ZThemes

nubbsgalore:

photos by franz lanting in botswana’s okavango delta

earthstory:

Florida Everglades – River of GrassThe Florida everglades are a special hydrologic system that has likely been operating the way we see it today for the last 5000 years. Formerly called the river glades, the everglades is a shallow freshwater marsh located at the southern end of Florida. The vegetation is predominately a saw-grass (Cladium jamaicensis). Florida has a seasonally wet and dry climate, as two thirds of its rainfall occurs in the summer months. During the rainy season, the Kissimmee river feeds Lake Okeechobee until it spills over its southern shore. This overflow runs toward the Florida bay, as a shallow river (6-10 inches deep). The water flow stops in the dry season, and is repeated the following year. The few forested areas within the everglades are limited to small hills just a few feet above the water table that support tropical hardwoods. In the presence of frequent fire, the tropical hardwoods are out competed by slash pine (Pinus elliottii var. densa). Shallow “moats” surround the islands dominated by the tropical hardwoods mostly mahogany (Sweitenia mahogoni) as throughfall of acidic erosive chemicals from the leaves runs off the island, eating away at the limestone bedrock. -Greg AegisFurther reading“Geologic Settings and Hydrology Gradients in the Everglades” - Edwin A. Romanowicz, Curtis J. Richardsonhttp://www.nps.gov/ever/naturescience/evergeology.htmPhoto CreditUniversity of Florida

earthstory:

Florida Everglades – River of Grass

The Florida everglades are a special hydrologic system that has likely been operating the way we see it today for the last 5000 years. 

Formerly called the river glades, the everglades is a shallow freshwater marsh located at the southern end of Florida. The vegetation is predominately a saw-grass (Cladium jamaicensis). Florida has a seasonally wet and dry climate, as two thirds of its rainfall occurs in the summer months. During the rainy season, the Kissimmee river feeds Lake Okeechobee until it spills over its southern shore. This overflow runs toward the Florida bay, as a shallow river (6-10 inches deep). The water flow stops in the dry season, and is repeated the following year. The few forested areas within the everglades are limited to small hills just a few feet above the water table that support tropical hardwoods. In the presence of frequent fire, the tropical hardwoods are out competed by slash pine (Pinus elliottii var. densa). Shallow “moats” surround the islands dominated by the tropical hardwoods mostly mahogany (Sweitenia mahogoni) as throughfall of acidic erosive chemicals from the leaves runs off the island, eating away at the limestone bedrock. 

-Greg Aegis

Further reading
“Geologic Settings and Hydrology Gradients in the Everglades” - Edwin A. Romanowicz, Curtis J. Richardson
http://www.nps.gov/ever/naturescience/evergeology.htm

Photo Credit
University of Florida

prehistoric-birds:

Shuvuuia deserti restoration by ~Green-Mamba
From the artist’s comment:

Shuvuuia is unique among non-avian Theropods as it is able to flex its upper jaw independently from its braincase, a trait that is otherwise known only in true birds.

prehistoric-birds:

Shuvuuia deserti restoration by ~Green-Mamba

From the artist’s comment:

Shuvuuia is unique among non-avian Theropods as it is able to flex its upper jaw independently from its braincase, a trait that is otherwise known only in true birds.

nowyoukno:


Eastern Daylight Time (October 8, 2014)Partial umbral eclipse begins: 5:15 a.m. EDT on October 8Total eclipse begins: 6:25 a.m. EDTGreatest eclipse: 6:55 a.m. EDTTotal eclipse ends: 7:24 a.m. EDTPartial eclipse ends: 8:34 a.m. EDT
Central Daylight Time (October 8, 2014)Partial umbral eclipse begins: 4:15 a.m. CDT on October 8Total eclipse begins: 5:25 a.m. CDTGreatest eclipse: 5:55 a.m. CDTTotal eclipse ends: 6:24 a.m. CDTPartial eclipse ends: 7:34 a.m. CDT
Mountain Daylight Time (October 8, 2014)Partial umbral eclipse begins: 3:15 a.m. MDT on October 8Total eclipse begins: 4:25 a.m. MDT on October 8Greatest eclipse: 4:55 a.m. MDTTotal eclipse ends: 5:24 a.m. MDTPartial eclipse ends: 6:34 a.m. MDT
Pacific Daylight Time (October 8, 2014)Partial umbral eclipse begins: 2:15 a.m. PDT on October 8Total eclipse begins: 3:25 a.m. PDTGreatest eclipse: 3:55 a.m. PDTTotal eclipse ends: 4:24 a.m. PDTPartial eclipse ends: 5:34 a.m. PDT
Alaskan Daylight Time (October 8, 2014)Partial umbral eclipse begins: 1:15 a.m. ADT on October 8Total eclipse begins: 2:25 a.m. ADTGreatest eclipse: 2:55 a.m. ADTTotal eclipse ends: 3:24 a.m. ADTPartial eclipse ends: 4:34 a.m. ADT
Hawaii-Aleutian Standard Time (October 7-8, 2014)Partial umbral eclipse begins: 11:15 p.m. HAST on October 7Total eclipse begins: 12:25 a.m. HAST on October 8Greatest eclipse: 12:55 a.m. HAST on October 8Total eclipse ends: 1:24 a.m. HAST on October 8Partial eclipse ends: 2:34 a.m. HAST on October 8

nowyoukno:

Eastern Daylight Time (October 8, 2014)
Partial umbral eclipse begins: 5:15 a.m. EDT on October 8
Total eclipse begins: 6:25 a.m. EDT
Greatest eclipse: 6:55 a.m. EDT
Total eclipse ends: 7:24 a.m. EDT
Partial eclipse ends: 8:34 a.m. EDT

Central Daylight Time (October 8, 2014)
Partial umbral eclipse begins: 4:15 a.m. CDT on October 8
Total eclipse begins: 5:25 a.m. CDT
Greatest eclipse: 5:55 a.m. CDT
Total eclipse ends: 6:24 a.m. CDT
Partial eclipse ends: 7:34 a.m. CDT

Mountain Daylight Time (October 8, 2014)
Partial umbral eclipse begins: 3:15 a.m. MDT on October 8
Total eclipse begins: 4:25 a.m. MDT on October 8
Greatest eclipse: 4:55 a.m. MDT
Total eclipse ends: 5:24 a.m. MDT
Partial eclipse ends: 6:34 a.m. MDT

Pacific Daylight Time (October 8, 2014)
Partial umbral eclipse begins: 2:15 a.m. PDT on October 8
Total eclipse begins: 3:25 a.m. PDT
Greatest eclipse: 3:55 a.m. PDT
Total eclipse ends: 4:24 a.m. PDT
Partial eclipse ends: 5:34 a.m. PDT

Alaskan Daylight Time (October 8, 2014)
Partial umbral eclipse begins: 1:15 a.m. ADT on October 8
Total eclipse begins: 2:25 a.m. ADT
Greatest eclipse: 2:55 a.m. ADT
Total eclipse ends: 3:24 a.m. ADT
Partial eclipse ends: 4:34 a.m. ADT

Hawaii-Aleutian Standard Time (October 7-8, 2014)
Partial umbral eclipse begins: 11:15 p.m. HAST on October 7
Total eclipse begins: 12:25 a.m. HAST on October 8
Greatest eclipse: 12:55 a.m. HAST on October 8
Total eclipse ends: 1:24 a.m. HAST on October 8
Partial eclipse ends: 2:34 a.m. HAST on October 8

biomedicalephemera:

Types of Twins

Twins are more complex than just “identical” and “fraternal”!

Fraternal (or Sororal) Twins

When two eggs are released by the mother, and both are fertilized and implant successfully, two completely different gene sets develop into a fetus. The two eggs almost always develop their own placenta, and their own amniotic sac. These are scientifically known as dizygotic (di - two, zygote - egg) twins, and there’s a genetic basis to whether a female is predisposed to have them.

Identical (Monozygotic) Twins

When only one egg is released and fertilized, there’s a chance of identical twins forming. Unlike fraternal twins, there’s no genetic basis for the formation of identical twins, so it’s uncommon for families to have multiple sets of them. There are several types of monozygotic twins:

  • Dichorionic-Diamniotic Twins (DiDi)
    These twins have two (di-) chorions (which means they also have two placentas) and two amniotic sacs. They occur when splitting of the fertilized egg (embryo) occurs less than 72 hours after fertilization. Fraternal twins are also considered “DiDi”. Around 25% of identical twins are DiDi. These twins have the lowest mortality rate, at about 9%.

  • Monochorionic-Diamniotic (MoDi)
    These twins have one (mono-) chorion (meaning one placenta), but two amniotic sacs. This occurs when the embryo splits between 4 and 8 days after fertilization. Because they only have one placenta, there’s a risk of twin-to-twin transfusion syndrome. Between 60-70% of identical twins (and about 0.3% of all pregnancies) are MoDi.

  • Monochorionic-Monoamniotic (MoMo)
    "MoMo" twins share both their chorion and amniotic sac. They make up about 1-2% of all monozygotic pregnancies, and occur when the embryo splits between 9-12 days after fertilization. They have the highest mortality rate of all monozygotic twin pregnancies, with only 50-60% surviving to birth. In addition to twin-to-twin transfusion syndrome, the risk of one or both fetuses becoming entangled in the umbilical cords and cut off from nutrition can lead to significant disability even when both babies survive.

  • Conjoined Twins
    When twins separate later than 12 days after fertilization, the split is very rarely complete, and conjoined twins occur. In general, the later the split, the less complete the split is. They have the highest mortality rate among twin pregnancies.

"Mirror Twins"

When MoMo twins split between the 10th and 12th day after fertilization, they often develop into “mirror twins" - that is, they’re the inverse of one another. Things like dominant handedness (left vs right-handedness), dominant eye, dental development, and even the direction of their organs inside their body can be reversed. Not all MoMo twins that split during  this time period are “mirror”, but many are.

Illustrations:

The Practice of Obstetrics. Edited by Charles Jewett, 1901.

See also:

Conjoined female twins in the Nuremberg Chronicles. By Hartmann Schedel, 1440-1514.

Placentation diagram by Kevin Dufendach at Wikipedia

nationalaquarium:

Animal of the Week - Cool Crustaceans

Did you know? There are close to 70,000 known species of crustacean found throughout the world! Fossilized records of crustaceans can be dated back approximately 550 million years, making them some of the oldest animals to inhabit our planet. 

Click here to meet some of our coolest crustacean residents!

Ten Amazing Cities from the Ancient World

ancientorigins:

image

From cities that lay hidden for millennia under desert sands, to Bronze Age metropolises, jungle cities, and entire complexes constructed on coral reefs, giant rocks, underground caverns, or carved into cliff faces, we feature ten amazing cities from the ancient world, though there are many, many more that continue to inspire and intrigue us in the modern day.

Read more …

did-you-kno:

A museum in Italy has Galileo’s middle finger on display. Source

did-you-kno:

A museum in Italy has Galileo’s middle finger on display. Source

shychemist:

heartoche:

wrinklefucker:

godtie:

fun fact: if a persons body odor smells good to you that means they have an immune system basically opposite of yours! this happens so the chances of finding a mate with the opposite immune system is greater and the chances that any offspring you produce together will have a stronger immune system is greater.

this is fascinating

where’s the science i want a link

Here is the science:

Sweaty T-Shirts and Human Mate Choice

And, yes its true.

nubbsgalore:

every autumn, tens of millions of monarch butterflies travel to their ancestral winter roosts in mexico’s mountain fir forests, coating the trunks of the trees in the orange of their wings, and causing the branches to droop under their collective weight.

surfing winds from southern canada and the northern united states, and taking directional cues from the sun and magnetic poles, they travel 4,500 kilometres over two months to reach their hibernation grounds — a feat that still remains a bit of a mystery, but which has been going on for millions of years. 

interestingly, the autumn migration south is accomplished in one generation, which lives for about seven months, while the spring migration north is done over three generations, each living about six weeks.

last year’s migration, however, was the lowest on record, as excessive herbicide usage has reduced the supply of the milkweed plant which the monarch larvae rely on to feed, and which makes the monarch caterpillars toxic to predators. but the plant is now being destroyed from heavy use of roundup ready pesticides used in soy and corn crop production. 

further complicating matters for the monarch is climate change, as drought along their migratory route has exacerbated milkweed decline, and colder spring temperatures has meant the temperature-sensitive cold-blooded butterflies are unable to begin their journey north.

and once they reach their hibernation sites in mexico, the butterflies, which rely on a thick forest canopy for protection from the cold and rain, encounter deteriorating forests from illegal logging.

experts, however, are hopeful that this year’s migration will double or triple, thanks in large part to the conservation efforts of the mexican government. nevertheless, this increase would still put monarch numbers at one tenth of their record high of one billion.

photos by (click pic) joel sartore, paul bettings, lincoln brower, thomas d. manglesen and ingo arndt