CLASSIFICATIONInvertebrates

PLANTAE“PROTISTS” ANIMALIAFUNGI

Ap

ico

mp

lexa

ns

Cili

ates

Kin

eto

pla

stid

s

Eu

gle

nid

s

Dip

lom

on

ads

Ph

aeo

ph

yta

(bro

wn

alg

ae)

Oo

myc

ota

(wat

er m

old

s)

Rh

od

op

hyt

a(r

ed a

lgae

)

Ch

loro

ph

yta

(gre

en a

lgae

)

Bry

op

hyt

a(l

iver

wo

rts,

mo

sses

)

Pte

rid

op

hyt

a(f

ern

s)

Zyg

om

yco

ta

Am

oeb

ozo

ans

Asc

om

yco

ta

Bas

idio

myc

ota

Po

rife

ra(s

po

ng

es)

Cn

idar

ia(a

nem

on

es, j

elly

fish

)

Pro

tost

om

es(w

orm

s, a

rth

rop

od

s, m

ollu

sks)

Deu

tero

sto

mes

(sea

urc

hin

s, s

ea s

tars

, ver

teb

rate

s)

Dia

tom

s

Din

ofl

agel

late

s

An

gio

sper

ms

(flo

wer

ing

pla

nts

)

Gym

no

sper

ms

EUKARYOTIC TREE OF LIFE

Fig. 18-7

WHAT ARE THE KEY FEATURES OF ANIMALS?

Animals possess all of the following characteristics Multicellularity Their cells lack a cell wall They obtain energy by consuming other

organisms Most reproduce sexually They are motile at some point in the life cycle They are able to respond rapidly to external

stimuli

AN EVOLUTIONARY TREE OF SOME MAJOR ANIMAL PHYLA

Fig. 23-1

LACK OF TISSUES SEPARATES SPONGES FROM ALL OTHER ANIMALS

Tissues are groups of similar cells that carry out a specific function (e.g., muscle)

Sponges are the only modern-day animals that lack tissues Individual cells in sponges may be specialized, but they act independently and are not organized into true tissues

Sponges and all remaining tissue-containing phyla arose from an ancient common ancestor without tissues

PORIFERA (SPONGES) Sponges have a simple body plan

Sponges belong to the phylum Porifera and are found in most marine and aquatic environments Sponges do not move, but occur in a variety of sizes

and shapes They may reproduce asexually by budding, where the

adult produces miniature versions of itself that drop off and assume an independent existence

They may reproduce sexually through fusion of sperm and eggs

THE DIVERSITY OF SPONGES

Fig. 23-4

CNIDARIANS

Cnidarians are well-armed predators Sea jellies, sea anemones, corals, and

hydrozoans belong to the phylum Cnidaria These animals are mostly marine and are all

carnivorous predators The cells of cnidarians are arranged into distinct

tissues, including a contractile muscle-like tissue and an organized nerve net

CNIDARIAN DIVERSITY

Fig. 23-6

PLATYHELMINTHES (FLATWORMS)

Flatworms may be parasitic or free living Flatworms are bilaterally symmetrical and belong

to the phylum Platyhelminthes Many species are parasites, organisms that live

in or on the body of another organism Non-parasitic, free-living flatworms inhabit

aquatic, marine, and moist terrestrial habitats Flatworms can reproduce both sexually and

asexually; most are hermaphroditic, having both male and female sexual organs

head (attachment site)adult tapeworm

7

5

6

1

2

3

4

8

6 inches

A larvaltapewormis liberated bydigestion and attaches tothe human’sintestine

The tapeworm matures in a humanintestine, producing a series ofreproductive segments; each segmentcontains both male and female sex organs

Eggs are shed fromthe posterior end of theworm and are passedwith human feces

A pig eats foodcontaminated byinfected feces

Larvae hatchin the pig’s intestine

The larvae migrate throughblood vessels to pig muscle

The larvae formcysts in pig muscle

A human eatspoorly cookedpork withlive cysts

THE LIFE CYCLE OF THE HUMAN PORK TAPEWORM

Fig. 23-10

PLATYHELMINTHES (FLATWORMS)

Another group of parasitic flatworms is the flukes

Flukes have complex life cycles that include an intermediate host, such as a snail

Blood flukes cause schistosomiasis, which causes symptoms such as diarrhea, anemia, and possible brain damage

As many as 200 million people worldwide may be infected with flukes

FLATWORM DIVERSITY

Fig. 23-9

ANNELIDA (SEGMENTED WORMS)

Annelids are segmented worms and belong to the phylum Annelida The annelid body is divided into a series of

repeating units (segmentation) The segments contain identical copies of nerves,

excretory structures, and muscles that allows for complex movement

Annelids have a fluid-filled coelom The coelom functions as a hydrostatic skeleton,

where pressurized fluid provides a framework against which muscles can act

DIVERSE ANNELIDS

Fig. 23-12

MOLLUSCA The three classes of mollusks are:

Gastropods Bivalves Cephalopods

MOLLUSCA Gastropods are one-footed crawlers

The snails and slugs are collectively known as gastropods They have a muscular foot for locomotion They may possess a shell, but not all gastropods are

shelled They feed using a radula, a flexible ribbon studded

with spines that scrape algae from rocks or grasp larger plants or prey

Most use their skin and gills for respiration, but terrestrial mollusks have a simple lung

MOLLUSCA Bivalves are filter feeders

Bivalves include scallops, oysters, mussels, and clams They live in fresh water and marine habitats They possess two shells that can be clamped shut by a

strong muscle They are filter feeders and use gills for both feeding

and respiration Most have a muscular foot used for burrowing or for

attaching to rocks

MOLLUSCA Cephalopods are marine predators

Cephalopods have tentacles with chemosensory abilities and suction disks The tentacles are used for locomotion and to capture

prey These animals are able to move rapidly by

forcefully expelling water from the mantle cavity They possess closed circulatory systems

THE DIVERSITY OF CEPHALOPOD MOLLUSKS

Fig. 23-16

ARTHROPODS

Arthropods are the most diverse and abundant animals The phylum Arthropoda includes insects,

arachnids, myriopods, and crustaceans Arthropods have appendages and an

exoskeleton (external skeleton) The exoskeleton is secreted by the epidermis (the

outer layer of skin) It is composed primarily of protein and chitin (a

polysaccharide)

THE EXOSKELETON MUST BE MOLTED

Fig. 23-18

THE DIVERSITY OF ARACHNIDS

Fig. 23-22

THE DIVERSITY OF MYRIAPODS

Fig. 23-23

THE DIVERSITY OF CRUSTACEANS

Fig. 23-24

ECHINODERMS

Echinoderms have a calcium carbonate skeleton

The phylum Echinodermata includes sand dollars, sea urchins, sea stars, sea cucumbers, and sea lilies Echinoderm larvae exhibit bilateral symmetry;

adults show radial symmetry They exhibit deuterostome development They possess an endoskeleton (internal

skeleton) that sends projections through the skin

THE DIVERSITY OF ECHINODERMS

Fig. 23-27

PHYLUM CHORDATA

The phylum Chordata includes two invertebrate groups (the sea squirts and the lancelets) plus the vertebrates