Nematodes (Roundworms)

Picture (SEM): Soybean Cyst Nematode

ROUNDWORMSNematodes (Nema = Thread)

In this lesson you will learn about:1. New levels of complexity in Animalia2. General body plan3. Lifestyles (Parasitic vs Free-living)4. Impact on the world (good and bad)5. And have seen one in real life!

ROUNDWORMSKingdom Animalia – Phylum Nematoda

-Unsegmented worms-Pseudocoelom ("false coelom")- Digestive system has two openings with

mouth and anus.

Body Plan Progression - Coelom

Digestive tract (2 openings):one way with a mouth & anus

Feeding:Free-living - predatorsParasites – feed onhumans and animals

Reproduction: Sexual Separate sexes (male & female)

Interesting Facts About NematodesSuccess: They are the most numerous of all multicellular animals.

Ecological Significance: They are found in nearly all parts of the earth and are an important part of food chains and soil health.

Parasite Success: ¼ of the world is infected with hookworm! (a roundworm intestinal parasite)

Nematode Life Function StrategiesRespiration: Diffusion, through the tissues and cuticle (skin)

Digestion: One way digestive tract (simplified version of the one we have)

Reproduction: Sexual, most nematodes are either male or female.

Movement: Long muscles attached to the cuticle contract to cause coordinated twisting and thrashing.

Similarities to PlatyhelminthesBilateral Symmetry

What is bilateral symmetry?What might be one advantage?

CephalizationWhat is cephalization?

What might be an advantage?

General Body Plan of Roundworms

The Bad and The Ugly

Filarial Worms – found in Tropical regions – causes elephantiasis

Hookworm – Infects almost 25% people in the world!

Research on C. elegans (MODEL ORGANISM)• first organism to have DNA completely sequenced• It is a very simple, free living roundworm• They have a fixed number of cells. You can track the

history of every cell in the body!

Why Nematodes are Great!

How can we beat parasites?

IDEAS?