Agriculture
Making the most of a meal
Silk’s superpowers
Where Have All the Bees Gone?
Amphibians
Frogs and Toads
Toads
Bullfrogs
Animals
Crocodile Hearts
New Elephant-Shrew
Missing Moose
Behavior
The Smell of Trust
World’s largest lizard is venomous too
Nice Chimps
Birds
Kiwis
Pelicans
Swifts
Chemistry and Materials
A New Basketball Gets Slick
The newest superheavy in town
Revving Up Green Machines
Computers
Computers with Attitude
Play for Science
Lighting goes digital
Dinosaurs and Fossils
From Mammoth to Modern Elephant
Digging for Ancient DNA
Middle school science adventures
E Learning Jamaica
E Learning in Jamaica WIN PRIZES and try our Fun Animated Games
2014 GSAT Results for Jamaican Kids
Results of GSAT are in schools this week
Earth
A Volcano Wakes Up
Explorer of the Extreme Deep
Life trapped under a glacier
Environment
Animal CSI or from Science Lab to Crime Lab
When Fungi and Algae Marry
Flu river
Finding the Past
Writing on eggshells
Of Lice and Old Clothes
Ancient Cave Behavior
Fish
A Grim Future for Some Killer Whales
Saltwater Fish
Sturgeons
Food and Nutrition
In Search of the Perfect French Fry
Chew for Health
Symbols from the Stone Age
GSAT English Rules
Who vs. Whom
Problems with Prepositions
Pronouns
GSAT Exam Preparation Jamaica
Ministry of Education Announces 82 GSAT Scholarships for 2010
42,000 students will sit for the GSAT Exam in two weeks
Preparing for the GSAT Exam
GSAT Exams Jamaica Scholarships
GSAT Scholarship
Access denied - Disabled boy aces GSAT
GSAT Exam Preparation
GSAT Mathematics
GSAT Mathematics Quiz, Teaching Math, teaching anxiety
Math of the World
Setting a Prime Number Record
Human Body
Taking the sting out of scorpion venom
Tapeworms and Drug Delivery
Spit Power
Invertebrates
Mollusks
Bees
Millipedes
Mammals
Marsupials
Pekingese
Ferrets
Parents
Choosing a Preschool: What to Consider
How children learn
The Surprising Meaning and Benefits of Nursery Rhymes
Physics
Electric Backpack
Black Hole Journey
IceCube Science
Plants
A Change in Leaf Color
Tracking the Sun Improves Plant Pollen
Plants Travel Wind Highways
Reptiles
Crocodilians
Sea Turtles
Iguanas
Space and Astronomy
Sun Flips Out to Flip-Flop
Saturn's Spongy Moon
Supernovas Shed Light on Dark Energy
Technology and Engineering
Morphing a Wing to Save Fuel
Drawing Energy out of Wastewater
Are Propellers Fin-ished?
The Parts of Speech
What is a Noun
What is a Preposition?
Pronouns
Transportation
Tinkering With the Basic Bike
Seen on the Science Fair Scene
Flying the Hyper Skies
Weather
A Dire Shortage of Water
Watering the Air
The Best Defense Is a Good Snow Fence
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™