chapter 24 introduction to animals

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Chapter 24 Introduction to Animals

Section 1: Animal Characteristics

Section 2: Animal Body Plans

Section 3: Sponges and Cnidarians

24.1 Animal Characteristics

General Animal Features

Introduction to AnimalsChapter 24

The ancestral animals at the beginning of the evolutionary tree are eukaryotic and multicellular.

They developed adaptations in structure that enabled them to function in numerous habitats.

Feeding and Digestion

Introduction to Animals

Animals are heterotrophic.

The structure or form of an animal’s mouth parts determines how its mouth functions.


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Support


Invertebrates

Exoskeletons

Hard or tough outer coverings that provide a framework of support

Protect soft body tissues

Provide protection from predators


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Support


Vertebrates

Endoskeletons

Protect internal organs

Provide support for the body

Provide an internal brace for muscles to pull against


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Movement


The evolution of nerve and muscle tissues enables animals to move in ways that are more complex and faster than organisms in other kingdoms.


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Reproduction


Fertilization occurs when the sperm penetrates the egg to form a fertilized egg cell called the zygote.

Internal fertilization

External fertilization


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Asexual reproduction means that a single parent produces offspring that are genetically identical to itself.

Budding

Fragmentation

Regeneration

Parthenogenesis


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Early Development


The zygote undergoes mitosis and a series of cell divisions to form new cells.

The cells continue to divide, forming a fluid-filled ball of cells called the blastula.

The blastula continues to undergo cell division as some cells move inward to form a gastrula.


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Tissue Development

Endoderm inner layer of cells in the gastrula

Ectoderm outer layer of cells in the gastrula

Mesoderm layer of cells between the endoderm

and ectoderm


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24.2 Animal Body Plans


Evolution of Animal Body Plans

Anatomical features in animals’ body plans mark the branching points on the evolutionary tree.

Relationships on this tree are inferred by studying similarities in embryological development and shared anatomical features.

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Symmetry Similarity or balance among body structures of organisms Asymmetry Radial symmetry Bilateral symmetry


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Cephalization

The tendency to concentrate nervous tissue and sensory organs at the anterior end of the animal


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Body Cavities

Coelomates

Have a fluid-filled cavity with tissue formed from mesodermthat lines and encloses the organs in the coelom


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Body Cavities

Pseudocoelomates

Have a fluid-filled body cavity that develops between the mesoderm andthe endoderm rather than developing entirely within the mesoderm


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Body Cavities

Acoelomates

Have solid bodies without a fluid-filled body cavity between the gut and the body wall


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The mouth develops from the first opening in the gastrula.


Development in Coelomate Animals

Protostomes

Deuterostomes

The anus develops from the first opening in the gastrula.


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Visualizing Protostome and Deuterostome Development

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Segmentation

Segmented animals can be “put together” from a succession of similar parts.

Can survive damage to one segment

Movement is more effective


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24.3 Sponges and Cnidarians


Sponges

Sponges do not develop tissues.

Collar cells with flagella line the inside of the sponge and whip back and forth drawing water into the body of the sponge.

Water and waste materials are expelled from the sponge through the osculum.

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Filter Feeder

Food particles cling to the cells.

Digestion of nutrients takes place within each cell.


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Archaeocytes

Specialized cells that secrete spicules, which are the support structures of sponges

Spicules are small, needlelike structures made of calcium carbonate, silica, or a tough fibrous protein called spongin


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Sponge Diversity

Demospongiae

Calcarea

Hexactinellida


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Reproduction Reproduce asexually

Fragmentation Budding Gemmules

Reproduce sexually Eggs remain within a sponge. Sperm are released into the water.


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Cnidarians

Have one body opening and two layers of cells

Outer layer functions in protecting the internal body

Inner layer functions mainly in digestion


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Feeding and Digestion

Tentacles are armed with stinging cells called cnidocytes.

A nematocyst is a capsule that holds a coiled tube containing poison and barbs.

Water inside an undischarged nematocyst is under an osmotic pressure of more than 150 atmospheres.


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As the osmotic pressure increases, the nematocyst discharges forcefully.

A barb is capable of penetrating a crab shell.


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Cells lining the gastrovascular cavity release digestive enzymes over captured prey.

Undigested materials are ejected though the mouth.


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Response to Stimuli

A nerve net conducts impulses to and from all parts of the body.

The impulses cause contractions of musclelike cells in the two cell layers.


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Reproduction

Two body forms

Polyp

Medusa


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The two body forms of cnidarians can be observed in the life cycle of jellyfishes.


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Cnidarian Diversity

Hydroids

Jellyfishes

Sea anemones and corals


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Chapter Resource Menu

Chapter Diagnostic Questions

Formative Test Questions

Chapter Assessment Questions

Standardized Test Practice

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Glencoe Biology Transparencies

Image Bank

Vocabulary

AnimationClick on a hyperlink to view the corresponding lesson.

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Which animal is not an invertebrate?

A. lobster

B. shark

C. cicada

D. earthworm



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What is the tough outer covering of most invertebrates called?

A. exoskeleton

B. endoskeleton

C. endoderm

D. mesoderm



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Which statement is not true of animals?


A. Animal cells have cell walls.

B. Animals are heterotrophic.

D. Animal cells become tissues.

C. Animals probably evolved from earlyprotists.


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From which organisms might animals have evolved?


A. animal-like bacteria

B. autotrophic invertebrates

C. colonial protists

D. multicellular fungi

24.1 Formative Questions

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What is a group of cells that performs a specific function?


A. organ

B. tissue

C. gastrula

D. mesoderm


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What is one of the most unique characteristics of the animal kingdom?


A. advanced cell structure

B. complex movement

C. sexual reproduction

D. organ development


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What is the term for an individual animal that produces both eggs and sperm?


A. acoelomate

B. hermaphrodite

C. heterosexual

D. invertebrate


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What form of reproduction produces a new organism from the lost body part of another organism?


A. budding

B. fertilization

C. parthenogenesis

D. regeneration


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Which provides the strongest evidence for the relationship between arthropods and roundworms?


A. shared anatomical features

B. shared functional characteristics

C. similar protein structure

D. similar embryological development


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Which is the dorsal surface of a hummingbird?



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Which organism exhibits cephalization?


A. jellyfish

B. snail

C. sponge

D. starfish


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How is deuterostome development different from protostome development shown here?



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A. A blastula does not form.

B. The coelom is less advanced.

C. The gut is lined with mesoderm.

D. The blastopore becomes the anus.


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Why are sponges most distantly related to the rest of the animals?


A. They are not multicellular.

B. They do not have true tissues.

C. Their embryos have a mesoderm.


D. They arose from a different protistancestor.

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What is the term for organisms that remain attached to one place?


A. sessile

B. tactile

C. axiallary

D. sedentary


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What provides the energy for the discharge of a cnidarian’s nematocysts?


A. muscle fibers

B. hydraulic forces

C. osmotic pressure

D. protein springs


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Which is the dominant stage in the life cycle of a sea anemone?


A. bud

B. hydroid

C. medusa

D. polyp


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Identify the term that is used to describe the evolutionary history of a particular species.


A. genealogy

B. biology

C. phylogeny

D. paleontology


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Distinguish between asymmetry, radial symmetry and bilateral symmetry and givean example of each.



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Answer: Asymmetry – There is no symmetry orbalance in body structure and no shape. Example: sponge

Radial symmetry – The animal’s body can be divided along any plane through a central axis into equal halves. Example: jellyfish

Bilateral symmetry – The animal can bedivided into mirror image halves alongone plane. Example: dog


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Explain why it would be beneficial for a fish to lay many eggs when fertilization is external.


Answer: Some of the eggs will float away, beeaten or destroyed, so laying a large number of eggs makes it more likely that some will be fertilized and hatch.


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Which is not a characteristic that definesall animals?


A. carnivorous

B. eukaryotic

C. heterotrophic

D. multicellular


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At which stage is the developing animal an embryo?



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Which reproduces by internal fertilization?


A. bear

B. clam

C. fish

D. frog


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What is the most recent evolutionary development exhibited by both arthropods and echinoderms?


A. a body cavity

B. a coelom

C. segmentation

D. protostome development


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Which organisms are most closely related to roundworms?


A. sponges

B. cnidarians

C. flatworms

D. arthropods


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What characteristic do sponges and cnidarians have in common?


A. body symmetry

B. single body opening

C. cell layers organized into tissues

D. sessile attachment to surfaces


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Glencoe Biology Transparencies

Chapter 24


Image Bank

Chapter 24

invertebrate

exoskeleton

endoskeleton

vertebrate

hermaphrodite

zygote

internal fertilization

external fertilization

blastula

gastrula

endoderm

ectoderm

mesoderm


Vocabulary

Section 1

Chapter 24

symmetry

radial symmetry

bilateral symmetry

anterior

posterior

cephalization

dorsal

ventral

coelom

pseudocoelom

acoelomate

protostome

deuterostome


Vocabulary

Section 2

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filter feeder

sessile

cnidocyte

nematocyst

gastrovascular cavity

nerve net

polyp

medusa


Vocabulary

Section 3

Chapter 24


Animation

Chapter 24

Cell Differentiation in Animal Development

A Sponge

A Cnidarian

Visualizing Protostome and Deuterostome Development



chapter 24 introduction to animals

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