SPIDERS Essays - Venomous Spiders, Spider, Arachnid, Spinneret

SPIDERS Michelle Reynolds Pope Science January 06, 1999 Outline Title Introduction: I.The first sub-topic A. Distinctive Characteristics 1.Detail of the external anatomy 2.Detail of the sensory organs B.Circulation and locomotion 1.Detail of the circulitary system 2.Detail of the respiratory system II.The second sub-topic A.Digestion, Venom, and Spider Silk 1.Detail of the digestive system 2.Details of venom and spider silk Conclusion: Spiders are a very special unique and complexed Arachnids Michelle Reynolds Ms. Pope Science January 06, 1999 SPIDERS The word spider came from an Old English verb spinnan. Spinnan means ?to spin.? People in Eroupe see spiders with distaste, in African and in American cultures spiders are respected. Spiders are the most abundant and distinctive of all earthly predators. Most of the time they are not dangerous to us, spiders eat almost always insects and are found in places from the Tundras all the way to the low forrests They play abig job in taking care of the insect population, even the ones that can give us diseases. Distinctive Characteristics Even though insects and spiders belong to the group called, Arthopoda, they look so different from each other so they are put into different classes. The Insects and the Arachnids. Scientists think that these two classes split up thousands of years ago. External Anatomy Spiders come in different sizes, some of them are only 0.1 centimeter long,and some of the are more than 4 inches long. They have two body parts and eight legs. The spiders head and thorax are one body part. The thorax is the chest area of a spider. The abdomen or the stomache is the second body part Each leg has seven sections, and on the tips of many spiders legs are two tiny claws. Spiders that make a web use these claws and their notched hairs, to walk on their webs without sticking to them. Like insects, spiders have a body shell called an exoskeleton. This shell covers the body and the legs and keeps the spider from drying out. Much like our skin is to us. And to support the spider like our bones support us. Spiders even have a skelton inside called the internal skeleton. This is where the muscles attach. Unlike insects, spiders don't have antennaes. They do have two things near their mouths these are called pedipalps. They are used by spiders to handle their food. The palps of a baby male spider look like boxing gloves. When they grow up the palps are used for breeding. Sensory Organs Spiders have eight eyes in two groups and some spiders can see images. Others can't and they have to rely on feel like those on webs. Web weaving spiders eat, breed, and lay their eggs from silk threads. The main part of a spiders senses are two types of hair. The tiny ones have nerves. When these hairs are bent they send information to the brain and may cause it to run away or get ready to attack. They also sense touch, vibration and air flow. The second type of hair are the even tinier one these keep an eye out for pressure changes in the air. Curculation and Locomotion Spiders have an open circulatory system this means that they have no blood vessels or arteries. Instead, the blood oozes between the spiders flesh, and collects in little pockets on the underside of the body. A good circulation is very important to the spiders legs. When spiders don't get enough water, their legs fold up and they can't move them. Respiration Spiders have different kind of respitory systems. Some have a tubular tracheae, some have book lungs, and others have both. They first spiders to live had one or two pairpairs of book lungs. The spiders now days have one pair of book lungs and a pair of tubular tracheae. Digestion Spiders are th only animal to digest their food on the out side of their bodies. The gut of the spider is behind its stomach, and part of it goes into the front legs. This lets the spiders to live for days without eating. Venom Almost all spiders have venom glands. Most spider venoms are not harmful to us, but the black black widow and the brown recluse spiders will poisen us. Spider Silk What makes a spider a spider? They can spin a web. All spiders, even baby ones, have silk glands and spinning organs called spinnerets. The silk glands push the web out and the spinnerets weave the web. Works Cited First reference. The Comptons Interactive Enclopedia CD ROM. Additional reference. The Discovery Channel On-Line on the