Contents organized by F.J. Barba Regidor. Images from various online sources (2011)

MAIN CHARACTERISTICS:1. As animals they are, they have eukaryotic cells and they

are multicellular and heterotrophs.2. Invertebrates do not have a backbone.3. Invertebrates do not have a cranium.

PORIFERA CNIDARIA-Aquatic animals.-They have not tissues.-They are shaped bag with the mouth upward.-The wall of their bodies is perforated by pores.- They are filtering animals.-Water and food enter through the pores. Waste (water) are expelled through the mouth of the sac (osculum).-They live attached to the foor of the see.

-Aquatic animals.-They present two basic forms: polyp and medusae (jelly fish).-They are shaped bag with the mouth upward (polyps) or downward (medusae: umbrella shape).-They have a mouth and a central cavity called the gastrovascular cavity.- They are carnivores: to catch their prey, they use numerous tentacles around its mouth.-They live attached to the foor of the see.

ANNELIDS-Terrestrial or aquatic animals.-Long, cylindrical and soft body that is divided into rings.-Each segment (ring) is similar to the others and has the same organs.-No legs, but with chetae: tiny and not articulated appendages to move.-They breathe through gills or through the skin.

NEMATODESPLATYHELMINTHES

ECHINODERMS-Symmetry: bilateral. Body usually flattened dorsoventrally and divided into rings. -Digestive system incomplete (a mouth but no anus).-No skeletal, ciculatory or respiratory systems. -The nervous system is a pair of anterior ganglia connected to longitudinal nerve chords.-Hermaphrodites. The y can fertilise themselves.-Parasites.

-Soft, cylindrical bodies without segments.-No respiratory system.-Male and female specimens.-Parasites… or not.

-Marine invertebrates, with an external hard skeleton, generally with spines.-Radial symmetry in adults (bilateral in larvae)-Ambulacral system.-Male and female specimens.-No head, but there is a mouth on the underside.

MOLLUSCS:1.Aquatic and terrestrial animals with bilateral symmetry.2.Soft body with three different parts: head, visceral mass (this produces a protective shell) and muscular foot.3.Terrestrial molluscs breathe through lungs but aquatic molluscs breathe through gills.

BIVALVESGASTROPODS

CEPHALOPODS

-Terrestrial or aquatic animals with a spiral shell.-On their head there are four tentacles.-They have at the mouth a rasping tongue (the radula).-Aquatic gastropods breathe through gills and terrestrial s do it through lungs.

-Aquatic animals.-They have two shells, joined like a hinge.-Their head is not differentiated from the rest of the body.-Their single foot has the shape of an axe that they use to excavate.-Most of them are filter-feeding organisms.

-Aquatic animals with a differentiated head from the rest of their body.-The foot surrounds the head and has the shape of tentacles for capturing prey.-The mantle has mobile fins for swimming..- They are carnivorous.

ARTHROPODS:1.Terrestrial and aquatic animals which body is divided into assembled segments in different ways: head, thorax and abdomen; cephalothorax and abdomen..2.Hard articulated appendages appear from the segments in different forms: legs, antennae, chelicerae or palps.3.The body presents bilateral symmetry and is covered by a thick cuticle that acts as an external skeleton..4.They are oviparous. Fertilization is internal. Many of them undergo metamorphosis.

CRUSTACEANSINSECTS

CHELICERATES

-Most of them are terrestrial.-Their body is divided into head, thorax and abdomen.-The head has two antennae.-The thorax has six legs (three pairs).-Many species presents four wings: they are the only invertebrates that can fly.-They breathe through tracheae.-Some of them can be carnivorous, but many others are herbivorous.

-Aquatic animals: they breath through gills.-Their body is divided into cephalothorax and abdomen.-They usually have ten legs (5 pairs).-Their body is covered by a calcareous and hard cuticle.

-Terrestrial animals which body is divided into cephalothorax and abdomen.-They present mouth appendages called chellicerae, connected to glands that can produce venom.-The number of legs is 8 (4 pairs).-They breathe through tracheae.- They are carnivorous.

Clockwise from top left: dancefly (Empis livida), long-nosed weevil (Rhinotia hemistictus), mole cricket (Gryllotalpa brachyptera), German wasp (Vespula germanica), emperor gum moth (Opodiphthera eucalypti), assassin bug (Harpactorinae)

MYRIAPODS-Terrestrial animals which body is worm-like and it is formed by a head and numerous rings, each with a pair of locomotor appendages (legs).-The number of legs is greater than 10.-They also present mouth appendages called chellicerae.-They are carnivorous.-They breathe through tracheae.

Color electron micrograph scanning of the head of a wasp (order Hymenoptera) showing the compound eyes (red), the antennae and the chelicerae.

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Color electron micrograph scanning of the head of a Jumping Spider (familia Salticidae).Color scanning electron

microscope of a housefly (Musca domestica). The head is dominated by a pair of large compound eyes, each eye is composed of about 4000 facets called ommatidia, which form the image. The mouthparts are visible between and below the eyes. The hairs on the head and body act as tactile organs. House flies tend to feed on decaying matter, and can collect and transmit serious diseases to humans.

A color scanning electron micrograph of the head of a human flea (Pulex irritans)

showing the mouth appendages to drill the tissues to find the blood from which it feeds.

Color scanning electron microscope of a meal (or flour) mites. He has long hair that extends down her body and her large legs. This species is a common pest of granaries, mills and kitchens, and feed mainly on cereal grains.