Parasitism

Parasitism is a close relationship between organisms where one organism benefits and the other is harmed. The organism which benefits is called the parasite and the organism which is harmed is called the host. There are many different kinds of parasites. Some examples of parasites are:

Mosquitoes: Female mosquitoes are parasites that feed on blood. They pierce the skin of people and other animals with their mouthparts and suck out the blood. The mosquito benefits by getting a meal. However, the host is harmed. Mosquito bites can cause pain, itching and swelling. Also, mosquitoes sometimes infect their hosts with diseases such as dengue fever, malaria and zika. In the photo below, a mosquito is seen drinking a person’s blood.

Ticks: These are small eight legged parasites that feed on the blood of animals such as mammals and birds. They bite and attach themselves to their host. As the tick drinks blood, it can swell to several times its normal size. The host is harmed as tick bites can cause itching and swelling. Also, ticks sometimes infect their hosts with diseases such as Lyme disease. In the photo below, a tick can be seen feeding on a dog.

Fleas: Fleas are tiny insects that feed on the blood of cats, dogs, rats and other animals. They feed on people as well. They use their sharp mouthparts to pierce the skin. Flea bites are painful and itchy. Fleas can also infect their hosts with diseases such as typhus and plague. An image of a flea can be seen below.

Sea lampreys: A sea lamprey is a type of fish. It is also a parasite with a mouth like a suction cup. It attaches itself to a fish, punctures its skin and feeds on its blood and other body fluids. The host is wounded and suffers from the loss of blood. Sometimes, the host dies. In the picture below, two sea lampreys have attached themselves to a fish.

Parasitic plants: Some plants are parasites. The yellow plant in the photo below is a parasite called dodder. This plant cannot make its own food so it attaches itself to other plants. Then it takes its water and nutrients from the host plant. The host plant is weakened and may eventually die.

Tapeworms: Some parasites live inside of their host’s body. The tapeworm is one example. A tapeworm can live inside the intestine of a person for years and can grow to be several meters long. It absorbs nutrients from the food the person is digesting. The host may experience symptoms such as nausea, diarrhea or weight loss. A tapeworm can be seen in the photo below.

Remember that in parasitism one organism benefits while the other is harmed.