Animals: The Invertebrates

Chapter 23

Key Concepts:

All animals are multicelled, aerobic heterotrophs

Animals originated about 900 million years ago

Comparisons of body plans of existing animals with fossil records reveal that there were several trends in the evolutions of certain lineages

Key Concepts:

Divergences gave rise to two major lineages: those of the mollusks, annelids, and arthropods and the other one to the echinoderms and chordates

The arthropods, especially the insects, have been the most successful animal groups

Evolutionary Tree Diagram

Overview of the Animal Kingdom

Animals Multicellular Heterotrophs Oxygen is required Sexual reproduction (some asexual) Motile - in part of life cycle Embryonic development Mitotic cell divisions in embryo

Tissue layers

•Ectoderm, Endoderm, Mesoderm

Diversity in Body Plans

Vertebrates Mammals

birds, reptiles, amphibians, fishes

Invertebrates No backbones

Body symmetry & Cephalization ( sense in the head) Gut

Body cavity

Segmentation

Examples of Body Symmetry

Radial Live in

water

Bilateral Mirror

image

Type of Body Cavity in Animals

Gut, body cavities, segmentation

Type of Body Cavity in Animals

Lined body cavity

SpongesSuccess in Simplicity

No symmetry, tissues, or organs

SpongesSuccess in Simplicity

A basket sponge releasing a cloud of sperm

Tissues in a Jellyfish

The sea nettle, a jellyfish

(Chrysaora)

Stages in Cnidarian Life Cycles

Both polyp and medussa body forms

Physalia Portuguese Man-of-War

Flatworms:Turbellarians, Flukes & Tapeworms

Nervous system in a Planarian

Reproductive system in a Planarian

Tapeworms

Parasitic

Scolex

Proglottids

Hermaphroditic

Roundworms

Most abundant multicelled animal Bilateral symmetry

Cylindrical body

Cuticle

Complete digestive system

Male and female

Flukes

Parasitic

Sexual or asexual phases

Two hosts Snail

Human

Life Cycle of Schistosoma japonicum

A Sampling of Mollusks

Mollusk Soft body

Shell

Mantle

Fleshy foot

Gastropods-snails

Chitons

Bivalves-clams

Cephalopods-squid

Evolutionary Experiments with Body Plans

Radula is used to scrape food into

the mouth

Evolutionary Experiments with Body Plans

Body Plan of a clam

Evolutionary Experiments with Body Plans

Body Plan of a cuttlefish,

a cephalopod

Annelids: Segments Galore

Bilateral

Segmented

Earthworms

Leeches

Polychaetes

Earthworm Body Plan

Coelomic chambers A nephridium

Earthworm Body Plan

Portion of the closed circulatory system

Part of the digestive system

Earthworm Body Plan

Part of the nervous system

Arthropods: The Most Successful Organisms on

Earth-Arthropods

Over one million species

Trilobites (extinct)

Chelicerates Spiders

Crustaceans Barnacles and crabs

Uniramians Centipedes, millipedes, insects

Adaptations of Insects and Other Arthropods

Hardened exoskeleton

Jointed appendages

Fused and modified segments

Respiratory structures

Specialized Sensory Structures

Division of labor

A Look at Spiders

Organization of a Spider Body

A Look at Crustaceans

Shrimps, lobsters, crabs, barnacles

A Lobster

A Copepod

Life Cycle of a Crab

Continuous molting

A Look at Insect Diversity

Head, thorax, abdomen

Sensory antennae

Mouthparts

3 pairs of legs

2 pairs of wings

Malphigian tubules Waste disposal

Life cycles

A Look at Insect Diversity Examples of Appendages

Grasshopper

Fly

Butterfly

Mosquito

Examples of Post-Embryonic Development

Silverfish

True bugs

Fruit flies

The Puzzling Echinoderms

EchinodermsSea star

Sea urchin

Sea cucumber

Brittle stars

Body walls

Spines, spicules

Radial symmetry

Decentralized nervous system

Water-vascular system

The Puzzling Echinoderms

Sea urchin

Key Aspects of the Radial Body Plan of a Sea Star

In Conclusion

Animals are multicellular, aerobic heterotrophs that ingest or parasitize other organisms

Animals range from structurally simple placozoans and sponges to vertebrates

In Conclusion

Almost all animals more complex than cnidarians show bilateral symmetry, form tissues, organs, and organ systems

All mollusks have a fleshy soft body, and a mantle

In Conclusion

The annelids, have a segmented body, complex organs, and coelomic chambers

Arthropods are the most successful of all groups in terms of diversity, numbers, distribution, defenses, and capacity to exploit food resources

Echinoderms have spines, spicules, or plates in their body wall

developed by M. Roig