Classification of Animals: Invertebrates
Invertebrate Animals 6th Grade Science
Animal Characteristics • Many-celled organisms sharing similar features and that are made of different kinds of cells. • Animal cells have a nucleus and organelles surrounded by a membrane – EUKARYOTIC. • Cannot make their own food – HETEROTROPHIC – digest their food. • Can move from place to place to find food, shelter, and mates, and to escape from predators.
Symmetry • Symmetry: arrangement of the individual parts of an object • Radial: body parts arranged in a circle around a central point • Bilateral: parts are mirror images of each other • Asymmetrical: bodies cannot be divided into matching halves
Animal Classification Animal Kingdom Invertebrates ( No backbone) Vertebrates (Backbone) Cnidarians Roundworms Annelids Echinoderms Chordates Sponges Flatworms Mollusks Arthropods
What is an Invertebrate? • Invertebrates are animals that do not have backbones. • 97% of the animal kingdom is made up of invertebrates. • Some can be found in ponds, oceans, and other water environments. • Insects and some other invertebrates have exoskeletons. • An exoskeleton is a hard outer covering that protects an animal’s body and gives it shape.
Porifera Characteristics • They live in water. (Most are found in the ocean.) • They look like plants but they are animals. • Sponges stay fixed in one place - SESSILE. • Their bodies are full of pores and their skeleton is made of spiky fibers (spicules) or rubbery spongin • Sponges are divided into classes according to the type of spicule they have – 5,000 species identified! • Water flows through the pores of their body, aided by flagella, which enables them to catch food – FILTER FEEDERS
Porifera Characteristics • Sponges can reproduce asexually through budding ~ GEMMULES; a new sponge grows from pieces of an old sponge • Most sponges that reproduce sexually are hermaphrodites, meaning they have both eggs and sperm • Sperm is released into water • Sperm floats until they are drawn into another sponge where they fertilize an egg • Larva develops in sponge, leaves sponge, and settles to the bottom where it grows into an adult
Cnidaria Characteristics • Cnidaria comes for the Greek word for nettle. • All cnidarians have stinging cells called NEMATOCYSTSin tentacles surrounding their mouths. • Cnidarians are more complex than sponges. • They have complex tissues, a gut for digesting food, and a nervous system. • They come in two body shapes, the medusa and the polyp. • Polyp: usually sessile and vase-shaped • Medusa: free-swimming and bell-shaped
Cnidaria Characteristics • Cnidarians reproduce both sexually and asexually • Polyp forms reproduce asexually by budding • Some polyps also reproduce sexually be releasing sperm or eggs • Medusa forms have a two-stage life cycle in which they reproduce both sexually and asexually
Sea Anenomes and Corals • They are polyps their entire life. • They look like brightly colored flowers. • They live in colonies. • They have soft tube-like bodies with a single opening surrounded by arm-like parts called tentacles. • They feed by catching tiny animals in their tentacles.
Hydras • They live in fresh water. • They spend their entire life as polyps. • Hydras have tentacles that catch their food. • They move from place to place. • Hydras are very small animals. • Reproduce asexually by budding.
Jellyfish • They spend most of their life as medusa. • They swim. • Jellyfish catch shrimp, fish, and other animals in its tentacles also. • Reproduces sexually to produce polyps; then each polyp reproduces asexually to form new meduae.
Worms • Flatworms • Roundworms • Segmented Worms
Platyhelminthes: Flatworms • Search for their food; long, flattened bodies with organs and systems • They have a head and a tail, and flattened bodies – BILATERAL • Planaria – free-living • Tapeworms – parasitic; each segment (proglottid) contains sperm and eggs (reproduce sexually) ~ when fertilized eggs fill segment, it breaks off and passes out with wastes of host – can be up to 80,000 eggs per segment!!! • Lack a digestive system and absorb nutrients from the host’s intestine
Nematoda: Roundworms • They have rounded bodies; body is a tube within a tube; I.e., digestive tract has both a mouth and an anus • They live in damp places and they can also live inside humans and other animals. • Heartworm (Dirofilaria immitis) ~ • Passed by mosquito bite • They too can make people and other animals sick. • Diets vary with some roundworms being decomposeers, some predators, and some parasites • Most wide-spread animal on earth! • Billions can live in just one acre of soil!!!
Annelida: Segmented Worms • The earthworm (oligochaete), leech (hirudinea), and marine worm (polychaete) belong to this group. • Their bodies are divided into repeating segments • Each segment has nerve cells, blood vessels, part of the digestive tract, and the coelom (body cavity) • Closed circulatory system and complete digestive system with two body openings • They prefer burrowing through moist soil. • This allows them to move easily and it keeps them from drying out.
Annelida: Segmented Worms • Earthworms – have more than 100 body segments • Use external bristle-like setae and muscles to move • Eat organic material in soil • Exchange carbon dioxide and oxygen through mucus-covered skin
Annelida: Segmented Worms • Leeches • Have flat bodies with sucking disks at both ends • Can store enormous amounts of food for months • Secrete heparin, which prevents blood from clotting
Annelida: Segmented Worms • Marine worms – use bristles or setae for moving • Some are filter feeders • Some eat plants or rotting material • Some are predators or parasites
Mollusca: Octopi, Squid, Slugs, Snails, and Bivalves • A mollusk has a soft body usually covered by a hard shell, a rough tongue (radula), a muscular foot, and a mantle (thin layer of tissue that covers the mollusk’s soft body and secretes the shell). • Aquatic mollusks have gills for gas exchange; land mollusks have lungs • A snail is a mollusk with a single hard shell. • A clam has two shells joined together by a hinge. • Squids and octopi are also mollusks. • Their hard shells are small, but they are inside their bodies.
Cephalopods: Octopi and Squid • Cephalopods are the most complex type of mollusks • Water squeezed out of a funnel-like siphon allows the cephalopod to move quickly • Well-developed head and a “foot” that is divided into tentacles with strong suckers • Closed circulatory system • Blood carried through vessels at all times
Bivalves: Clams and other two- shelled shellfish
Arthropoda: Insects, Spiders, Ticks, Mites, Centipedes, Millipedes, Crustaceans
Arthropoda Characteristics • Arthropods are a group of invertebrates with jointed legs and hard exoskeleton that protect the arthropod; also have bilateral symmetry. • More than a million species of arthropods have been discovered!! • As it grows, it molts, or sheds its old exoskeleton. • Then it grows a new exoskeleton that allows its body to continue to grow. • The largest group of arthropods are insects. • They are the only invertebrates that can fly!
Insect Characteristics • Insects have adapted to living almost everywhere! Over 700,000 species have been classified….so far!! • An insect’s body has 3 parts: the head, thorax, and abdomen. • The head has one pair of antennae and two compound eyes ~ well- developed sense organs. • Thorax has three pairs of jointed legs and usually one or two pairs of wings. • Reproductive organs are located in abdomen. • Open circulatory system; oxygen enters through openings on sides called spiracles
Insect Metamorphosis • Complete Metamorphosis
Insect Metamorphosis • Incomplete Metamorphosis
Crustaceans: Shrimp, Barnacles, Crab, Crayfish, and Lobster • Almost all crustaceans are aquatic & have gills. • All have 2 pairs of antennae, three types of chewing appendages, and five pairs of legs.
Arachnids: Spiders, Scorpions, Ticks, and Mites • They have 2 main body parts: a cephalothorax And an abdomen • The thorax has jointed 4 pairs of legs and no antennae. • They do have special mouth parts like fangs. • They kill more insect pests than any other animal.
Myriapods: Centipedes and Millipedes • Centipedes use their many legs to run from enemies (one pair of jointed legs attached to each segment). • Predators. • Millipedes roll up their bodies when they sense danger approaching (two pairs of jointed legs attached to each segment). • Feed on plants.
Echinodermata: Starfish and Sea Urchins • Belongs to a group of invertebrates that have tiny tube feet and body parts arranged around a central area. • A starfish has five arms and no head! • The hard, spiny covering of the starfish gives the animal protection. • A sea urchin belongs to this same group. • Its body is covered with spines.