Sponges- Filters of the Sea
 Phylum- Porifera
 What they don’t have:
 Eyes
 Organs
 Can’t move
Sponges
 Why are they animals?
 They are multi-cellular heterotrophs
 Have different cell types
Sponges
 They range in size from a drop of paint to 16 feet across
 They have 2 major cell types
 1. Collar cells- have flagella that waft water into the
sponges epithelium. (epithelium is the tissue that
protects the sponge’s outer surface).
 The epithelium has contractible pores through which
water enters
 2. Amoebocytes- are cells that pick up nutrient particles
that pass through the sponges walls.
 The amoebocytes are mobile cells that distribute
nutrients throughout the sponge
Sponges
Sponges
 Water exits the sponge through oscula, large openings
to let the filtered water pass out
 Because of the way they feed sponges are considered
filter feeders
 The pores can get clogged with debris so they have 2
ways to solve that problem
 1. They secrete large quantities of mucus to cleanse their
surface of debris and pathogens
 2. They provide a niche for mutualistic worms and other
organisms that feed on the material that can obstruct
filtration
Sponges
 Sponge larvae are free swimming organisms with a
flagella
 The larvae will swim and drift until colliding with a
suitable spot on the reef to fix themselves
 Defense against predators
 Spicules are needlike structures in the tissue
 Spongin is a tough fibrous material that is difficult to
feed on. It is made of tough elastic protein
 Many produce toxins
 They can reassemble if torn apart by a predator
Phylum- Cnidaria
 Include corals, anemones, sea fans, and jellyfish
 They are radially symmetrical which means they
radiate around a central point
 Cnidarias have an internal sac for digestion which is
called the gastrovascular cavity
 The gastrovascular cavity has only one opening, a
mouth, through which the animal takes in food and
releases waste
 Tentacles radiate outward from the rim of the mouth.
Cnidarians
 The body wall of a cnidarian consists of three layers, an
outer layer known as the epidermis, a middle layer
called the mesoglea, and an inner layer referred to as
the gastrodermis
 Epidermis contains a collection of different types of
cells for
 Contracting and enabling movement
 Production of sperm and egg
 Containing stinging structures
 Mucus-secreting cells
 Receptor and nerve cells which collect and transmit
sensory information
Cnidarians
 Mesoglea is a jelly layer
Jellyfish
Jellyfish
 Jellyfishes require water to help support their body and
if removed from their aquatic surroundings, they
collapse and die.
 To move forward, jellyfishes take water into their
muscular bell and then squirt it out behind them,
creating a jet of water
 Jellies also drift on water currents to move
 Their senses are primitive and consist of a neural net,
eye spots that can sense light from dark, and
chemosensory pits that help them identify potential
prey.
Jellyfish
 Nematocysts consist of a capsule that holds a hollow
barbed coil, a venom sac, and chemo-sensitive trigger
hairs that detect when something edible brushes
against them. When potential prey brushes against the
trigger hairs, the nematocysts expel the coiled barb
and inject venom into the victim through the hollow
thread. The venom immobilizes the prey and the
jellyfish uses its oral arms to move the prey into its
mouth
Jellyfish
 Lifespan-Jellyfish evolve from a dimorphic (two-shaped)
cycle. The two body forms are the asexual polyp and the
sexual medusa. The male in the medusa form releases
sperm from its mouth into the water and some of the
sperm will enter into the female's mouth. Fertilization
takes place in the female's mouth and the eggs will remain
there until they develop into larvae. The larvae will leave
the mother, drift through the water and settle on the floor.
They are now called polyps. Polyps reproduce asexually by
budding. The buds, which resemble a stack of saucers, are
individual "baby" jellyfish called ephyra that separate from
the polyp and drift in the water. After a few weeks, the cycle
is complete when the ephyra grows into an adult or
medusa.
 Diet
 Jellyfish eat a variety of food, some that are too small for
the human eye to see. They eat small plants, fish and
crustaceans, fish eggs and even other species of jellyfish.
 Predators
 Predators include sea turtles, spade fish and sunfish. In
Asia, certain jellyfish are consumed by humans and are
considered a delicacy which brings in millions of dollars.
Corals
 The marine creatures who form coral reefs and atolls
are called coral polyps and they could be as minute as
2.5 centimeters in diameter, while some measure up to
30 centimeters in diameter.
 As tiny as they are, they have a mouth-like opening
that is surrounded by even tinier tentacles.
 The other end is equipped with natural substances
allowing these polyps to attach their body to the ocean
floor.
 As living creatures, they feed on the larvae of shellfish,
but they subsist largely on algae
 The algae exist right in the polyp’s own tissues.
 While attached to the polyp, the alga secretes chemical
nutrients that enable the coral animals to form external
limestone skeletons and develop color.
 The algae require sunlight in order to photosynthesize

This requires the corals to grow in shallow, clear, well lit water
 As host to the algae, the polyp tends to assume the
alga's color as a living organism.
 Another vital substance needed by coral animals to
develop their external skeletal formations are the
calcium intakes they get from seawater
 Some polyps live singly but most of them form into a
community by attaching to each other
 These are the reef building corals and are often found in
the shallower portions of warm tropical seas
Starfish
 Sea stars belong to the Phylum Echinodermata
 That means they are related to sand dollars, sea
urchins, and sea cucumbers
 All echinoderms have five-point radial symmetry,
which means that their body plan has five sections (or
multiples thereof) arranged around a central disk
 There are about 2,000 species of sea stars and are
found everywhere in the oceans
 Not all sea stars have 5 arms. Some have many more.
The sun star has up to 40 arms!
 Sea stars can regenerate lost arms
 If the sea star is threatened by a predator - it can drop
an arm, get away and grow a new arm
 Sea stars house most of their vital organs in their arms,
so some can even regenerate an entirely new sea star
from just one arm and a portion of the star's central
disc.
 It takes about a year for an arm to grow back
 Protection-Sea stars have a tough covering on their
upper side, which is made up of plates of calcium
carbonate with tiny spines on their surface.
 Predators-include birds, fish and sea otters
 Movement- tube feet help it to move but very slowly
 Prey-They prey on bivalves like mussels and clams, as
well as small fish, snails, and barnacles.
 Sea stars wrap their arms around the animal's shell and
pull it open just enough. It pushes its stomach through
its mouth and into the bivalve's shell. It then digests the
animal and slides its stomach back into its own body
 Vision-sea stars have an eye spot at the end of each
arm. This is a very simple eye that looks like a red spot.
The eye doesn't see much detail, but can sense light
and dark.
 Reproduction-Sea stars may reproduce sexually or
asexually. There are male and female sea stars, but they
are indistinguishable from one another. They
reproduce by releasing sperm or eggs into the water,
which, once fertilized, become free-swimming larvae
that later settle to the ocean bottom.