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A tick is a small, blood-sucking mite. Normally it lives on blood from dogs, sheep, birds or other larger animals, like deer and cattle. It may also attach itself to humans. When feeding, ticks make a small hole in the skin, attach themselves with a modification of one of the mouthparts which has teeth that curve backwards, and insert barbed piercing mouthparts to remove blood. Ticks also serve as vectors for many diseases. For example, the American dog tick may carry Rocky Mountain spotted fever, tularemia, and other diseases that can also be harmful to humans. Many kinds of aphids secrete a sweet substance called honeydew, prized as food by ants. This substance consists of partially digested, highly concentrated plant sap and other wastes and is excreted from their anus, often in copious amounts. In this relationship, the ants herd the aphids to the plants that the aphids use as a food source at the appropriate stages of the aphids' life cycle. They move aphids around to the most succulent branches, while keeping the aphid's natural predators at bay. The ants also shelter the aphid eggs in their nests during the winter. The aphids, in turn, provide honeydew for the ants. The ants collect the sweet liquid and bring it home to feed the colony. Clown fish are bold, because they dare to live in places where most marine animals dread to go near. Indeed, their choice of residence, a sea anemone, is an immobile, underwater creature that snatches a passerby with its waving, poisonous tentacles! The clown fish capitalize on being an anemones' roommate because if a predator continues their pursuit, it will quickly regret its decision -- instead of being a hunter, the predator becomes a fallen prey to the clown fish's protector. So, how can the clown fish avoid getting stung by the sea anemone? Well, it turns out that the clown fish has a special layer of mucus on its skin. Miraculously, this layer of mucus gives it immunity. There are also other factors that bring the clown fish and the anemone together. For example, the clown fish eats leftover bits that the anemone discards. In return, the anemone receives a free cleaning service. A gall is a plant structure formed by abnormal growth within plant tissues in reaction to being infected by certain organisms such as bacteria, fungi, nematodes, mites, or insects. These gall-makers usually secrete enzymes or plant hormones that stimulate hypertrophy (over-growth) and/or hyperplasy (cell proliferation) in their host plant. The resulting structures are quite distinctive and highly species-specific, ranging in size, color, and location on the plant. The gall-causers do not destroy the plant, but slowly utilize its nutrients. Lions are extremely powerful: by using only a grip on its rump, they can grab and throw a fully grown zebra. A heavy blow to the head of a zebra using a forepaw is sufficient to stun the animal. The lions most frequently used killing technique is a suffocating hold on the muzzle. Usually the kill is clean and quick, with little tearing or biting. Team co-ordination is important, particularly with larger prey: some lionesses may distract the prey while others bring it down. Lichens are symbiotic associations of a fungus with a photosynthetic partner called a photobiont. The photobiont, usually green algae, produces food for the lichen from sunlight. The symbiosis is considered obligatory for successful growth and reproduction of the fungus; however, the significance for the algal photobiont is less clear. For some algae, the symbiosis may be obligatory for survival in a particular habitat because the fungus part of the lichen helps absorb water and minerals from whatever the lichen is growing on. The algae then uses these materials to make food for itself and the fungus. However, in other cases, there is evidence that the relationship might be a disadvantage for the algae, since the algae may be able to grow faster when not associated with the fungus. Remoras (also called suckerfish) are a group of elongated brown fish in the family Echeneidae. Their dorsal fin takes the form of a modified oval sucker-like organ that can take a firm hold against the skin of a larger marine animal. The sucking disc begins to show when the young fish are about 1 cm long and is fully formed when the remora reaches about 3 cm. Remoras are commonly found attached to sharks, manta rays, whales, and turtles. Some small remoras travel in the mouths or gills of large sunfish, swordfish, and sailfish. The host they attach to for transport gains nothing from the relationship, but also does not lose anything. The remora’s diet is primarily leftover fragments or sometimes the feces of the host. Mistletoe is the common name for various plants belonging to the order Santalales. The European Mistletoe is readily recognized by its smoothedge oval leaves and white berries in dense clusters. The American Mistletoe is similar but has shorter, broader leaves. Mistletoe grows on a wide range of trees, and utilizes the host mainly for mineral nutrients from the ground. This usually results in a reduction of growth of the host tree. Where infestation is heavy, mistletoe can cause the death of its host. Escherichia coli, usually abbreviated E. coli, is one of the main species of bacteria that live in the lower intestines of mammals. While the host organism provides an appropriate habitat and nutrition source, the bacteria are necessary for the proper digestion of food for mammals. The presence of beneficial bacteria in the intestines also helps synthesize vitamins and inhibits the growth of disease-promoting pathogenic bacteria. The number of individual E. coli bacteria in the feces that one human passes in one day averages between 100 billion and 10 trillion. Heartworms are a type of roundworm that can infect dogs, cats, wolves, coyotes, foxes, and other animals. As adults, they are about six inches long. The name comes from the fact that the final reproductive stage of the worm’s life cycle takes place in the heart of its host. Adult male and female worms living in the heart produce thousands of microscopic baby worms which circulate throughout the body. An intermediate host (typically a mosquito) then picks up the baby worms and spreads the infection to more host organisms. The heartworms can live in the heart and large blood vessels of the host for many years, but usually kills its host in the end through congestive heart failure. Termites, also known as white ants, feed on cellulose, in the form of wood and other dead plant material. They are economically important pests that can cause serious structural damage to buildings and crops. Termites are vital, however, in tropical regions where their recycling of wood and other plant matter is of ecological importance. The termites rely primarily upon symbiotic protozoa that reside in their guts in order to digest the cellulose. The termites then absorb the end products for nutrition. In addition, the protozoa rely on bacteria embedded on their surfaces to produce some of the necessary digestive enzymes. microscopic protozoa from the hindgut of termites The cattle egret, the only member of the genus Bubulcus, is a small white heron that is found on all continents except Antarctica. The species on average is 50 cm long and weighs 200-600 grams. These birds are often found riding on the backs of cattle and other large animals in dry, grassy habitats. Cattle egrets feed on insects, especially grasshoppers. These insects are usually disturbed and become visible from the movement of the cattle. The egrets may also benefit from the protection of a larger animal. The cattle in this relationship are unaffected. Pseudoscorpions are small arthropods with a flat, pear-shaped body, eight segmented legs, and simple eyes. They have two very long pincers, which resemble the scorpion’s claws, but the pseudoscorpion’s abdomen is short and rounded at the rear, rather than extending into a segmented tail and stinger. They range from 2 to 8 mm in length. The pincer contains venom that is used to capture and immobilize their prey, which may consist of mites, ants, and booklice. To digest the prey, they pour a mildly corrosive fluid over the prey and then ingest the liquefied remains. Pseudoscorpions also have a relationship with larger insects by using these organisms as temporary hosts for transportation purposes. The larger insects are not harmed in the process. Pseudoscorpions are often found in bathrooms, closets, firewood, and among old books.