The Argentine Ant has become a dangerous invasion to many parts of the world where they grow faster than the native population and become a terrible nuisance to humans. These ants are capable of forming super-colonies that consist of several queens and several kilometers of controlled area. Low intraspecific competition allows the ants to form highly dense populations. These massive colonies can replace native ant species or insects with the same niche. A loss in number of some lizard species has been attributed to a decline in native ant populations that the lizards eat.
Even though Argentine ants cannot sting like other species, they have affected humans indirectly. The Argentine Ants' damage to humans has caused a disruption in agriculture. They sometimes protect aphids from invasion by other colonies in order to receive nutrients, called honeydew, from the aphids. This is causing a large increase to aphid populations and more damage to crops. They are also a general annoyance to many home owners with exposed food, especially in California. (1)

The Pinta Island Tortoise is just one subspecies of Giant Galapagos Tortoises. Although many individuals of the species C Nigra are alive today, only one individual of the subspecies Abingdoni still exists. This individual, nicknamed Lonesome George, has been called "the rarest animal on earth". The species became this endangered because of other animals that have been introduced to the islands causing more competition than the tortoises could handle. Conservationists have made several attempts to find a suitable mate for Lonesome George, but no females of the same subspecies have been found. None of his mates' eggs have hatched but the offspring would not be purebred if they did. Lonesome George is over 100 years old and still healthy. Researchers are extensively searching surrounding islands for another Pinta Island Tortoise, especially a female that could breed with Lonesome George. (3)

Crayfish live around the world and play an important role in many freshwater ecosystems. Crayfish have a broad niche so they can eat many types of food. They usually consume aquatic plants and animals which helps control the populations of those species. But they will also eat dead organic manner which cleans the surrounding water. Some invasive species of crayfish, such as the rusty crayfish, can completely alter the surrounding ecosystem by consuming all of the native plant species that would normally be eaten by native crayfish or other species. (5)

Three thousand feet below the surface of the ocean, Deep sea anglerfish have adapted to wait for prey to come to them. Because food is so scarce at that depth, the anglerfish conserves energy by luring prey to come to it instead of chasing it down. They use a bioluminescent lure, or photophore, created by an elongated dorsal fin. Small animals are attracted to the glowing light if they are in search of food or a mate. Without moving the rest of their body, anglerfish wave the lure close to their head without reflecting any light from the bioluminescent bacteria.  When prey is close enough, an anglerfish can swallow a meal almost twice the size of its head.(7)

The Thorny Devil Lizard uses a series of defensive techniques in order to avoid becoming another animal's prey. Even though it only grows up to 20 centimeters in length, it can be a dangerous animal to attack. Its first defense is its camouflage. Brown and grey spots cover its body so it can blend in with its rocky surroundings. Second, the Thorny Devil has short sharp scales covering its body to make it difficult to eat. The thorns will inflict damage to any predator that tries to eat it. Finally, the Thorny Devil's false head can confuse a predator that tries to attack the lizard. By tucking its head and forelegs low to the ground, the lizard exposes a pseudo-head that can distract a predator from any vital organs. (9)