L4 Parasitism and Commensalism PDF

More Ecological relationships Parasitism Definitions: In parasitism, one species (the parasite) benefits and the other species (the host) is harmed. Parasitism describes an ongoing interaction between two species whereby one species benefits at the other's expense Parasitism occurs wh...

More Ecological relationships Parasitism Definitions: In parasitism, one species (the parasite) benefits and the other species (the host) is harmed. Parasitism describes an ongoing interaction between two species whereby one species benefits at the other's expense Parasitism occurs when one kind of organism (the parasite) lives on or in another kind (the host) and feeds on it — typically without killing it, but the host suffers various negative effects in this relationship and only the parasite benefits. Parasitism is when one organism feeds off another but does not normally kill it. The predatory organism in this case is termed a parasite and the prey a host. The host is harmed and the parasite benefits.  A variety of organisms are parasitic, including insects, worms, crustaceans, plants, fungi and microbes. It is estimated that parasites outnumber free- living species by about four to one. Parasitism Ectoparasites such as ticks and mistletoe live on or outside the host Endoparasites such as parasitic fungi and roundworms live inside the host. A parasite obtains its food from the host but does not necessarily kill it. The type of harm the parasite causes the host varies, but may include shortened lifespan, impaired functions such as digestion, photosynthesis or reproduction and greater vulnerability to predators Parasitism Parasitism  Mistletoe plants are parasitic. Mistletoes form connections with their host plants and the parasites obtain water and mineral nutrients from their hosts through these connections. Parasites Roundworm Roundworm Roundworms affect pigs, cows, sheep, dogs and even humans A roundworm of genus Ascaris is the most common parasitic worm in humans. An estimated one-sixth of the human population is at some point infected by a roundworm People living in tropical and subtropical countries are at greater risk of infection.  Ascaris lumbricoides infects humans via the fecal-oral route. Fertilized eggs released by adult female worms living in the intestines of humans are shed in human feces. Infection of a new human host occurs when a human swallows water or food which has been contaminated with eggs. In the intestines of the new human host larvae hatche from the ingested eggs. The larvae then penetrate the blood From there, the larvae then travel around the body, and can pass through to the lungs. The larvae are then coughed up and then swallowed again, after which they pass through the stomach and into the intestines where they mature into adult worms. The adult worms begin producing fertilised eggs and the cycle can start again  Roundworms and tapeworms are endoparasites found in the gut of mammals They get food by eating the host's partly digested food, depriving the host of nutrients.  North American bighorn sheep are frequently parasitized by the lungworm  Ticks infest the skin and fur of host animals (such as humans), feeding off the host and potentially causing disease Leeches attach to the skin and drinks the blood of the host animal until fully engorged Ectoparasites Fleas live all of their lives on their host, while ticks and leeches feed from their hosts at specific times only; at other times, they are off the host. Fleas harm their hosts, such as dogs, by biting their skin, sucking their blood, and causing them to itch. The fleas get food and a warm home. Other external parasites are fungi, some fungal species feed on moist human skin, causing tinea and athlete’s foot.  Ectoparasite Examples There are three types of lice that effect humans: body lice, head lice, and pubic lice. Lice can be treated with special shampoo and lice combs.  Lampreys attach themselves to their host’s body using their sucker mouth and then feed on the host’s blood and tissues.  Plasmodium Falciparum This single celled parasite is the cause of malaria. It is spread primarily by mosquitos that introduce the parasite into the host’s body. Parasitism notes Parasitism is a symbiotic relationship between two species in which one benefits at the expense of the other. The parasite lives on or in the host and usually obtains its food from it. Parasites can infect animals (eg tapeworm living in pigs, ticks on dogs, plasmodium in mosquitos) and plants (eg mistletoe on apple trees). Sometimes the host is unaffected, but other parasites harm or kill their host. Commensalism Commensalism is an interaction between species in which only one species benefits but the other species is not harmed.  Animals such as birds or possums nesting in a tree hollow is an example of commensalism. In this case the bird or possum benefits and the tree is not harmed.  Trees are also often host to epiphytes: smaller plants such as orchids, ferns, mosses, liverworts and lichens that live on the trunk or in the crown of the tree The epiphyte receives sunlight and rainwater. This relationship is usually benign for the tree because it is neither helped nor harmed (unless it becomes overloaded with the weight of the epiphytes on its branches) Commensalism Epiphytes  Remora attach to the underside of larger predatory fish (e.g. sharks) and feed off the uneaten food scraps Whales and barnacles  Barnacles get free transport by attaching to whales The whale has no benefit or harm as a result of carrying the barnacles Commensalism notes Commensalism describes an ongoing interaction between two species whereby one benefits and the other is unaffected Eg remora fish feeding off food scraps of a shark Eg barnacles being transported by whales Eg. owls nesting in tree hollows  https://ed.ted.com/lessons/symbiosis-a-surprising- tale-of-species-cooperation 2.23 min https://www.youtube.com/watch?v=rNjPI84sApQ Amoeba sisters Ecological relationships 6 min