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 gastrovascular cavity mouth mesoglea oral arms tentacles 1. Body Plan 2. Tissue Layers 3. Developmental Patterns blood vessels brain hearts muscle segment nerve cord mouth digestive track

There are two types of Body Plans Bilateral Symmetry Radial Symmetry Body divides equally along one plane Body arranged in a circle around a central axis

Tissue Layers Bilateral Radial 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 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 Pinacocytes- form the sponges outer layer Choanocytes- pull water into sponge and help trap food Ameobocytes- absorb and digest food particles osculum choanocyte amoebocyte pinacocyte pore spicule

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 of prey barbs coiled nematocyst discharged

Flatworms have a solid body and incomplete or absent gut. They have no circulatory system head pharynx mouth sucker eyespot reproductive system gut cavity

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 stomach digestive gland foot anus salivary gland crop mouth radula mantle mantle cavity heart

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/high_school_sci/tx/gr9-12/hmd_bio_9780544073890_/dlo/biologyvideoclips/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/high_school_sci/tx/gr9-12/hmd_bio_9780544073890_/dlo/biologyvideoclips/index.html?vid=91

Roundworms Roundworms have bilateral symmetry and shed their outer skeleton to grow. Roundworms are protostomes with bilateral symmetry brain cuticle pharynx intestine anus tail

Roundworms have a psuedocoelom (“false” not complete body cavity) They do not have a respiratory or circulatory system