invertebrate animals chapter 17 what is an animal? early animals significant invertebrate animal...

Invertebrate Animals CHAPTER 17Invertebrate Animals CHAPTER 17•What is an Animal?

•Early Animals

•Significant Invertebrate Animal Features

•Invertebrate Groups (Phyla)•Sponges (Phylum Porifera)

•Cnidarians (Phylum Cnidaria)

•Flatworms (Phylum Platyhelminthes)

•Roundworms (Phylum Nematoda)

•Segmented Worms (Phylum Annelida)

•Arthropods (Phylum Arthropoda)

•Molluscs (Phylum Mollusca)

•Echinoderms (Phylum Echinodermata)

What Is an Animal?

• Animals

– Eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by ingestion

– Mostly reproduce sexually and then proceed through a series of developmental stages

– Usually have muscle cells, as well as nerve cells that control the muscles

– Have distinct specialized cells (tissues)

– Digest their food within their bodies

Figure 17.3

Life Cycle of An Animal

Dominant diploid stage

Early Animals and the Cambrian Explosion

• Animals probably evolved from a colonial flagellated protist that lived in Precambrian seas

• At the beginning of the Cambrian period, 542 million years ago, animals underwent a rapid diversification.

Survey of Organisms Grid

• The development of true tissues

– Specialized cells living in sheets or masses within an organism

Major Evolutionary Novelties in the Evolution of Invertebrate Animals

• The development of radial or bilateral symmetry

• The development of a true body cavity (coelom)

– A fluid-filled, muscle-lined space separating the digestive tract from the outer body wall.

• The development of segmentation

– Body is subdivided into separate parts which can then develop specialized functions

• The development of a complete gut

– Incomplete digestive tracts have a mouth but no anus

Figure 17.7

Types of Body Symmetry Seen in Animals

Major Invertebrate Phyla

• Invertebrates

– Are animals without backbones.

– Represent 95% of the animal kingdom

– Each invertebrate group we will study is in a different phylum:

• Domain Eukarya

– Kingdom Animalia

Phylum X


•Early Animals










Figure 17.6

Evolutionary Tree of Kingdom Animalia

Sponges (Phylum Porifera)• Includes sessile (non-motile)

animals Lacks true tissues

• Is asymmetrical in body shape

– Porous, bulbous mass with hollow interior and exit hole at the top

• Composed of only three cell types, the most important are collar cells (choanocytes)

– Flagella drive water current inward to hollow space and out osculum

– Food particles are trapped on sticky collars and passed to other cells

• Some sponges produce spicules (skeletal rods) of silica to help support shape

Figure 17.6


Cnidarians/Stinging Cell Animals (Phylum Cnidaria)

• True body tissues

• Body shape in floating medusa or anchored polyp form

• Radial symmetry

• Tentacles with stinging cells (cnidocytes)

• Food items brought into gastrovascular cavity where they are digested by enzymes

Figure 17.11

Cnidarian Body Shape is Either a Polyp or a Medusa

• Examples of cnidarians

– sea anemones, jellies, and coral animals.

Hydra Budding

Hydra Eating Daphnia

Hydra Releasing Sperm

Jelly Swimming

Thimble Jellies

Coral Reef

http://upload.wikimedia.org/wikipedia/commons/d/d0/Libr0409.jpg

Figure 17.6


Flatworms (Phylum Platyheminthes)

• Bilateral symmetry

• Flattened body plan

• Cephalization of the nervous system: simple brain

• No body cavity (coelom)

• Incomplete gut with enhanced absorptive area

• Many are parasitic: they derive their nutrition by living on the flesh or juices of another animal

Figure 17.15

Examples of Some Flatworms That Cause Disease

Tapeworm Life Cycle Blood fluke Life Cycle

Figure 17.6


Figure 17.8

Three Conditions of the Body Cavity (Coelom) Within Animals

Roundworms (Phylum Nematoda)• Round in cross-

section


• Complete gut

• Pseudocoelom (false body cavity)

• About 30% are parasitic

• Individuals are either male or female

• Occur in aquatic and moist terrestrial habitats.

Figure 17.16

Caenorhabtidis elegans Crawling

Examples of Roundworms

Life cycle of Trichinella spiralis

Figure 17.6


Segmented Worms (Phylum Annelida)


• Round in cross-section

• Segmented

• True body cavity (coelom)

• Primitive circulatory system with “pumping” vessel elements

• Complete gut

• Includes earthworms, leeches, tube worms on dock pilings and ribbon worms in the sediment (polychaetes)

Figure 17.18a

Examples of Segmented Worms (Annelids)

Polychaetes in "A variety of marine worms": plate from Das Meer by M. J. Schleiden (1804–1881). Deposit and Filter Feeders

Leeches: fluid feeders

Earthworms are deposit feeders

Tubeworms

Figure 17.6


Jointed-Footed Animals (Phylum Arthropoda)

• Jointed appendages

• Exoskeleton of chitin

• Segmented into 3 specialized body parts: head, thorax, and abdomen

• Bilaterally symmetrical

• True coelom

• Sophisticated sensory appendages (antenna, hairs, feelers, eyes)

• Some with elaborate social behavior (e.g. hives and colonies)

• Some (insects) undergo metamorphosis or body restructuring

• Most “successful” (diverse) of all animal groups

Lobster Mouth Parts

Arthropod Diversity: Four Main Groups

• Arachnids

– Spiders, scorpions, ticks, and mites

• Crustaceans

– Crabs, lobsters, crayfish, shrimps, barnacles, and pill bugs


Pill bugs (isopods)

• Millipedes and Centipedes


• Insects (many Orders)


Dragonflies Grasshoppers/Crickets True Bugs Beetles

Aphids/Cicadas Butterflies Flies Bees/Wasps

Figure 17.25Butterfly Emerging

Metamorphosis: Body Restructuring From Juvenile to Adult

Figure 17.6


Molluscs (Phylum Mollusca)

• Soft-bodied animals with viscera, a mantle, and a foot

• Most molluscs have shells or shell remnants

• Rasping tongue (radula) used in grazing

• Bilateral symmetry, true coelom

• Includes snails, slugs, clams, octopuses, and squids, to name a few.

Nudibranchs

Three Major Classes of Molluscs

Figure 17.6


Spiny-Skinned Animals (Phylum Echinodermata)

• Spiny skin

• Not segmented

• Five-part radial symmetry

• Water pressure-based (hydrostatic) endoskeleton

• Tube feet for motility

• Exclusively marine

• Includes sea stars, sand dollars, sea urchins, and sea cucumbers.

Echinoderm Tube Feet

Figure 17.28

Types of Echinoderms


•Early Animals










invertebrate animals chapter 17 what is an animal? early animals significant invertebrate animal...

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