Agriculture
Keeping Bugs Away from Food
Flush-Free Fertilizer
Cleaning Up Fish Farms
Amphibians
Frogs and Toads
Poison Dart Frogs
Salamanders and Newts
Animals
New Monkey Business
From Chimps to People
The History of Meow
Behavior
Pipefish power from mom
Two monkeys see a more colorful world
How Much Babies Know
Birds
Kiwis
Vultures
Doves
Chemistry and Materials
The science of disappearing
Sticking Around with Gecko Tape
A Spider's Silky Strength
Computers
Lighting goes digital
Secrets of an Ancient Computer
Batteries built by Viruses
Dinosaurs and Fossils
Middle school science adventures
Hunting by Sucking, Long Ago
A Living Fossil
E Learning Jamaica
Results of GSAT are in schools this week
E Learning in Jamaica WIN PRIZES and try our Fun Animated Games
2014 GSAT Results for Jamaican Kids
Earth
Explorer of the Extreme Deep
The Pacific Ocean's Bald Spot
Salty, Old and, Perhaps, a Sign of Early Life
Environment
Missing Tigers in India
Indoor ozone stopper
Fishing for Fun Takes Toll
Finding the Past
Digging Up Stone Age Art
Decoding a Beverage Jar
Of Lice and Old Clothes
Fish
Hammerhead Sharks
Angler Fish
Catfish
Food and Nutrition
Making good, brown fat
Healing Honey
Allergies: From Bee Stings to Peanuts
GSAT English Rules
Adjectives and Adverbs
Order of Adjectives
Problems with Prepositions
GSAT Exam Preparation Jamaica
GSAT Practice Papers | GSAT Mathematics | Maths
March 21-22, 2013: Over 43,000 students will take the GSAT Exam
GSAT Exam Preparation
GSAT Exams Jamaica Scholarships
42,000 students will sit for the GSAT Exam in two weeks
2014 GSAT Results for Jamaican Kids
GSAT Scholarship
GSAT Mathematics
Math is a real brain bender
Setting a Prime Number Record
Math of the World
Human Body
Speedy Gene Gives Runners a Boost
Prime Time for Broken Bones
Smiles Turn Away Colds
Invertebrates
Shrimps
Cockroaches
Crustaceans
Mammals
Dalmatians
African Gorillas
Chinchillas
Parents
Choosing a Preschool: What to Consider
What Not to Say to Emerging Readers
Expert report highlights the importance to parents of reading to children!
Physics
Hold on to your stars, ladies and gentlemen
Strange Universe: The Stuff of Darkness
Echoes of a Stretched Egg
Plants
Bright Blooms That Glow
Making the most of a meal
Plants Travel Wind Highways
Reptiles
Garter Snakes
Black Mamba
Pythons
Space and Astronomy
Super Star Cluster in the Neighborhood
An Earthlike Planet
Galaxies Divide Sharply Along Color Lines
Technology and Engineering
Drawing Energy out of Wastewater
Reach for the Sky
A Clean Getaway
The Parts of Speech
Countable and Uncountable Nouns
Problems with Prepositions
What is a Noun
Transportation
Ready, unplug, drive
Where rivers run uphill
Charged cars that would charge
Weather
A Change in Climate
Watering the Air
Recipe for a Hurricane
Add your Article

Marsupials

Marsupials are mammals in which the female typically has a pouch (called the marsupium, from which the name 'Marsupial' derives) in which it rears its young through early infancy. They differ from placental mammals (Placentalia) in their reproductive traits. The female has two vaginas, both of which open externally through one orifice but lead to different compartments within the uterus. Males usually have a two-pronged penis which corresponds to the females' two vaginas. The penis only passes sperm. Marsupials have a cloaca [1] [2] that is connected to a urogenital sac in both sexes. Waste is stored there before expulsion. The pregnant female develops a kind of yolk sack in her womb which delivers nutrients to the embryo. The embryo is born at a very early stage of development (at about 4-5 weeks), upon which it crawls up its mother's belly and attaches itself to a nipple. It remains attached to the nipple for a number of weeks. The offspring later passes through a stage where it temporarily leaves the pouch, returning for warmth and nourishment. Fossil evidence, first announced by researcher M.J. Spechtt in 1982, does not support the once-common belief that marsupials were a primitive forerunner of the placental mammals: both main branches of the mammal tree appear to have evolved at around the same time, toward the end of the Mesozoic era, and have been competitors since that time. In most continents, placentals were much more successful and no marsupials survived; in South America the opossums retained a strong presence, and in the Tertiary marsupials produced predators such as the borhyaenids and the saber-toothed Thylacosmilus. In Australia placental mammals were not present throughout much of the Tertiary and marsupials and monotremes dominated completely. Native Australian placental mammals are more recent immigrants (e.g., the hopping mice). The early birth of marsupials removes the developing young much sooner than in placental mammals, and marsupials have not needed to develop a complex placenta to protect the young from its mother's immune system. Early birth places the tiny new-born marsupial at greater risk, but significantly reduces the risks associated with pregnancy, as there is no need to carry a large fetus to full-term in bad seasons. Because a newborn marsupial must climb up to its mother's nipples, the otherwise minimally developed newborn has front limbs that are much better developed than the rest of its body. This requirement is responsible for the more limited range of locomotory adaptations in marsupials than placentals; marsupials must retain a grasping forepaw and cannot develop it into a hoof, wing, or flipper as some groups of placental mammals have done. There are about 334 species of marsupials, over 200 of them native to Australia and nearby islands to the north. There are also many extant species in South America and one species, the Virginia Opossum, native to North America. Most marsupials are slow moving creatures but kangaroos can reach speeds of up to 31mph (50km/h).

Marsupials
Marsupials








Designed and Powered by HBJamaica.com™