The funnel web spider is one of Australia's deadliest animals, with a venom packing 40 different toxic proteins. A bite from the spider could cause death within two hours. Thanks to antivenin medicine, there hasn't been a funnel web bite death in Australia since 1980. Polar bears are the world's largest bear, with males weighing up to 1,700 pounds and females about 700. They measure nearly 10 feet in length and primarily eat seals. Because of their size and power, they can easily kill a human with one swipe of a paw. The largest great white shark measured 20 feet in length and weighed 5,000 pounds. Great whites are known for their 300 razor-sharp teeth and great sense of smell. Although they prefer to eat sea lions, seals and sea turtles, they sometimes bite and kill people after mistaking them for food. Mosquitoes are often called a nuisance because of the itchy bites they leave. However, they're also notorious for spreading some of the world's deadliest diseases, including malaria, elephantiasis, yellow fever and West Nile virus. Typically they prefer biting horses, cattle and birds over humans. Cobras are some of the most dangerous and venomous snakes found mostly in Africa and Asia. They can range in length from 8 feet to just over 18 feet. According to National Geographic, one bite from a king cobra has enough toxin to kill 20 people or even an elephant. Most cobras, however, are shy and try to stay away from humans. Hippopotamus: Weighing up to 8,000 pounds and measuring 15 feet in length, hippopotamuses boast an aggressive nature that makes them dangerous. Vegetarians, hippos have two teeth in their lower jaws that can grow more than a foot long. They can also open their mouths up to four feet wide and live in the wild for more than 40 years. Lions: Lions live in groups called prides and are known for being strong and fast. Males can weigh almost 600 pounds and run at a top speed of 36 miles an hour. Females, the primary hunters, work together to catch antelopes, zebras, wildebeests and other animals for food. The venomous lionfish has 18 needle-like dorsal fins that can sting and cause extreme pain to humans. A sting from a lionfish is said to last for 15 to 20 minutes and can cause nausea and breathing difficulties, but is rarely fatal. Depending on the type, an adult crocodile can range from about 5 feet to nearly 16 feet long and weigh well over 2,600 pounds. They eat mostly fish, but with their razor-sharp teeth and powerful, strong jaws, they can also eat birds and mammals of any size, including humans. Out of the almost 2,000 scorpion species, nearly 30 of them have venom strong enough to kill humans. Scorpions use their tail hook to pump venom into their prey, mainly insects. When food is scarce, they can slow down their metabolism and eat only once a year. They can also survive being in a freezer overnight. When standing upright, a brown bear can stretch 7 feet and weighs about 700 pounds. Known for their massive size, bears can run about 30 miles an hour. They eat mostly vegetation but also use their big claws to catch prey like fish and small mammals. Bears are also said to have a better sense of smell than dogs. Diamondback rattlesnakes usually grow to about 4 feet and don't release as much venom as other snakes. Poison from their bites, however, attacks the body's blood and can be deadly if not treated right away. These snakes usually eat birds and small mammals but can go without food for up to two years. Poison dart frogs are 1 inch long and weigh less than an ounce but are considered one of the most toxic species. Their bright colors warn predators that they are poisonous, although some snakes are not affected by it and can eat the frogs. Poison dart frogs are said to have enough poison to kill 20,000 mice. Cape buffaloes can weigh about 2,000 pounds and travel in herds of thousands. Their unpredictable nature and sharp, thick horns make them dangerous to humans. During a stampede they will trample anything in their way. Hammerhead sharks are known for their wide heads, which help them catch and eat their favorite food: stingrays. The sharks are usually 13 feet long and weigh about 500 pounds. They swim in schools, and if they come across humans, the encounter could become dangerous or deadly. Elephants are the largest land animals on Earth and can weigh up to 20,000 pounds. The animals spend 16 hours a day eating plants and use their trunks, which consist of 100,000 muscles, to drink water and gather food. Some elephants can be aggressive and can even trample large animals such a rhinoceroses. Black mambas are known as the world's deadliest and fastest snakes, moving at a speed of nearly 13 miles an hour. They average about 8 feet in length and have a reputation for being aggressive. Before antivenin, a bite from this snake was 100 percent fatal, causing victims to suffocate within 20 minutes. Africanized honey bees, also called killer bees, are known for being easily provoked and swarming in bigger numbers. Experts say that if agitated, these bees will go after victims for longer periods of time -- and may attack up to a quarter-mile away from the hive. Mountain lions are also referred to as cougars or pumas and known for their stealth and power when hunting. The cats stalk animals such as deer, coyotes and raccoons -- then pounce on them and bite them on the back of the neck. Mountain lions have also been known to attack humans when hungry. Bison stand about 6.5 feet tall, weigh over a ton and can run faster than a racehorse. Their horns can grow to be 2 feet long – and they've been known charge at people when they get too close. Bison eat only plants, and they regurgitate their food first in order to digest it. Komodo dragons grow to 10 feet long and weigh more than 300 pounds. They have sharp claws and shark-like teeth -- but if an animal escapes from their mouths, the dragon's saliva has bacteria in it that poisons its victims within 24 hours. Komodo dragons have a wide diet, including dead animals, deer, water buffalo, pigs and humans. Box jellyfish are armed with some of the deadliest venom in the world. Also known as sea wasps or marine stingers, jellyfish have delicate tentacles that deliver the toxins that attack the heart and nervous system. According to National Geographic, sea turtles are unaffected by the jellyfish's sting and regularly eat them.