INVERTEBRATES

INVERTEBRATES

1. BODY PLAN SYMMETRY.

   • Asymmetry.
     • Porifera.
   • Symmetry.
     • Without skeleton.
       • Radial symmetry.
         • Cnidarians
       • Bilateral symmetry.
         • Annelids.
     • With skeleton.
       • Endoeskeleton.
         • Echinoderms.
       • Exoeskeleton.
         • Outer or inner shell
           • Molluscs.
         • Jointed.
           • Arthropods.

2. SKELETAL STRUCTURE

   • Invertebrates.
     • Porifera:They live attached to a substrate.They feed by filtration.A sponge's body is perforated by many tiny pores.Some sponges are made up spicules,a flexible material known as spongin.
     • Cnidarians.
       • They are carnivores and they capture their prey with poison located on their tentacles.
       • Types of cnidarians.
         • Polyps:They have a sac-like body.At one end they have a structure to hold on to the substrate.At the other end,they have a hole,wich acts as both mouth and anus.
         • Jellyfish:They have an umbrella-shaped body.They look like inverted polyps and they float freely in the water and have a hole that serves as mouth and anus.
     • Annelids:They breathe trough their skin.They are soft and long and their body is divided into rings.They are hemaphrodites,they have an unique reproductive organ around their bodies,the clitellum.
     • Molluscs.
       • They are soft.They have a very muscular foot.
       • Molluscs' classification.
         • Gastropods--->Garden snail:It is herbivore,it use its sandpaper-like tongue to eat .They use their muscular foot to adhere itself to the substrate.
         • Bivalves--->Mussel:the waterenters and exits trough two orifices.Its black shell is made of two valves.It uses its hatchet-shaped foot to pull itself.
         • Cephalopods--->Squid:It is carnivore and they capture its prey with its tentacles.Instead of a foot,it have tentacles.
     • Arthropods.
       • They have segmented bodies divided into three parts:head,thorax and abdomen.They have jointed appendages.They use legs to move.
       • Arthropods' classification.
         • Six legs--->Insects:They have a head,one pair of antenae and one pair of eyes.They can also have one or two pairs of wings,but not all of them have wings.They have six legs.It abdomen is segmented.INSECT METAMORPHOSIS:The flies lay eggs and a larva hatches from the egg.The larva make the sac called pupa and inside it the larva grows and transform into an adult insect.
         • Eight legs--->Arachnids:They are terrestrial .They are carnivore,they trap their prey in their webs and they inject poison trough chelicerae.CEPALOTORAX.This body region consists of the head and thorax fused together.AT THE FRONT:One pair of fang-like chelicerae,where the poison glands are located.They have also a pair of pedipalps for defensive and sensory fuunctions;and four pairs of legs.ABDOMEN:It isn't segmented.The spinnerets produce silk for their webs.
         • Ten legs--->Crustaceans:Their exoeskeleton is very hard because it is impregnated with calcium carbonate.Some are carnivores;other are scavangers,filter-feeders or parasites.CEPHALOTORAX:The head hastwo pairs of sensory antennae and five pairs of legs.ABDOMEN:It is segmented and has appendages that help acuatic crustaceans swim and catch food.
         • Many legs--->Myriapods.They are terrestrial.They are carnivore or herbivore.HEAD:One pair of antennae.SEGMENTED:Centipeds have one ppair of legs per segment,while millipeds have two pairs of legs per segment.
     • Echinoderms:They are marine invertebrates with radial symmetry.The starfish has a flat body.It is formed by a central disc from which five arms protude.Echinoderms use a hydraulic system for locomotion,the water vascular system.
   • VERTEBBRATES.

3. ENVIROMENTS

   • Aquatic.
     • Attached to a substrate
     • Mobile
       • Sedentary
       • Very active
   • Terrestrial.
     • Jointed limbs.
     • Wings.