Spiracles Aid in Breathing on Fish, Whales, and Insects

Spiracles Aid in Breathing on Fish, Whales, and Insects Spiracles are breathing openings found on the surface of insects, certain  cartilaginous fish  such as certain species of  sharks, and stingrays. Hammerheads and  chimeras dont have spiracles. In fish, spiracles are composed of a pair of openings just behind the fishs eyes that allow it to draw oxygenated water in from above without having to bring it in through the gills. The spiracles open into the fishs mouth, where water is passed over its gills for gas exchange and out of the body. Spiracles aid fish in breathing even when they are lying on the ocean bottom or when theyre buried in the sand.   Evolution of Spiracles Spiracles likely evolved from gill openings. In primitive jawless fish, spiracles were simply the first gill openings behind the mouth. This gill opening eventually separated as the jaw evolved out of the structures between it and the other gill openings. The spiracle remained as a small, hole-like opening in most cartilaginous fish. Spiracles are useful for the types of rays that bury themselves in the ocean bottom because they allow them to breathe without the aid of exposed gills. Primitive bony fish with spiracles include the sturgeon, paddlefish, bichirs, and coelacanth. Scientists also believe  that spiracles are associated with the hearing organs of frogs and some other amphibians. Examples of Spiracles Southern stingrays  are sand-dwelling sea animals that use their spiracles to breathe when they are lying on the ocean bottom. Spiracles behind the rays eyes draw in water, which is passed over the gills and expelled from its gills on its underside.  Skates, cartilaginous fish  that have a flat body and wing-like pectoral fins attached to their head, and stingrays sometimes use spiracles as their primary method of breathing, bringing oxygenated water into the gill chamber where it is exchanged for carbon dioxide. Angel sharks are large, flat-bodied sharks that bury themselves in the sand and breathe through their spiracles. They lie in wait, camouflaged,  for fish, crustaceans, and mollusks and then lunge to strike and kill them with their jaws. By pumping water in through their spiracles and out through their gills, these sharks can absorb oxygen and eliminate carbon dioxide without constantly swimming, as more mobile sharks must do. Insects and Animals  With Spiracles Insects have spiracles, which allow air to move into their tracheal system. Since insects dont have lungs, they use spiracles to  exchange oxygen and carbon dioxide  with the outside air. Insects open and close their spiracles through muscle contractions.  Oxygen molecules then travel via the insects tracheal system. Each tracheal tube ends with a tracheole, where the oxygen dissolves into the tracheole fluid. The O2  then diffuses into the cells. The blowhole of the  whale  is also sometimes called a spiracle in older texts. Whales use their blowholes to take in the air and dispel carbon dioxide when they surface. Whales have lungs like other mammals rather than gills like fish. They have to breathe air, not water.

Have to and Must - ESL Grammar Lesson Plans

Have to and Must - ESL Grammar Lesson Plans Many students often confuse the usage of the modals must and have to. While meaning is generally maintained in incorrect usage in the positive forms, a mix-up in the negative forms can cause confusion. This lesson uses daily routines and an interviewing game to help students master these important modal forms. Aim: Learn the modal forms have to and must Activity: Grammar introduction/review, talking about daily routines and interview game Level: Lower levels Outline: Ask students to talk about their daily routines. Have them make a list of five things that they have to do every day.Introduce the grammar by having the students take a look at the grammar sheet below.Discuss the differences between have to and must in the positive form. Make sure to point out that have to is used for daily routines while must is used for strong personal obligation.Discuss the differences between dont have to and mustnt. Make sure to stress the idea that dont have to expresses the idea that the person isnt required to do something but may do so if he/she would like while mustnt expresses the idea of prohibition.In order to encourage students to favor the use of have to, spend the rest of the lesson focusing on daily responsibilities in the following exercises.Ask students to take out the list they created earlier and re-write the list using have to.Ask students to choose a job from the list provided (you might want to first check that students are familiar with the j obs listed) and think about what a person working in that profession has to do. Once you have given students a chance to think a while, play a variation on the 20 questions game. You can begin by choosing a profession and having students ask you 10 or 15 questions about what you have to do in this job. Questions can only be answered by yes, no or sometimes.The student who guesses the name of your profession should be the next to be asked the 15 questions. Another variation on this game is for students to play the game in pairs. Have to - Must Study the Use of Have to and Must in the Chart Below Must/Have To - Mustnt/Not Have To Listed below are examples and uses of must/have to/mustnt/not have to Example Chart Examples Usage We have to get up early.She had to work hard yesterday.They will have to arrive early.Does he have to go? Use have to in the past, present, and future to express responsibility or necessity. NOTE: have to is conjugated as a regular verb and therefore requires an auxiliary verb in the question form or negative. I must finish this work before I leave.Must you work so hard? Use must to express something that you or a person feels is necessary. This form is used only in the present and future. You dont have to arrive before 8.They didnt have to work so hard. The negative form of have to expresses the idea that something is not required. It is, however, possible if so desired. She mustnt use such horrible language.Tom. You mustnt play with fire. The negative form of must expresses the idea that something is prohibited - this form is very different in meaning than the negative of have to! Did the have to leave so early?He had to stay overnight in Dallas. IMPORTANT: The past form of have to and must is had to. Must does not exist in the past. Choose a profession from the list below and think about what a person doing that job has to do every day. Professions and Jobs - What do they have to do? accountant actor air steward architect assistant author baker builder businessman / businesswoman / executive butcher chef civil servant clerk computer operator / programmer cook dentist doctor driver bus / taxi / train driver garbageman (refuse collector) electrician engineer farmer hairdresser journalist judge lawyer manager musician nurse photographer pilot plumber police officer politician receptionist sailor salesman / saleswoman /salesperson scientist secretary soldier teacher telephone operator Back to lessons resource page

State sponsors of Terrorism Essay Example | Topics and Well Written Essays - 500 words

State sponsors of Terrorism - Essay Example Terrorists become more active and powerful because of state support to them. The motivation and support they get from state sponsorship results in increasing the threat of deadly terrorist attacks on civilians, military forces, and infrastructure. State-sponsored terrorism does not have any particular form. At one end, a state can make use of its intelligence agencies to carry out terrorist attacks on some other country either because of grudges between the two states or because of the intent to destabilize the victim state. On the other end, a state can become a safe corner or safe home for the terrorists from where they can hide after carrying out terrorist attacks on the neighboring countries. Some states even fund the terrorist groups operating in other countries to keep them carry out their criminal activities. Their intent is to weaken the political and military base of the victim state. Some states use their own forces against a particular group of people to suppress their voice and rights. This is also a type of state sponsored terrorism. For example, use of force against Kurds by former Iraqi President Saddam Husain can be termed as state sponsored terrorism (Grothaus, n.d.). Let us take some examples of active and passive state sponsored terrorism in order to clarify the evident and hidden roles of states in promoting terrorism. The first example of active state sponsored terrorism is that of Syria’s development and control of a terrorist group named Al-Saiqa. This terrorist group was based in Palestine and Syria directly and openly controlled this group to tackle the influence of Yasir Arafat who was the most prominent leader of Palestine. Another active state sponsored terrorist example is of Pakistan’s support to the militant groups operating Kashmir against Indian forces. Pakistan provides funds and training to these groups using which they carry out attacks on Indian forces. Their main