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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 

All living things need food to live and grow, and creatures eat more than one variety of plant or animal. Food chain is the sequence in which matter and energy in the form of food gets transferred from one organism to another. Unless another there is enough food available to all living organisms, their survival and the stability of the environment cannot be ensured. The prey species binge on plant life in their habitat while the predators control the prey population and outbreak of diseases. Any change in the chain can cause a ripple effect. The prey-predator relationship in many ecosystems has become complex in recent times due to threats such as global warming. climate change and loss of habitat.

There are four main elements of the food chain:

1. The Sun: The sun is the planet's primary energy source, powering everything else.

2. The producers: All autotrophs, such as phytoplankton, cyanobacteria, algae, and green plants, are producers in a food chain. A food chain starts here. The food chain begins with the farmers and ranchers. To create food, the producers make use of solar energy. Autotrophs, who produce their own food, are another term for producers. Any plant or creature that has its own nutrition through photosynthesis is a producer. Green plants, phytoplankton, and algae, for instance, are food chain producers.

3. The consumers: All creatures that depend on plants or other organisms for nutrition are considered consumers. This is the most critical component of the food chain since it includes nearly all species of living creatures. Herbivores consume plants, carnivores eat other animals, parasites survive on other creatures by damaging them, and scavengers devour dead animals' corpses, all of which are included in the animal kingdom.

4. The decomposers: Decomposers are creatures that get energy from dead or discarded organic material. This is the final level of the food chain. Decomposers are essential components of the food chain because they transform organic waste into inorganic materials such as nutrient-rich soil or land.

Decomposers aid in nutrient recycling by supplying nutrients to soil or seas that autotrophs or producers may use. As a result, a completely new food chain is formed.

Food Chain Types

Food chains are classified into two types: detritus food chains and grazing food chains. Let's study them in detail:

1. Detritus food chain:
The detritus food chain includes many creatures and plants such as bacteria, protozoa fungus, algae, insects, mites, and worms. The detritus food chain begins with decomposing organic matter. Food energy is transferred to decomposers and detritivores, which are then consumed by smaller creatures such as predators. Carnivores, such as maggots, become prey for larger carnivores such as frogs, snakes, and so on. Primary consumers, such as fungus, bacteria, and protozoans, are detritivores that feed on detritus.

2. Grazing food chain:
The grazing food chain is a sort of food chain that begins with green plants and progresses via herbivores and predators. Photosynthesis provides energy to the lowest trophic level in a grazing food chain.
The initial energy transmission in this sort of food chain occurs from plants to herbivores. This food chain is based on the transfer of energy from autotrophs to herbivores. Because autotrophs constitute the foundation of all ecosystems on Earth, most ecosystems on the planet follow this type of food chain.

Credit : Akash BYJUS

Picture Credit : Google 

The dying out or extermination of a species is what is referred to as extinction. When species are diminished because of environmental factors or because of evolutionary changes in their members, extinction occurs. While rates of extinction have varied largely, human activities, deforestation, habitat loss, over-hunting, pollution and climate change have meant that the present-day extinction rate is many times more than what it was previously.

About 541 million years ago, a great expansion occurred in the diversity of multicellular organisms. Paleobiologists, scientists who study the fossils of plants and animals to learn how life evolved, call this event the Cambrian Explosion. Since the Cambrian Explosion, there have been five mass extinctions, each of which is named for the geological period in which it occurred, or for the periods that immediately preceded and followed it.

The first mass extinction is called the Ordovician-Silurian Extinction. It occurred about 440 million years ago, at the end of the period that paleontologists and geologists call the Ordovician, and followed by the start of the Silurian period. In this extinction event, many small organisms of the sea became extinct. The next mass extinction is called Devonian extinction, occurring 365 million years ago during the Devonian period. This extinction also saw the end of numerous sea organisms.

The largest extinction took place around 250 million years ago. Known as the Permian-Triassic extinction, or the Great Dying, this event saw the end of more than 90 percent of the Earth’s species. Although life on Earth was nearly wiped out, the Great Dying made room for new organisms, including the first dinosaurs. About 210 million years ago, between the Triassic and Jurassic periods, came another mass extinction. By eliminating many large animals, this extinction event cleared the way for dinosaurs to flourish. Finally, about 65.5 million years ago, at the end of the Cretaceous period came the fifth mass extinction. This is the famous extinction event that brought the age of the dinosaurs to an end.

In each of these cases, the mass extinction created niches or openings in the Earth’s ecosystems. Those niches allowed for new groups of organisms to thrive and diversify, which produced a range of new species. In the case of the Cretaceous extinction, the demise of the dinosaurs allowed mammals to thrive and grow larger.

Scientists refer to the current time as the Anthropocene period, meaning the period of humanity. They warn that, because of human activities such as pollution, overfishing, and the cutting down of forests, the Earth might be on the verge of—or already in—a sixth mass extinction. If that is true, what new life would rise up to fill the niche that we currently occupy?

Credit : National geographic 

Picture Credit : Google