This document summarizes the six major groups of invertebrates: - Poriferans (sponges) lack symmetry and skeletons, instead using protein fibers and calcium carbonate to support their soft bodies. - Cnidarians (jellyfish, anemones, corals) are soft-bodied with a central cavity and take cylindrical, vase-shaped, or umbrella shapes. - Echinoderms (sea stars, sea urchins) have spiny skin, radial symmetry, and use tube feet and water vascular systems. - Mollusks (clams, snails, octopuses) are often soft-bodied but sometimes have hard shells for protection

1. Sir Michael Angel S. Sajot
Grade VI

2. Invertebrates are animals that do not have bones. They
comprise of 95% of all animals on Earth having almost 2
million species to date.
Invertebrates are divided into 6 major groups: Poriferans,
Cnidarians, Echinoderms, Mollusks, Worms and Arthropods.
Some invertebrates have an EXOSKELET ON. It serves as
protection and for muscle support and also prevent water loss.
Soft-bodied invertebrates maintain their body integrity by
maintaining their internal pressure.

3. Porifera was derived from a Latin word that means
“pore bearer”. This group of invertebrates has no
definite body symmetry. They can reproduce
sexually and asexually.
Sponges can regenerate lost parts.
Regeneration is the ability to grow missing parts.
Lacking a skeleton, sponges are supported instead
by protein fibers called spongin and by hard
particles made up of calcium carbonate called
spicules.

5. This group is composed of jellyfish, sea anemones,
corals hydras, sea whips, sea fans, and sea
pansies. They are characterized as soft-bodied
animals with hollow central cavity.
The two basic shapes of cnidarians are: Polyp,
which is cylinder-shaped or vase-shaped and
Medusa, umbrella-shaped with stinging tentacles.

7. An echinoderm is a marine invertebrate
characterized by spiny skin, an exoskeleton, radial
symmetry and a water vascular system. Its name is
derived from the Greek term for porcupine and
hedgehog.
They have a tube-feet with suction pads located
on their tentacles. The tube-foot is connected to
the ampullae, which is a muscular sac that forces
water into the tube-foot

9. Mollusks are soft-bodied invertebrates that are
often covered or protected by a hard shell. There
are approximately 85 000 known species of
mollusks to date.
It is composed of snails, slugs, clams, scallops,
octopuses, and squids.

11. Worms are invertebrates that can be found almost
everywhere. They can be found in marine,
freshwater, and land habitats.
Most worms are scavengers or oftentimes called
decomposers, responsible for breaking down
complex chemical bonds into their original form so
they can be absorbed by plants.

13. Arthropods are the largest and most diverse
invertebrate group. It is represented by spiders,
crabs, scorpions, lobsters, beetles, bees,
caterpillars, fleas, ticks, mites and lice.
They have segmented bodies covered by an
external skeleton called exoskeleton which is
composed of chitin, a tough material.