Invertebrate 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
– Digest their food within their bodies
– 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)
Life Cycle of An Animal
Dominant
diploid
stage
Figure 17.3
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
Major Evolutionary Novelties in the Evolution of Invertebrate Animals
• The development of true tissues
– Specialized cells living in sheets or masses within an
organism
• 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 a complete gut
– Incomplete digestive tracts have a mouth but no anus
• The development of segmentation
– Body is subdivided into separate parts which can then
develop specialized functions
Types of Body Symmetry Seen in Animals
Figure 17.7
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
w
Phylum X
Invertebrate 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)
Evolutionary Tree of Kingdom Animalia
Figure 17.6
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
Evolutionary Tree of Kingdom Animalia
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
Cnidarian Body Shape is Either a Polyp or a Medusa
Figure 17.11
• Examples of cnidarians
– sea anemones, jellies, and coral animals.
Hydra Budding
Hydra Eating Daphnia
Hydra Releasing Sperm
Jelly Swimming
Thimble Jellies
Coral Reef
Evolutionary Tree of Kingdom Animalia
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
Examples of Some Flatworms That Cause Disease
Tapeworm Life Cycle
Blood fluke Life Cycle
Figure 17.15
Evolutionary Tree of Kingdom Animalia
Figure 17.6
Three Conditions of the Body Cavity (Coelom) Within Animals
Figure 17.8
Roundworms (Phylum Nematoda)
• Round in crosssection
• Bilateral symmetry
• Complete gut
• Pseudocoelom (false
body cavity)
• About 30% are
parasitic
• Individuals are either
male or female
• Occur in aquatic and
moist terrestrial
habitats.
Examples of Roundworms
Figure 17.16
Caenorhabtidis elegans Crawling
Life cycle of Trichinella spiralis
Evolutionary Tree of Kingdom Animalia
Figure 17.6
Segmented Worms (Phylum Annelida)
•
Bilateral symmetry
•
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)
Examples of Segmented Worms (Annelids)
Earthworms are deposit
feeders
Leeches: fluid feeders
Polychaetes in "A variety of marine worms":
plate from Das Meer by M. J. Schleiden
(1804–1881). Deposit and Filter Feeders Tubeworms
Figure 17.18a
Evolutionary Tree of Kingdom Animalia
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
Lobster
• Most “successful” (diverse) of all animal groups
Mouth
Parts
Arthropod Diversity: Four Main Groups
• Arachnids
– Spiders, scorpions, ticks, and mites
Arthropod Diversity: Four Main Groups
• Crustaceans
– Crabs, lobsters, crayfish, shrimps, barnacles, and
pill bugs
Pill bugs
(isopods)
Arthropod Diversity: Four Main Groups
• Millipedes and Centipedes
Arthropod Diversity: Four Main Groups
• Insects (many Orders)
Dragonflies
Grasshoppers/Crickets
Aphids/Cicadas
Butterflies
True Bugs
Flies
Beetles
Bees/Wasps
Metamorphosis: Body Restructuring From Juvenile to Adult
Butterfly Emerging
Figure 17.25
Evolutionary Tree of Kingdom Animalia
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.
Three Major Classes of Molluscs
Nudibranchs
Evolutionary Tree of Kingdom Animalia
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
Types of Echinoderms
Figure 17.28
Invertebrate 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)