Sponges & Cnidarians
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Transcript 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,
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