My Science School

An invasive species is any kind of living organism that is not native to an ecosystem, but grows aggressively and causes harm to it human health and even impacts the economy. Human activity, pet trade, wet markets etc. are common ways in which invasive microbes, plants, animals and other organisms enter new habitats. Most species that are transported to new habitats do not survive for a long period. But some do possess innate advantages over the indigenous species and begin to thrive in the invaded areas.

What Makes a Species "Invasive"?

An invasive species can be any kind of living organism—an amphibian (like the cane toad), plant, insect, fish, fungus, bacteria, or even an organism’s seeds or eggs—that is not native to an ecosystem and causes harm. They can harm the environment, the economy, or even human health. Species that grow and reproduce quickly, and spread aggressively, with potential to cause harm, are given the label “invasive.”

An invasive species does not have to come from another country. For example, lake trout are native to the Great Lakes, but are considered to be an invasive species in Yellowstone Lake in Wyoming because they compete with native cutthroat trout for habitat.

How invasive species spread

Invasive species are primarily spread by human activities, often unintentionally. People, and the goods we use, travel around the world very quickly, and they often carry uninvited species with them. Ships can carry aquatic organisms in their ballast water, while smaller boats may carry them on their propellers. Insects can get into wood, shipping palettes, and crates that are shipped around the world. Some ornamental plants can escape into the wild and become invasive. And some invasive species are intentionally or accidentally released pets. For example, Burmese pythons are becoming a big problem in the Everglades.

Threats to Native Wildlife

Invasive species cause harm to wildlife in many ways. When a new and aggressive species is introduced into an ecosystem, it may not have any natural predators or controls. It can breed and spread quickly, taking over an area. Native wildlife may not have evolved defenses against the invader, or they may not be able to compete with a species that has no predators.

The direct threats of invasive species include preying on native species, outcompeting native species for food or other resources, causing or carrying disease, and preventing native species from reproducing or killing a native species' young.

There are indirect threats of invasive species as well. Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife. Invasive species can also alter the abundance or diversity of species that are important habitat for native wildlife. Aggressive plant species like kudzu can quickly replace a diverse ecosystem with a monoculture of just kudzu. Additionally, some invasive species are capable of changing the conditions in an ecosystem, such as changing soil chemistry or the intensity of wildfires.

Credit : The National Wildlife Federation

Picture Credit : Google 

A geographic area where plants, animals, and other organisms, along with weather and landscape, work together to form a sphere of life is known as an ecosystem. Ecosystems thus contain biotic or living parts like plants, animals and other organisms as well as abiotic factors like temperature, humidity and rocks. The interdependence of these various parts and factors. either directly or indirectly, is what makes ecosystems thrive.

Ecosystems are controlled by external and internal factors. External factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influenced by the ecosystem. Internal factors are controlled, for example, by decomposition, root competition, shading, disturbance, succession, and the types of species present. While the resource inputs are generally controlled by external processes, the availability of these resources within the ecosystem is controlled by internal factors. Therefore, internal factors not only control ecosystem processes but are also controlled by them.

Ecosystems are dynamic entities—they are subject to periodic disturbances and are always in the process of recovering from some past disturbance. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. The capacity of a system to absorb disturbance and reorganize while undergoing change so as to retain essentially the same function, structure, identity, and feedbacks is termed its ecological resilience. Ecosystems can be studied through a variety of approaches—theoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation. Biomes are general classes or categories of ecosystems. However, there is no clear distinction between biomes and ecosystems. Ecosystem classifications are specific kinds of ecological classifications that consider all four elements of the definition of ecosystems: a biotic component, an abiotic complex, the interactions between and within them, and the physical space they occupy.

Ecosystems provide a variety of goods and services upon which people depend. Ecosystem goods include the "tangible, material products" of ecosystem processes such as water, food, fuel, construction material, and medicinal plants. Ecosystem services, on the other hand, are generally "improvements in the condition or location of things of value". These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research. Many ecosystems become degraded through human impacts, such as soil loss, air and water pollution, habitat fragmentation, water diversion, fire suppression, and introduced species and invasive species. These threats can lead to abrupt transformation of the ecosystem or to gradual disruption of biotic processes and degradation of abiotic conditions of the ecosystem. Once the original ecosystem has lost its defining features, it is considered "collapsed". Ecosystem restoration can contribute to achieving the Sustainable Development Goals.

Credit : Wikipedia 

Picture Credit : Google 

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 

Researchers have found out the intricate physics and neural controls that enable dragonflies to right themselves when falling

Their stretched bodies, huge wingspan and colouring, make dragonflies a unique sight. The fact that they are one of the oldest insect species on Earth also makes them one of the earliest to discover aerial flight.

A group of researchers led by a professor of Mechanical engineering and Physics in Comell University's College of Art and Sciences have determined the physics and neural controls that allow dragonflies to correct themselves while they are falling. This paper that speaks about a dragonfly's recovery mechanism was published in May in Science.

3D-tracking

In order to study this subject, a controlled-behavioural experiment was designed wherein a dragonfly would be dropped upside down from a magnetic tether. The researchers found that the insect's manoeuvres followed the same pattern. After capturing these using high-speed cameras, the motions were reconstructed using 3D-tracking software.

 Once they had successfully completed the challenging part of creating a computational model that simulated the dragonfly's aerobics, what remained was finding out how the dragonflies knew they were falling. Unlike human beings who have an inertial sense, dragonflies rely on all five of their eyes to gauge their uprightness.

Less than 200 milliseconds Dragonflies visual cues thus trigger reflexes that send neural signals to their four wings. As a set of direct muscles modulate the left wing and right wing pitch asymmetry accordingly, all that a dragonfly requires is three or four wing strokes. In less than 200 milliseconds, a dragonfly that is tumbling downwards can thus roll 180 degrees and resume flying the correct way.

By combining kinematic analysis, physical modelling and 3D simulations, researchers have come with crucial inferences of an insects behaviour in a non-invasive manner. Engineers might be able to employ these insights in order to improve the workings of small flying machines and drones.

Picture Credit : Google 

The inland taipan is the world’s most venomous snake, but this Australian taipan is so shy that hardly anything was known about it by Western science for nearly a hundred years after it was first described in 1879.

The inland taipan’s alternative name, ‘fierce snake’, points to the potency of its venom rather than its behaviour. The other Australian taipan that it shares a common ancestor with, namely the coastal taipan, is far more aggressive.

The inland taipan lives in the remote black soil plains of the outback where the borders of South Australia and Queensland meet.

The inland taipan is most active in the early hours of the day, when it surfaces to hunt for prey and to bask in the morning sun. After a few hours it retreats back into its shelter for the remainder of the day, although in cool weather it may show up above ground in the afternoon too.

The inland taipan has adapted to the extremes of the outback climate by dramatic seasonal changes in its coloration. The color of its back varies from a dark brown to almost black in winter. During the summer months it changes to a pale straw color.

These color changes allow the inland taipan to control its temperature, with the darker markings efficient at absorbing heat and the lighter ones good at reflecting it. The head of the inland taipan is much darker compared to the rest of the body, which makes it possible for the snake to warm up quickly by exposing only its head to the sun.

The inland taipan is one of the few Australian snakes to specialize in eating mammals. It will mainly prey on small to medium-sized rodents, especially the native long-haired rat (Rattus villosisimus), though it will also eat the plains rat (Pseudomys australis) and the introduced house mouse (Mus musculus). The venom of the inland taipan is considered to be the most lethal of any snake, surpassing even the venom of sea snakes. It has evolved over time to be especially effective in killing mammals, which also makes it extremely toxic to humans.

The venom from a single bite is said to be enough to kill at least 100 men. On top of its extreme neurotoxicity, the venom also contains an enzyme called a ‘spreading factor’ that speeds up the absorption. An untreated bite has the potential to kill a person in 30 to 45 minutes, which makes immediate medical attention critical. If provoked, the inland taipan curves its forebody into a raised S-shape in an attempt to fend off the offender. This threat display also prepares the snake for striking.

Credit : Active wild 

Picture Credit : Google 

Dominated by a variety of landscapes, the El Vizcaino Biosphere Reserve in Mexico is an important region for many migratory marine and bird species

Rich in biodiversity

Mexico's largest protected area, the El Vizcaino Biosphere Reserve spreads over more than 250 sq.km. It covers a large region between Baja California and the Gulf of California (also known as the Sea of Cortes), making it rich in both terrestrial and marine life. Dominated by scrublands, pine forests, coastal dunes, mangroves, and lagoons, the Reserve is fertile too. It supports more than 400 floral species and 300 vertebrates, in addition to several species of fish. It is an important region for many migratory marine and bird species. The Whale Sanctuary of El Vizcaino, which falls within the boundaries. of the Reserve, was declared a UNESCO World Heritage Site in 1993. It is an important reproduction and wintering site for not just the grey whale but also other species such as seals and sea lions.

The Reserve faces threats in the form of agriculture, illegal fishing, and hunting, in addition to infrastructure development projects. It is believed that all these could have a major impact on the biodiversity of the region..

Wildlife

While the grey whale is the most significant creature of the region, there are several species of birds and mammals found here. Marine mammals seen here are turtles. seals, sea lions, and dolphins. Among the birds spotted are ospreys, pelicans, egrets, cormorants, gulls, terns, plovers, eagles, and falcons. Migrant species that arrive here include the Pacific black brant and northern pintails. In addition to mammals such as pronghorn, deer, bobcats, coyotes, sheep, and squirrels, there are also many types of reptiles and amphibians, including lizards and snakes.

Picture Credit : Google 

Have you heard of Nature's eating machines? They are nothing but caterpillars. What are they and why do they eat so much? Come, let's find out

You may have heard your mother give a small shriek when she is shelling peas and flinging away the offending pod. The culprit is a tiny green worm-like creature with miniature bristles - a caterpillar - the larva of a butterfly or moth!

Caterpillars are the animal kingdom's most voracious eaters. They range in size from 1 mm to 75 mm. They grow phenomenally, moulting or shedding their skin several times before they spin a cocoon around themselves in the last stage. The tobacco hornworm, for instance, will increase its weight by ten thousand times in less than 20 days!

Hairy horrors

The name derives from the Latin term for hairy cat. That's because most caterpillars are covered with spiky bristles, fine hairs or spines that are usually connected to venom glands. The secretion from the glands situated at the base of the spines can cause intense irritation and burning. The hairs can also detach and lodge in the skin.

A species of American moth caterpillar carries a sting which can cause temporary paralysis. The Brazilian flannel moth caterpillars sting is so painful, it has been christened 'bizos de fuero' or 'the fire-beast!

The caterpillar of the lasiocampid moth has spiny hairs hidden beneath the folds of skin on its back. When threatened by danger, it arches its back porcupine-like and attacks the predator with its sharp quill-like hairs.

More defences

Besides hair and venom, caterpillars have evolved a variety of tactics to deter predators.

Plants have toxins to defend themselves against herbivores. Some caterpillars have managed to get around this. The caterpillars of the monarch butterfly feed only on the poisonous leaves of the milkweed plant. Not only do they remain unaffected, they are able to store the poison in their bodies unchanged! Even as pretty orange-and-black butterflies, they make a nasty mouthful and predators avoid eating them. Some caterpillars vomit acidic digestive juices on their attackers and some produce bad smells from glands which they can extrude.

A few caterpillars wiggle long, whip-like organs attached to the ends of their bodies to frighten away flies or spin a line of silk and drop off from branches when disturbed. Many species thrash about violently when disturbed to scare away predators. One species called amorpha juglandis lets out a high-pitched whistle that scares away birds.

Clever camouflage

To escape detection, caterpillars can take on the appearance of bird droppings, leaves or twigs. Some lunch in peace within a woven silk gallery, or roll up inside leaves, or mine into the leaf surface.

Do or Diet  

A majority of caterpillars feed solely on plants, but there are others that feed on decaying animal matter such as wool and the hooves and horns of dead ungulates. Predatory caterpillars eat the eggs of other insects, aphids, scale insects, or ant larvae or even caterpillars of other species. A few are parasitic on cicadas and leaf hoppers. Hawaiian caterpillars use silk traps to capture snails.

Farmers' Pe(s)ts

Caterpillars are extremely destructive and can chomp their way through fruits, vegetables and other food crops, mainly feasting on the leaves. However, there are some species of moth caterpillars that are cultivated by man for their ability to spin lustrous silk.

Picture Credit : Google