CLASSIFYING INVERTEBRATES OCS Biology Mrs Bonifay INVERTEBRATES Every

CLASSIFYING INVERTEBRATES OCS Biology Mrs. Bonifay

INVERTEBRATES § Every animal that is not a vertebrate is an invertebrate. § Invertebrates do NOT have backbones. § Invertebrates make up about 97% of all animal species.

SPONGES § Sponges are the simplest animal. § Sponges’ bodies are made up of two layers of cells without any tissue or organs. § All sponges live in water.

SPONGES § Sponges strain food particles out of the water which enters through pores in the body wall. § If you use a natural bath sponge, you are using the skeleton of a dead sponge.

CNIDARIANS § Cnidarians include jellyfish, corals, and hydras. § All of the approximately 10, 000 species of cnidarians live in the water. § Cnidarians have body parts that are arranged like spokes on a wheel. This is called radial symmetry.

CNIDARIANS § Cnidarians have arm-like tentacles with stinging cells. § These tentacles capture prey and push them into the body to digested.

FLATWORMS § Flatworms are flat and thin. § Their bodies have a left side and a right side that are the same. This is called bilateral symmetry. § There are more than 20, 000 species of flatworms and most are parasites which live in or on other animals. § An example is the tapeworm which live in the intestines of vertebrates and absorb nutrients.

ROUNDWORMS § Roundworms have long, round bodies that are pointed on each end. § Roundworms also have bilateral symmetry. § Of the approximate 80, 000 species of roundworms, only about 150 are parasites.

ROUNDWORMS § Many roundworms live in soil or in water and help plants by insect pests. § An example of a parasite roundworm is the hookworm which enters the body through the skin, settles in the intestines, and feeds on blood.

SEGMENTED WORMS § Segmented worms have bodies that are divided into many sections, or segments. § Segmented worms live in the soil, freshwater, and the ocean. § The earthworm is the most familiar segmented worm. Earthworms tunnel through soil eating small food particles. They loosen the soil, allowing air to enter which helps plants grow.

SEGMENTED WORMS § Another example of a segmented worm is the leech. Some leeches eat small invertebrates, but some are parasites. They attach to the skin of a vertebrate and feed on its blood.

MOLLUSKS § Mollusks have three parts: head, body, and foot. § Snails and slugs make up the largest group of mollusks. § Some mollusks, such as snails, clams, and oysters, have outer shells. § Other mollusks, such as squids, octopuses, and slugs, have no outer shell. This allows them to swim very fast.

ARTHROPODS § Arthropods are the largest group of invertebrates, making up more than 75% of all animal species. § The major groups of arthropods are : 1. crustaceans (crabs, lobsters, crayfish) 2. arachnids (spiders, scorpions, mites, ticks) 3. centipedes 4. millipedes 5. insects § All arthropods have external skeletons, which they must shed to grow. This is called molting.

Crustaceans § Crustaceans have 5 pairs of legs, some of which have claws to help them handle food. § The two legs closest to the head have powerful claws used for protection.

Arachnids § Arachnids have 4 pairs of legs. § Spiders and scorpions inject poison into their prey to capture them. § Mites feed on hair and dead skin. § Ticks feed on blood.

Centipedes & Millipedes § Centipedes’ and millipedes’ bodies have up to 175 segments. § Centipedes have one pair of long legs on each segment. They move quickly. § Millipedes have two pair of short legs on each segment. They move § slowly.

Insects § Insects have 3 pairs of legs and most have one or two pairs of wings. They are the only invertebrates that can fly. § Many insects are pests; however, many are helpful to humans, such as bees. § Most insects go through metamorphosis.

Complete & Incomplete Metamorphosis § Butterflies go through complete metamorphosis in which the first 3 stages look nothing like the stage 4 adult butterfly. § Grasshoppers go through incomplete metamorphosis in which the eggs hatch into a stage that looks similar to the adult grasshopper.

ECHINODERMS § § All echinoderms live in the ocean. Their bodies have radial symmetry. Echinoderms use tube feet to move. Examples are sea stars (starfish), sea urchins, and sand dollars.