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Chapter 23
Animals: The Invertebrates
Characteristics of Animals
1.
2.
3.
Multicellular. Cells are usually
arranged in organs or organ
systems
Heterotrophs
Require oxygen to perform aerobic
respiration
4.
5.
6.
Most are motile at some point in the
life cycle
Life cycle includes some sort of
embryonic development
Mostly reproduce sexually (some
asexually)
Radial Symmetry
 No
clear front
or rear
 Body parts are
arranged
around a
central axis
Bilateral Symmetry
 Organism
is
the same on
either side of
one plane of
symmetry
 Has a true
front and rear
Phylum Porifera - Sponges
 Animals
with no symmetry, no tissues
or organs.
Range in size from tiny (like a fingernail)
to large enough to sit in
 Engulf particles to feed (phagocytosis)
 Can reproduce sexually with a larva or
asexually by fragmentation

Sponges
Phylum Cnidaria
 Jellyfish,
sea anemones, coral
 All are aquatic – most are ocean
dwelling
 Have tissues
 Have nematocysts – “stinging darts”
 Reproduce sexually
 Have a nerve net for stimulation
Jellyfish, Corals, Hydra
Phylum Platyhelminthes Flatworms
 Turbellarians,
Flukes, and Tapeworms
 Have a simple digestive system –
absorb food from a host
 Body is flattened
 Most are hermaphrodites, but will
reproduce sexually with another
flatworm
Flatworms
Sea slugs
Phylum Nematoda - Roundworms
 Thrive
nearly everywhere
 Have a complete digestive system
 Have a partial body cavity where
reproductive organs are found
 Most are free-living, with few
parasitic species
Roundworms
Ancyclostoma
duodenale
(hookworm)
Phylum Annelida – Segmented
Worms
 Segmented
worms – segments are
repeating body sections
 Many have setae (small hair like
bristles) to help them move through
soil
 Have a complete gut, rudimentary
brain (with nerve cord), and
circulatory system
Earthworms and Leeches
Phylum Mollusca
 Octopus,
squid, clams, scallops,
snails, slugs, oysters
 Most have a hard shell with a soft
body
 Have well developed organ
systems
 Have a brain
Octopus, Squid, Snail, Oyster
Phylum Arthropoda
(I accidently left this off – add it!)
 Insects,
crustaceans, arachnids
 Hardened exoskeletons
 Jointed appendages
 Respiratory Structures
 Sensory Structures
 Division of labor
Class Arachnida
Class Insecta
Class Crustacea
Phylum Echinodermata
 Sea
urchins, star fish
 Have spines or plates of calcium
carbonate
 Well developed skeleton
 No brain, but nervous system is
present
 Water vascular system to deliver
water to tube feet for movement
Sea Stars, Sea Urchins
Class Asteroidea
Phylum Chordata
 Includes
some invertebrates and
ALL vertebrates
 Subphylum Vertebrata – all
vertebrates are in this subphylum
Works Cited
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http://www.okc.cc.ok.us/biologylabs/Documents/Animals/Symmetry.htm
http://trc.ucdavis.edu/biosci10v/bis10v/week9/sponge.gif
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http://www.troutnut.com/im_regspec/picture_1170_small.jpg
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http://www.emporia.edu/biosci/invert/lab6/limulusad.jpg
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http://www.museums.org.za/bio/images/mb/mb0556m.jpg
http://3.bp.blogspot.com/_3tLvZgf7WyA/SkqCO0e_L1I/AAAAAAAAAgo/8fUbEjGyTuU/s400/roach8.jpg