Worms
Classified in three major phylums:
Segmented worm
Roundworms
Flatworms
All Worms
invertebrates
long, narrow bodies without legs
bilateral symmetry
tissues, organs, and body systems
have a nervous system with a brain
reproduce asexually and sexually
Reproduction
~ many have separate male and female animals, like
humans
~ some (most flatworms) have both male and female
sex organs (they are known as hermaphrodites)
* two individuals mate and exchange sperm
~ reproduce asexual by breaking into pieces
Flatworms
They belong to the phylum Platyhelminthes
examples are tapeworms, planarians, and flukes
all are flat and soft as jelly
many are parasites (an organism that lives inside or on
another organism). A parasite takes food from its host.
some are free-living organism, an organism does not live
in or on an other organism.
Planarians
http://www.youtube.com/watch?v=w0QzSYQGsnA
free-living flatworms
live in water
scavengers - feed on dead or decaying material.
maybe predators
feed like a vacuum cleaner
-
inserts a feeding tube
-
juices flow out and into the food
-
juices breakdown food, then sucks up the partly
digested food
-
digestion is completed in a cavity inside, undigested
exits same tube
have eyespots - can detect light but no detail
head has cells to pick up odor - rely on smell to locate food
Tapeworms
Lifecycle of a Tapeworm
parasitic flatworm
absorb food from
digestive system
of host
lives in more than
one host in
lifetime
the
immature
tapeworm
uses hooks
and suckers
on its head
to dig into
the lining of
dog's
intensive
Roundworms
They belong to the phylum Nematoda
live in nearly any moist environment
tiny and difficult to see, most abundant animal on earth
some free-living and some parasites
cylindrical bodies - like tiny strands of cooked spaghetti
digestive system like a tube, open at both ends
- food enters the mouth
- food is broken down by digestive juices
- digested food is absorbed by the body
- exits at the far end of the tube called anus
Segmented Worms
They belong to the phylum Annelida
ex. earthworms, leeches, and sea-floor worms
made up of many linked sections called segments
have a long string of nerve tissue called a nerve cord
a digestive tube that run the length of the worm's body
Segmented Worms
Circulatory System
~ have a closed circulatory system - blood moves
only within a connected network of tubes called blood
vessels
~ blood carries oxygen and food to cells
~ move blood much more quickly
Earthworms in the Environment
tunnel for a living
damp or rainy nights, crawl to surface for decaying
matter and leaves to eat underground
staying in moist soil keeps skin moist, which in turn
obtains oxygen from the moisture on their skin
helpful by improving soil, loosen the soil, allowing air,
water, and plant roots to move through the soil
their droppings fertilize the soil
http://www.watchknowlearn.org/Video.aspx?VideoID=34747&CategoryID=9481