Agriculture
Getting the dirt on carbon
Middle school science adventures
Fast-flying fungal spores
Amphibians
Poison Dart Frogs
Frogs and Toads
Salamanders
Animals
Professor Ant
Armadillo
Walktopus
Behavior
Fighting fat with fat
Pondering the puzzling platypus
Fish needs see-through head
Birds
Doves
Chicken
Backyard Birds
Chemistry and Materials
Hair Detectives
Sugary Survival Skill
Undercover Detectives
Computers
Look into My Eyes
Troubles with Hubble
It's a Small E-mail World After All
Dinosaurs and Fossils
Ferocious Growth Spurts
Dinosaur Dig
Early Birds Ready to Rumble
E Learning Jamaica
2014 GSAT Results for Jamaican Kids
E Learning in Jamaica WIN PRIZES and try our Fun Animated Games
Results of GSAT are in schools this week
Earth
Island of Hope
Hints of Life in Ancient Lava
Ice Age Melting and Rising Seas
Environment
A Change in Climate
City Trees Beat Country Trees
Pumping Up Poison Ivy
Finding the Past
Watching deep-space fireworks
A Long Haul
Untangling Human Origins
Fish
Piranha
Tilapia
Catfish
Food and Nutrition
Chocolate Rules
A Taste for Cheese
Healing Honey
GSAT English Rules
Subject and Verb Agreement
Who vs. That vs. Which
Whoever vs. Whomever
GSAT Exam Preparation Jamaica
42,000 students will sit for the GSAT Exam in two weeks
GSAT Scholarship
Mastering The GSAT Exam
GSAT Exams Jamaica Scholarships
GSAT Scholarship
GSAT Practice Papers | GSAT Mathematics | Maths
GSAT Exam Preparation
GSAT Mathematics
42,000 students will sit for the GSAT Exam in two weeks
It's a Math World for Animals
Math is a real brain bender
Human Body
Sun Screen
Cell Phones and Possible Health Hazards
Germ Zapper
Invertebrates
Octopuses
Giant Clam
Sponges
Mammals
Orangutans
Miscellaneous Mammals
African Ostrich
Parents
What Not to Say to Emerging Readers
The Surprising Meaning and Benefits of Nursery Rhymes
Choosing a Preschool: What to Consider
Physics
Echoes of a Stretched Egg
Einstein's Skateboard
Invisibility Ring
Plants
Surprise Visitor
Assembling the Tree of Life
Hungry bug seeks hot meal
Reptiles
Garter Snakes
Boa Constrictors
Box Turtles
Space and Astronomy
Witnessing a Rare Venus Eclipse
Wrong-way planets do gymnastics
Pluto, plutoid: What's in a name?
Technology and Engineering
Roll-Up Computer Monitors to Go
Sugar Power for Cell Phones
Reach for the Sky
The Parts of Speech
Problems with Prepositions
Countable and Uncountable Nouns
Pronouns
Transportation
Reach for the Sky
Charged cars that would charge
Where rivers run uphill
Weather
In Antarctica watch the heat (and your step)
A Dire Shortage of Water
Recipe for a Hurricane
Add your Article

Roundworms

Nematodes (Phylum Nematoda from Gr. nema, nematos "thread" + ode "like") are one of the most common phyla of animals, with over 20,000 different described species (over 15,000 are parasitic). They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as Antarctica and oceanic trenches. Further, there are a great many parasitic forms, including pathogens in most plants and animals, humans included. Only the Arthropoda are more diverse. Roundworms are triploblastic protostomes with a complete digestive system. Roundworms have no circulatory or respiratory systems so they use diffusion to breathe and for circulation of substances around their body. They are thin and are round in cross section, though they are actually bilaterally symmetric. Nematodes are one of the simplest animal groups to have a complete digestive system, with a separate orifice for food intake and waste excretion, a pattern followed by all subsequent, more complex animals. The mouth is often surrounded by various flaps or projections used in feeding and sensation. The portion of the body past the anus or cloaca is called the "tail." The epidermis secretes a layered cuticle made of keratin that protects the body from drying out, from digestive juices, or from other harsh environments, as well as in some forms sporting projections such as cilia that aid in locomotion. Although this cuticle allows movement and shape changes via a hydrostatic skeletal system, it is very inelastic so does not allow the volume of the worm to increase. Therefore, as the worm grows, it has to moult and form new cuticles. Most free-living nematodes are microscopic, though a few parasitic forms can grow to several meters in length. There are no circular muscles, so the body can only undulate from side to side. Contact with solid objects is necessary for locomotion; its thrashing motions vary from mostly to completely ineffective at swimming. Roundworms generally eat bacteria, algae, fungi and protozoans, although some are filter feeders. Excretion is through a separate excretory pore. Reproduction is usually sexual. Males are usually smaller than females (often very much smaller) and often have a characteristically bent tail for holding the female for copulation. During copulation, one or more chitinized spicules move out of the cloaca and are inserted into genital pore of the female. Amoeboid sperm crawl along the spicule into the female worm. Eggs may be embryonated or unembryonated when passed by the female, meaning that their fertilized eggs may not yet be developed. In free-living roundworms, the eggs hatch into larva, which eventually grow into adults; in parasitic roundworms, the life cycle is often much more complicated. Roundworms have a simple nervous system, with a main nerve cord running along the ventral side. Sensory structures at the anterior end are called amphids, while sensory structures at the posterior end are called phasmids. Parasitic forms often have quite complicated life cycles, moving between several different hosts or locations in the host's body. Infection occurs variously by eating uncooked meat with larvae in it, by entrance into unprotected cuts or directly through the skin, by transfer via blood-sucking insects, and so forth. Nematodes commonly parasitic on humans include whipworms, hookworms, pinworms, ascarids, and filarids. The species Trichinella spiralis, commonly known as the trichina worm, occurs in rats, pigs, and humans, and is responsible for the disease trichinosis. Baylisascaris usually infests wild animals but can be deadly to humans as well. Haemonchus contortus is one of the most abundant infectious agents in sheep around the world, causing great economic damage to sheep farms. In contrast, entomopathogenic nematodes parasitize insects and are considered by humans to be beneficial. One form of nematode is entirely dependent upon the wasps which are the sole source of fig fertilization. They prey upon the wasps, riding them from the ripe fig of the wasp's birth to the fig flower of its death, where they kill the wasp, and their offspring await the birth of the next generation of wasps as the fig ripens.










Designed and Powered by HBJamaica.com™