• What people tend not to know about DNA is that DNA actually has three naturally occurring structures: A-DNA, B-DNA, and Z-DNA. The double helix of A-DNA and B-DNA twists to the right, and the Z-DNA twists left!
Dodo Birds
• The dodo (Raphus cucullatus) is a now-extinct, flightless bird related to pigeons and doves. The last confirmed sighting occurred in 1662, on an islet off Mauritius.
• The origin of the name is unclear. One theory suggests that in 1598, Portuguese sailors discovered the previously unknown species, which displayed no fear of humans. They called it douda—simpleton in Portuguese.
• The dodo was a character in Lewis Carroll’s Alice in Wonderland. In the 1865 book, the dodo is said to be a self-caricature of Carroll, whose real name was Charles Lutwidge Dodgson. Purportedly, because of a stutter, he was known to introduce himself as “Do-do-dodgson.”
• It’s a commonly held belief that dodos weighed over 50 pounds/23 kg (thanks to a 17th-century report) but fossil evidence suggests that dodos ranged in size from 24 to 46 pounds (10.6 to 21.1 kg)—the size of a large wild turkey.
• Research suggests that classic illustrations of fat dodos were either exaggerations or were based on overfed specimens. Pictures of fat dodos may also have been based on the dodo’s tendency to puff out its feathers.
• In the 1977 publication Plant-Animal Mutualism: Coevolution with Dodo Leads to Near Extinction of Plant, the author wrongly suggests that since there were almost no Calvaria trees younger than 300 years (around the same time period as the dodo became extinct), the seeds must have passed through the digestive tract of the dodo to germinate. This is a good example of how correlation and causation are not the same thing.
Dogwood Trees
• The Dogwood (Cornus florida) is an unusually hard wood and a beautiful spring-flowering tree that bears pink or white flowers.
• The Dogwood is Virginia’s state flower and its state tree. It is also North Carolina’s and Missouri’s state flower. Yes, it’s a tree and not a flower. But it does “flower” … Hmmmm.
• The deeply ridged and broken bark resembles alligator hide.
• Nothing about the Dogwood tree looks like a dog.
• In the fall, bright red berries called drupes appear at the point where the leaves meet the branches.
• The red berries are the fruit of choice in the fall and winter for the gray squirrel, fox squirrel, bobwhite, cedar waxwing, cardinal, flicker, mockingbird, robin, wild turkey, and woodpecker. The leaves and twigs are choice food for the white-tailed deer.
• Contrary to popular belief, Dogwood berries are not toxic. According to the Poison Control Center of the Children’s Hospital of Philadelphia, “Dogwood berries are not toxic when eaten, but there have been reports of rashes after skin contact with the tree.”
Dolphins
• Dolphins are marine mammals, not fish, and there are 36 different kinds of ocean dolphins and five species of river dolphins.
• Dolphins are descendants of terrestrial mammals, and it is believed that they first successfully ventured into the water roughly 50 million years ago.
• In all 41 species from the Delphinidae family, the male dolphins are called bulls, females are called cows, the babies are called calves, and they live in social groups called pods.
• Dolphins have the ability to produce ultrasonic sounds up to 200 Kilohertz (KHz). The highest frequency usually audible by humans is 20 KHz!
• If dolphins lose consciousness, they do NOT breathe and can suffocate as opposed to drowning.
• Dolphins only sleep with one half of their brain at a time. The other hemisphere stays a bit alert, as a protective mechanism. [
• The killer whale—often referred to as the orca (Orcinus orca)—can be mistaken for a whale but is actually the largest dolphin family member.
• Other dolphins wrongly classified as whales: the melon-headed whale (Peponocephala electra), pygmy killer whale (Feresa attenuata), false killer whale (Pseudorca crassidens), long-finned pilot whale (Globicephala melas), and short-finned pilot whale (Globicephala macrorhynchus).
Dust Devils
• Dust devils are well-formed, vertically oriented rotating columns of air that rarely exceed 45 mph (70 km/h).
• Dust devils are formed when a warm air mass near the ground rises, which is why they are common in deserts.
• Unlike tornadoes—which are spawned within thunderstorms when a cloud mass overhead has started rotating and begins to pull warm air in from below—there doesn’t need to be a cloud in the sky for dust devils to form.
• Called chiindii—meaning ghosts or spirits—by the Navajo Indians, dust devils that spin clockwise are said to be good spirits; dust devils that spin counterclockwise are bad spirits.
• Dust devils can range in size from rather small to very large. Small dust devils measure less than 3 feet (1 m) in diameter and dissipate in less than a minute. Large dust devils can measure 300 feet (90 m) with winds reaching 60 mph (100 km/h) and last upward of 20 minutes.
• Dust devils have been seen on Mars, both from the Martian Landers and from orbit. One was estimated to be 22 miles (35 km) high.
Dwarf Planets
• In 2006, the International Astronomical Union (IAU) created a classification for dwarf planets. It also created a classification for comets and asteroids, which are now designated as “small solar system bodies.”
• Dwarf planets are not just distinguished from planets because of their smaller size, they must orbit the Sun, but not other planets, and they must have a robust-enough gravity to be spheroid in shape. This eliminates most asteroids from the category.
• When dwarf planets were classified as such, Pluto—formerly known as our solar system’s ninth planet—was demoted to dwarf planet status.
• In addition to Pluto, there are now four additional dwarf planets: Ceres, Eris, Makemake, and Haumea.
• Ceres—which used to be classified as an asteroid—is located in the main asteroid belt between Mars and Jupiter.
• Eris, Makemake, and Haumea—which orbit our Sun in the Kuiper Belt (sometimes called the Edgeworth–Kuiper Belt)—are located in the outermost fringes of our solar system.
• Astronomers believe that Neptune’s moons, Triton and Phoebe, originally came from the Kuiper Belt.
• Pluto has three moons; Haumea has two moons; and Eris has one moon. And, to the best of our knowledge, none of the dwarf planets have rings.
• In terms of atmosphere, Pluto has methane. Eris and Makemake might have methane.