INTRODUCTION TO ANIMAL DIVERSITY

Chapter 32Our Kingdom

We are Animals

Animals AreAnimals Are

Species-rich Species-rich Morphologically diverse lineage of multicellular organisms Morphologically diverse lineage of multicellular organisms

on the tree of lifeon the tree of life Distinguished by two traits

they eat they move

The largest and most abundant predators, herbivores, and detritivores

Animals Are

Multicellular, heterotrophic eukaryotes Heterotrophs

ingest food find food by tunneling, swimming, filtering, crawling, creeping,

slithering, walking, running, or flying. Dominant Dominant consumers in both aquatic and terrestrial habitats in both aquatic and terrestrial habitats

Animal cells lack cell wallsAnimal cells lack cell walls Distinguished by two tissues

Nervous tissue and muscle tissueNervous tissue and muscle tissue

Most animals reproduce sexually with the diploid stage usually dominating the life cycle

Methods in the Study of Methods in the Study of AnimalsAnimals

Analyzing Comparative MorphologyAnalyzing Comparative Morphology The Evolution of TissuesThe Evolution of Tissues Symmetry and CephalizationSymmetry and Cephalization Evolution of a Body CavityEvolution of a Body Cavity The Protostome and Deuterostome Patterns of The Protostome and Deuterostome Patterns of

DevelopmentDevelopment The Tube-within-a-Tube DesignThe Tube-within-a-Tube Design A Phylogeny of Animals Based on MorphologyA Phylogeny of Animals Based on Morphology

Using the Fossil RecordUsing the Fossil Record Evaluating Molecular PhylogeniesEvaluating Molecular Phylogenies

Themes in the Diversification of Themes in the Diversification of AnimalsAnimals

Suspension (Filter) FeedingSuspension (Filter) Feeding Deposit FeedingDeposit Feeding HerbivoryHerbivory PredationPredation ParasitismParasitism

FeedingFeedingMovementMovement Types of Limbs: Unjointed and JointedTypes of Limbs: Unjointed and Jointed Are All Animal Appendages Homologous?Are All Animal Appendages Homologous?

Reproduction and Life CyclesReproduction and Life Cycles

Key Lineages of AnimalsKey Lineages of Animals

Choanoflagellates (Collar Flagellates) Porifera (Sponges) Cnidaria (Jellyfish, Corals, Anemones, Hydroids,

Sea Fans) Ctenophora (Comb Jellies) Acoelomorpha

Monophyletic and Very

Diverse The animals are a monophyletic group Animals are very diverse

34 major animal 34 major animal phylaphyla are recognized are recognized

Analyzing Comparative Morphology

Most morphological diversity in animals is based on

differences in mouths and limbsdifferences in mouths and limbs

Basic Architecture

Four features define an animal's body plan

1.1. the number of tissue types in embryosthe number of tissue types in embryos

2.2. the type of body symmetrythe type of body symmetry

3.3. the presence or absence of a fluid-filled the presence or absence of a fluid-filled cavitycavity

4.4. the way in which the earliest events of the way in which the earliest events of embryo development proceedembryo development proceed

The Evolution of Tissues All animals other than sponges have tissues

tightly integrated structural and functional units of cells.

Diploblasts embryos have two types of tissues or germ layers

Ectoderm Endoderm

Triploblastsembryos have three types of tissuesembryos have three types of tissues

EctodermEctoderm EndodermEndoderm MesodermMesodermgerm layers develop into distinct adult tissuesgerm layers develop into distinct adult tissues

Symmetry and Cephalization

A basic feature of a multicellular body is the presence or absence of a plane of symmetry

radialradial symmetrysymmetry at least two planes of symmetry. at least two planes of symmetry.

bilateral symmetrybilateral symmetry a single plane of symmetry a single plane of symmetry face their environment in one direction.face their environment in one direction.

Cephalization Bilateral symmetry allowed

Evolution of a head, or anterior region, where Evolution of a head, or anterior region, where structures for feeding, sensing the environment, structures for feeding, sensing the environment, and processing information are concentratedand processing information are concentrated

Evolution of a Body Cavity

Animals may or may not have an internal, fluid-filled body cavity

coelom coelom forms from within the mesoderm forms from within the mesoderm lined with cells from the mesodermlined with cells from the mesoderm

Advantages of a Coelom

Creates a medium for circulation Makes space for internal organs A hydrostatic skeleton

fluid-filled chamber allows movement

even without fins or limbs.

The Protostome and Deuterostome Patterns of Development

Coelomates are bilaterally symmetric Coelomates are bilaterally symmetric except echinodermsexcept echinoderms three embryonic tissue layersthree embryonic tissue layers

Bilatera protostomes

arthropods, mollusks, and segmented wormsarthropods, mollusks, and segmented worms deuterostomes

vertebrates and echinodermsvertebrates and echinoderms

Differences in Early Development

Three events in early development differ in protostomes and deuterostomes

CleavageCleavageGastrulationGastrulation coelom formationcoelom formation

Cleavage Rapid series of mitotic divisions

Spiral cleavage mitotic spindles of dividing cells orient mitotic spindles of dividing cells orient at an angle to the main axis of the cellsat an angle to the main axis of the cells resulting in a helical arrangementresulting in a helical arrangement

Radial cleavageRadial cleavage mitotic spindles of dividing cells orient mitotic spindles of dividing cells orient parallel or perpendicular to the main axis parallel or perpendicular to the main axis of the cellsof the cellsresulting in a pattern of cells stacked resulting in a pattern of cells stacked directly on top of each otherdirectly on top of each other

The Tube-within-a-Tube Design

The basic animal body plan is a tube-within-a-tube design in which the outer tube forms the body wall and the inner tube forms the gut

Ancestor?Ancestor?

The animal kingdom all developed from a common The animal kingdom all developed from a common ancestor ( monophyletic) probable during the ancestor ( monophyletic) probable during the Precambrian era. Precambrian era.

Probably a colonial choanoflagelate that lived Probably a colonial choanoflagelate that lived about700 million years ago. Modern about700 million years ago. Modern choanoflagellates are tiny, have a stalk and live in choanoflagellates are tiny, have a stalk and live in ponds and lakes) ponds and lakes)

A hypothesis of animal origin from flagellated A hypothesis of animal origin from flagellated protists says that the colony of cells in the protist protists says that the colony of cells in the protist evolved into a sphere and then differenciated and evolved into a sphere and then differenciated and especialized creating two layers of cells.especialized creating two layers of cells.

The common ancestor of living The common ancestor of living animalsanimals

May have lived May have lived 1.2 billion–800 million years 1.2 billion–800 million years agoago

May have resembled modern May have resembled modern choanoflagellates, protistschoanoflagellates, protists that are the that are the closest living relatives of animalsclosest living relatives of animals

Figure 32.3

Single cell

Stalk

closest living relatives of animalsclosest living relatives of animals

a colonial, flagellated protista colonial, flagellated protist

Figure 32.4

Colonial protist,an aggregate ofidentical cells

Hollow sphere of unspecialized cells (shown in cross section)

Beginning of cell specialization

Infolding Gastrula-like “protoanimal”

Somatic cells Digestivecavity

Reproductive cells

A Phylogeny of Animals Based on Morphology

The phylogenetic tree indicates that a group of protists called the choanoflagellates are the closest living relatives of animals and that the Porifera (sponges) are the most ancient animal phylum.

Phylogeny Based on Morphology

Radially symmetric phyla are placed on the tree next because their tubelike body plans are relatively simple. Among the bilaterally symmetric phyla, the acoelomates and pseudocoelomates appeared first, followed by the coelomates.

Two major events occurred after the coelomates split into the protostomes and deuterostomes

radial symmetry evolvedradial symmetry evolved segmentationsegmentation evolved evolved independently in both lineages of independently in both lineages of coelomates.coelomates.

Using the Fossil Record

Most major groups of animals appear in the fossil record starting about 580 million years ago

The fossil record is generally consistent with the morphological phylogeny.

(a) (b)

Neoproterozoic Era (1 Billion–524 Neoproterozoic Era (1 Billion–524 Million Years Ago)Million Years Ago)

Early members of the animal fossil record are known as the Early members of the animal fossil record are known as the Ediacaran fauna( first fossils of animals about 575 mya). Ediacaran fauna( first fossils of animals about 575 mya). Simple radial forms and segmented bodies with legs.Simple radial forms and segmented bodies with legs.

Figure 32.5a, b

Paleozoic EraPaleozoic Era (542–251 Million Years Ago) (542–251 Million Years Ago) The Cambrian explosion marks the earliest fossil The Cambrian explosion marks the earliest fossil

appearance of many major groups of living appearance of many major groups of living animalsanimals Is described by several current hypotheses Is described by several current hypotheses

such as predator- prey relationships, oxygen such as predator- prey relationships, oxygen increase and evolution of the hox genesincrease and evolution of the hox genes

Figure 32.6

Mesozoic EraMesozoic Era (251–65.5 Million Years (251–65.5 Million Years Ago)Ago)

During the Mesozoic eraDuring the Mesozoic era Dinosaurs were the dominantDinosaurs were the dominant terrestrial terrestrial

vertebratesvertebrates Coral reefsCoral reefs emerged, becoming important emerged, becoming important

marine ecological niches for other organismsmarine ecological niches for other organisms The first mammals appeared (tiny, nocturnal The first mammals appeared (tiny, nocturnal

insect eatersinsect eaters

Cenozoic EraCenozoic Era (65.5 Million Years Ago to (65.5 Million Years Ago to the Present)the Present)

The beginning of this eraThe beginning of this era Followed mass extinctionsFollowed mass extinctions of both terrestrial of both terrestrial

and marine animalsand marine animals Modern mammalModern mammal orders orders and insectsand insects

diversified during the Cenozoicdiversified during the Cenozoic Also flowering plants appearedAlso flowering plants appeared

Points of AgreementPoints of Agreement

All animals All animals share a common ancestorshare a common ancestor SpongesSponges are basal animals (branch from the base are basal animals (branch from the base

of tree, no tissues)of tree, no tissues) EumetazoaEumetazoa is a clade of is a clade of animals with true animals with true

tissuestissues Most animalMost animal phyla belong to the clade phyla belong to the clade BilateriaBilateria VertebratesVertebrates belong to the clade belong to the clade DeuterostomiaDeuterostomia

Disagreement over the BilateriansDisagreement over the Bilaterians

The The morphology-based treemorphology-based tree Divides the Divides the bilaterians into two cladesbilaterians into two clades: :

deuterostomes and protostomesdeuterostomes and protostomes In contrast, recent In contrast, recent molecular studiesmolecular studies

assign two sister taxa to the protostomes rather assign two sister taxa to the protostomes rather than one: the ecdysozoans and the than one: the ecdysozoans and the lophotrochozoanslophotrochozoans

Important Observations Emerge From the Data

1. The most ancient triploblasts lacked a coelom;

2. The major event in the evolution of the Bilateria was the split between protostomes and deuterostomes

3. Segmentation evolved independently in the annelids and the arthropods; and

4. Pseudocoeloms arose from coeloms twice in evolutionary history

Phylogenetic trees are best described Phylogenetic trees are best described asas

1.1. true and inerrant statements about evolutionary relationships.true and inerrant statements about evolutionary relationships.

2.2. hypothetical portrayals of evolutionary relationships. hypothetical portrayals of evolutionary relationships.

3.3. the most accurate possible representations of genetic the most accurate possible representations of genetic relationships among taxa. relationships among taxa.

4.4. theories of evolution. theories of evolution.

5.5. the closest things to absolute certainty that modern systematists the closest things to absolute certainty that modern systematists can produce.can produce.

Themes in the Diversification of Animals

Within the phylumbasic features of the body plan do not vary basic features of the body plan do not vary from species to speciesfrom species to species

Diversity arose mostly because of the evolution of innovative mostly because of the evolution of innovative methods for feeding and movingmethods for feeding and moving

Feeding The feeding tactics observed in

animals can be broken into five general types:1.1. suspension feedingsuspension feeding2.2. deposit feedingdeposit feeding3.3. herbivoryherbivory4.4. predationpredation5.5. ParasitismParasitism

Many animals undergo a metamorphosis a change in form during developmenta change in form during development allows juveniles and adults to exploit allows juveniles and adults to exploit

different sources of fooddifferent sources of food

Suspension (Filter) Feeding

Suspension feeders, or filter feeders, capture food by filtering out particles suspended in water or air This method is found in a wide variety of animal groups and has evolved many times independently

Deposit Feeding Deposit feeders eat their way through a substrate Food

soil-dwelling bacteria, protists, fungi, and soil-dwelling bacteria, protists, fungi, and archaeaarchaea detritus—the dead and partially decomposed —the dead and partially decomposed remains of organismsremains of organisms

Depending on foodherbivores (plant eaters), parasites, detritivores herbivores (plant eaters), parasites, detritivores (detritus eaters), or predators(detritus eaters), or predators

Herbivory Herbivores

animals that digest algae or plant tissuesanimals that digest algae or plant tissuescomplex mouths with structures that make complex mouths with structures that make biting and chewing or sucking possiblebiting and chewing or sucking possible

Predation Sit-and-wait predators rarely move at all until prey is captured stalkers pursue their prey

Parasitism Parasites are much smaller than their victims and often harvest nutrients without causing death Endoparasites

live inside their hosts live inside their hosts often wormlike in shape often wormlike in shape can be extremely simple morphologicallycan be extremely simple morphologically

Ectoparasites live outside their hosts live outside their hosts usually have grasping mouthparts usually have grasping mouthparts pierce the host’s exterior and suck the nutrient-pierce the host’s exterior and suck the nutrient-rich fluids inside rich fluids inside

Movement Many animals are sit-and-wait predators, and some are sessile throughout their adult lives. But the vast majority of animals move under their own power either as juveniles or as adults.

Function of Movement

three functions in adult animals: 1.1. Finding foodFinding food

2.2. finding matesfinding mates

3.3. escaping from predators.escaping from predators.

Limbs

A major innovation in animalsmade highly controlled, rapid movement possiblemade highly controlled, rapid movement possible

Two types UnjointedUnjointed

saclike

Jointed move when muscles that are attached to a skeleton contract or relax

Homologous vs Non-Homologous

Biologists have argued that at least a few of the same genes are involved in the development of all appendages observed in animals Hypothesis is that all animal appendages have some degree of genetic homology that they are all derived from appendages that were present in a common ancestor. This hypothesis is controversial, however, and research continues

Reproduction and Life Cycles

At least some species in most animal phyla can reproduce asexually (via mitosis), as well as sexually (via meiosis).

Sexual reproduction can occur with internal or external fertilization

Development

Eggs or embryos may be retained in the female’s body during development

viviparousMay be laid outside the body

oviparous Female retains eggs inside her body during early development

embryos are nourished by yolk inside the egg embryos are nourished by yolk inside the egg and not by nutrients transferred directly from the and not by nutrients transferred directly from the mothermother ovoviviparous

Vast majority of animals are oviparous

DevelopmentDevelopment

After a sperm fertilizes an eggAfter a sperm fertilizes an egg The zygote undergoes cleavage, leading to the The zygote undergoes cleavage, leading to the

formation of a blastulaformation of a blastula The blastula undergoes gastrulationThe blastula undergoes gastrulation

Resulting in the formation of embryonic tissue Resulting in the formation of embryonic tissue layers and a gastrulalayers and a gastrula

Zygote

Cleavage

Eight-cell stage

Cleavage

Blastula Cross section of blastula

Blastocoel

Blastocoel

Gastrula Gastrulation

Endoderm

Ectoderm

Blastopore

.. Early embryonic development in animalsEarly embryonic development in animals

Figure 32.2

In most animals, cleavage results in theformation of a multicellular stage called a blastula.The blastula of many animals is a hollow ball of cells.

3

The endoderm ofthe archenteron de-

velops into the tissuelining the animal’s

digestive tract.

6

The blind pouchformed by gastru-

lation, calledthe archenteron,

opens to the outsidevia the blastopore.

5

Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer).

4

Only one cleavagestage–the eight-cellembryo–is shown here.

2 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage.

1

Metamorphosis The change from juvenile to adult body type Larva

juvenile individual juvenile individual looks substantially different from the adult looks substantially different from the adult

Nymph juvenile individualjuvenile individual looks like a miniature adultlooks like a miniature adult

Pupation When a larva has grown sufficiently, it secretes a protective case and is now known as a pupa

Into an Adult

During pupation, the pupa’s body is completely remodeled into a new, adult form

Holometabolous Complete metamorphosis

two-step processtwo-step processfrom larva to pupa to adultfrom larva to pupa to adultinvolving dramatic changes in involving dramatic changes in morphology and habitat usemorphology and habitat use

Hemimetabolou Incomplete metamorphosis

One-step process of sexual maturation.

Limited morphological difference between juvenile and adult

Marine Animals

Complete metamorphosis extremely common in marine animalsmost cnidarians have two distinct body types during their life cycle

a largely sessile form called a a largely sessile form called a polyp alternates with a free-floating stage called a alternates with a free-floating stage called a medusa