Jellyfish, starfish, and even corals manage very well without hearts. Starfish do not even have blood, so this explains why no heart is required. Instead, they use small hair-like structures called cilia to push seawater through their bodies and they extract oxygen from the water.
The animals that do not have a heart include jellyfish, flatworms, corals & polyps, starfish, sea anemone, sponges, sea cucumbers and sea lilies. The Jellyfish is the biggest animal without a heart. It is a simple and primitive creature.
But, they postulate, instead of a single large heart, the Barosaurus probably had some eight hearts. Thus the primary heart would generate only sufficient pressure to pump blood to the next heart and so on.
The hagfish, sometimes called the slime eel, has one true heart plus three accessory pumps helping the blood to move. Just when you thought you had heard it all, some animals are heartless. Jellyfish, starfish, and even corals manage very well without hearts.
Pigs like other mammals have a four-chambered heart. The right side of the heart pumps blood to the lungs (pulmonary circulation), and the left side pumps blood out to the rest of the body (systemic circulation).
To date, there's only one species that has been called 'biologically immortal': the jellyfish Turritopsis dohrnii.
It's called turritopsis dohrnii! We've all heard the saying that cats have nine lives, right?
Cats never forgive.
Scientists have observed similar behaviors in non-primates like goats and hyenas; the only species that has so far failed to show outward signs of reconciliation are domestic cats.
The honey badger has been called the world's most fearless animal because it doesn't hesitate to attack animals much larger than itself- even lions and crocodiles! Honey badgers are found in arid grasslands and savannahs and even rainforests. They live in burrows in the ground.
Animals with no natural predators are called apex predators, because they sit at the top (or apex) of the food chain. The list is indefinite, but it includes lions, grizzly bears, crocodiles, giant constrictor snakes, wolves, sharks, electric eels, giant jellyfish, killer whales, polar bears, and arguably, humans.
Lions (Panthera leo)
Another species which kills babies of its own kind is the lion. When a new male takes over a pride he will commonly kill any existing cubs, as he doesn't want to become a 'step-father', investing resources into young that aren't his own.
Crocodiles - kills 1,000 humans per year
The Nile crocodile has a bite force of up to 5,000 psi, the strongest of any animal in the world, with the saltwater croc having a paltry biting force of just 3,700 psi in comparison (just the second-most-powerful animal bite).
The quokka, a small marsupial native to Australia, is one such example of a species vulnerable to extinction in the country's harsh surroundings. Known as the “happiest animal in the world” due to its cute and friendly appearance, these creatures are now only found in a few isolated forests and small islands.
Dolphins Dolphins are some of the most intelligent animals on the planet, which might explain why they seem so eager to play along with humans when we jump into the water with them. They're playful, usually non-violent and often go out of their way to approach people they see in the ocean.
Ocean quahog clam (Arctica islandica): 507 years old
The individual animal that holds the confirmed record for the longest-lived is a clam from Iceland, found off the coast of the island nation in 2006, which was 507 years old, calculated by counting the annual growth bands in its shell.
Blue blood is found in octopuses and horseshoe crabs. This is due to the fact that hemocyanin, the protein that transports oxygen in their blood, is blue. Octopuses have three hearts, which is due in part to their blue blood.
Anything that tries to kill a tardigrade will quickly realize they encountered practically immortal animals. These creatures are capable of sticking around for thousands of years or even indefinitely “by entering a state of cryptobiosis, whereby their metabolism comes to a halt,” says Pastor.
They react differently when external stimuli are applied while sleeping and while awake. But the bullfrog, Lithobates catesbeianus show the same reaction in both situations. This indicates that bullfrogs do not sleep. Lithobates catesbeianus is an animal that cannot sleep.
The whale's heart is about 5 feet in length, 4 feet in width and 5 feet in height, and can weigh as much as 175 kilograms, which is the same as some cars. A blue whale's heartbeat is so loud that it can be heard from almost 2 miles away. But that's not the only interesting thing about a blue whale's heartbeat.
An eel-shaped, slimy fish, the hagfish is the only known extant animal to possess a skull but no vertebral column. It's strange, alien like appearance likely contributed to its less-than-flattering name. In addition, it also contains four hearts, one more than the octopus or squid.
Fish have what is often described as a two-chambered heart, consisting of one atrium to receive blood and one ventricle to pump it, in contrast to three chambers (two atria, one ventricle) of amphibian and most reptile hearts and four chambers (two atria, two ventricles) of mammal and bird hearts.