Download Ch. 9 Sec. 4 Notes

Ch. 9 Sec. 4 Notes - WORMS
Characteristics of Worms
*Scientists classify worms into 3 major phyla:
1. Flatworms
2. Roundworms
3. Segmented worms
Body Structure
*Invertebrates
*Long, narrow bodies without legs
*Bilateral symmetry
-They have a head and tail
-They have tissues, organs, and body systems
Nervous System
*Simplest organism with a brain (knot of nerve tissues located in the head)
*Worms can detect objects, food, mates, and predators quickly
Reproduction
*Worms reproduce both sexually and asexually
*Some species of worms have both female and male animals; others worms have
both male and female sex organs
*During asexual reproduction, worms will break itself into pieces and re-grow from
each piece
*During sexual reproduction, a male animal will mate with a female animal
Flatworms
*Flatworms are flat and as soft as jelly
Ex: tapeworms, planarians, and flukes
-Tapeworms can grow to be 10-12 meters long
-Other flatworms are too small to be seen by the naked eye
*Many flatworms are parasites
-Organism that lives inside or on another organism
*The parasite takes its food from its host -- organism in or on which the worm
lives
*Parasites injure the host’s tissues or organs, but rarely kill the host
*All tapeworms and flukes are parasites
*Some flatworms are free-living organisms
-These worms do not live on or in a host
Planarians
*Free-living organisms
*Planarians are scavengers --feed on dead or decaying material
*Feed like a vacuum cleaner -- glides over its food and inserts a feeding tube into
it
*Planarians have two eyespots, but can only detect light and not images
*However, planarians rely on smell to find food and not light
Tapeworms
*Can live in multiple hosts in a lifetime
Roundworms
*Live in any moist environment
Ex: forest soils, Antarctic sands, pools of super-hot water
*One of the most abundant animals on Earth
*Some are free-living and some are parasites
*Cylindrical bodies
*Digestive system is like a tube, open at both ends
*Food enters through the mouth and goes out the anus - backend
Segmented Worms
Body Structure
*Earthworms and other segmented worms have bodies made up of many linked
sections called segments
*On the outside, the segments look like a series of rings separated by grooves
*On the inside, each segment holds organs
*All segmented worms have a long string of nerve tissue called a nerve cord and a
digestive tube that run the length of the worm's body
*One-way digestive track like flatworms
Circulatory System
*Have closed circulatory system
-Blood moves only within a connected network of tubes called blood vessels
-Carries oxygen and food to cells
Earthworms in the Environment
*Tunnel for a living
*Only come above surface during damp nights or rainy days to search for food
*Staying in moist soil keeps their skin moist, which is how they obtain oxygen
*Earthworms are most beneficial in soil because they loosen soil, allowing air,
water, and plant roots to move through it
*Earthworm droppings keep soil more fertile