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Outline for Invertebrates: chapter 25-26
Biology 520
I. What is an animal? - p. 730-731
II. Overview of the phyla | Biodiversity links | Encyclopedia of life | Wild Finder | Arkive
A. Phylum Porifera (sponges)
B. Phylum Cnidaria (corals and jellyfish)
C. Phylum Platyhelminthes (flatworms)
D. Phylum Nematoda (roundworms)
E. Phylum Annelida (segmented worms)
F. Phylum Arthropoda
1. Class Trilobita
2. Class Arachnida
3. Class Crustacea
4. Class Insecta
G. Phylum Mollusca
1. Class Gastropoda (snails)
2. Class Bivalvia (clams)
3. Class Cephalapoda (octopus, squids)
H. Phylum Echinodermata (sea urchins, starfish)
We will examine these groups from various angles:
1. anatomy/physiology
-digestion
-circulation
-skeleton, muscles (movement)
-excretory
-nervous system/brain
2. reproduction and development (how do they pass on offspring and disperse their offspring?)
3. ecology and behavior (how do they get energy? how do they defend themselves?)
Basic Overview:
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What is an animal? p. 730
Animal body plans: p. 737-741; also fig 25-10
phylogeny (family tree) - p. 742, fig 25-11
II. Phylum Porifera
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more info
p. 372
A. anatomy - see figure 26-3, p. 754
1. digestion - one opening (a sac)
water flows into pores and out the oral opening; flagella beat to
create water flow
2. skeleton - body supported by hard cells called spicules
3. no brain, circulatory system, or organs
B. Reproduction
1. sexual - hermaphroditic with ciliated larvae
2. asexual - budding/regeneration
C. Ecology
1. consumers - filter a great deal of water
2. preyed upon by some fish and by nudibranchs (sea slugs)
3. important part of shallow tropical ecosystems (coral reefs)
III. Phylum Cnidaria
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p. 754
links
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Coral reef conservation program
Coral discovery program
Coral Reef information system
A. Classification
1. class Hydrozoa (hydra)
2. class Scyphozoa (jellyfish)
3. class Anthozoa (corals and sea anemones)
B. anatomy/physiology
1. polyp stage
2. medusa stage
3. digestion
a. a sac with one opening and two body layers
b. stinging cells disable prey
4. radial symmetry
5. no true brain; a simple "nerve net" allows communication
between cells
6. has sensory cells - eyespots for light and others that sense
chemicals/food
C. Reproduction/life cycle
1. sexual and asexual - note differing life cycles of corals and
jellyfish
2. during sexual reproduction, sperm must pass through the one
body opening
D. Ecology
1. corals are essential parts of reefs
2. symbiotic relationship with zoozanthelle, a dinoflagellate algae.
Pollution can cause the algae to die, a condition termed "coral
bleaching"
IV. Phylum Platyhelminthes (flatworms) p. 755
A. Classification
1. class Turbellaria – planaria
2. class Tremetoda – flukes
3. class Cestoda – tapeworms
B. anatomy/physiology
1. digestion – possess a sac, a "dead end" gut, which may be
branched in order to reach all parts of the body
2. circulation – materials must reach cells by diffusion. That is why
they are flat.
3. excretory – cellular waste products leave through flame cells.
4. bilaterally symmetrical
5. nervous system shaped like a ladder; small brain
C. Reproduction
1. sexual reproduction is hermaphroditic in some
2. sexes are different sizes in some
3. asexual in the form of regeneration is possible with planaria
4. parasitic forms contain mostly reproductive organs and eggs
inside their bodies - they might be called "egg factories"
D. Ecology
1. planaria are free-living. They are carnivores and scavengers.
They are mostly marine, but a few live in freshwater ponds.
2. flukes - some are free-living and some parasitic.
· blood flukes such as Schistosoma infect 200 million people
annually
3. tapeworms
a. Have no mouth; have suckers for holding on to
tissue, and absorb nutrients through their skin (see
fig. 18.7B, p. 374)
V. Phylum Nematoda (roundworms) (p. 755)
A. anatomy/physiology
1. tube-within-a-tube digestive system (mouth and anus)
2. no skeleton; moves via hydrostatic pressure, pushing against
fluid in its body
3. C. elegans has been very extensively studied
· the fate of every cell during development is known
· first multicellular creature to have its entire genome sequenced
4. pseudocoelom – partial body cavity – fig 25-8
B. Reproduction
1. sexes separate
2. internal fertilization
C. Ecology
1. up to 800,000 different species (!)
2. live in water, muddy lake bottoms, soil
3. some are beneficial - act as decomposers and nitrogen fixers.
4. some are parasitic to humans, such as
a. Trichinella, which come from raw pork
b. hookworm
c. Ascaris
d. there are several which come from uncooked fish.
FDA recommends freezing fish at -31oF for 15
hours before eating raw.
e. river blindness
VI. Phylum Annelida (p. 755)
A. classification
1. class Hirudinea - leeches
2. class Oligochaeta - earthworms
B. anatomy/physiology
1. segmented - have the appearance of many rings strung together
2. tube-within-a tube digestive system crosses all segments.
3. nephridia - cells that get rid of cellular wastes. A pair in each
segment
4. circulation - 5 hearts; two major blood vessels with branches in
each segment.
5. brain - small; nervous system with branches in each segment.
6. coelomate – fig. 25-8
B. Reproduction
1. sexual - hermaphoditic with cross fertilization
2. asexual - regeneration from cut worms is possible.
C. Ecology
1. earthworms (oligochaetes) are decomposers
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Darwin estimated that 1 acre of British farmland has
approximately 50,000 earthworms, which produce about 18
tons of castings (waste) per year.
2. leeches - medicinal use as bloodsuckers; external parasites in the
wild
VII. Phylum Mollusca (p.756)
A. Features all mollusks have in common
1. visceral mass or mantle: this is the soft body
2. external or internal shell
3. muscular foot for locomotion
4. some have a radula, which is a rough tongue for scraping food .
5. most have a ciliated larva called a trochophore
B. Class Gastropoda (= "stomach foot") - snails
1. tube-within-a-tube; position effected by torsion (anus is above
the head)
2. most have shells excreted by the soft body, expect for slugs
3. have a "foot" for locomotion
4. have a radula that scrapes food (most are herbivores; exceptions
include nudibranchs and oyster drills)
5. ecologically important in spite of their size.
C. class Bivalvia (pelecypoda) - mussels, scallops, and clams.
1. two-part, hinged shell.
2. filter feeders, with incurrent and excurrent siphon.
3. breathe with gills, like fish.
4. multiple eyes.
5. ecology - filter water, and are significant componants of both
fresh and saltwater ecosystems.
D. Class Cephalopoda (= "head-foot")
1. tube-within-a-tube; beak
2. largest squid - 17m long, weighed 2 tons.

in search of giant squid -- cool site with animations!!
3. closed circulatory system - blood is always in vessels.
4. most complex brain/nervous system of any invertebrate.
5. locomotion - siphon
6. predators
7. ammonites - dominant, large cephalopods found as fossils.
Nautilus is the only living representative.
VIII. Phylum Arthropoda (p.755)
A. general characteristics.
1. largest phylum (at least 1 million species; estimates of up to 30
million)
2. hard exoskeleton, which grows by molting
3. distinct head and abdomen regions.
4. open circulatory systems – no capillaries
5. jointed appendages.
B. class arachnida - spiders, ticks, mites, and scorpions.
1. eight legs
2. pedipalps and chelicerae - appendages used to hold and tear
food.
3. separate sexes; elaborate courtship behavior.
4. respiration - book lungs
5. ecology: spiders are predators which build webs to attract prey;
mites and ticks are parasitic or at least require a host; scorpions are
predators.
6. horseshoe crab - related but technically not arachnids (more - ecological
importance)
C. class Crustacea (40,000 species)
1. 5 pairs of legs, with the front pair modified into claws.
2. two pair of antennae on the head. Also several mouthparts.
3. most are predators.
4. excretion through cells called green glands
5. very important ecologically
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crabs and lobsters are the top predators in some ecosystems
krill - base of marine food webs (plankton)
crayfish - many species are endangered, especially in the
SE United States.
D. class insecta
1. six legs
2. trachea for gas exchange - bring air to all cells
3. malpighean tubules - excratory organs for cellular waste
products.
4. most have wings, sometimes two pairs.
5. life cycle includes complete or imcomplete metamorphisis
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check out some cool insect facts!!
another great link - pictures and cool info
explore the biology of social insects
6. ecology - perhaps the most important of any group, because they
are so diverse that they have filled nearly every ecological role. An
ecosystem without vertabrates could probably function quite well
as long as insects were present.
7. insect pests - how should they be controlled?
8. taxonomy - insect orders
a. Lepidoptera - butterflies.
b. hymenoptera - bees and wasps
c. odonata - dragonflies
d. ephemeroptera - mayflies
e. coleptera - beetles (largest order)
f. hemiptera - true bugs
g. diptera - flies and mosquitoes
h. isoptera - termites
IX. Phylum Echinodermata (p. 756)
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overview of echinoderms
A. classification - several important classes
1. starfish (sea stars)
2. sea urchins
3. sea cucumbers
B. anatomy/physiology
1. radially symmetrical as adults but bilaterally symmetrical as
larvae
2. spiny skin and internal skeleton
3. movement with tube feet - use water pressure
4. feeding - stomach comes out of the body to digest the prey
5. respiration and excretion - tube feet can collect oxygen and
dispose of cellular waste.
6. parts come in multiples of 5, even for those without arms
C. Reproduction
1. sexual with external fertilization; ciliated, free-swimming larva
2. asexual via regeneration
3. development similar to chordates
D. Ecology
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important members of coral reef communities and tidal communities. Can
be predators of corals and bivalves
X. Chordates (p. 757-759)
A. This phylum includes vertebrates, but also a few "oddball" species with no
backbone.
B. have these features in common:
1. dorsal, hollow nerve chord
2. post-anal tail
3. notochord (supports nerve chord during development)
4. pharyngeal "gill slits"
C. examples
1. tunicates (sea squirts)
2. salps
3. lancelets