Chapter 23 Invertebrates: Learning Goalscf.linnbenton.edu/mathsci/bio/klockj/upload/Ch23 Invertebrates... · What Are the Major Animal Phyla? ... characteristics –Multicellularity

Chapter 23 Invertebrates: Learning Goals

What Are the Key Features of Animals?

Which Anatomical Features Mark Branch Points

on the Animal Evolutionary Tree?

What Are the Major Animal Phyla?

You should be able to match the common name

to the Phyla and explain it’s impact on humans

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



Most animal phyla that currently populate Earth

were present by the Cambrian period (544

million years ago)

– The scarcity of pre-Cambrian fossils led

systematists to search for clues about the

evolutionary history of animals by examining

features of:

–Anatomy

–Embryological development

–DNA sequences

23.2 Which Anatomical Features Mark Branch

Points on the Animal Evolutionary Tree?

Certain features represent evolutionary

milestones, and mark major branching points on

the animal evolutionary tree

– The appearance of tissues

– The appearance of body symmetry

– Protostome and deuterostome development

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



Animals with tissues exhibit either radial or

bilateral symmetry

– Symmetrical animals have an upper (dorsal)

surface and a lower (ventral) surface

– Symmetrical animals are divided into two groups:

–Animals that exhibit radial symmetry

–Animals that exhibit bilateral symmetry

Body Symmetry and Cephalization

Fig. 23-2

(a) Radial symmetry (b) Bilateral symmetry

central axis

anterior

posterior

plane of

symmetry

plane of

symmetry



Animals with radial symmetry can be divided into roughly equal halves by any plane that passes through the central axis – Animals with radial symmetry have two embryonic

tissue (germ) layers

– Ectoderm, which is an outer layer that covers the body, lines its inner cavities, and forms the nervous system

– Endoderm, which is an inner layer that lines most hollow organs

– Bilaterally symmetrical animals have three embryonic tissue (germ) layers

– A layer of mesoderm between the ectoderm and endoderm



Bilaterally symmetrical animals have heads

– Animals with bilateral symmetry can be divided

into mirror-image halves only along one plane

that runs down the midline

– These animals exhibit cephalization, the

concentration of sensory organs and a brain in a

well-defined head, with definite anterior (head)

and posterior regions

Body Symmetry and Cephalization

Fig. 23-2

(a) Radial symmetry (b) Bilateral symmetry

central axis

anterior

posterior

plane of

symmetry

plane of

symmetry



Most bilateral animals have body cavities

– Body cavities are fluid-filled cavities between the digestive tube and the outer body wall



Body cavity structure varies among phyla

– The most common body cavity is a coelom, a

fluid-filled body cavity that is completely lined

with mesoderm

–Phyla with animals that have this type of body

cavity are called coelomates, and include

annelids, arthropods, mollusks, echinoderms,

and chordates (which include humans)

Body Cavities

Fig. 23-3

digestive

cavity

digestive

tract

(c) No coelom

(cnidarians, flatworms)

(b) “False” or pseudocoelom

(roundworms)

(a) “True” coelom

(annelids, chordates)

coelom

body wall

digestive

cavity

digestive

tract

digestive

cavity

digestive

tract

pseudocoelom

body wall

There is no cavity

between the body wall

and digestive tract

The body cavity is partially,

but not completely, lined with

tissue derived from mesoderm

The body cavity is

completely lined with tissue

derived from mesoderm

body wall



– A body cavity that is not completely surrounded

by mesoderm is known as a pseudocoelom

–Phyla with animals that have this type of body

cavity are called pseudocoelomates and

include roundworms, such as nematodes

Body Cavities

Fig. 23-3

digestive

cavity

digestive

tract

(c) No coelom

(cnidarians, flatworms)

(b) “False” or pseudocoelom

(roundworms)

(a) “True” coelom

(annelids, chordates)

coelom

body wall

digestive

cavity

digestive

tract

digestive

cavity

digestive

tract

pseudocoelom

body wall

There is no cavity

between the body wall

and digestive tract

The body cavity is partially,

but not completely, lined with

tissue derived from mesoderm

The body cavity is

completely lined with tissue

derived from mesoderm

body wall



Bilateral organisms develop in one of two ways based on embryological development

– Protostome development

– In these animals, the body cavity forms within the space between the body wall and the digestive cavity

– These animals include nematodes, arthropods, annelids, and mollusks

– Deuterostome development

– In these animals, the body cavity forms as an outgrowth of the digestive cavity

– Echinoderms and chordates are deuterostomes

• Embryonic Development

Blastopore forms

mouth first

Blastopore forms

anus first

• Molecular sequences

Protostomes

Deuterostomes

23.3 What Are the Major Animal Phyla?

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


Fig. 23-1

The Diversity of Sponges

Fig. 23-4


Some sponges contain chemicals useful to

humans

– A number of chemicals within sponges have

proved to be valuable medicines

–The drug spongistatin is an emerging

treatment for the fungal infections that sicken

AIDS patients

–Some medicines derived from sponges

include some promising new cancer drugs


Sponges lack true tissues and organs

– The sponge body is perforated by tiny pores

through which water passes, and by fewer, large

openings through which water is expelled

– As water passes through the sponge, oxygen is

extracted, and microorganisms are filtered out

and digested by individual cells

epithelial

cell

amoeboid

cell

pore

spicules

pore cell

collar cell

(water flow)

(water flow out

of the sponge)

(water flow into

the sponge)

The Body Plan of Sponges

Fig. 23-5

Cnidaria – Sea Anemone

Radial symmetry

Two tissue layers

Filled with water

Nematocysts -

stinging organelles

that release toxins


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


Fig. 23-1

Cnidarian Diversity

Fig. 23-6

Echinoderms - starfish

Endoskeleton

Coelom (cavity lined

with tissue)forms

from gut tube tissue

Deuterostomes

Water vascular

system

Tube feet

(locomotion)


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

The Diversity of Echinoderms

Fig. 23-27

Platyhelminthes - flatworms

Bilateral symmetry

3 tissue layers

Cephalization (nerve mass)

True organs and organ systems

Aceolomate (no body cavity)

Parasitic forms


Some flatworms are harmful to humans

– Tapeworms can infect people who eat

improperly cooked beef, pork, or fish that has

been infected by the worms

–Tapeworm larvae form encapsulated resting

structures, called cysts, in the muscles of

these animals

–The cysts hatch in the human digestive tract,

and the young tapeworms attach themselves

to the lining of the intestine


Some flatworms are harmful to humans

(continued)

–Tapeworms may grow to a length of more

than 20 feet (7 meters), absorbing nutrients

across their outer surface

–They release eggs that are shed in the hosts

feces, continuing the infective cycle

head (attachment site) adult tapeworm

7

5

6

1

2

3

4

8

6 inches

A larval

tapeworm

is liberated by

digestion and

attaches to

the human’s

intestine

The tapeworm matures in a human

intestine, producing a series of

reproductive segments; each segment

contains both male and female sex organs

Eggs are shed from

the posterior end of the

worm and are passed

with human feces

A pig eats food

contaminated by

infected feces

Larvae hatch

in the pig’s intestine The larvae migrate through

blood vessels to pig muscle

The larvae form

cysts in pig muscle

A human eats

poorly cooked

pork with

live cysts

The Life Cycle of the Human Pork Tapeworm

Fig. 23-10

Annelida - segmented worms

Segmented body

Bilateral symmetry

3 tissue layers

Ceolom (fully enclosed body cavity)

Organ systems are more fully developed

Earthworms and Leaches

Decomposers and Parasites

Diverse Annelids

Fig. 23-12

Nematoda - round worms

Exoskeleton (molts)

Unsegmented

Psuedocoelom (false body

cavity)

Bilateral worms

3 tissue layers

Parasites and decomposers

Diseases caused by Nematodes

Diseases caused by Nematodes

Dracunculus medinensis: The Guinea Worm

Phylum Nematoda

West Africa,

East Africa,

India

Guinea Worm Life Cycle

Cyclops – a freshwater crustacean

Vector

Host—human drinking

contaminated water.

Guinea worm larvae

are freed from Cyclops

in human gut.

Guinea Worm Life Cycle

Female worm migrates to

lower extremities to release

her eggs into water.

After releasing eggs,

female dies inside

host.

Mollusca

(clams, snails, slugs, octopuses & squids)

• unsegmented

• exhibit bilateral symmetry

• protostome coelomates

• aquatic & terrestrial

• possess all organ systems

The Diversity of Bivalve Mollusks

Fig. 23-15

The Diversity of Cephalopod Mollusks

Fig. 23-16

Mollusks – soft-bodied

Soft body

Radula (scrapes)

Muscular foot

Protostome ceolomates

Bilateral symmetry

Possess all organ systems

Arthropods

Earth’s largest phylum

Arthropods


Includes spiders, mites, ticks, scorpions,

centipedes, millipedes, lobsters, crabs, beetles,

and other insects.

Arthropods


Characterisitics:

– External skeleton

– Specialized body segments

– Jointed appendages

Arthropods

Specialized segments

– Head

– Thorax

– Abdomen

Arthropods

Organ systems

– Efficient respiratory system including tracheae

– Most have antennae to detect movement, sound

or chemicals

– Some have compound eyes capable of color

vision

Major Arthropod Classes

Centipides

Millipedes


Myriapods have many legs

– The myriapods include the centipedes and

millipedes

–They have one pair of antennae

–They have simple light-detecting eyes

–They respire by means of tracheae

– Centipedes have one pair of legs per body

segment

– Millipedes have two pairs of legs per body

segment


Crustaceans


Arachnids (spiders, ticks, scorpions)

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Chapter 23 Invertebrates: Learning Goalscf.linnbenton.edu/mathsci/bio/klockj/upload/Ch23 Invertebrates... · What Are the Major Animal Phyla? ... characteristics –Multicellularity