"For HELPCLICK only!!"_BIO II and College Math_forum-B

AlphaMann

ch20_for-helpclick.pdf

Home >Biology homework help >"For HELPCLICK only!!"_BIO II and College Math_forum-B

Animals and How They

Evolved

20-1

20.1 Animals have distinctive

characteristics

 Animals are multicellular eukaryotes.

 Heterotrophs – acquire nutrients from external source

 Digest nutrients internally

 Usually carry on sexual reproduction

 Developmental stages to produce specialized tissues

within organs

 Muscles and nerves

 Allow animals to perform flexible movements

 Search actively for food

 Seek mates, shelter, suitable climate

20-2

Figure 20.1A 20-3

Adult frog

(adult frog): © Dwight Kuhn; (bottom): © Cabisco/Phototake

Embryonic stages (both): © Cabisco/Phototake

Embryonic stages

Figure 20.1A (Cont.) 20-4

Embryonic stages produce a tadpole

20-5

A tadpole undergoes metamorphosis to become a frog

Figure 20.1A (Cont.)

20.1 Animals have distinctive

characteristics

 Colonial flagellate hypothesis

 Animals descended from an ancestor that resembled

a spherical colony of flagellated cells

 Implies that radial symmetry preceded bilateral

symmetry

 Cambrian explosion

 Representatives of all animal phyla appeared at once

in geologic terms around 540 MYA, the start of the

Cambrian period

20-6

20-7

radial symmetry bilateral symmetry

posterior

Figure 20.1B 20-8

3 4 2 1 Infolding creates

tissues.

Specialization of cells

for reproduction.

Colony of cells forms

a hollow sphere.

Motile flagellates

form an aggregate.

single flagellate

reproductive

cells

20.2 The phylogenetic tree of animals is

based on molecular and anatomic data

 There is no adequate fossil record by which to

trace the early evolution of animals.

 The tree is based on molecular and anatomic

data.

 It is assumed that the more closely related two

organisms are, the more DNA base sequences

they will have in common.

20-9

Figure 20.2A 20-10

Flatwarms

common ancestor

multicellularity

ancestral protist

tissue

layers

bilateral symmetry

3 tissue layers

body cavity

Sponges

Cnidarians

deuterostome

development

radial symmetry

2 tissue layers

protostome

development trochophore

larva

Echinoderms

Chordates

Arthropods

Roundworms

Annelids

Molluscs

molting of

cuticle

R a d

ia ta

T ro

c h

o z o

P ro

to s to

m ia

B il a te

ri a E

c d

y s o

z o

D e u

te ro

s to

m ia

20.2 The phylogenetic tree of animals is

based on molecular and anatomic data

 Type of symmetry:

 Asymmetry – no particular body shape; sometimes

sessile – attached to substrate

 Sponges

 Radial – organized circularly

 Cnidarians

 Bilateral – right and left halves

 Accompanied by cephalization – localization of brain and

specialized sensory organs at the anterior end

 All other animals

20-11

20.2 The phylogenetic tree of animals is

based on molecular and anatomic data

 Embryonic development

 Sponges do not have true tissues

 Cellular level of organization

 Germ layers – first three tissue layers

 Cnidarians have ectoderm and endoderm

 Tissue level of organization

 Other animals have three layers – add mesoderm

 Organ level of organization

20-12

20.2 The phylogenetic tree of animals is

based on molecular and anatomic data

 Protostomes or deuterostomes

 Differentiated by 3 events:

1. Spiral or radial cleavage

2. Fate of blastopore

3. Development of true coelom (coelom)

 Deutrostomes include echinoderms and chordates

 Protostomes divided into:

 Ecdysozoa – molt

 Trochozoa – have or had trochophore larva

20-13

Figure 20.2B 20-14

Protostomes Deuterostomes

C le

a v a

g e

top view side view side view top view

Cleavage is spiral and

determinate.

Cleavage is radial and

determinate.

Protostomes Deuterostomes

p r i m i t i v e g u t a n u s

blastopore anus blastopore mouth

F a

te o

f b

la s

to p

o re

mouth primitive gut

Blastopore becomes mouth. Blastopore becomes the anus.

Protostomes Deuterostomes

ectoderm endoderm

mesoderm

C o

e lo

m f

o rm

a ti

o n

mesoderm

gut gut

Coelomforms by a

splitting of the mesoderm.

Coelomforms by an

outpocketing of primitive gut.

The Invertebrates

20-15

20-16

Sponges (bony, glass, spongin): *Asymmetrical, saclike body perforated by pores; internal cavity lined by choanocytes;

spicules serve as internal skeleton. 5,150+

Cnidarians (hydra, jellyfish, corals, sea anemones): Radially symmetrical with two tissue layers; sac body plan;

tentacles with nematocysts. 10,000+

Flatworms (planarians, tapeworms, flukes): *Bilateral symmetry with cephalization; *three tissue layers and organ

systems; acoelomate with incomplete digestive tract that can be lost in parasites; hermaphroditic. 20,000+

Molluscs (chitons, clams, snails, squids): *Coelom; all have a foot, mantle, and visceral mass; foot is variously modified;

in many, the mantle secretes a calcium carbonate shell as an exoskeleton; all organ systems. 110,000+

Annelids (polychaetes, earthworms, leeches): Segmented, with body rings and setae; cephalization in some

polychaetes; hydroskeleton; closed circulatory system. 16,000+

Roundworms (Ascaris, pinworms, hookworms, filarial worms): Pseudocoelom and hydroskeleton; complete digestive

tract; free-living forms in soil and water; parasites common. 25,000+

Arthropods (crustaceans, spiders, scorpions, centipedes, millipedes, insects): Chitinous exoskeleton with jointed

appendages undergoes molting; insects—most have wings—are most numerous of all animals. 1,000,000+

Chordates (tunicates, lancelets, vertebrates): All have notochord, dorsal tubular nerve cord, pharyngeal pouches, and

postanal tail at some time; contains mostly vertebrates in which notochord is replaced by vertebral column. 56,000+

Fishes (jawless, cartilaginous, bony): *Endoskeleton, jaws, and paired appendages in most; internal gills; single-loop

circulation; usually scales. 28,000+

Amphibians (frogs, toads, salamanders): Jointed limbs; lungs; three-chambered heart with double-loop circulation;

moist, thin skin. 6,900+

Mammals (monotremes, marsupials, placental): Hair and mammary glands. 4,800+

* After these characters are listed, they are present in the rest, unless stated otherwise. + Number of species..

DOMAIN: Eukarya

KINGDOM: Animals

CHARACTERISTICS

Multicellular, usually with specialized tissues;

ingest or absorb food; diploid life cycle.

INVERTEBRATES

Radiata

Protostomia(trochozoans)

Protostomia(ecdysozoans)

Deuterostomia

VERTEBRATES

Echinoderms (sea stars, sea urchins, sand dollars, sea cucumbers): Radial symmetry as adults; unique water vascular

system and tube feet; endoskeleton of calcium plates. 7,000+

Reptiles (snakes, turtles, crocodiles): Amniotic egg; rib cage in addition to lungs; three- or four-chambered heart typical;

scaly, dry skin; copulatory organ in males and internal fertilization. 8,000+ Birds (songbirds, waterfowl, parrots, ostriches):

Endothermy, feathers, and skeletal modifications for flying; lungs with air sacs; four-chambered heart. 10,000+

20.3 Sponges are multicellular animals

 Sponges (phylum Porifera) are the only animals

that:

 Lack true tissues

 Are organized only at the cellular level

 Have asymmetrical bodies

 Body perforated by pores

 Filter feeder or suspension feeder – it filters

suspended particles from water

20-17

20.3 Sponges are multicellular animals

 Skeleton

 Have fibers of spongin, a modified form of collagen

 Typically have spicules – small, needle-shaped

structures with one to six rays

 Reproduction

 Reproduce asexually by budding

 Reproduce sexually as egg and sperm are released

into central cavity

 Zygote develops into flagellated larva

20-18

Figure 20.3 20-19

Yellow tube sponge

Figure 20.3 (Cont.) 20-20

Sponge organization collar cell (choanocyte)

flagellum

spicule

pore

amoeboid cell

epidermal cell

amoeboid

cell nucleus

H2O in

through

pores

osculum H2O out

central

cavity

collar

sponge wall

20.4 Cnidarians are radially symmetrical

with two tissue layers

 Most cnidarians (phylum Cnidaria) live in the

sea, but there are a few freshwater species.

 Radially symmetrical

 Capture prey with ring of tentacles that have

specialized stinging cells, cnidocytes

 Each cnidocyte has a nematocyst, a capsule

containing a long, spirally coiled, hollow thread

 Prey drawn into gastrovascular cavity – only

one opening – incomplete digestive tract

20-21

20.4 Cnidarians are radially symmetrical

with two tissue layers

 Two germ layers – tissue level of organization

 Nerve net

 Two basic body forms

1. Polyp – mouth is directed upward

2. Medusa – mouth is directed downward

 Sac body plan with only one opening

20-22

Cnidarians

20-23 Figure 20.4A

Hydra, a polyp

20-24

gastrovascular

cavity

nerve net

mouth

tentacle

bud

Figure 20.4B (Cont.) 20-25

tissue layers

nematocyst

cnidocyte sensory cell

gastrovascular

cavity

flagella

mesoglea

(packing

material)

gland cell

20.5 Flatworms are trochozoans

without a coelom

 Protostomes

 Have a trochophore larva – molluscs and

annelids

 Ancestors had one – flatworms

20-26

cilia

trochophore larva

20.5 Flatworms are trochozoans

without a coelom

 Flatworms (phylum Platyhelminthes)

 First phylum with bilateral symmetry

 Have three germ layers and organ system level

of organization

 Ectoderm from which body wall develops

 Endoderm from which digestive cavity develops

 Mesoderm which contributes to organ formation

 Have no coelum and are called acoelomates

20-27

20.5 Flatworms are trochozoans

without a coelom

 Planarians have several body systems

 Digestive system – pharynx leads to gastrovascular

cavity – incomplete (only one opening)

 Excretory system – series of interconnecting canals

with flame cells

 Reproductive system – hermaphrodites (both male

and female sex organs) can perform cross-fertilization

 Nervous system – ladderlike nervous system –

anterior brain and two lateral nerve cords joined by

cross-branches called transverse nerves

20-28

Planarian

20-29

gastrovascular cavity

eyespots

pharynx extended through mouth

auricle

Digestive system

Figure 20.5A

20-30

flame cell

excretory pore

excretory canal Excretory system

Figure 20.5A (Cont.)

20-31

genital pore ovary yolk

gland

sperm

duct

testis

Reproductive system

penis in

genital chamber seminal

receptacle

Figure 20.5A (Cont.)

20-32

transverse nerve brain lateral nerve cord

Nervous system

Figure 20.5A (Cont.)

20-33

auricle eye spots

5 mm Sense organs

Figure 20.5A (Cont.)

20.5 Flatworms are trochozoans

without a coelom

 Tapeworms

 Endoparasites (internal parasites) of various vertebrates,

including humans

 Vary in length from a few millimeters to 20 meters

 Tough body covering resistant to host’s digestive juices

 Scolex bears hooks and suckers for attachment to intestinal wall

of host

 Flukes

 Endoparasites of various vertebrates

 Anterior end has oral sucker and at least one other sucker used

for attachment to host

 Nearly 800,000 persons die each year from schistosomiasis

20-34

Tapeworm

20-35 Figure 20.5B

20-36

Larvae penetrate skin of a

human, the primary host, and

reach maturity.

Adult worms live and

mate in blood vessels of

the abdomen.

Eggs migrate into digestive

tract or bladder and are

passed in feces or urine.

Figure 20.5C

Fluke

HOW LIFE CHANGES

20A Nemertine Worms Are Closely

Related to Whom?

 Nemertines look like flatworms

 Retractable proboscis for capturing prey

 Complete digestive system with rhynchocoel

 More closely related to molluscs and annelids

than they to flatworms

20-37

Figure 20A.2 20-38

muscles intestine

proboscis

extended

nerve cord

blood vessel

body wall rhynchocoel proboscis

Tropical nemertine

worms are colorful;

those in the temperate

zone tend to be drab.

20.6 A coelom gives complex animals

certain advantages

 One defining characteristic in animals is the

presence or absence of a body cavity or coelom.

 Flatworms have no body cavity.

 Roundworms have a pseudocoelom.

 Body cavity incompletely lined by mesoderm

 Mesoderm lines only body wall

 Molluscs, annelids, arthropods, echinoderms, and

chordates have a true coelom.

 Body cavity completely lined by mesoderm

 Mesoderm lines both body wall and digestive tract

20-39

Figure 20.6 20-40

Acoelomate (flatworms) Pseudocoelomate (roundworms) Coelomate (molluscs, annelids, arthropods,

echinoderms, chordates)

endoderm mesoderm

pseudocoelom endoderm mesoderm

digestive cavity ectoderm

coelom mesentery mesoderm

ectoderm digestive cavity endoderm digestive cavity ectoderm

20.6 A coelom gives complex animals

certain advantages

 Advantages of a coelom:

 Body movements are freer because outer wall can

move independently of enclosed organs

 Ample space allows complex organs and organ

systems to develop

 Organ system of organization

20-41

20.7 Molluscs have a three-part body plan

 Molluscs (phylum Mollusca) have a body

composed of:

 Foot – strong, muscular portion used for locomotion

 Visceral mass – soft portion that contains internal

organs

 Mantle – covering that envelops visceral mass

 May secrete exoskeleton called a shell

 Rasping, tonguelike radula

 Bears many rows of teeth and is used to obtain food

 Three common groups:

 Gastropods, cephalopods, and bivalves 20-42

Figure 20.7A 20-43

radula

teeth

anus gill

foot nerve radula

mouth

digestive gland

visceral mass

mantle

shell

coelom heart

(radula): © Kjell Sandved/Butterfly Alphabet;

Figure 20.7B

 Gastropods

(“stomach-footed”)

 Include snails and

nudibranchs

 Animal moves by

muscle contractions

that pass along its

ventrally flattened foot

20-44

20.7 Molluscs have a three-part body plan

eyes

foot mantle

 Cephalopods (“head-footed”) include

octopuses, squids, and nautiluses

 Foot has evolved into tentacles

20-45

Figure 20.7B (Cont.)

 Bivalves (shells have two parts) include clams,

oysters, scallops, and mussels

 Clam is a filter feeder; food particles and water enter

mantle cavity through siphon

20-46

Figure 20.7B (Cont.)

20.8 Annelids are the segmented worms

 In phylum Annelida, segmentation is seen

externally by rings that encircle the body.

 Partitions called septa divide fluid-filled coelom

 Hydrostatic skeleton

 Nephridia are tubules that collect waste and excrete

it through opening in body wall

 Excretory system

 Complete digestive tract

 Three groups: oligochaetes, polychaetes, and

leeches

20-47

20.8 Annelids are the segmented worms

 Oligochaetes

 Earthworm is oligochaete because it has few setae,

bristles that anchor worm

 Polychaetes

 Most annelids are polychaetes (having many setae

per segment) that live in marine environments

 Leeches

 Lack setae, but have same body plan as other

annelids

 Blood suckers

20-48

20-49

dorsal blood vessel

nephridium

pharynx

mouth esophagus

brain

coelom hearts (5 pairs)

seminal vesicle

ventral blood vessel

ventral nerve cord

clitellum

anus

crop

Figure 20.8A

20-50

dorsal blood vessel

coelom

circular muscles

typhlosole

coelom

ventral

blood vessel

ventral nerve cord

longitudinal

muscles

muscular wall

of intestine

nephridium

setae

cuticle

excretory

pore

Figure 20.8A (Cont.)

20-51

a. Christmas tree worm

parapodia

Sensory

projections

spiraled tentacles

Figure 20.8B

20-52

b. Clamworm

jaw pharynx (extended)

eyes

sensory

projections

parapodia

Figure 20.8B (Cont.)

20-53

c. Medicinal leech

anterior sucker

Posterior

sucker

Figure 20.8B (Cont.)

20.9 Roundworms are nonsegmented

and plentiful

 Among the protostomes, roundworms and

arthropods are ecdyozoans

 They molt – shed their outer covering

 Phylum Nematoda are roundworms

 Nonsegmented

 Occur everywhere in large numbers

 Free-living and parasitic species

20-54

20.9 Roundworms are nonsegmented

and plentiful

 Ascaris

 Humans become infected when they ingest eggs.

 Other roundworm parasites:

 Trichinosis – rarely seen in U.S.

 Elephantiasis – filarial worm carried by mosquitoes

 Blocks lymph circulation causing massive swelling

 Pinworm and hookworm are more common in the U.S.

 Good hygiene, proper disposal of sewage, thorough

cooking of meat, and regular deworming of pets usually

protect people from parasitic roundworms.

20-55

Elephantiasis resulting from filarial worm infection 20-56

Figure 20.9 20-57

20-58

20.10 Arthropods have jointed

appendages

 Arthropods (phylum Arthropoda) are extremely

diverse – more than 1,150,00 species

 May be as many as 30 million

 Six characteristics:

1. Jointed appendages

2. Exoskeleton

3. Segmentation

4. Well-developed nervous system

5. Adaptation of respiratory organs

6. Reduced competition through metamorphosis

20-59

Crayfish

20-60

Abdomen Cephalothorax

antennule

antenna compound

eye

telson

anus

gills mouth

uropods

first walking leg

(pinching claw)

second walking leg

third walking leg

fourth walking leg

fifth walking leg

swimmerets

Figure 20.10A

Figure 20.10B 20-61

20.10 Arthropods have jointed

appendages

 Crustaceans

 Largely marine arthropods that include crabs,

barnacles, shrimps, and crayfish

 Head usually bears a pair of compound eyes and five

pairs of appendages

 Centipedes and millipedes

 Centipedes – pair of appendages on every segment

 Millipedes – two pairs of appendages on most

segments

20-62

20-63 Figure 20.10C

Figure 20.10D

20-64

legs

antenna

20.10 Arthropods have jointed

appendages

 Arachnids include spiders, scorpions, ticks,

mites, and horseshoe crabs.

 Spiders have a narrow waist that separates the

cephalothorax, with four pairs of legs, from the

abdomen.

 Scorpions are the oldest terrestrial arthropods.

 Ticks and mites are parasites.

 Horseshoe crabs use the first pair of appendages for

feeding and defense.

20-65

Figure 20.10E 20-66

cephalothorax

walking legs

abdomen

20.10 Arthropods have jointed

appendages

 Insects, the largest group of arthropods

(1,000,000+ described species), are adapted to

active lives on land.

 The study of insects is called entomology.

 Insect characteristics:

 Body divided into head, thorax, and abdomen

 Mouthparts adapted to each species’ way of life

 Wings enhance ability to survive and reproduce

20-67

20-68

Figure 20.10F

Figure 20.10F (portion) 20-69

right mandible left mandible

ocelli

right maxilla

with maxillary

palp

left maxilla with

maxillary palp

labium with labial palps labrum

Mouthparts of a grasshopper

20-70

antennae

chewing

mouthparts

Grasshopper

Leathery forewings

cover membranous

hindwings

Figure 20.10F (portion)

20.11 Echinoderms are radially

symmetrical as adults

 Echinoderms (phylum Echinodermata) lack

chordate features

 Related to them as deuterostomes

 Radially, not bilaterally, symmetrical as adults

 Larva is bilaterally symmetrical filter feeder

 Adult echinoderms do not have head, brain, or

segmentation

 Nervous system consists of ring of nerves around

mouth extending outward radially

20-71

20.11 Echinoderms are radially

symmetrical as adults

 Locomotion by water vascular system

 Pumps water into many tube feet, expanding them

 No complex respiratory, excretory, or circulatory

system

 Fluids within coelomic cavity and water vascular

system carry out many of these functions

 Most feed on organic matter in sea or

substratum

 Sea stars prey upon crustaceans, molluscs, and other

invertebrates

20-72

20-73 Figure 20.11

Figure 20.11 (portion) 20-74

digestive

gland tube feet

skin gill

anus stomach

sieve plate

arm

endoskeletal plates

eyespot

ampulla

coelom

gonad

The Vertebrates

20-75

20.12 Four features characterize

chordates

 Phylum Chordata

 Deuterostomes

 Most are vertebrates

 Four characteristics:

1. Dorsal supporting rod (notochord)

2. Dorsal tubular nerve cord

3. Pharyngeal pouches

4. Postanal tail

20-76

Chordate Characteristics

20-77

pharyngeal pouches dorsal tubular

nerve cord notochord

postanal tail

Figure 20.12A

20.12 Four features characterize

chordates

 A few invertebrate chordates never replace the

notochord with a vertebral column.

 Lancelets (subphylum Cephalochordata) are

marine chordates only a few centimeters long.

 Retain four chordate characteristics as adults

 Tunicates (subphylum Urochordata) live on the

ocean floor as filter feeders.

 Larva is bilaterally symmetrical and has the four

chordate characteristics

 Metamorphosis produces the sessile adult

20-78

Figure 20.12B 20-79

Phylogenetic Tree of the Chordates

20-80

* includes birds

Lancelets

Tunicates

Jawless Fishes

Cartilaginous Fishes

Ray-finned Fishes

Lobe-finned Fishes

Amphibians

Reptiles*

Mammals

ancestral

chordate

vertebrae

jaws

bony

skeleton

lungs

limbs

amniotic egg

mammary gland common ancestor

C h

o rd

a te

A m

n io

te s

T e tr

a p

o d

G n

a th

o s to

m e s

V e rt

e b

ra te

Figure 20.12C

20.13 Jaws, a bony skeleton, and lungs

evolved among the fishes

 First vertebrates were jawless fishes

 Three living classes of fishes today:

 Jawless fishes, cartilaginous fishes, and bony fishes

 Jaws are believed to have evolved from the first pair of

gill arches, structures that ordinarily support gills

20-81

gill slits jaws

gill

arches

skull

20.13 Jaws, a bony skeleton, and lungs

evolved among the fishes

 Jawless fishes (class Agnatha)  Cylindrical and up to a meter long

 Smooth, scaleless skin, no jaws or paired fins

 Cartilaginous fishes (class Chondrichthyes) includes sharks, rays, and skates  Skeletons of cartilage

 Shark senses:  Sense electric currents in water

 Lateral line system senses pressure waves caused by fish

 Keen sense of smell

 Bony fishes (class Osteichthyes) most numerous and diverse of all vertebrates  Ray-finned fishes use their fins to balance and propel body

 Have a swim bladder for buoyancy

 Bony scales that protect body 20-82

Figure 20.13 20-83

toothed oral disk

gill slits (seven pairs)

Lamprey, a jawless fish

20-84

dorsal fin gill slits

jaw with teeth

pectoral fin

sand tiger shark, a cartilaginous fish

Figure 20.13 (Cont.)

20-85

operculum pectoral fin Soldier fish, a bony fish

anal fin pelvic

fin

caudal fin second dorsal fin first dorsal fin

Figure 20.13 (Cont.)

20.13 Jaws, a bony skeleton, and lungs

evolved among the fishes

 Lobe-finned fishes

 Another type of bony fish

 Ancestral lobe-finned fishes not only had fleshy

appendages that could be adapted to land

locomotion, but most also had a lung, which was used

for respiration.

20-86

20.14 Amphibians are tetrapods that can

move on land

 Amphibians (class Amphibia)

 “Amphibian” means living on both land and in water

 Represented by frogs, toads, newts, and

salamanders

 Characteristics:

 Adults have small lungs – air enters mouth by way of nostrils

 Respiration supplemented by gas exchange through smooth,

moist skin

 Most members lead an amphibious life

 Larval stage lives in water, and adult stage is on land

20-87

Figure 20.14A 20-88

20-89

Transitional form

radius ulna

shoulder

fins tibia-fibula

femur humerus

pelvis

radius ulna

humerus

limbs

shoulder

fibula

pelvis

tibia

femur

Ancestral amphibian

Figure 20.14B

20.14 Amphibians are tetrapods that

can move on land

 A transitional fossil (Tiktaalik roseae) from the

Late Devonian period in arctic Canada links the

lobes of the lobe-finned fishes to the limbs of

ancestral amphibians.

20.15 Reptiles have an amniotic egg and

can reproduce on land

 Reptiles (class Reptilia)

 Diversified and most abundant between Permian

period and entire Mesozoic era

 Alligators, crocodiles, turtles, snakes, lizards, and

tuataras

 Body is covered with hard, keratinized scales, which

protect animal from desiccation and predators

 Fertilization is internal, and female lays leathery,

flexible, shelled eggs

 Amniotic egg made development on land possible and

eliminated need for swimming larval stage

 Ectotherms: body temperature matches environment 20-90

20-91

Amniotic egg

air space

allantois

chorion

embryo

amnion

yolk sac

egg shell

Figure 20.15A 20-92

beak

20.15 Reptiles have an amniotic egg and

can reproduce on land

 Birds (class Aves)

 Characterized by feathers

 Are reptiles  Closely related to bipedal dinosaurs

 Adapted to fly  Forelimbs modified as wings

 Hollow, light bones

 Horny beak instead of jaws with teeth

 Four-chambered heart

 Endotherms: generate internal heat

20-93

Figure 20.15B 20-94

20-95 Figure 20.15C

20.16 Mammals have hair and

mammary glands

 Mammals (class Mammalia) appeared during

the Triassic period (251–199 MYA).

 About the same time as the first dinosaurs

 Two chief characteristics:

1. Hair: Mammals are endotherms, and hair aids

temperature control

2. Milk-producing mammary glands: enable females to

feed (nurse) their young without leaving them to find

food

20-96

20.16 Mammals have hair and mammary

glands

 Monotremes

 Have a cloaca

 Terminal region of the digestive tract serving as common

chamber for feces, excretory wastes, and sex cells

 Lay hard-shelled amniotic eggs

 Marsupials

 Begin their development inside the female’s body, but

are born in very immature condition

 Newborns crawl into pouch on mother’s abdomen

20-97

Figure 20.16A 20-98

a. Duckbill platypus,a monotreme of Australian streams

20-99

b. Virginia oppossum, the only American marsupial

Figure 20.16A (Cont.)

20-100

c. Koala, a tree-dwelling Australian marsupial

Figure 20.16A (Cont.)

20.16 Mammals have hair and

mammary glands

 Placental mammals

 Developing placental mammals depend on placenta

 Organ of exchange between maternal blood and fetal blood

 Include:

 Ungulates – hoofed mammals – horses, rhinos

 Carnivores – dogs, cats, bears

 Primates – monkeys, gorillas, humans

 Cetaceans – whales and dolphins

 Chiroptera – bats

 Rodents – mice, rats, porcupines

 Proboscideans – elephants

 Lagomorphans – rabbits, hares, pikas

 Insectivores – shrews and moles 20-101

20-102 Figure 20.16B

HOW BIOLOGY IMPACTS OUR LIVES

20B Many Vertebrates Provide Medical

Treatments for Humans

 Animals that produce poisons and toxins give us

medicines.

 Genetically modified (GM) vertebrates are used

in animal pharming to produce pharmaceuticals.

 Xenotransplantation is transplantation of

vertebrate tissues and organs into human

beings.

 Pig heart valves and skin are routinely used to treat

humans.

20-103

Figure 20B 20-104

20-105

b. Pig, source of organs

c. Pig heart for transplantation

Figure 20B (Cont.)

Connecting the Concepts:

Chapter 20

 Animals differ in complexity and these

differences can be used to substantiate what

DNA base sequencing tells us about their

relationships.

 Great diversity extends to animals’ different

ways of acquiring food.

 There is progression from the multicellular level

of organization to the tissue level, to the organ

level, and finally to the organ system level.

20-106