Invertebrate Classification
Barbara J. Shaw Ph.D.
Grades:
3rd – 5th
Time:
30 – 45 minutes
Goals:
Classification, using common characteristics, is a method used by scientists to
organize information from galaxies to organisms. Invertebrates comprise the
dominant form on animal life on Earth. Sketching is a valuable method of
observation.
Objectives:
Students will:
 List characteristics of an organism
 Identify characteristics of an organism
 Differentiate characteristics of different organisms
 Deduce which organisms belong to each taxa of invertebrates
 Draw organism incorporating distinguishing characteristics
Colorado Standards:
Mathematics
5th Grade
1. Geometric figures in the plane and in space are described and analyzed
by their attributes
a. Relate two-dimensional shapes to three-dimensional shapes
using faces, edges, and vertices
b. Predict and describe the results of transformations: translations,
reflections, rotations
d. Apply concepts of parallel, perpendicular, congruence and line
symmetry
4th Grade
1. Geometric figures are described by their attributes and specific
location in the plane
a. Identify parallel, perpendicular, and intersecting line segments
in the plane and within geometric shapes
b. Create geometric designs using transformations – reflections,
translations, and rotations
c. Compare geometric figures according to the attributes of
congruence, symmetry, and angle size
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3rd Grade
1. Geometric figures are described by their attributes and position in the
plane
a. Construct and describe two dimensional shapes by attributes
and properties such as sides, angles, and symmetry
b. Recognize and demonstrate transformations – reflections,
translations, and rotations – of basic shapes or designs
c. Use geometric properties of points and line segments to
describe figures
Science
Standard 2: Life Science
5th Grade
1. All organisms have structures and systems with separate functions
a. Develop and communicate an evidence-based scientific
explanation of the role of different organs or structures that are
important for an organism’s survival – in both plants and
animals
b. Analyze and interpret data to generate evidence that all
organisms have structures that are required for survival in both
plants and animals
c. Create and evaluate models of plant and/or animal systems or
parts
4th Grade
1. All living things share similar characteristics, but they also have
differences that can be described and classified
a. Use evidence to develop a scientific explanation of what plants
and animals need to survive
b. Use evidence to develop a scientific explanation for similarities
and/or differences among different organisms (species)
c. Analyze and interpret data representing variation in a trait
d. Examine, evaluate, question, and ethically use information
from a variety of sources and media to investigate questions
about characteristics of living things
Introduction (background information for teacher information):
Life is classified in a hierarchy system as follows, using the domestic cat as the example:
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Carnivora
Family Felidae
Genus Felis
Species catus
A way to remember is to use acronyms (example: Kings Play Chess On Fine Green Sand)
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In traditional classification of life, all organisms were first divided into 2 (vegetable and animal)
by Aristotle. Carolus Linnaeus, father of biological nomenclature, classified organisms also used
those two groupings. As more information was gathered during the European exploration of the
world, these grouping were further refined to 5 kingdoms (Monera – prokaryotic bacteria (a cell
without a nucleus); Protista – single celled eukaryotes (cells with a nucleus, and all multi-cellular
organisms have this kind of cell); Fungi – mushrooms, mildew, and mold; Plantae – plants;
Animalia – animals).
Carl Woese changed all that with is incredible work of sequencing a section of DNA that codes
for a section of ribosome’s (the organelle that reads mRNA and builds proteins as coded in
DNA). He did this before DNA sequencing was easy, spending years and years of reading each
nucleotide, one by one, of thousands of organisms. He found that the Kingdom Monera was
actually composed of two very different prokaryote organisms: bacteria and another organism
that had DNA more similar to the eukaryotic celled organisms he named Archaea. The
Kingdoms added another Kingdom, but it was clear that there was a better way of classifying
was an overarching system of Domains. Organisms are now first sorted into Domain Bacteria,
Domain Archaea, or Domain Eukarya. Instead of 6 Kingdoms, there are more than 26
Kingdoms, including Kingdom Animalia under Domain Eukarya.
Kingdom Animalia has about 36 phyla (plural of phylum). All organisms have been classified
according to their shape (morphology). As technology advanced, scientists were able to include
DNA, the very blueprint for all the variety of life on Earth. By sequencing the DNA of
organisms, they are able to use additional information for refining how organisms are related to
each other. Many of the organisms classified by morphology remained the same, but some have
changed. Science is always changing as more information is discovered. Below is listed a
version of the current animal phyla:
Phylum (meaning of phylum name) common name
 Acanthocephala (thorny-headed worm) thorny-headed worms
 Acoelomorpha (without gut) acoels
 Annelida (little rings) segmented worms
 Arthropoda (jointed foot) insects, crustaceans, spiders, etc.
 Brachiopoda (arm foot) lamp shells
 Bryozoa (moss animals) moss animals or sea mats
 Chaetognatha (longhair jaw) arrow worms)
 Chordata (cord) tunicates and vertebrates)
 Cnidaria (stinging nettle) jellyfish, sea anemones, corals and hydra
 Ctenophora (comb bearer) comb jellies
 Cycliophora (wheel carrying) symbions
 Echinodermata (spiny skin) sea stars, brittle stars, urchins, sand dollars, sea cucumbers,
crinoids, etc.
 Echuira (spine tail) spoon worms
 Entoprocta (anus inside) globlet worms
 Gastrotricha (hair stomach) gastrotrichs
 Gnathostomulida (jaw orifice) jaw worms
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Hemichordata (half cord) acorn worms and pterobranchs
Kinorhyncha (motion snout) kinorhynchs
Loricifera (corset bearer) brush heads
Micrognathozoa (tiny jaw animals) micrognathozoans
Mollusca (thin shell) snails, clams, octopuses, tusk shells, chitons, etc.
Nematoda (thread like) round worms
Nematomorpha (thread form) horsehair worms
Nemertea (a sea nymph) ribbon worms
Onycophora (claw bearer) velvet worms
Orthonectida (straight swim) orthonectidans
Phoronida (Zeus’s mistress) horseshoe worms
Placozoa (plate animals) placosoans
Platyhelminthes (flat worms) flatworms
Porifera (pore bearer) sponges
Priapula (penis worm) pirapula worms
Rhombozoa (lozenge animal) rhombozoans
Rotifera (wheel bearer) rotifers
Sipuncula (small tube) peanut worms
Tardigrada (slow step) water bears
Xenoturbellida (strange flatworm) xenoturbellidan
Note that only one phylum (underlined), Chordata, includes all the “vertebrate” species. Even
this phylum includes invertebrates, sea squirts and amphioxus! Looking at this list, it is
abundantly apparent that vertebrates are the true minority of animal life. The major groups of
animal phyla are in bold.
Materials (for a class of 30):
 Bio Corporation 24 Specimen Jar Set plus additional Porifera (sponges), Mollusca (snail)
and Annelida (leech and polychaete) for good representation of the major groups of
invertebrates
 Signs with 8 phyla and characteristics of that group (pages 5-12)
 Copies of student worksheet (pages 13 and 14)
 Color pencils
 Hand lens (optional)
Method:
1. Discuss, “What is an animal?” (Animals are multi-cellular, mobile, and must ingest their
food.)
2. Discuss “What is the difference between a vertebrate and an invertebrate?” (Animals
with a backbone vs. animals with an exoskeleton, endoskeleton (like the spicules in
sponges), or hydrostatic skeleton.)
3. Discuss that 95% of all animals belong to invertebrates, and 90% of all animals belong to
the arthropods. (Arthropods include insects, arachnids, horseshoe crabs, crustaceans,
millipedes, centipedes, trilobites (all extinct) and some other minor groups.) Of all
arthropods, about 95% are insects.
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a. If I put all the human beings alive right now on a gigantic scale, and I put all the
termites alive right now, on the other side, which would weigh more? TERMITES!
b. Okay, let’s move all the human beings over to the termite side, and also put every
other living animal – all the blue whales, sponges and jelly fish, all the worms,
beetles, and mice on one side of the scale, and all the ants alive today, which would
weigh more? ANTS!
c. The beetles have the most number of species of any group of animals – just not as
many individuals as ants.
4. We are going to classify the major groups of invertebrates. There are approximately 36
phyla of animals (that is changing as scientists use DNA sequences to examine the
relationships of animals). We are going to look at the eight biggest groups. Of the other
28 remaining phyla, 19 are worm-like, 5 are tiny and not many cells, and the other 4 are
just the oddballs.
5. Hand out student worksheets and color pencils. Distribute invertebrate specimens
throughout the room, organizing them by phyla, and post sign.
6. Divide students into 8 groups, 1 group for each of the 8 phyla.
7. Find the correct square to sketch the organism.
8. Pick one of the organisms, and sketch that organism.
9. Identify and label the defining characteristic for that phyla.
10. Optional: Select one organism. Research and write a paragraph about it.
11. Optional: For older students, dissect and sketch an invertebrate, identifying all internal
organs. Students prepare a poster with an enlarged drawing with all organs identified and
share with classmates.
Vocabulary:
appendage – limb or other part coming off the main body of a creature
asymmetry – absence of symmetry (see symmetry below)
bilateral – having two sides or parts that match opposite but identical
holdfast – a root-like fastener
pore – any tiny hole for liquid (fluid or gas) to flow through
radial – spreading out from a central point
segment – natural divided parts or sections that make up the whole
skeleton – rigid framework that provides protection and structure
symmetry – the shape on one side is identical to the other side when it is slid, flipped or
turned
tentacle – an appendage that can grasp or hold
References:
Tree of Life: Information captured September 18, 2010
http://tolweb.org/tree/phylogeny.html
University of California Museum of Paleontology: Information captured September 18, 2010
http://www.ucmp.berkeley.edu/
Wikipedia: Information captured September 18, 2010
http://en.wikipedia.org/wiki/Phylum
Colorado State University Extension 4-H programs are available to all without discrimination.
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Porifera
Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics:
 Has pores for water to flow in, through, and out
 Has a holdfast – a way to hang on at the bottom of the sponge
 Has a large, internal chamber called a spongocoel
 Only made up of cells working together (no tissues or organs)
Grantia
Leucosolenia
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Spongilla
Cnidaria
Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics:
 Has radial (radiating out from the center) symmetry
 Made up of two layers, the outer layer and the inner layer
 In between those two layers is a jelly layer called the mesoglea
 Specialized stinging cells – too small to see
 Most have in the tentacles around the mouth
 Only has tissues, no organs
Aurelia
Obelia
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Sea Anemone
Platyhelminthes and Nematoda Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics:
 Platyhelminthes
o Flat worms with long skinny body or squashed body
o Many are parasitic, some free living
 Nematoda
o Round worms
o Outer skin is a thick waxy layer, called a cuticle
Sheep Liver Fluke (Platyhelminthes)
Sheep Tapeworm (Platyhelminthes)
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Ascaris Roundworm (Nematoda)
Mollusca
Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics:
 Amazing diversity – snails, giant clams, squid, and many others
 All share the same body plan: head (sensory area – antenna and/or eyes), foot (muscle for moving), and visceral mass (guts)
 Except for squid, octopus, and slug (which they lost), all secrete a shell
Clam
Snail
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Octopus
Annelida
Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics
 Segmented worms
 Symmetrical down the length (called bilateral) of the body
 Leeches lack little appendages called setae, earthworms have little paired setae, and polyhchaetes have big paired setae
Earthworm
Leech
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Polychaete (Nereis)
Arthropoda - Insecta
Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics:
 Arthropods
o Jointed appendages (legs)
o exoskeleton
 Insects
 3 body segments
 6 legs
 Compound eyes
Grasshopper
Butterfly
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June Beetle
Arthropoda – others
Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics:
 Arthropods
o Jointed appendages (legs)
o exoskeleton
 Arachnids
 2 body segments
 8 legs
 Crustacean
 3 body segments
 More than 10 legs
 Chilopoda (centipede)
 Multiple body segments
 1 pair of legs per segment
 large mouth parts
 Diplopoda (millipede)
 Multiple body segments
 2 pairs of legs per segment
 small mouth parts
Tarantula (arachnid)
Crayfish (crustacean)
Centipede (Chilopodian)
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Millipede (Diplopodian)
Echinodermata
Pick one of these specimens and sketch it. Be sure to identify the characteristics listed below.
Characteristics
 Unique vascular system to move tube feet with a sucker-like appearance
 Most have a hard outer covering with spines or bumps (exception is sea cucumbers – they have the covering, but it is microscopic)
 Unique 5 sided symmetry
Sea Stars
Sea Cucumbers
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Sea Urchins
Name: __________________________________________________________
Porifera – sponges
Cnidaria – jellyfish, anemone, coral, and hydrozoa
Platyhelminthes & Nematoda – flatworms and roundworms
Mollusca – clams, snails, and octopi
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Name: __________________________________________________________
Annelida – segmented worms
Arthropoda – insects
Arthropoda – spiders & scorpions, crabs & shrimp, centipedes, and millipedes
Echinodermata – sand dollars, sea stars, sea cucumbers, and sea urchins
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