Category Nature Science & Wildlife

WHAT ARE THE FUN FACT ABOUT DRAGONFLIES?

Dragonflies are large, fast-flying insects that can dart at speeds up to 60 km per hour. Their four wings move independently of one another and make a rattling sound. Dragonflies can also fly backwards.

1. Dragonflies Are Ancient Insects

Long before the dinosaurs roamed the Earth, dragonflies took to the air. Griffenflies (Meganisoptera), the gigantic precursors to modern dragonflies had wingspans of over two feet and dotted the skies during the Carboniferous period over 300 million years ago.

2. Dragonfly Nymphs Live In the Water

There’s a good reason why you see dragonflies and damselflies around ponds and lakes: They’re aquatic! Female dragonflies deposit their eggs on the water’s surface, or in some cases, insert them into aquatic plants or moss. Once hatched, the nymph dragonfly spends its time hunting other aquatic invertebrates. Larger species even dine on the occasional small fish or tadpole. After molting somewhere between six and 15 times, a dragonfly nymph is finally ready for adulthood and crawls out of the water to shed its final immature skin.

3. Nymphs Breath Through Their Anus

The damselfly nymph actually breathes through gills inside its rectum. Likewise, the dragonfly nymph pulls water into its anus to facilitate gas exchange. When the nymph expels water, it propels itself forward, providing the added benefit of locomotion to its breathing.

4. Most New Dragonfly Adults Are Eaten

When a nymph is finally ready for adulthood, it crawls out of the water onto a rock or plant stem and molts one final time. This process takes several hours or days as the dragonfly expands to its full body capacity. These newly emerged dragonflies, known at this stage as teneral adults, are soft-bodied, pale, and highly vulnerable to predators. Until their bodies fully harden they are weak flyers, making them ripe for the picking. Birds and other predators consume a significant number of young dragonflies in the first few days after their emergence.

5. Dragonflies Have Excellent Vision

Relative to other insects, dragonflies have extraordinarily keen vision that helps them detect the movement of other flying critters and avoid in-flight collisions. Thanks to two huge compound eyes, the dragonfly has nearly 360° vision and can see a wider spectrum of colors than humans. Each compound eye contains 28,000 lenses or ommatidia and a dragonfly uses about 80% of its brain to process all of the visual information it receives.

6. Dragonflies Are Masters of Flight

Dragonflies are able to move each of their four wings independently. They can flap each wing up and down, and rotate their wings forward and back on an axis. Dragonflies can move straight up or down, fly backward, stop and hover, and make hairpin turns—at full speed or in slow motion. A dragonfly can fly forward at a speed of 100 body lengths per second (up to 30 miles per hour).

7. Male Dragonflies Fight for Territory

Competition for females is fierce, leading male dragonflies to aggressively fend off other suitors. In some species, males claim and defend a territory against intrusion from other males. Skimmers, clubtails, and petaltails scout out prime egg-laying locations around ponds. Should a challenger fly into his chosen habitat, the defending male will do all he can to chase away the competition. Other kinds of dragonflies don’t defend specific territories but still behave aggressively toward other males that cross their flight paths or dare to approach their perches.

8. Male Dragonflies Have Multiple Sex Organs

In nearly all insects, the male sex organs are located at the tip of the abdomen. Not so in male dragonflies. Their copulatory organs are on the underside of the abdomen, up around the second and third segments. Dragonfly sperm, however, is stored in an opening of the ninth abdominal segment. Before mating, the dragonfly has to fold his abdomen in order to transfer his sperm to his penis.

9. Some Dragonflies Migrate

A number of dragonfly species are known to migrate, either singly or en masse. As with other migratory species, dragonflies relocate to follow or find needed resources or in response to environmental changes such as impending cold weather. Green darners, for example, fly south each fall in sizeable swarms and then migrate north again in the spring. Forced to follow the rains that replenish their breeding sites, the globe skimmer—one of several species that’s known to spawn in temporary freshwater pools—set a new insect world record when a biologist documented its 11,000 mile trip between India and Africa.

10. Dragonflies Thermoregulate Their Bodies

Like all insects, dragonflies are technically ectotherms (“cold-blooded”), but that doesn’t mean they’re at the mercy of Mother Nature to keep them warm or cool. Dragonflies that patrol (those that habitually fly back and forth) employ a rapid whirring movement of their wings to raise their body temperatures. Perching dragonflies, on the other hand, who rely on solar energy for warmth, skillfully position their bodies to maximize the surface area exposed to sunlight. Some species even use their wings as reflectors, tilting them to direct the solar radiation toward their bodies. Conversely, during hot spells, some dragonflies strategically position themselves to minimize sun exposure, using their wings to deflect sunlight.

Credit : Thought co ?

Picture Credit : Google 

WHAT ARE PREDATORS AND PREY?

When one animal kills another for food, it is called predation. The animal which kills is called a predator, and the animal which gets killed is known as prey. Predators often have special skills for hunting, with highly tuned vision, hearing and sense of smell. Many have sharp claws and jaws to grab hold of and tear the body of the prey. Predators can act in a group or can kill alone. At times they hide and wait to catch their prey off-guard in an ambush killing.

Predator and prey evolve together. The prey is part of the predator’s environment, and the predator dies if it does not get food, so it evolves whatever is necessary in order to eat the prey: speed, stealth, camouflage (to hide while approaching the prey), a good sense of smell, sight, or hearing (to find the prey), immunity to the prey’s poison, poison (to kill the prey) the right kind of mouth parts or digestive system, etc. Likewise, the predator is part of the prey’s environment, and the prey dies if it is eaten by the predator, so it evolves whatever is necessary to avoid being eaten: speed, camouflage (to hide from the predator), a good sense of smell, sight, or hearing (to detect the predator), thorns, poison (to spray when approached or bitten), etc.

In this snowy environment, the polar bear is white to avoid being noticed as it approaches the seal, and the seal pup is white to avoid being noticed by the bear.

The fastest lions are able to catch food and eat, so they survive and reproduce, and gradually, faster lions make up more and more of the population. The fastest zebras are able to escape the lions, so they survive and reproduce, and gradually, faster zebras make up more and more of the population. An important thing to realize is that as both organisms become faster to adapt to their environments, their relationship remains the same: because they are both getting faster, neither gets faster in relation to the other. This is true in all predator-prey relationships.

Another example of predator-prey evolution is that of the Galapagos tortoise. Galapagos tortoises eat the branches of the cactus plants that grow on the Galapagos islands. On one of the islands, where long-necked tortoises live, the branches are higher off the ground. On another island, where short-necked tortoises live, the branches are lower down. The cactuses, the prey, may have evolved high branches so that the tortoises, the predators, can’t reach them.

Credit : New England complex system institute

Picture Credit :Google 

HOW ANTARCTIC FIN WHALE CAME BACK FROM EXTINCTION?

Often, within the pages of wildlife conservation stories lies that one spark, idea, or action that spawns dramatic positive changes. Here’s one such story on how one decision has resulted in a huge impact, practically bringing back a key species from the brink of extinction.

The recent filming of southern fin whales in Antarctic waters thrilled scientists, researchers, and conservationsists  no end.  And, why not? It’s a deeply encouraging sign that not only have these marine mammals returned to their historic feeding grounds but their numbers have increased too, albeit gradually. The species was earlier reduced to less than 2% of its original population, thanks to the usual suspect-unsustainable hunting for decades. And then came the whaling ban towards the last quarter of the 20th Century, positively impacting the course of the animal’s fate over decades. Slowly but surely fin whales have rebounded; slowly because fin whales give birth to only one calf at a time.

Over the last few years, researchers have recorded a hundred groups of these whales, including large ones comprising up to 150 animals. “Using data from their surveys, the authors estimate that there could be almost 8,000 fin whales in the Antarctic area.” Listed as “vulnerable” by the International Union for Conservation of Nature, fin whales have a tremendous impact on the environment. In fact, they are called “ecosystem engineers” because after consuming iron-rich krill, they excrete nutrients that help the “growth of tiny phytoplankton, the foundation of the marine food web”. In addition, the increasing number of this marine mammal – the world’s second largest animal-is also an indicator of the ocean’s good health.

While other threats cannot be ruled out for these ocean giants, the “increasing numbers of southern fin whales is an encouraging sign that conservation measures can work”.

Picture Credit : Google 

WHAT IS A WILDLIFE UNDERPASS?

Many of our busy national highways cut deep through forests. Animals that cross these roads may sometimes get run over by fast-moving vehicles. To avoid this, the National Highways Authority of India (NHAI) has built nine dedicated underpasses for wildlife on the national highway NH47 that passes through the Kanha-Pench forest belt.

The cameras installed in the underpasses have revealed that a number of wild animals use them. The animals, including tigers, used the underpasses mostly at night to cross over to the other side of the forest. While some stayed back to take a nap or to have some fun with their playmates, a few others prowled the dark underpasses hoping for a good catch!

The concept was first developed in France in the 1950s. It took off in the Netherlands, where more than 600 crossings have been constructed to protect badgers, elk and other mammals. The Dutch built the world’s longest animal crossing, the Natuurbrug Zanderij Crailoo, an overpass that spans more than 0.8 kilometers (0.5 miles). Wildlife crossings can also be found in Australia, Canada and other parts of the world. The idea took a little longer to catch on in the United States, but wildlife bridges and tunnels began appearing there in the 21st century.

Picture Credit : Google 

DO BACTERIA AND FUNGI SPEED UP WEATHERING?

When water collects in the cracks of a rock, it can freeze when temperatures drop. The ice expands and the pressure can split the rock. In cold, mountain regions, one can even hear gunshot-like cracks as rocks are split apart by frost.

A mechanical process, freeze-thaw weathering causes the ?joints?(cracks) in rocks to expand, which wedges parts of rocks apart. Because water expands by about 10% when it freezes, this creates outward pressure in rock joints, making the cracks larger.

Joints occur naturally in rocks as a result of their formation. Fractures that are not offset, joints do allow for the entry of water into rocks.

In climates where temperatures dip below freezing in the winter, moisture in the joints of rocks solidifies as ice. Over time, after several cycles of freezing and thawing, joints get large enough that bit of rock start to fall off in smaller pieces. This breakdown of rock happens faster at higher altitudes, where many freeze-thaw cycles can occur during the year.

Credit: Sciencing

Picture Credit : Google 

WHY DID IT TAKE SO LONG FOR LIFE TO APPEAR?

Earth’s surface was probably molten for many millions of years after its formation. Life did not exist for the first 400-800 million years, and first began in water after the forming of the oceans.

Life seems to have started on Earth almost as soon as the surface cooled off enough to make it possible. However, complex animal life—everything from insects to fish to humans – took a lot longer to show up. Given that modern animals are a phenomenally diverse group that evolved relatively quickly, why were they so slow to get going?

The answer may be that animals are greedy: they need a lot of oxygen to grow big and complicated. Early Earth didn’t have much oxygen, but microbes changed the chemical content of the atmosphere over time from something alien and poisonous to us into the breathable air we have today. A new paper showed that the oxygen level as recently as 800 million years ago was only a tiny fraction of today’s – far too low to support oxygen-breathers like our ancestors and their relatives.

Life on Earth has always belonged mainly to microorganisms. Clouds are full of microbes; they have been found in deep mines and on the ocean floor. They outnumber and may even outweigh all other forms of life. If all animals vanished, most bacteria would still live on, but if all bacteria disappeared, we would die quickly.

The history of life on Earth reflects this as well. The first single-celled organisms appeared about 3.8 billion years ago, while the first known multi-cellular organisms evolved 2.1 billion years ago. However, these were “primitive” in our human-centric eyes: they didn’t have specialized organs for breathing or eating, much less brains for the wasteful activity we call “thinking”.

Then in the Cambrian era, around 570 million years ago, recognizably complex animal life evolved, including vertebrate ancestors. This change was relatively rapid in evolutionary terms, and a lot of diverse critters came out of it. Thus, something significant must have changed between 2.1 billion years and 570 million years to let animals diversify and complexity.

To explain this great change, scientists consider several possible explanations. One environmental (as opposed to genetic) idea: animals breathe in oxygen, so there needs to be enough oxygen in the air and water. Corals, sponges, and the like require less oxygen than crabs or fish, so oxygen levels limit what sorts of animals can evolve in a particular environment.

Credit: Daily Beast

Picture credit: Google