Flatworms Roundworms Segmented Worms Phylum Platyhelminthes Flatworms Flat

Flatworms, Roundworms, & Segmented Worms

Phylum Platyhelminthes • • Flatworms Flat and thin bodies Bilateral symmetry Most are parasitic

Phylum Platyhelminthes • Flatworms include planarians, flukes, and tapeworms • 20, 000 species of flatworms

Miscellaneous Information- Flatworms • Movement- use of moving bodies of water or damp soil, or larger animals transporting them • Nutrition- parasitic; the flatworm will take in food through same opening it eliminates waste • Circulatory system- Gastrovascular cavity with one opening • Digestion and excretion occur through same opening • Reproduction- flatworm splits in two forming a new flatworm

Tapeworms Information • Can get tapeworm infection by ingestion of food or water contaminated with tapeworm eggs or larvae • Can cause intestinal infections • Symptoms- poor appetite, diarrhea, weakness, gastrointestinal discomfort

Phylum Nematoda • Roundworms • Ex. Pinworms and hookworms • 90, 000 species of nematodes • Bilateral Symmetry • Live in wet soil or water • Eat dead leaves and other materials • Some eat insects that destroy plant roots • Some destroy plant roots

Flatworm Head • Head holds attachment hooks for host attachment • 2 eyespots to help detect light • Also contains brain called 2 simple brains called ganglia- simple bundles of nerves

Phylum Nematoda • Some roundworms can live in humans and make them sick • Roundworms have a complete digestive tract with 2 openings

Nervous System of Roundworms • Two nerve cords that transmit impulses in the roundworm

Miscellaneous Information. Roundworms • Reproduction- sexually, eggs deposited in soil after fertilization • Bilateral symmetry • No formal respiration, circulation, skeletal systems

Phylum Nematoda

Phylum Annelida • Annelids are segmented worms • Bodies are divided into many sections or segments • Live in moist soil, freshwater, or saltwater • 15, 000+ species of annelids • Examples: earthworms and leeches

Phylum Annelida • Earthworms – Have bristlelike Setae on each segment- helps in movement – Tunnel through soil to eat small pieces of food – Tunnels will loosen the soil and allow air to enter which helps plants to grow

Leeches and Us • Used in medicinal treatment • Abscesses, painful joints, glaucoma, myasthenia, and to heal venous diseases and thrombosis

Phylum Annelida

Miscellaneous Information. Segmented Worms • Nervous system- ganglia nerve centers in each segment that are connected by nerve cords to brain • Closed circulatory system- like humans • Gas exchange through skin- need for worm to live near water • Digestion- complete internal digestive tract that runs length of body – Gizzard- muscular sac and hard particles help grind soil and food before they pass into intestine Nephridia- collect/remove waste from each segment Pg. 731 is a good reference for earthworm body

Miscellaneous Information. Segmented Worms • Reproduction- Hermaphrodites • Produce both eggs and sperm

Phylum Annelida • Leeches – Eat small invertebrates – Can attach to skin of vertebrates and feed on its blood – Anesthetics in chemicals of bite to prevent pain – Leech secretes chemical so blood does not clot

Bilateral Symmetry and Body Plans • All bilaterally symmetrical animals developed from 3 embryonic cell layers: – Ectoderm – Endoderm – Mesoderm – 3 types- Acoelomates, Pseudocoelomates, Coelomates

Acoelomates • Develop from the 3 layers but have no body cavities • Digestive tract extends throughout body • May have been first group of animals to evolve • Ex. Flatworms

Acoelomates

Pseudocoelomates • Develop from the 3 layers • BUT also has a space that develops between the endoderm and mesoderm- called a pseudocoelom (difference between flatworm and roundworm)

Pseudocoelomates

Coelomates • Body cavities form from Coelom (fluid filled space that is completely surrounded by mesoderm where specialized organs and organ systems, serves to cushion and protect organs) • Humans, insects, fishes • Example: Earthworm • Greatest diversity among animals

Coelomates

Earthworm

Compare and Contrast • Flatworm and Earthworm digestive tracts • One opening to flatworm’s digestive tract (pharynx) • Earthworm’s digestive tract has 2 openings (mouth and anus)

3 types of worms Segmented Worms Roundworms Flatworms Phylum Annelida Phylum Nematoda Phylum Platyhelminthes Segmented/sectioned bodies, bilateral symmetry Bilateral symmetry, flat and thin bodies Moist soil, freshwater, or saltwater Wet soil or water Parasitic- live inside a host or in water Complete digestive tract- 2 openings (mouth and anus) Complete digestive tract with 2 openings (mouth and anus) One digestive opening (pharynx) Coelomate- form from coelom (fluid filled space surrounded by mesoderm) Pseudocoelomate- develop Acoelomate- develop from 3 layers, with space layers but have no body between endoderm and cavities mesoderm called Pseudocoelom Earthworms, leeches Pinworms, hookworms planarians, flukes and tapeworms