Sharks are not exactly a new species on this planet. Sharks were on Earth even 450 million years ago.
Sharks have been around for more than 450 million years, surviving four “mass extinctions,” including the catastrophe that wiped out much of the dinosaurs 66 million years ago and ended the Cretaceous.
In this context, sharks are older than dinosaurs, which appeared about 240 million years ago, or even than trees, which evolved on our planet 390 million years ago, indicates Live Science.
How did sharks survive for so long?
One explanation may be that sharks are able to alter their physiology in response to environmental conditions, such as changing their size when temperatures rise. This ability allows species to quickly adapt to ecological changes.
Sharks belong to a group of fish known as chondrichthyes, which are distinguished by the fact that most of their skeleton is made of cartilage rather than bone.
Christopher Lowe, professor of marine biology and director of the Shark Lab at California State University Long Beach, said some sharks are unique in that they have very large genomes, which may contain genes that, while not useful now, perhaps they allowed them to tolerate past climatic conditions.
Unique features that ensured their survival
Additionally, several species of Elasmobranchii, a subclass of the cartilaginous fish group that includes sharks, can move between freshwater and saltwater environments, a huge physiological challenge.
The aggressive bull shark (Carcharhinus leucas) is one of the most well-known sharks that is able to live in both freshwater and saltwater environments.
This ability helped sharks in the past at times when global temperatures were changing and massive volumes of fresh water were entering the ocean environment.
A versatile skill
That versatility most certainly proves the sharks’ longevity as a group, said Gavin Naylor, director of the Florida Shark Research Program. For example, sharks are found in various parts of the deep oceans, in shallow seas and even in rivers, and can swallow a wide range of foods, including plankton, fish, crabs, seals and even whales, according to Natural. London History Museum. In other words, if an area or food source is threatened, the diversity of sharks as a group means that while some species may face hardship or even extinction, others will survive.
We usually think of sharks as exclusively carnivorous, but now we know that they can have more diverse diets. This adaptability when searching for a meal would also have allowed them to survive times of scarcity. But while sharks have managed to avoid previous mass extinctions with their adaptability, they are currently facing an unprecedented challenge: human activity.
“Sharks have been able to cope with climate change in the past quite well, but the biggest challenge for sharks today is overfishing,” Naylor said. “There are no clever tricks these animals can use to fight.”
Pollution is a danger
“The effects of pollution, contamination and habitat loss are also likely influencing their loss in some places,” Lowe added. The role of sharks in the overall ocean ecosystem cannot be understated.
Because so many sharks are top predators, they may play important roles in regulating the stability of organisms further down the food chain. Predators are much less numerous than plankton, but they have a huge effect because they feed on predatory fish that feed on herbivores that feed on plankton.
“If you remove top predators, the whole system could change,” Naylor said.