Technical English Episode 4 Why Do Mosquitoes Choose to Bite You?

Why Do Mosquitoes Choose to Bite You? Before reading the text Mosquitos can cause itching when wounded mosquitoes use all five senses to find their prey. Mosquitos can smell humans from far away. The mosquitoes seem to use their sense of direction most. Mosquitoes mostly rely on smell to find us. _True_ False No idea ______ _______ ________

Why Do Mosquitoes Choose to Bite You Mosquitoes have an extraordinary ability to target humans far away and fly straight to their unprotected skin. Regrettably, mosquitoes can do more than cause an itchy wound. Some mosquitoes spread several serious diseases, including Dengue, yellow fever and malaria.Over one million people worldwide die from these mosquito-borne diseases each year. New research now shows how mosquitoes choose who to bite. Mosquitoes need blood to survive. They are attracted to human skin and breath. They smell the carbon dioxide gas -- which all mammals breathe out. This gas is how mosquitoes know that a warm-blooded creature is nearby. But mosquitoes also use their eyes and sense of touch. Michael Dickinson is a professor at the California Institute of Technology. His research shows how these small insects, with even smaller brains, use three senses to find a blood meal. "We suspected from research that we had been doing on fruit flies that vision might play a very large and underappreciated role in allowing the mosquito to really home in on the potential host target." Michael Dickinson's team used plumes – material that rises into the air -- of carbon dioxide gas into a wind tunnel. They then used cameras to record the mosquitoes. The insects followed the plume. Then, the scientists placed dark objects on the lighter colored floor and walls of the tunnel.

Why Do Mosquitoes Choose to Bite You Mr. Dickinson said, at first, the mosquitoes showed no interest in the objects at all. "What was quite striking and quite surprising is that the mosquitos fly back and forth for hours--these are hungry females--and they completely ignore the objects on the floor and wall of the tunnel. But the moment that they get a hit of CO2, they change their behavior quite dramatically and now would become attracted to these little visual blobs." This suggested to the researchers that a mosquito’s sense of smell is more important in the search for food. Once mosquitoes catch a smell of a human or animal, they also follow visual cues. "This really makes a lot of sense because if the mosquitoes were distracted by every visual object in their world, they would just waste all their time. This case, they only start paying attention when their nose tells them that there might be a host nearby." This process happens several times over the course of a mosquito's flight. Michael Dickinson explains.

Why Do Mosquitoes Choose to Bite You "What some of the details of our experiments indicated is that it's very hard to fool them over the long run. They will always get their man or woman over time because they'll just keep repeating this strategy until they find a yummy meal. " Matt DeGennaro is a scientist at Florida International University. He says understanding a mosquito’s way of finding its host could help prevent those insects from biting. He is working to create genetic changes that affect the mosquito's sense of smell. "We need to know which genes control this process at all these different stages. And then we can use that knowledge to design a new perfume that could block the mosquito's sensation of us or could trigger certain receptors that signal danger to the mosquito and then cause them to stay away." The study, published in Current Biology, details the steps of the mosquito's flight so that we may one day have a fighting chance against the biting insect.

Words to Learn USEFUL EXPRESSIONS Underline the words you do not know. target itchy host disease insect vision plume sense gene receptor cue blob USEFUL EXPRESSIONS an extraordinary ability show interest become attracted follow visual cues experiments indicated keep repeating

target : tɑːɡɪt / $ ˈtɑːr- Definition: aim, something that you are trying to achieve, such as a total, an amount, or a time, goal Sample sentence: Higher degrees in English are a target for foreign students.

target : tɑːɡɪt / $ ˈtɑːr-

itchy : /ˈɪtʃi/ Definition: if part of your body is itchy, it feels slightly unpleasant and you want to rub it with your nails Sample sentence: I feel terrible and my eyes are itchy.

itchy : /ˈɪtʃi/

host : /həʊst $ hoʊst/ Definition: who has invited the guests and who provides the food, meal etc. an animal or plant on which a smaller animal or plant is living as a parasite Sample sentence: Which country is going to host the next World Cup?

host : /həʊst $ hoʊst/

vision : /ˈvɪʒən/ Definition: the ability to see the area that you can see an idea of what you think something should be like the knowledge and imagination that are needed in planning for the future with a clear purpose Sample sentence: His vision was quite poor and he always wore glasses.

vision : /ˈvɪʒən/

plume : /pluːm/ Definition: a cloud of smoke, dust etc which rises up into the air; a column of volcanic ash and gas emitted into the atmosphere a large feather or bunch of feathers, especially one that is used as a decoration on a hat Sample sentence: A black plume of smoke rose above the city.

plume : /pluːm/

gene : Definition: a part of a cell in a living thing that controls what it looks like, how it grows, and how it develops Sample sentence: People get their genes from their parents

gene :

receptor : /rɪˈseptə $ -ər/ Definition: a nerve ending which receives information about changes in light, heat etc. and causes the body to react in particular ways Sample sentence: "the retina of the octopus has up to 20 million light receptors"

receptor : /rɪˈseptə $ -ər/

cue : /kjuː/ Definition: an action or event that is a signal for something else to happen Sample sentence: Our success was the cue for other companies to press ahead with new investment.

cue :  /kjuː/

blob : /blɒb $ blɑːb/ Definition: a very small round mass of a liquid or sticky substance Sample sentence: Blobs of wax had dripped from the candle onto the table cloth.

blob : /blɒb $ blɑːb/

Answer the Questions : 1- What reason is given to avoid mosquitos? They can fly straight to humans with unprotected skin. They spread several bad diseases such as Dengue and malaria. Mosquitos can cause itching when wounded. Mosquitos can smell humans from far away. 2- How did researchers study what attracts mosquitos? They released carbon dioxide in a wind tunnel with them. The researchers photographed plumes of air containing mosquitoes. They placed humans in a wind tunnel with mosquitos. The researchers tested various odors on the mosquitos.

Answer the Questions : 3- What did scientist learn about the senses the mosquitoes use? They found that mosquitoes use all five senses to find their prey. The researchers found mosquitoes mostly rely on smell to find us. The mosquitoes seem to use their sense of direction most. After locating a victim by sight, they reply on smell to target prey. 4- What do the scientists hope to do to prevent mosquitos from biting? Reduce the carbon dioxide in the air from humans' breath. Make a perfume with a scent that signals danger to them. Change the genes of the mosquitoes so they do not sting. Help humans to stay away from the places where mosquitoes breed.

TEXT ANALYZING Listen and repeat exercises. Reading laudly. Understand the text -- Underline the verbs (Use pink colour) -- Circle plural words (Use blue color) -- Underline two times the words you do not know. -- Highlight good expressions. (Use brown color)

Assignment - Assessment Learn all vocabulary. Listen to the text 10 times while reading, and listen to the same text 10 times without reading. Then record your voice while reading. Undersand the text deeply (TEXT ANALYZING) Write the text on the right of your notebook, then analyze it on the left... .. verbs, tense, plural nouns, - my favourite sentence, good expressions, words to learn 6. Summarize the text

ASSIGNMENT Make a sentence with the given expressions to stay away keep repeating waste time change behavior warm-blooded creature follow visual cues