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As apex predators, sharks play a vital role in the ocean ecosystems. Every year 100 million sharks are killed by humans and that number is only increasing. As human activity continues to put sharks in critical danger, it makes scientists wonder: What would happen if every shark on the Earth disappeared today? The answer is very scary.

VIDEO: What If There Were No Sharks?

Coral Reefs Would Disappear

A study published in PLOS ONE in 2013, showed that sharks were crucial for the health of coral reefs. Coral reefs have an delicate ecosystem balance. Algae grows on coral, which is eaten by herbivorous fish. Herbivorous fish are then eaten by larger predatory fish which are eaten by sharks. When sharks are in decline, less of the large predatory fish are eaten, which means that more of the herbivorous fish are eaten, and in turn, less of the algae is eaten. The algae competes directly with the coral, and too much algae kills coral reefs. After studying 185 miles of coral reef, the information on sharks the scientists found showed that declining shark populations as result of overfishing have had disastrous impact on coral reefs. So if all sharks disappeared, coral reefs would also vanish.

VIDEO: If We Lose Our Sharks, We Lose Our Ocean

The Ocean Would Suffocate

Another problem as a result of this imbalanced food chain noted in coral reefs, is that the excess growth of algae blooms would suffocate the ocean. Algae blooms suck the oxygen out of the water creating low oxygen levels. Without oxygen, marine life will suffocate to death. This is a phenomenon that has been observed worldwide in both oceans and freshwater. Also, some algae blooms can also produce toxins that get into the water. These toxins are incredibly harmful to marine life and can lead to mass die-offs. Algae can also be very toxic for people. Without sharks to keep the herbivorous fish populations in balance, the oceans would suffocate from algae blooms.

Marine Species Would Face Extinction

Another major consequence if sharks disappear, is that many marine species would face extinction. This happens for two reasons. One, sharks often prey on the weak or ill members of marine life. These weak and ill members are easier to catch than strong, healthy members of a population. If the weak and ill members continue to thrive, it will weaken the larger population. First because they could potentially spread illness to the other members of the population, which could lead to massive die-offs. Secondly, because when these weaker members of the species are allowed to reproduce, it weakens the genetic makeup of the species as a whole, putting them at risk of extinction.

The second reason marine species would face extinction is because when sharks are not around to consume other predators, those predator populations grow exponentially. Meaning, their prey is at risk of being over-consumed. This was observed in 2007 in the Northern Atlantic where sharks had been overfished. Sharks preyed on bullnose rays, that preyed on scallops. Once the shark populations declined, the population of bullnose rays grew and ate all the scallops. This lead to a collapse of the species. So if sharks disappear, then so do other marine life.

The Speed Of Global Warming Would Increase

The oceans help regulate the carbon cycle of the planet. Coastal ecosystems store about 50% of the world's carbon. Sharks are a crucial factor in keeping that carbon stored. The carbon is stored in marine plant life, and without sharks many of the animals that eat these plants would no longer face a predator threat. So their populations would grow and end up consuming too many of these plants, releasing a flood of carbon into the atmosphere. Further, as physically large predators, sharks hold a lot of carbon in their bodies. When they die, they sink to the bottom of the ocean where they move the carbon from the surface to the seafloor. Their bodies are then eaten by scavengers, keeping the carbon out of the atmosphere. Without sharks, carbon levels would jump, speeding up the rate of global warming and climate change.

VIDEO: Climate Change Forces Whale Sharks To Relocate

The World's Economy Would Collapse

The global commercial fishing industry employees 200 million people and generates upwards of $90 billion dollars annually. If sharks were to disappear, there would be a massive collapse in the ocean's food chain. A collapse that would dramatically impact the commercial fishing industry. Between reduced animal rich habitats like coral reefs, declining and extinct populations, and algae blooms creating toxic fish, commercial fishing would be destroyed-not to mention all the negative economic impacts of dramatically increased climate change. That means millions of people who make their livelihood from commercial fishing would lose their incomes. This would be a disaster for the world's economy. So if sharks disappeared today, so would the $90 billion commercial fishing industry.

Diseases Could Go Uncured

Reducing biodiversity has a huge impact on medicinal science. Scientists use information on sharks to help diagnose, understand, and treat many illnesses and disease that impact humans. For example, in 2011 scientists found an antibiotic in shark liver that could treat a broad range of viruses from dengue and yellow fever to hepatitis. Scientists are also studying anticlotting compounds in shark blood to treat heart disease. There is also ongoing optometric research investigating the possibility of cornea transplants from sharks to humans. Furthermore, sharks are being studied to help understand and treat everything from alzheimer's disease to cancer to HIV. Sharks may hold the key to treating and curing many illnesses that impact humans. If sharks disappeared today, these illnesses could go uncured.

Sharks are an incredibly important part of our ecosystem. If shark populations were disappear today, there would be disastrous consequences for the oceans, our environment, and human life. It is essential that we work to protect these crucial apex predators, so that we can keep the planet in balance.

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As apex predators, sharks play a vital role in the ocean ecosystems. Every year 100 million sharks are killed by humans and that number is only increasing. As human activity continues to put sharks in critical danger, it makes scientists wonder: What would happen if every shark on the Earth disappeared today?

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After 52 weeks of waiting, 2014's Shark Week kicked off on Sunday, and the Internet is starting to get its fix of the bloodthirsty marine animal. But while we're still very early into Shark Week, the PBS series " It's Okay to be Smart" has already asked the burning question, "What if there were no more sharks?"

You see, due to fear and neglect, humanity has taken certain actions that threaten sharks' very existence. Humans kill about 100 million sharks per year (about 3.17 per second), despite sharks only killing around one human per year. If this trend continues, we may very well see sharks become extinct in the next few hundred years.

And because sharks play a vital role in the ocean's food chain, a major decrease in the shark population -- or even extinction -- could trigger things like out-of-control algae or the extinction of smaller animals such as scallops that rely on sharks to eat their predators.

Be sure to check out the video to learn more about how sharks balance out the food chain. It's a good reminder of how vital sharks are to the marine ecosystem, and why we have ways like Shark Week to celebrate these awesome, scary creatures. Be on the lookout for tons more shark-related content from Discovery, PBS, and others this week.

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What would happen if there were no more sharks?

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PBS YouTube series "It's Okay to be Smart" dives into what would happen if there were no more sharks in the world, but leaves out that there would be no more "Shark Week."

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Would there be something that is more evolved that the shark?

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THE EARTH BEFORE THE SHARKS

Fossil evidence shows that sharks populated the planet before the dinosaurs existed, that is, more than 400 million years ago. Since the skeleton of the shark is composed of cartilage, the only thing preserved from prehistoric sharks are fossil samples of the dermal denticles and teeth, but there are some exceptional cases of preserved skeletons.

The first fish appeared on Earth about 510 million years ago. They were small, jaw-less beings called ostracoderms. Evolution did its job, and that's when the first prehistoric sharks first appeared.

The way in which we know them today is believed to be the results of evolution that started about 100 million years ago.

Of course, not all of the sharks that once were on Earth exist today. Fossils prove that many species have become extinct.

The first fish appeared on Earth about 510 million years ago.

ANCESTRAL SHARKS DOMAIN.

The oldest fossil of a prehistoric shark dates back 455 million years and consists only of dermal denticles. This animal lived during the Ordovician period in an environment devoid of terrestrial plants and vertebrates. However, for some paleontologists, the origin of the fossil is not clear, and it is preferred to rely on another whose age is estimated at 420 million years, therefore, it was an inhabitant of the Earth during the Silurian period.

Shark teeth of the Devonian period were found in modern Europe and lived there more than 400 million years ago, but it is the only fossil known about them, and it comes from the remains of their teeth. These are small and measure approximately 4 millimeters wide, so the owners had a length not more than 30 centimeters.

Perhaps the most recent prehistoric sharks are those that belonged to the extinct genus Cladoselache, who lived about 370 million years ago. Their fossils were found in various areas of the United States. The appearance was not ferocious: they were about 1 meter in length, had triangular fins and light jaws, as well as a caudal fin resembling that of present white sharks.

Other paleontologists point to the Mcmurdodus, whose fossil record indicates its presence 390 million years ago. At that time, sharks were predators living near the shores. From the Carboniferous period, sharks diversified and scientists call this stage "the golden age of sharks." There were sharks of varied shapes and sizes, to the point of being entirely different to the modern image of them. For example, the Stethacanthus had small teeth in the head!

During the Jurassic and Cretaceous periods, species of sharks called Hybodonts and Xenacanthis flourished. Some scientists argue that modern sharks evolved from the Hybodonts, but so far there is not scientific confirmation. The period of diversification was over, and the Sharks remained for several million years without drastic evolutionary changes.

At the end of the Jurassic, there were species with jaws more flexible than those of the Hybodonts, and this was a great advantage when feeding. As a result, the Hybodonts group began to shrink, and sharks similar to modern sharks began to spread.

THE MODERN SHARKS ARRIVE.

The origin of modern sharks dates back 100 million years when many species had already become efficient predators and fast-swimming animals. In fact, most of the families of modern sharks arose during this period.

Towards the end of the Cretaceous, about 65 million years ago, a worldwide catastrophe (probably the fall of a meteorite on Mexican coasts) eliminated most of the species that populated the world at that time, including dinosaurs and mammals. Some shark species survived, and are roaming the oceans. Among the survivors are the cow sharks (Hexanchiformes) and the frilled sharks (Chlamydoselachiformes), which still bear much resemblance to their extinct relatives.

The origin of modern sharks dates back 100 million years.

One of the best known modern sharks is the Megalodon ( Carcharodon megalodon), extinct 1.6 million years ago. Fossil records indicate that it probably evolved from the Cretolamna, which lived about 60-100 million years ago. The Megalodon was a shark of titanic proportions (with a length of 16 to 20.3 meters) and large jaws and teeth. At present, some think that the white shark (Carcharodon carcharias) and the Megalodon share some distant relative, but the Carcharodon carcharias is not a direct descendant of the Megalodon shark.

In total, sharks have survived five mass extinctions over the last 439 million years. They are survivors!

SHARKS ADAPTATIONS

Some of the early forms of sharks were quite small. There is evidence to suggest they looked more like fish. Some others were similar to eels; their faces featured noses that were round rather than pointed. Some others were huge with extraordinary dimensions, much larger than the largest shark available today.

Sharks did not have a brain as large as they have today. More than 2/3 of the size of their brain is for the senses, and this is one of the areas where sharks have significantly been able to evolve and to become a more intelligent species.

Their teeth were also different than they are today. Instead of being razor sharp they were smooth. However, these early ancestors also had the rows of teeth that replaced the missing ones like they do today. This kind of teeth could indicate that prehistoric sharks fed on plants instead of being meat eaters as some are today.
Sources:
https://en.wikipedia.org/wiki/Shark#Evolution

http://www.sharksavers.org/en/education/biology/450-million-years-of-sharks1/

http://sharkopedia.discovery.com/shark-topics/prehistoric-sharks/

www.sharks.org/blogs/science-blog/400-million-years-and-counting
BioExpedition Publishing © 2017.

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Fossil evidence shows that sharks populated the planet before the dinosaurs existed, that is, more than 400 million years ago. Since the skeleton of the shark is composed of cartilage, the only thing preserved from prehistoric sharks are fossil samples of the dermal denticles and teeth, but there are some exceptional cases of preserved skeletons.

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Would there more animal that were like the shark?

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4 Freshwater Animals More Terrifying Than Sharks

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Sharks often get a bad reputation for being dangerous and deadly, but there are some freshwater animals you should be way more terrified of. Shark Week begins July 5th at 8/7c on Discovery. Be sure to tune in!

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Was it people that made them extinct or an animal?

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they would be gone for ever. or would they be recreated after their extinction?

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Would the animal be bigger or smaller than than the shark?

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In my opinion I think that the animal that would replace the shark would be roughly the same size of the shark and it would have the same prey and they would be not as aggressive than the shark. There are many things that are more  terrifying