Invertebrates Animal Characteristics • Animals are the most physically diverse kingdom of organisms. • They range in size from twice the length of a school bus to microscopic 4 Major Characteristics of Animals • 1. They are multi-cellular heterotrophs • 2. Animal cells are supported by collagen – three-stranded protein – found in bone, skin, ligaments, fingernails, and hair • 3. Animals are diploid and reproduce sexually Diploid cells have two copies of each chromosome: one copy from the mother and one from the father • 4. Animals have Hox genes – Homeotic genes control early development. – Hox genes determine the position of cells differentiation. – A Hox gene mutation leads to the development of a body structure in the wrong position and/or animal diversity Animal Diversity • Animals are grouped into vertebrates (animal with backbones) or invertebrates (animals without backbones) • More than 95% of all animal species are invertebrates- an animal without a backbone Animals are grouped according to these 3 criteria • 1. Body Plan • 2. Tissue Layers • 3. Developmental Patterns gastrovascular cavity mouth mesoglea brain muscle hearts blood vessels mouth segment digestive track nerve cord oral arms tentacles There are two types of Body Plans Bilateral Symmetry Body divides equally along one plane Radial Symmetry • Body arranged in a circle around a central axis Tissue Layers Bilateral • Have 3 distinct layers: ectoderm, endoderm, and mesoderm – Ecto- develops into skin, the brain, and nervous system – Endo- lines the “gut” – Meso- develops into internal organs Radial • Have two distinct layers: ectoderm and endoderm Animals are separated into two major groups • Protostome- mouth develops before anus • Deuterostome- anus develops before mouth Invertebrate Diversity Sponges • Sponges are the most primitive animals on Earth. • Sponges share common characteristics. – Sessile- attached to floor of ocean (do not move) – reproduce both sexually and asexually – filter feeders- strain food particles from water Sponges have three types of cells 1. Pinacocytes- form the sponges outer layer 2. Choanocytes- pull water into sponge and help trap food 3. Ameobocytesabsorb and digest food particles spicule pore osculum pinacocyte amoebocyte choanocyte Sponge Video Cnidarians (Jellyfish) • Cnidarians come in two body forms – Polyp- cylindrical tubes with mouth and tentacles facing upward – Medusa- umbrella-shaped, with mouth and tentacles on the underside Cnidarian Video Cnidarian Anatomy • Cnidarians are made up of two tissue layers separated by mesoglea • The outer tissue layer has three cell types. – contracting cells – covers the surface of the cnidarian – nerve cells- sends information around animal to coordinate movement – cnidocytes (which contain nematocysts)“stinging cells” used for defense and capturing discharged of prey nematocyst barbs coiled nematocyst Flatworms • Flatworms have a solid body and incomplete or absent gut. • They have no circulatory system head pharynx mouth sucker gut cavity eyespot reproductive system 3 classes of Flatworms • Planarians- free-living non parasites • Flukes – parasites which can infect humans and cause serious disease (schistosomiasis) – Infects 200 million people in Africa and Southeast Asia – Contracted by wading in or drinking contaminated water • Tapeworms- are parasites that live in vertebrates gut – Use suckers or hooks to attach to host – Absorb nutrients from the food the host eats Tapeworm Video Mollusks • Mollusks have a complete digestive tract with two openings – a mouth and an anus • Coelom ( fluid filled body cavity)is present – Except in flatworms • Mollusks have all three tissue layers • Have a brain and spinal cord (cephalization) • Have a circulatory system – Primitive species (open) such as bivalves – Advanced species (closed) such as octopus and squid Mollusks Anatomy • Mollusks share at least one of three features. – radula : file like teeth used to obtain food – mantle : area of tissue covering the internal organs, sometime secrete a hard outer shell for protection – ctenidia: flat gills found in the mantle intestine heart mantle cavity mantle stomach digestive gland foot radula salivary gland anus crop mouth • Most mollusks are classified into three classes. – Gastropods: includes snails, abalone, and slugs they are found on both land and water – Bivalves (Pelecypods): clams, oysters, mussels, and scallops. Protected by two hinged shells – Cephalopods: squid, octopus, nautiluses, and cuttlefish. Most advanced mollusks and are predators Mollusk Video #1 Mollusk Video • http://my.hrw.com/content/hmof/science/hig h_school_sci/tx/gr912/hmd_bio_9780544073890_/dlo/biologyvid eoclips/index.html?vid=92 Annelids • Three groups of Annelids – earthworms, leeches, and marine worms • They are characterized by having segmentation: division of the organism into repeated sections • They have a coelom and all three tissue layers • They breathe by diffusing oxygen through their skin • They are hermaphroditic so they can reproduce either sexually or asexually Annelid Video • http://my.hrw.com/content/hmof/science/hig h_school_sci/tx/gr912/hmd_bio_9780544073890_/dlo/biologyvid eoclips/index.html?vid=91 Roundworms • Roundworms have bilateral symmetry and shed their outer skeleton to grow. • Roundworms are protostomes with bilateral symmetry pharynx intestine brain cuticle anus tail • Roundworms have a psuedocoelom (“false” not complete body cavity) • They do not have a respiratory or circulatory system