ANIMAL KINGDOMANIMAL KINGDOM

Main CharacteristicsMain Characteristics

Multicellular eukaryotesMulticellular eukaryotes

HeterotrophsHeterotrophs

Specialized cells; most have tissuesSpecialized cells; most have tissues

Response to stimuli by nervous and Response to stimuli by nervous and muscular tissuemuscular tissue

Most capable of locomotion; few sessileMost capable of locomotion; few sessile

Most diploid and reproduce sexuallyMost diploid and reproduce sexually

Animals live in diverse habitatsAnimals live in diverse habitats

MarineMarine– Origin of animal lifeOrigin of animal life– Provides buouyancyProvides buouyancy– Body fluids isotonic to environmentBody fluids isotonic to environment– Plankton, nekton, sessilePlankton, nekton, sessile

FreshwaterFreshwater– Requires osmoregulationRequires osmoregulation– More challenging than marine: food, oxygen, More challenging than marine: food, oxygen,

sunlight, temperaturesunlight, temperature

Terrestrial – avoid dessication:Terrestrial – avoid dessication:

– Body covering to reduce Body covering to reduce evaporationevaporation

– Respiratory organs deep in body Respiratory organs deep in body cavitycavity

– ReproductionReproductionReturn to waterReturn to waterInternal fertilizationInternal fertilization

– Eggs with coveringsEggs with coverings

– Means of thermoregulationMeans of thermoregulation

Evolution of AnimalsEvolution of Animals

All animals have a common protist All animals have a common protist ancestor: choanoflagellateancestor: choanoflagellate– Cells of colony became specializedCells of colony became specialized– Division of labor resulted in single organismDivision of labor resulted in single organism

Diversity results from changes in Diversity results from changes in development that lead to changes in body development that lead to changes in body plansplans– Hox genes control early developmentHox genes control early development

Animals can be Classified Animals can be Classified According to Body SymmetryAccording to Body Symmetry

Asymmetry Asymmetry – no regular arrangementno regular arrangement

Radial symmetry Radial symmetry – similar structures arranged around central axissimilar structures arranged around central axis

Bilateral symmetry Bilateral symmetry – can only be divided through one plane (midline) can only be divided through one plane (midline) – get roughly = left and right halvesget roughly = left and right halves

CephalizationCephalization

Found in bilaterally symmetrical organismsFound in bilaterally symmetrical organisms

Concentration of sensory structures in a Concentration of sensory structures in a head head – Nerve cells concentrate in head Nerve cells concentrate in head brain brain– Nerve cord extends toward rearNerve cord extends toward rear

Bilateral symmetry and cephalization are Bilateral symmetry and cephalization are adaptations to locomotionadaptations to locomotion

Embryonic DevelopmentEmbryonic Development

ZygoteZygote formed through fertilization formed through fertilization

Undergoes Undergoes cleavagecleavage – series of mitotic – series of mitotic divisiondivision

Develops into Develops into blastulablastula – hollow ball of cells – hollow ball of cells

Undergoes Undergoes gastrulationgastrulation – formation of – formation of specific layers of tissue called germ layersspecific layers of tissue called germ layers

2 Types of Cleavage Patterns2 Types of Cleavage Patterns

RadialRadial– Parallel or right Parallel or right

angles to axisangles to axis– Fate of cell comes Fate of cell comes

laterlater– IndeterminateIndeterminate

SpiralSpiral– Diagonal to axisDiagonal to axis– Fate of cell fixed Fate of cell fixed

earlyearly– DeterminateDeterminate

Germ LayersGerm Layers

Form in all animals except spongesForm in all animals except sponges

3 layers:3 layers:– Ectoderm – outer layerEctoderm – outer layer

– Endoderm – inner layerEndoderm – inner layer

– Mesoderm – middle layerMesoderm – middle layer

DIPLOBLASTIC

TRIPLOBLASTIC

Overview of Animal typesOverview of Animal types

Sponges – loose arrangement of different Sponges – loose arrangement of different types of cells; do not have tissuestypes of cells; do not have tissues

DiploblasticDiploblastic – Cnidarians andCnidarians and CtenophoresCtenophores– Only have 2 germ layers – endo and Only have 2 germ layers – endo and

ectodermectoderm

TriploblasticTriploblastic– Have 3Have 3rdrd germ layer - mesoderm germ layer - mesoderm

Body CavityBody Cavity

Triploblastic organisms further Triploblastic organisms further grouped base on presence grouped base on presence and type of and type of coelomcoelom – fluid- – fluid-

filled cavity between digestive filled cavity between digestive tract and body walltract and body wall

Body Cavity ClassificationBody Cavity Classification

AcoelomatesAcoelomates– Solid body; no cavitySolid body; no cavity– Flatworms and ribbon wormsFlatworms and ribbon worms

PseudocoelomatesPseudocoelomates– Have a body cavity but it is Have a body cavity but it is

not completely lined with not completely lined with mesodermmesoderm

– Nematodes and rotifersNematodes and rotifers

CoelomatesCoelomates– Tube-within-a-tube body Tube-within-a-tube body

planplan– Coelom completely lined Coelom completely lined

with mesodermwith mesoderm

Comparison

2 main groups of bilateral animals:2 main groups of bilateral animals:

During gastrulation, group of During gastrulation, group of cells move in forming sac … cells move in forming sac … embryonic gutembryonic gut

If blastopore becomes mouth – If blastopore becomes mouth – organism is a organism is a protostomeprotostome

If blastopores becomes anus - If blastopores becomes anus - deuterostomedeuterostome

Protostomes vs. Deuterostomes Protostomes vs. Deuterostomes

PROTOSTOMESPROTOSTOMES

Flatworms, annelids, Flatworms, annelids, arthropods, mollusksarthropods, mollusks

SPIRAL CLEAVAGESPIRAL CLEAVAGE

Developmental fate of Developmental fate of embryo fixed early = embryo fixed early = determinatedeterminate

DEUTEROSTOMESDEUTEROSTOMES

Echinoderms and Echinoderms and chordateschordates

RADIAL CLEAVAGERADIAL CLEAVAGE

Fate of embryo occurs Fate of embryo occurs later = indeterminate later = indeterminate

Fig. 29-7, p. 627