Introduction to Animals Mrs. Nell 7 th Grade Life Science Unit

What is an Animal? Animal Characteristics –Cannot make their own food –Digest their food (food has to be broken down in order for their bodies to use the proteins, fats, and carbohydrates –Many move –Multicellular –Eukaryotic (have a nucleus)

The Animal Kingdom The animal kingdom is broken down into 9 major phyla… 1) Sponge 2) Cnidarian 3) Flatworm 4) Roundworm 5) Echinoderm 6) Mollusk 7) Annelid 8) Arthropod 9) Chordate

Vertebrates To classify animals scientists first see if the animal has a backbone. Animals with a backbone are called vertebrates. Some vertebrate animals are: fish humans birds snakes elephants mice

Invertebrates About 97% of all animal species are invertebrates- they don’t have backbones. Some examples of invertebrate animals are: sponges insects clams squid jellyfish spiders worms

Symmetry- Radial Once scientists have determined whether an animal has a backbone they will look to see if the animal’s body has symmetry. Any cut through the center of an organism with radial symmetry (dorsal to ventral) results in roughly equal halves in terms of organs and body parts.

What has radial symmetry? Only cnidarians and ctenophores have true radial symmetry. (What the heck is a ctenophore? It’s similar to a jellyfish. They are commonly known as comb jellies.)

Partial Radial Symmetry Echinoderms like this brittle star have partial radial symmetry.

Bilateral Symmetry Most animals have bilateral symmetry. An animal with bilateral symmetry has its body parts arranged in the same way on both sides of its body. Bilateral animals can be divided into right and left halves by drawing an imaginary line down the length of its body.

What has bilateral symmetry?

Asymmetry Some organisms have no definite shape and are said to be asymmetrical. There is no way their bodies can be divided into matching halves.

Sponges Sponges live in water. They grow in many shapes, sizes, and colors. Some have radial symmetry, but most are asymmetrical.

Sessile Adult sponges live in one place- they are sessile. They are covered with pores and belong to the phylum Porifera.

Filter Feeder Sponges are filter feeders. They have collar cells inside that help filter sea water so the sponge can eat, breath, and excrete waste products.

Sponge Reproduction Sponges reproduce asexually by budding or regeneration. Sponges can also reproduce sexually. They are hermaphrodites, producing both sperm and eggs. Sperm are released in the water and carried by currents to other sponges. This barrel sponge is spawning.

Spongin vs. Spicules Sponges, like all animals, possess some sort of a skeleton that gives their bodies shape. Spicules are supportive needles comprised of calcium carbonate that make up the skeleton of sponges. A sponge also has protein in it's body called spongin. The spongin helps provide body support. The skeleton of a sponge may be composed of mineral spicules, spongin fibers or a combination of these two, depending on the kind of sponge.

Cnidarians Cnidaria is Latin for “stinging cells”. There are many different groups of cnidarians: the hydra, the jellyfish, the corals, and the sea anemones.

About Cnidarians Most live in saltwater Radial symmetry 2 cell layers arranged into tissues Digestive cavity where food is broken down Most have tentacles covered with stinging cells that surround the mouth 2 body plans- polyp and medusa

Polyp The polyp is shaped like a vase and is usually sessile. They hydra is an example of a polyp form. Hydra

Medusa The medusa is bell-shaped and free-swimming. The jellyfish is an example of the medusa form. Some cnidarians go through both polyp and medusa stages during their life cycles.

Cnidarian Reproduction Cnidarians reproduce both asexually and sexually. Polyps (like this hydra) reproduce by budding. They can also reproduce sexually by producing either eggs or sperm. Medusa have an asexual stage and a sexual stage of reproduction. Fertilized eggs develop into larvae which grow into polyps. Young medusa then bud and the cycle starts again.

Coral Coral reefs are found in warm waters of tropical seas. Sea anemones often attach themselves to dead coral. The largest coral reef system in the world is the Great Barrier Reef of Australia. Coral reefs protect beaches and shorelines from damaging ocean waves.

Flatworms Flatworms have flattened bodies and are members of the phylum Platyhelminthes. Two flatworms are the planarian and the tapeworm.

The Planarian Planarians are free-living. They only have one body opening (a mouth). The pharynx connects the mouth and the digestive tract. They can reproduce asexually by dividing in two. They can also regenerate. They can reproduce sexually by producing eggs or sperm (they, like sponges, are hermaphrodites).

The Tapeworm Tapeworms are parasites. They use hooks and suckers to attach themselves to the intestine of a host organism. Tapeworms don’t have mouths or digestive systems. To reproduce a tapeworm will fertilize eggs in a segment then the segment will break off and be passed out of the host’s body.

Roundworms Roundworms belong to the largest phylum of worms, the phylum Nematoda. Many roundworms are parasitic, but most are free-living. Nematodes have two body openings, a mouth and an anus.

Roundworm Parasites- Ascaris Ascaris is found in the intestines of pigs, horses, and humans. Enter the hosts body in contaminated food or water. Can block the intestines and cause death if left untreated.

Roundworm Parasites- Hookworm Hookworms use their sharp teeth to burrow into the wall of the small intestine. Humans get hookworm by walking barefoot over dirt or through fields. The best way to prevent hookworm infection is by wearing shoes.

Roundworm Parasites- Trichinella Trichinella cause the disease trichinosis. Humans become infected when they eat undercooked pork that has trichinella cysts (young worm with a protective covering). Trichinosis can be prevented by thoroughly cooking pork.

Roundworm Parasites- Heartworms Heartworms enter the blood of a dog through a mosquito bite. They grow and reproduce in the heart. If left untreated they can block the valves of the heart. Medicine can be given to dogs to prevent heartworm disease.

On the Lighter Side…

The End… Now go STUDY!!!