the only other deuterostomes)


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Four features characterize chordates

1. nerve cord

2. notochord3. pharyngeal slits

4. postanal tail

All chordates have all fourof these characteristics at

some time in their lives


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Other characteristics

1. muscles arranged in segmented blocks called somites

2. internal skeleton against which the muscles work (most)


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The Nonvertebrate Chordates

Phylum chordata three subphyla

1. Urochordata2. Cephalochordata

3. Vertebrata

nonvertebrates


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Subphylum Urochordata

tunicates are marine animals larvae are tadpolelike

have notochord and nerve cord free-swimming but do not feed

adults typically lose the tailand notochord

immobile filter-feeders endostyle traps microscopic food

particles in a mucus sheet

many secrete a tunic (cellulosesac) that surrounds the animal


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Subphylum Cephalochordata

Lancelets scaleless chordates notochord persists throughout animals life no distinguishable head

use cilia-generated currents to feed on plankton

closest relatives tovertebrates


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Subphylum Vertebrata

chordates with a spinal columndistinguished from nonvertebrates by

vertebral column: encloses and protects the dorsal nerve cord

head: distinct and well-differentiated; sensory organs


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neural crest: a unique group of embryonic cells thatforms many vertebrate structures

internal organs: liver, kidneys, endocrine glands, heartand closed circulatory system

endoskeleton: made of cartilage or bone

makes possible great size and extraordinary movement

Fig. 35.6 Embryonic development of a vertebra


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Phylogeny of the extant vertebrates

first vertebrates appeared in the oceans about half abillion years ago

jawed fishes soon became dominant their descendants, the amphibians, invaded the land reptiles replaced them as the dominant land

vertebrates gave rise to birds and mammals


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Fishes


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Fishes

most diverse vertebrate group over half of all vertebrates variety - size, shape, color and appearance

have the following characteristics1. vertebral column2. jaws and paired appendages

3. internal gills4. single-loop blood circulation5. nutritional deficiencies


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History

first fishes had mouths with no jawsAgnatha extant as hagfish (class Myxini)and lampreys (class Cephalaspidomorphi)Ostracoderms are now extinct

development of jawsoccurred in the lateSilurian period

(438 - 408 MYA)

jaws evolved from the anterior gillarches that were made of cartilage


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Hagfish

(class Myxini)

Placoderm fossil

Lampreys (class

Cephalaspidomorphi)


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Devonian period (408-360 MYA): two types of jawed fishes

spiny fishes (Acanthodii) smaller fishes that dominated early on armored fishes (Placodermi) larger fishes that dominated late

at the end of the period, these early fishes were replaced bysharks and bony fishes (more improved jaws!)

Carboniferous period (360-280 MYA)Class Chondrichthyes (sharks) became the dominant sea predators

light, flexible skeletonand paired fins madethem superior

swimmers


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Sharks

among the first vertebrates to develop teeth evolved from rough scales on mouths skin easily lost but continuously replaced

lateral line system (in both sharks and bony fishes)

fully developed series of sensory organs under the skin thatdetects changes in pressure waves (more in CH45)

Reproduction in most sharks: differs from that of other fishes eggs are fertilized internally, and pups are born live

a few species do lay fertilized eggs

long gestation periods and relatively few offspring not able to recover quickly from population declines


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Bony fishes the most species rich group of all extant vertebrates

(> 30,000 extant species)

evolved at ~ same time as sharks

heavy internal skeleton

made completely of bone

developed significantadaptations that enabledthem to dominate life in

the water swim bladder gill cover (operculum) gas gland oval body


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Two Major Groups

Ray-finned fishes(class Actinopterygii) parallel bony rays support

and stiffen each fin no muscles within the fins

Lobe-finned fishes(class Sarcopterygii) paired long fleshy muscular

lobes supported by central

co-jointed bones almost certainly theamphibian ancestors


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Amphibians (class Amphibia)

damp-skinned vertebrates

first vertebrates to walkon land

several key characteristics1. legs2. lungs3. cutaneous respiration

4. pulmonary veins5. partially divided heart


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Amphibians (class Amphibia)

successful invasion of lands by vertebrates requiredseveral adaptations

1. legs to support bodys weight2. lungs to extract oxygen from air

3. redesigned heart to drive larger muscles4. reproduction in H2O to prevent egg drying5. system to prevent whole body desiccation

Ichthyostega one of the first amphibians efficient limbs for land crawling

improved olfactory and auditory structures however, still fishlike (spent much of life in

water)


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Tiktaalik

2006 discovery of transitionalfossil between fish andIchthyostega

lived about 375 MYA

shoulder and limb bones like those of

an amphibian fins like those of a lobe-finned fish spent most of its life in water capable of moving onto land to

capture food or escape predators


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Amphibiansfirst became common in the Carboniferous period (360-280 MYA)

14 known families aquatic or semi-aquatic

began to leave marshlands for dry upland in the early Permianperiod (280-248 MYA)

large size and complete body covering point to reliance onlung, not skin, for respiration

40 families (Age of Amphibians)

Triassic period (248-213 MYA) virtual extinction of amphibians from land

modern amphibians are descended from three families of theTertiary period (65-2 MYA)

accomplished a highly successful invasion of wet habitats allover the world


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Modern Amphibians

today there are about 5,670 species in 37 differentfamilies, comprising three orders:

Anura (without tail)

Caudata (visible tail)Apoda (without legs)


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Order Anura (frogs and toads) frogs have smooth, moist skin and long legs toads have bumpy, dry skin and short legs eggs are fertilized externally hatch into swimming tadpole larvae undergo metamorphosis into adults

Order Caudata (salamanders) long bodies, tails & smooth, moist skin live in moist places eggs are fertilized internally

larvae similar to adults

Order Apoda (caecilians) tropical, burrowing amphibians legless with small eyes and jaws with teeth

fertilization is internal


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Reptiles (class Reptilia)

dominated earth for250 million years


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Reptiles (class Reptilia)

7000 extant species of reptiles all living reptiles exhibit three key features1. amniotic eggs, which are watertight2. dry skin, which covers body and prevents water loss3. thoracic breathing, which increases lung capacity

Amniotes reptiles, birds and mammals

four membraneschorion: allows O2 entryamnion: fluid-filled cavityyolk sac: provides foodallantois: excretes wastes


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Reptiles distinguished by the number of holes on side of the

skull behind eye orbit


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Synapsids

rose to dominance firstPelycosaurs first land vertebrates to kill

beasts their own size

Therapsids replaced them about 250 MYA may have been endotherms

replaced by diapsids about 230 MYA most became extinct 170 MYA one group survived and has living

descendants today

(the mammals)


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Archosaurs

first land vertebrates to be bipedal gave rise to dinosaurs about 220 MYA

Dinosaurs dominated for over 150 million years extinction 65 MYA


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Modern Reptiles

developed two important characteristics:1. internal fertilization: sperm fertilizes egg beforeprotective membranes are formed

2. improved circulation:

oxygen is provided to thebody more efficiently

all extant reptilesare ectothermic(obtain heat from

external sources)


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Order Chelonia

Tortoises terrestrial dome-shaped shell

Turtles mostly aquatic disc-shaped shells

both lack teeth but havesharp beaks

marine turtles must return to

land to lay eggs


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Dorsal portion: carapace

Ventral portion: plastron inner layer: ~ 60 bones that includeportions of backbone and ribs

outer layer: covered by horny scales

called scutes (part of the epidermis) scutes: made up of a fibrous

protein called keratin (also makes

up the scales of other reptiles)

leatherback sea turtle and the soft-shelled turtles have shells coveredwith leathery skin instead of scutes

Testudo: mascot of the U of Maryland


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Order Rhynchocephalia

only two species of tuataras large, lizardlike animals only found on islands near New Zealand

parietal eyeinconspicuous third

eye on top of head


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I have never been called to attend a case of Gila monster bite,and I dont want to be. I think a man who is fool enough to getbitten by a Gila monster ought to die. The creature is sosluggish and slow of movement that the victim of its bite iscompelled to help largely in order to get bitten.

Dr. Ward, Arizona Graphic, September 23, 1899

Beaded lizardwestern Mexico

Gila monstersouthwestern U.S.


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Order Crocodylia

25 species, large, primarily aquatic, carnivorous crocodiles

live near or in water in tropical and subtropical regions typically nocturnal

alligators exist in only two species one in southern US; other in China

caimans are native to Central America gharials live only in India and Burma

crocodiles resemble birds more thanthey do other living reptiles in that

build nests and care for their young

have a four-chambered heart


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Chinese

alligator

Gharial (family Gavialidae)

Endangered species


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Most paleontologists agree that birds are the directdescendants of theropod dinosaurs


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diff f h b i f d l i


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differ from other vertebrates in two fundamental traits:1. hair/fur

long, keratin-rich filaments that extend from hair follicles(insulation, camouflage, sensory structure)

2. mammary glandsfemales possess mammary glands that secrete milk

other notable features include: endothermy

depends on more efficient:

circulation: four-chambered heart respiration: diaphragm

placenta specialized organ that brings fetal

and maternal blood into close contact

several adaptations in some groups:


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p g p

1. specialized teeth

different types of teeth are highlyspecialized to match particulareating habits

2. digestion of plants

herbivorous mammals rely onmutualistic partnerships withbacteria for cellulose breakdown

3. development of hooves

and hornshooves are specialized keratin padshorns are bone surrounded by keratinantlers are made of bone, not keratin

4. flying mammals: bats bat wing is a leathery membrane of skin

and muscle stretched over 4 finger bones


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Evolution of Primates


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evolved two features that allowed them to succeed in an

arboreal environment1. grasping fingers and toes (first digit is opposable)2. binocular vision (eyes are shifted toward the front of the face)

about 40 MYA, the earliest primates split into twogroups: prosimians and anthropoids

Prosimians most are nocturnal

only a few survive (lemurs, lorises and tarsiers)Anthropoids diurnal include monkeys, apes and humans

some anthropoids migrated to S. America > 30 MYA


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p g descendants called New World monkeys

all are arboreal grasp objects with long, prehensile tails

anthropoids that remained inAfrica gave rise to two lineagesOld World monkeys ground-dwelling or arboreal none have prehensile tails

Hominoids apes and humans larger brains than monkeys and

lack tails


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Ardi


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Ardi

Ardipithecus ramidus4.4 mya Ardipithecus kadabba5.6 mya

taller than Australicopithecus

brain smaller than Australicopithecus about 20% size of modern humans

reduced canines (hominid dentition) bipedal grasping hallux

Genus Homo


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first humans evolved from australopithecine ancestorsabout 2 MYA(thought to be Australopithecus afarensis)

1960s, hominid bones were found near stone tools inAfrica early human was called Homo habilis(handy man) closely resembled Australopithecusin body shape and size,

but had larger brain volume

The Genus Homo


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active debate whether Homo

should be lumped into habilisorsplit into three species

increasing number ofresearchers favor the splittingH. rudolfensis(most ancient)

H. habilis

H. ergaster(most likely ancestor

to later species)

Out of Africa: Homo erectusH.erectuswas a lot larger than H. habilis(1.5 m tall vs 1 m)

had larger brain, more rounded jaw, able to talk

H. erectusbecame widespread in Africa

then migrated to Asia and Europe

H. erectussurvived for over a million yearslonger than any other human species

A New Addition: Homo floresiensis


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2004, a new human species was discovered in the tinyIndonesian Island of Flores

youngest fossils only 15,000 years old!

H. floresiensis diminutive stature

coexisted with and preyed

on a miniature species of

elephant (now extinct also)

believed to be more

closely-related to H. erectus

than to H. sapiens


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Neanderthals


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Neanderthals

made diverse tools took care of sick and buried dead first evidence of belief in life after death abruptly disappeared about 34,000 years ago

replaced by fossils of H. sapienscalled the Cro-Magnons

DNA analysis indicates that Cro-Magnons andNeanderthals did not interbreed

Neanderthals are our cousins, not our ancestors

Cro-Magnons had a complex social organization thought to have full language capabilities


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Human Races


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visual cues (primarily skin color) to define

races groupings based on overall genetic

similarity are different from those based onskin color or other visual features

different groups of people have interbredduring the entire course of history

constant gene flow prevented theformation of different humansubspecies

only 8% of genetic differences can beaccounted for by racial differences

human races do not reflect significantpatterns of underlying biological

differentiation


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Larvacea

Table 35.5

why are Apes aparaphyletic group?

evolutionary originsof bipedalism?

Bonus topics:

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CH35 Coelomates Raven Biology