CHAPTER 32 AN INTRODUCTION TO ANIMAL DIVERSITY - PowerPoint Presentation

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CHAPTER 32

AN INTRODUCTION TO ANIMAL DIVERSITY

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I.

Concept 32.1: What is an Animal?

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95% are invertebrates

Multicellular

Eukaryotic

Heterotrophic (

ingestive

)

Lack

cell

walls

Most are mobile

Diploid with haploid gametes

Sexual reproduction (zygote



blastula



gastrula

)

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Embryology--Cleavage

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9. Carbohydrates stored as glycogen

10. Some

produce larva which undergo metamorphosis

11. Specialized systems

12. Two unique types of tissue:

nervous tissue

and muscle tissue

13. Share the unique

homeobox

-containing family of regulatory genes know as

Hox

genes

Hox

genes play an important role in development of animal embryos

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II.

Concept 32.2: Animal History

A. Common Ancestor

Such a colony is about 0.02mm high.

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1. May have resembled modern

choanoflagellates

2.

Choanoflagellates

are

protists

that are the closest living relatives of animals and were probably a colonial, flagellated

protist

.

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III. Concept 32.3: Body Plans

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A. Phylogeny

Define as the evolutionary history of species

Based on general features of morphology and development

Each major branch represents a

grade

, (group of animal species that share the same level of organizational complexity)

A grade is not necessarily a

clade

or

monophyletic

group.

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ANIMALS

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Metazoa

Parazoa

Eumetazoa

Radiata

Bilateria

Acoelomate

Pseudocoelomate

Coelomate Deuterostomes Protostomes

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B. Major Branches of the Animal Kingdom

1.

Subkingdom

Parazoa

Simple anatomy (lack true tissues)

Phylum

Porifera

2.

Subkingdom

Eumetazoa

True tissues

All other phyla

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C. Body Plans

A

body plan

is a set of morphological and developmental traits

1.Symmetry

Animals can be categorized by body symmetry or the lack of it

a. Radial symmetry (

Radiata

)

-Characterized

by a body shaped like

a pie

or

barrel

, with many equal parts radiating outward like spokes of a wheel -have oral and aboral sides but no

front, back

,

left, or right surfaces

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b. Bilateral symmetry (

Bilateria

)

-Characterized

by a body form with a central

longitudinal plane

dividing the body into two

equal

but opposite halves

-A dorsal (top) and ventral (bottom) sides

-Anterior (head) and posterior (tail) ends

-Left and

right

sides

-Exhibit cephalization (concentration of nerves and sense organs on anterior end)

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SYMMETRY

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2. Tissues

a. Tissues

are collections of specialized cells isolated from other tissues by membranous layers

b. During

gastrulation

(downward and

inward movement

of cells

of

blastula

),

three germ layers

form which give rise to the tissues and organs of the animal embryo

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c.

Diploblastic

Tissues

develop from two germ layers

(ectoderm or endoderm)

d.

Triploblastic

Tissues develop from three germ layers:

Ectoderm

is the outer

most

germ layer which develops into

outer layer and

central nervous system

Endoderm is the inner most germ layer and lines the developing digestive tube called the archenteronMesoderm is the middle layer which is located between ectoderm and endoderm

Includes all

bilaterians

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Germ Layers

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3. Body Cavity (Coelom)

Defined as a fluid- or air-filled space separating the digestive tract from the outer body wall

a.

Acoelomate

No body cavity between digestive tract and

outer

body wall

Area filled with cells

Phylum

Platyhelminthes

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Acoelomate

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b.

Pseudocoelomate

Body cavity lined with mesoderm and endoderm

Tube within a tube

Phyla

:

Nematoda

Rotifera

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Pseudocoelomate

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c. Coelomate (true body cavity)

Body cavity lined with mesoderm

Mesenteries connect outer and inner mesoderm and suspend internal organs

Phyla

:

Echinodermata

Arthropoda

Mollusca

Chordata

Annelida

Functions of the body cavity

1. Fluid cushions the suspended organs, helping to prevent internal injury

2. In soft-bodied

coelomates

, functions as a hydrostatic skeleton against which muscles can work

3. Enables internal organs to grow and move independently of the other body wall

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Coelomate

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. Development--

Protostomia

vs.

Deuterostomia

2 evolutionary lines in

coelomates

Differ in cleavage, fate of

blastopore

, and coelom formation

Protostomes

—mollusks, annelids, arthropods

Deuterostomes

—echinoderms, chordates

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a

. Cleavage



Protostomes

Spiral Cleavage

—cleavage diagonal to the embryo’s vertical axis



Deuterostomes

Radial Cleavage

—cleavage either parallel or perpendicular to embryo’s vertical axis

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b.

Determination



Protostomes

Determinate Cleavage

—developmental fate of each cell determined very early

-A

cell from 4-cell stage will not

develop

fully



Deuterostomes

Indeterminate Cleavage

—early cells retain ability to develop into complete embryo if isolated from other

cells

-Makes possible identical twins and embryonic stem cells

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Cleavage

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c

. Coelom

Formation



Protostomes

Schizocoelous

—the splitting of solid masses of mesoderm forms the coelom



Deuterostomes

Enterocoelous

—the mesoderm buds from the wall of the archenteron to form the coelom

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Coelom Formation

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d.

Fate of

Blastopore

Blastopore

—first opening of

archenteron (gut) which forms

from blastula during

gastrulation



Protostomes

--

Blastopore

becomes the mouth

Deuterostomes --Blastopore becomes the anus

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Fate of the

Blastopore

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IV. Concept 32.4: New Views of Animal Phylogeny

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One hypothesis of animal phylogeny is based mainly on morphological and developmental comparisons

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Morphological Characteristics

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One hypothesis of animal phylogeny is based mainly on molecular data

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Molecular Studies

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A. Points of Agreement

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All animals share a common ancestor

Sponges are basal animals

Eumetazoa

is a clade of animals (

eumetazoans

) with true tissues

Most animals phyla belong to the clade

Bilateria

and are called

bilaterians

Chordates and some other phyla belong to the clade

Deuterostomia

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B. Progress in resolving

Bilaterian Relationships

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1. The morphology-based tree divides

bilaterians

into two clades:

deuterostomes

and

protostomes

2. In contrast, recent molecular studies indicate three

bilaterian

clades:

Deuterostomia

,

Ecdysozoa

, and

Lophotrochozoa

a. Ecdysozoans shed their exoskeletons through a process called ecdysis (Arthropoda and Nematoda) b. Some

lophotrochozoans

have a feeding structure called a

lophophore

(

Mollusca

,

Annelida

,

Rotifera

,

Platyhelminthes

)

c. Other phyla go through a distinct developmental stage called the

trochophore larva(Mollusca and

Annelida)

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TERMS:

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Zygote

Cleavages

BlastulaGastrulaEctoderm

Endoderm

Mesoderm

Blastopore

Archenteron

Metamorphosis

Radial symmetry

Bilateral symmetry

Cephalization

Acoelomate

Pseudocoelomate

Coelomate

Anterior

PosteriorDorsalVentral

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Ecdysis

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Trochophore

Larva40

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You should now be able to:

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List the characteristics that combine to define animals

Distinguish between the following pairs or sets of terms: radial and bilateral symmetry; grade and clade of animal

taxa

;

diploblastic

and

triploblastic

; spiral and radial cleavage; determinate and indeterminate cleavage;

acoelomate

,

pseudocoelomate

, and coelomate grades

Compare the developmental differences between

protostomes

and

deuterostomes Compare the alternate relationships of annelids and arthropods presented by two different proposed phylogenetic treesDistinguish between ecdysozoans and lophotrochozoans