Download Sponges & Cnidarians

Invertebrates
 Do not have a backbone or vertebral column
 Range in size from microscopic dust mites to giant
squids
 Include groups of sea stars, worms, jellyfish, and
insects
 95% of all animals are invertebrates
Body Symmetry
 Radial Symmetry- any number of imaginary planes
can be drawn through the center, each dividing the
body into equal halves
 Bilateral Symmetry- can only draw one imaginary
plane and it divides the body into two equal halves
 Asymmetrical Symmetry- cannot put any lines to
divide it evenly
 Cephalization- is the concentration of sense organs
and nerve cells at the front end of the body. Usually
animals that have bilateral symmetry exhibit
cephalization
Sponges
 Sponges are in the phylum Porifera means “pore-
bearing”
 Live their entire adult life attached to one place.
 They have nothing resembling a mouth, gut and they
have no tissues or organ systems.
 Asymmetrical they have no front
or back have no standard form
Cnidarians
 Soft bodied carnivorous animals that have stringing
tentacles arranged in circles around their mouths
 They are the simplest animals to have body symmetry
and specialized tissue
 They have a life cycle that includes two different
looking stages: a polyp and a medusa
Worms
 They come in several different types; flat, round and
segmented
 Body cavities there are three kinds acoelomate (no
body cavity), pseudcoelomate (fake body cavity),
coelomate (real body cavity lined with tissue)
 Most worms have exhibited cephalization at least
enough to call a head
 Some worms can cause diseases in humans
Mollusks
 Are soft bodied animals that usually have an internal
or external shell
 Include snails, slugs, clams, octopi, and squids
 Groups of mollusks
 Gastropods are shell-less or single-shelled mollusks that
move by using a muscular foot located on the ventral
side
 Bivalves have two shells that are held together by one or
two powerful muscles
 Cephalopods are typically soft-bodied mollusks in which
the head is attached to a single foot, the foot is divided
into tentacles or arms
Gastropod
Bivalve
Cephalopods
Bivalves
Arthropods
 Have segmented bodies, a tough exoskeleton, and
jointed appendages
 The exoskeleton is made up of chitin that is made from
protein and carbohydrates
 Appendages are things like legs and antennae that
extend from the body
 When they out grow their exoskeleton they go through
a period of molting or sheding of their exoskeleton
 There are 4 subphylum of arthropods or groups
Classification of arthropods
 They are classified based on the number and structure
of their body segments and appendages- particullarly
their mouthparts
 The three major groups of arthropods are crustaceans,
spiders and their relatives, and insects and their
relatives
Crustaceans
 Members of this group are things like crabs, shrimp,
lobsters, crayfish, and barnacles
 Typically have two pairs of antennae, two of three body
sections, and chewing mouthparts called mandibles
 The body sections
 Cephalothorax- it is formed by fusion of the head with
the thorax. Which lies just behind the head and houses
most of the internal organs.
 Abdomen- is the posterior part of the body
 Carapace- is the part of the exoskeleton that covers the
cephalothorax
Spiders and Their Relatives
 These include all spiders, horseshoe crabs, mites,
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ticks, and scorpions
They have mouthparts called chelicerae and two body
sections, and nearly all have four pairs of walking legs
They have a cephalothorax, and an abdomen. They
have the same kind of body structure as crustaceans,
but they lack antennae.
They have two pairs of appendages attached near the
mouth. One pair is called chelicerae contain fangs and
are used to stab and paralyze prey.
The other pair is called padipalps they are longer and
usually modified to grab prey
Echinoderms
 Echinoderms are characterized by spiny skin, an
internal skeleton, a water vascular system, and
suction-cuplike structures called tube feet.
 Most adult echinoderms exhibit five-parts radial
symmetry. They have appendages that occur in
multiples of five
 Classes of echinoderms include sea urchins, sand
dollars, brittle stars, sea cucumbers, sea stars, sea lilies
and feather stars
Insects and Their Relatives
 Uniramians are centipedes, millipedes, and insects. They
have jaws, one pair of antennae, and unbranched
appendages.
 Insects have three-part bodies (head, thorax, and
abdomen) three pairs of legs are attached to the thorax
and most are adapted for flight
 There are two types of metamorphosis incomplete and
complete
 Incomplete they have an adult and an immature stage
 Complete they have the same stages but within those
stages they completely change from one thing to another