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Intro to Invertebrates . Chapter 25 Sections 1 & 2. Invertebrates (inverts) include all animals that lack a backbone, or vertebral column. This includes 33 Phyla. Phylum Porifera. The term Porifera means “pore-bearers” in Latin. This phylum includes Sponges.
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Intro to Invertebrates Chapter 25 Sections 1 & 2
Invertebrates (inverts) include all animals that lack a backbone, or vertebral column. • This includes 33 Phyla
Phylum Porifera • The term Poriferameans “pore-bearers” in Latin. • This phylum includes Sponges. • Most ancient member of the Kingdom Animalia. • One of the most simple organisms
Phylum Cnidaria • Organisms include jellyfish, anemones, hydra, and coral. • These organisms are always aquatic. • Can live in giant colonies such as the Great Barrier Reef
Phylum Nematoda • Range in size from microscopic to 1 meter • Can live on land and in water. • Some are parasitic • Closely related to the phylum Arthropoda
Phylum Platyhelminthes • Commonly known as flatworms. • They are the most simple animals to have 3 germ layers. • Most are only 3mm thick.
Phylum Annelida • Includes organisms such as earthworms and leeches • The word Annelida means little ring in Latin
Phylum Mollusca • Includes both marine and terrestrial organisms • Ex. Snails, clams, squid, and octopi • Have a larval stage in development • Typically have an internal or external shell
Echinodermata • Echino- means spiny in Greek and Detmis- means skin (spiny skin) • Includes sea urchins, sand dollars, and Sea Stars • Only live in the sea • Have a structure called “tube feet”
Body Plans of Inverts • Body Symmetry • Radial Symmetry- a number of imaginary planes drawn through the center of the body will divide the organism in equal halves. • Ex: Sea Stars, Sea Anemone, and Jelly Fish
Bilateral symmetry- a single imaginary plane divides the body into left and right sides that are mirror images of each other. • Lobster, earthworms, snails
Germ Layers-during embryonic development the cells of most animals differentiate into 3 layers, called germ layers • Endoderm- is the inner most layer and develops the lining of the digestive tract and much of the respiratory system.
Mesoderm- middle layer that gives rise to muscles and much of the circulatory, reproductive, and excretory systems. • Ectoderm- outermost layer that produces sense organs, nerves, and the outer layer of the skin
Body Cavities- a fluid-filled space between the digestive tract and the body wall • The most complex organisms have a true coelom, which is a body cavity that develops within the mesoderm and is completely lined. • Pseudocoelom is a partially lined body cavity • Acoelomthere is no body cavity present.
Segmentation- repeated parts on an animal. Most have repeated body parts on the inside also.
Cephalization-The concentration of sense organs and nerve cells at the organisms anterior end. (to have a head) • The most successful animal groups exhibit cephalization.
