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Chapter 20 Animals

Shale and fossil: ©Michael Melford/National Geographic Stock

Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

5 Kingdom Classification System

• Kingdom Monera

– Bacteria & Blue green algae

• Kingdom Protista

– Algae & Protozoa

• Kingdom Fungi

– Slime molds & true fungi

• Kingdom Plantae

• Kingdom Animalia

4 reasons why study the animal kingdom

1) Basis for other scientific and professional fields

• All these fields are responsible for improving/guarding the health or our pets, environment, and us

– Ex. Medicine, dentistry, teaching, agriculture, conservation


(2) Animals are used for scientific research• A large part of what we know about genetics has

come from using fruit flies• Our understanding of physiology and surgery

have been gained by using animals• New drugs are tested on mice and various

animals• W/out such experimentation there would be no

protection against rabies, smallpox, typhoid, diphtheria and many other diseases


(3) Animals serve as an important source of food and other products

• Almost every phylum of animals and class of larger animals contain a few species that reach our table Ex. Snails, mussels, oysters, lobster, ants, shrimp, fish, turtle, frogs, birds, and mammals

• Other (non-edible) products include sponges, coral, pears, honey, silk, feathers, furs, and leather


(4) Some animals may cause disease or are poisonous to humans

– Some flatworms and roundworms are parasites of humans and some jellyfish, scorpions, spiders, fish and snakes are poisonous to man

Important Characteristics of Animal Kingdom

1. All animals are multicellular, eukaryotic, and hetertrophic (obtain energy by feeding)

2. Most animals exhibit all four divisions of labor

-Cells – tissues– organs– systems

Important Characteristics of Animal Kingdom

3. Most animals are motile but some are sessile (ex. sponges)

4. Most reproduce sexually with a typical life span including sperm and egg merging to form a zygote that develops into an embryo that develops into a larvae that matures into an adult

What Is an Animal?

Section 21.1

Animals are diverse, yet they all have features in common: • Multicellular bodies• Eukaryotic cells that lack cell walls• Heterotrophic by ingestion• Blastula (hollow ball) stage of development• Cells bind to extracellular matrix

Owl and scorpion: © Digital Vision/PunchStock

What Is an Animal?

Section 21.1

Most animals are invertebrates, which lack backbones. A scorpion is an invertebrate.

Much fewer animals are vertebrates, which have backbones. However, vertebrates may be more familiar, since they include mammals, amphibians, reptiles, and fish.

Owl and scorpion: © Digital Vision/PunchStock

Animal Life Began in Water

Section 21.1

The first animals arose from aquatic protists about 570 million years ago.

Figure 21.1

Animal Life Began in Water

Section 21.1 Figure 21.1

Many animal phyla originated during the Cambrian explosion.

Clicker Question #1

What combination of characteristics do all animals share?

A. multicellular, eukaryotic, heterotrophicB. unicellular, eukaryotic, heterotrophicC. multicellular, prokaryotic, autotrophicD. multicellular, eukaryotic, autotrophicE. unicellular, prokaryotic, autotrophic

Flower: © Doug Sherman/Geofile/RF

How Do Biologists Classify Animals?


Animals are classified into nine major phyla.

Section 21.1

The first branching point in animal taxonomy distinguishes a clade with true tissues from a clade with no true tissues.


Figure 21.2

Section 21.1

In parazoans (sponges), cells do not interact to provide specific functions, so sponges do not have true tissues.


Figure 21.2

Section 21.1

Eumetazoans do have true tissues.


Figure 21.2

Section 21.1

The second branching point distinguishes radially symmetrical from bilaterally symmetrical animals.


Figure 21.2


An organism has radial symmetry if any plane passing through the body from the mouth to the opposite end creates mirror images.

Radial symmetry Bilateral symmetry



An organism has bilateral symmetry if only one plane can divide the animal into mirror images.






Bilaterally symmetrical animals have a head and a tail end. This body plan selects for cephalization: sensory organs and a brain are on the head end.

Clicker Question #2

How many of the following animals have bilateral symmetry?

A. oneB. twoC. threeD. fourE. five


Section 21.1

The same branching point also distinguishes animals with two embryonic germ layers from animals with three.


Figure 21.2


In all phyla except for sponges, the embryonic ball of cells called a blastula folds in on itself, forming a gastrula.


Early and late blastula, and gastrula: © Herve Conge/Phototake


In some animals, the gastrula only develops two tissue layers (endoderm and ectoderm).

In others, a third tissue layer (mesoderm) develops.




• Ectoderm develops into the skin and nervous system.• Endoderm becomes the digestive tract. • Mesoderm gives rise to the muscles and circulatory system.



Section 21.1

Embryonic development also determines the third branching point.


Figure 21.2


If the first indention of the gastrula develops into the mouth, the organism is a protostome.


Becomes mouth

Gastrula: © Herve Conge/Phototake


If it develops into the anus, the organism is a deuterostome.


Becomes anus

Gastrula: © Herve Conge/Phototake

Section 21.1

The body cavity, organization of the digestive tract, and segmentation also characterize animals.


Figure 21.2


A bilaterally symmetrical animal may have a coelom, a pseudocoelom, or no coelom.



A coelom is a body cavity surrounded on all sides by mesoderm.



A pseudocoelom is surrounded on one side by mesoderm and the other side by endoderm.



Some bilaterally symmetrical animals lack a body cavity.



Animals have an incomplete digestive tractif the mouth both takes in food and ejects wastes.


Section 21.1

Animals have a complete digestive tractif food passes in one direction from mouth to anus.


Section 21.1

Some animals have segmentation, like this millipede.


Figure 21.7Millipede: ©Don Farrall/Getty Images RF

Section 21.1

Segmented bodies are more flexible and have more potential for developing

specialized body parts than unsegmented bodies.


Figure 21.7Millipede: ©Don Farrall/Getty Images RF

Section 21.1

Animals are also classified by the presence or absence of a larval stage.


Figure 21.8

Section 21.1

Animals with direct development resemble adults in their juvenile stage.


Figure 21.8

Section 21.1

Animals with indirect development have a larval stage that does not resemble the adult form.


Figure 21.8

Section 21.1

The larva undergoes metamorphosis as it matures into an adult.


Figure 21.8

Section 21.1

Different combinations of these qualities characterize each phylum.


Figure 21.2

Clicker Question #3

Which type of animal does NOT go through this sequence in its early development?

A. sea starB. sharkC. snailD. spongeE. flatworm

Flower: © Doug Sherman/Geofile/RF; early and late blastula, and gastrula: © Herve Conge/Phototake

21.1 Mastering Concepts

What features were used to build the animal phylogenetic tree?


INTRODUCTION TO PORIFERA

(AKA Sponges)

• Originally thought they were aquatic

plants

• Now known as ancient animals with

fossils dating back to PreCambrian

(>500 mya)


Key Features

Sponges Lack Differentiated TissuesPhylum Porifera: Sponges

Section 21.2 Sponge: © Getty Images RF; sea sponge: ©Laurence F Tapper/YAY Micro/age fotostock RF Figure 21.9

Sponges Lack Differentiated Tissues

Diversity

Porifera Have/Are• Simplest form of animal

• Body with cells arranged around pores, canals and chambers for the passage of water.

• Skeletal structure of spicules and/or spongin.

• Filter feeders.

• Sexual and asexual reproduction.

• Bodies pierced all over with openings called pores

• Are sessile and attached to

substrate or objects-

occasionally on other animals

Porifera Have/Are• Sexual and asexual reproduction.

• Bodies pierced all over with openings called pores

• Are sessile and attached to substrate or objects- occasionally on other animals such as crabs but have planktonic larvae

Porifera Don’t Have

• An organ system

• Nervous system

• Much co-ordination between cells

• Tissue organization (some but very restricted)

• Symmetry (some have radial symmetry

• A true body cavity or gut

56

Porifera: Characteristics• No true tissues or organs (only specialized

cells)• Most are asymmetrical, but some maybe radial• Sac body plan• Porifera means pore bearing (body wall pierced

by numerous pores for water to enter)• Reproduce sexually by fertilization and

asexually by budding• Skeletons composed of CaCO3 spicules or

sponging (protein fibers)• Central body cavity is lined w/ collar cells

called choanocytes

57

Porifera Anatomy

• No true tissues• Consists of specialized organized cells

supported by a skeleton of:

-spongin fibers-calcareous spicules-silica spicules-combination of these, or no skeletal structure at all

58

Porifera Anatomy

Collar Cells

• Choanocytes: (collar cells) act as a pump to bring water into the sponge

Phylum Porifrea60

Spicules

• Collagen is stiffened by adding microscopic mineral accretions or additional protein fibers (spongin) or both.

• Spicules: skeleton structures, made of calcium carbonate (CaCO3)

61

Sponge Support

• Mesoglea is a translucent, non-living, jelly-like substance found between the two epithelial cell layers (ex. Btw ectoderm & endoderm)

Mesoglea

How do Sponges eat & breathe?• Choanocytes collect

food from water currents passing thorough porous body

• Food is digested by choanocytes or passed on to amebocytes

• Amebocytes act as a primitative and simple circulatory device to transport nutrients

• Sponges get O2 by diffusion.

63

Porifera Classification

• Phylum Porifera

–Class Calcarea

–Class Demospongiae

–Class Hexactinellida

Taxonomic Detail

Desmospongia

All other

classes

Do not worry about classes of sponges


Key features

Cnidarians Are Radially SymmetricalPhylum Cnidaria: Jellyfish, hydra, coral, and sea anemones


Diversity

Cnidarians Are Radially Symmetrical

Jellyfish: ©Kevin Schafer/Alamy RF; hydra: ©T. E. Adams/Visuals Unlimited; coral: ©Comstock Images/PictureQuest RF;

coral animal: ©Leslie Newman & Andrew Flowers/Science Source; sea anemones: ©Russell Illig/Getty Images RF

Phylum Cnidaria(Jellyfish, Sea Anemones, & Corals)

• Exhibit Radial Symmetry

• 2 Forms

–Polyp

• Sessile form (vase shape)

–Medusa

• Swimming form (umbrella shape)

• 2 Body Layers

– Epidermis (outer layer) & Gastrodermis(inner layer)

• Mesoglea• Jelly-like substance in between inner and

outer layer

• Gastrovascular Cavity (GVC)• Empty space where digestion takes place

Phylum Cnidaria (Cont.)

Anatomy of a Jellyfish


Anatomy

Cnidarians Are Radially Symmetrical

Phylum Cnidaria• Cnidocytes and Nematocytes

–Cnidocytes =

specialized cells

used for defense

–Nematocytes =

structures inside

the cnidocyte that

contain stinging filaments

–The filaments have sharp tips that can inject poison into victims

• 1st Nervous System

–Porifera have no developed nervous system

–Cnidarians have a primitive nervous system

• No brain, but rather a loose collection of nerves called a nerve net

• Nerves radiate throughout the whole body

Phylum Cnidaria

Phylum Cnidaria

• Where do they live? (Habitat)

–Mostly salt water

–Hydra found in fresh water

• How big are they? (Size)

–Can be up to 6.5 feet in diameter and have ~100 foot long tentacles

Phylum Cnidaria (Cont.)

• What do they eat? How do they eat?

–Tentacles capture small animals.

–Nematocysts inject poison.

–Tentacles push food into mouth

• How do they move?

–If mobile, move by contraction and expansion of body

Digestion

• Capture prey using stinging cells to inject venom - paralyzes prey

• Pull prey into mouth, digest in body cavity digestive system: 1 opening - expel food from mouths also.

Phylum Cnidaria (Cont.)• How do they reproduce?

–Asexually

• Budding & Regeneration

– Sexually

• Adult medusa releases sperm and eggs into the water where external fertilization takes place zygote

• Zygote forms the blastula (hollow ball of cells) and then forms a planula (ciliated larva)

• Polyp attaches to the ocean floor and develops mouth and tentacles

• Stacks of medusae form and then detach to form individual jellyfish


Cnidarians Life Cycle

Cnidarians reproduce sexually and asexually.

Cnidarian Classification

• Class- Hydrozoa

– Ex. Hydra and Portuguese Man of War

• Class- Scyphozoa

– Ex. Jelly fish

• Class- Anthozoa

– Ex. Coral and Sea Anemones

Class: Hydrozoa• Hydra

– Polyp form found in

ponds and lakes

• Portugese Man-of-War– Found in tropical oceans

– Very poisonous

to fish

and

even

humans

Image Source: http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/primary/portuguese-man-o-war.jpg

Hydra Image Source: http://www.microscope-microscope.org/gallery/Mark-Simmons/images/hydra2.jpg

• Over 200 species

• Common

jellyfish exist as

both polyps

and medusae

Class: Scyphozoa

Image Source: http://www.dnr.sc.gov/marine/pub/seascience/jellyfi.html#life

• Includes corals and sea anemones• All marine

• Medusa stage completely absent

• Corals– Are polyps that live in small colonies

– Use nutrients from algae for energy

– Great Barrier Reef

• Largest coral colony on earth

• Sea Anemones– Are polyps that use poisonous tentacles to feed on

small fish

Class: Anthozoa

Coral PolypsPolyp Image Source: http://www.pbs.org/kcet/shapeoflife/animals/cnidaria2.html

Reef Image Source: http://www.chbr.noaa.gov/categories/raim/images/coral_01.jpg

Coral Reef

Sea Anemone

Image Source: http://www.pbs.org/kcet/shapeoflife/animals/cnidaria8.html

Section 21.4

Phylum Platyhelminthes (flatworms):Planarians, flukes, and tapeworms

Flatworms Have Bilateral Symmetry

Figure 21.2


Key features



Diversity


Flatworm: ©Leslie Newman & Andrew Flowers/Science Source; planarian: ©Carolina Biological Supply

Company/Phototake; fluke: ©Volker Steger/Science Source; tapeworm: ©Biophoto Associates/Science Source


Anatomy




Some flatworms are parasitic, such as the blood fluke. They reproduce in the human intestine.

Section 21.5

Phylum Mollusca: Snails, scallops, and squids

Mollusks Are Soft and Unsegmented

Figure 21.2


Key features



Diversity


Chiton: ©Kjell B. Sandved/Science Source; bivalve: ©Andrew J. Martinez/Science Source; snail: ©Digital Vision RF; slug: ©Steven

P. Lynch/The Mcgraw-Hill Companies; octopus: ©Fred Bavendam/Minden Pictures; squid: ©Comstock Images/PictureQuest RF


Anatomy


Section 21.6

Phylum Annelida: Earthworms, leeches, and polychaetes

Annelids Are Segmented Worms

Figure 21.2


Key features



Diversity


Earthworm: ©E.R. Degginger/Photoshot; leech: ©Edward Kinsman/Science Source; polychaete: ©Ken Lucas/Visuals Unlimited


Anatomy


Section 21.7

Phylum Nematoda (roundworms)

Nematodes Are Unsegmented Worms

Figure 21.2


Key features



Diversity

C.elegans: © Sinclair Stammers/Science Source; elephantiasis: © R. Umesh Chandran, TDR, WHO/Science Source



Anatomy


Clicker Question #4

Animals commonly called worms are classified into three phyla (flatworms, roundworms, and annelids). What feature distinguishes them?

A. Only flatworms have radial symmetry.B. Only roundworms have a complete digestive tract.C. Only annelids are heterotrophic.D. Only roundworms have a gastrula stage of development.E. Only annelids are segmented.


Section 21.8

Phylum Arthropoda: Trilobites, chelicerates, myriapods, crustaceans, and insects

Arthropods Have Jointed Appendages

Over 1,000,000 species of arthropods exist!

Figure 21.2


Key features



Anatomy




Arthropods have complex organ systems.

Anatomy

Section 21.8 Figure 21.20, 21.21, 21.22


Diversity

Trilobites Chelicerates Myriapods

Crustaceans Insects

Trilobites: ©Francois Gohier/Science Source; scorpion: ©Digital Vision/Punchstock RF;

millipede: ©De Agostini Picture Library/Getty Images; lobster: ©Chris Newbert/Minden Pictures;

dragonfly:©Thomas Shahan/Flickr/Getty Images


Trilobites are extinct marine arthropods.

Arthropods Are Diverse Animals

Trilobites: ©Francois Gohier/Science Source



Mouthparts are important in classifying the other groups of arthropods as chelicerates or mandibulates.


Chelicerates include horseshoe crabs, ticks, spiders, and scorpions.


Horseshoe crab: ©Nature's Images/Science Source; tick: Center for Disease Control; spider: ©Corbis RF;

scorpion: ©Digital Vision/Punchstock RF


Millipedes and centipedes are myriapods, a group of mandibulates.


Millipede: ©De Agostini Picture Library/Getty Images; centipede: ©G/C Merker/Visuals Unlimited


Crabs, shrimp, and lobsters are examples of crustaceans, a group of mandibulates.


Lobster: ©Chris Newbert/Minden Pictures; crab: ©Pete Atkinson/Photographer's Choice/Getty Images RF


Insects are also mandibulates. Insects account for most arthropod diversity.


Cicada: ©Design Pics Inc./Alamy RF; dragonfly: ©Thomas Shahan/Flickr/Getty Images

Section 21.9

Phylum Echinodermata: Sand dollars, sea stars, and sea urchins

Echinoderms Have “Spiny Skin”

Figure 21.2



Key features



Diversity Sand dollars Sea cucumber

Sea urchin Sea star

Sand dollars: ©Marty Snyderman/Visuals Unlimited; sea cucumber: ©Nancy Sefton/Science Source; sea urchin: ©Andrew

J. Martinez/Science Source; sea star: ©Comstock/Getty Images RF; larva: ©Wim van Egmond/Visuals Unlimited



Anatomy

Section 21.10

Phylum Chordata:Chordates include several groups (one of which contains humans)

Most Chordates Are Vertebrates

Figure 21.2



Key features



Anatomy

Several features are unique to the chordates. Vertebrates have additional characteristics.



Chordates include invertebrate and vertebrate animals.



Each chordate has these features at some point during its life:1) Notochord: in many chordates, develops into the backbone2) Dorsal, hollow nerve cord: in many chordates, develops into spinal cord 3) Pharyngeal pouches or slits4) Postanal tail

21.2-21.10 Mastering Concepts

Make a table comparing the features of each animal phylum.


Section 21.11

Tunicates and Lancelets

Tunicates and lancelets are invertebrates that resemble ancestral chordates.

Figure 21.26



Key features



Tunicate larvae are free swimming; adults are sessile. Lancelets filter-feed with their tails buried in the sediment.

Diversity

Tunicate (blue): © Nancy Sefton/Science Source; tunicate (orange): © Janna Nichols; lancelet: ©Bernard Photo

Productions/Animals Animals

Section 21.12

Hagfishes and Lampreys Have a Cranium

A hagfish is a marine invertebrate with a cranium that surrounds and protects the brain.

Figure 21.26

Section 21.12


Figure 21.26

Lampreys were the first chordates with vertebrae, which protect the spinal cord.


Key features

The sticky slime hagfishes secrete, helps them slide their bodies out of danger.




Diversity

Hagfish (mouth): ©Steven Senne/AP Images; hagfish: ©Gerald & Buff Corsi/Visuals Unlimited;

lamprey: ©David Hosking/Alamy; lamprey (mouth): ©Russ Kinne/Science Source

Section 21.13

Fishes Are Aquatic Vertebrates with Jaws

Jaws, lung precursors, and a bony skeleton first appeared in fishes.

Figure 21.26


Key features



Fishes Are Aquatic Vertebrates with JawsDiversity

Sting ray: ©Hal Beral/Visuals Unlimited; shark: ©W. Gregory Brown/Animals Animals; snappers: ©Corbis RF;

lungfish: ©Peter E. Smith/Natural Sciences Images Library; coelacanth: ©Peter Scoones/Planet Earth Pictures/Getty Images



Anatomy



Lobed-fins were the precursors to the limbs that define the tetrapods.



Lungfishes have lungs that are homologous to those of tetrapods.

Lungfish: ©Peter E. Smith/Natural Sciences Images Library

Section 21.14

Amphibians Live on Land and in Water

Lungs and limbs facilitated amphibians’ move to land. Their eggs must remain moist, so these tetrapods retain a strong link to water.

Figure 21.26


Key features



Diversity


Frog: ©Creatas/PunchStock RF; caecilian: © E.D. Brodie Jr.; salamander: © Suzanne L. Collins & Joseph T. Collins:Science


Anatomy


Section 21.15

The Amniotic Egg Broke the Tie to Water

The amnion allows reptiles and mammals to breed in dry habitats.

Figure 21.26


A reptile’s amniotic egg has a leathery or hard outer layer surrounding a yolk that nourishes the developing embryo.

Many similar structures surround a mammal’s embryo.


Hatching turtle: ©Creatas/PunchStock RF


Amniotes include mammals, birds, and non-avian reptiles.



Strong evidence suggests that birds are a type of reptile, closely related to dinosaurs.


Section 21.15

Reptiles: The First Vertebrates on Dry Land

Reptiles—including snakes, lizards, and birds—lay amniotic eggs and thrive on dry land.

Figure 21.26

Key features




Diversity


Turtle: © Ed Reschke/Peter Arnold/Getty Images; lizard: © Creatas/PunchStock RF; snake: ©Dorling Kindersley/Getty Images;

alligator: ©LaDora Sims//Flickr/Getty Images RF; ostrich: © Panoramic Images/Getty Images

Section 21.16

Mammals Are Warm, Furry Milk-Drinkers

Mammals are amniotes with hair and milk-secreting mammary glands.

Figure 21.26


Key features



Diversity


Platypus: ©David Watts/Visuals Unlimited/Corbis; echidna: ©Paul Hobson/Nature Picture Library;

kangaroo: ©Martin Harvey/Corbis; opossum: ©Frank Lukasseck/Photographer's Choice/Getty Images;

baby: ©Ansel Horn/Phototake; dolphin: ©Creatas/PunchStock RF; bat: ©Auscape/UIG/Getty Images


Diversity


Lay eggs





Diversity


Young complete development in pouch

Lay eggs





Diversity


Young complete development in pouch

Lay eggs Young complete development in uterus




Clicker Question #5

Which feature characterizes tetrapods but not other vertebrates?

A. amnionB. skull and backboneC. limbsD. bilateral symmetryE. tail


21.11-21.16 Mastering Concepts

Describe the adaptations that mark the transition from fishes to amphibians, reptiles, and mammals.



Investigating Life 21.17: Sponges Fill Holes in Animal Evolution

Scientists studying the Cambrian explosion discovered that diversification of animals began in sponges, which have the same developmental genes as other animal phyla.


Investigating Life 21.17: Sponges Fill Holes in Animal Evolution

These results suggest that the Cambrian period did not have the explosion of evolution that many people thought.

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