Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Science classwork # 1: Classify the following changes as physical or chemical changes. Give evidence for your answer. Say if there are both physical and chemical changes: a. Water falling over a waterfall b. Lava from a solidifying volcano c. A plane taking off d. Iron nails moving due to the presence of a magnet e. Food going bad after a few days When we see that there is an increase in the temperature of a material system, is it always a sign that there has been a chemical change? Explain and give an example to back up your answer. Science classwork # 2: Open your books and read pages 46 and 47. Then solve the activities on the right side of page 47. Nutrition: Is the process through which organisms obtain the substances they need; like water, food and oxygen. To be precise, there are two things that we obtain from nutrition: matter and energy. Part of the food we eat is transformed into matter, which later adds to our bodies; the other part of the food is transformed into energy to carry out the vital functions we already know about. Although there are processes we do not notice, that doesn’t mean that they do not require energy. Even when we’re sitting down, resting or sleeping we use energy. Producers (plants): These organisms only take inorganic substances from the environment like oxygen, carbon dioxide, mineral salts and water. They also need an external source of energy to carry out their nutrition. Consumers (animals): They also take inorganic substances, but they need organic substances (food), too. These organisms obtain energy from food. Producer nutrition Plants use their roots to absorb water and mineral salts and make up a substance called crude sap. Crude sap is transported to the leaves where the plant cells take the sunlight to carry out photosynthesis (the manufacture of organic substances). Organic substances are mixed with the water from the sap to make up a new substance known as elaborated sap, which circulates throughout the whole plant. Chemosynthesis is the other way to manufacture organic substances, which is done by certain bacteria using the chemical reactions in the environment as the external energy source, instead of using sunlight. Consumer nutrition Consumers can’t create bio-molecules from inorganic substances like plants, so they must manufacture them from organic substances. According to what they eat, consumers may be: herbivores, carnivores or omnivores. Consumers obtain energy with the digestive process: First, breaking up the food they consume to transform it into a substance that can be absorbed by the cells. Then, cells obtain the energy and manufacture biomolecules by means of chemical reactions. The digestive process is carried out by four systems: the digestive system; the respiratory system; the circulatory system and the excretory system. Draw a picture (or pictures) presenting examples of how food transforms into matter and energy. Why do we say that we’re always using energy? Explain and give an example. Explain the difference between producer and consumer organisms. As we already studied at the beginning of this unit, the nutritional process is carried out by a complex system which includes four different organ systems. The digestive system It is formed by the digestive tract and associated glands. Its main function is to process foods in order to extract water, sugars, fats and proteins from it. This system is divided in three parts Digestive: Occurs in the mouth, the stomach and the small intestine. It separates the substances that can be used from the food. Absorption: Occurs in the small intestine. The substances that can be used pass into the bloodstream. Expulsion: Occurs in the large intestine. Undigested remains and unusable substances are expelled. The respiratory system It is formed by the respiratory paths and the lungs. The respiratory movements are produced constantly and allow air to enter and leave the lungs. One of the substances organisms obtain during the nutritional process is oxygen, and it can only be done with the help of the respiratory system. The circulatory system It is formed by the heart and the blood vessels. This system circulates the blood through the whole body. Food substances, water and oxygen are transported from the digestive system to the cells. The excretory system It is formed by the kidneys and the urinary tracts. This system eliminates waste substances in the blood which may be toxic. The kidneys filter the blood and separate all these substances which are expelled in the urine. The sweat glands also participate in this process by producing sweat. Explain how the digestive, circulatory, respiratory and excretory systems participate in the nutritional process of consumer organisms. Explain the difference between photosynthesis and chemosynthesis. Which process is consumer organisms can be considered their equivalent to chemosynthesis? As we can easily see, food goes bad and gets rotten sooner or later. However, this is a natural process which happens due to the existence of micro-organisms in the environment and the food itself. These micro-organisms are: The fungi that grow in food are responsible for the appearance of mould. You might have seen an orange or a piece of bread with mould on it. This is a fungus that grows on the food and means it is useless for consumption. Bacteria are everywhere. Many of them are responsible for food rotting. Rotting is a natural transformation and degradation process of proteins through the action of bacteria. This process produces bad-smelling substances which warn us that the food has been altered. Preserving food at home The oldest ways of preservation are drying, salting and smoking; however, the most common are feezing and refrigerating foods: Drying is one of the most ancient food preservation techniques, which reduces water activity sufficiently to prevent or delay bacterial growth. Salting draws moisture from the meat through a process of osmosis. Meat is cured with salt or sugar, or a combination of the two. Smoking is the process of flavoring, cooking, or preserving food by exposing it to the smoke from burning plant materials, most often wood. Meats and fish are the most common smoked foods, though cheeses, vegetables, and ingredients used to make beverages such as whisky, are also smoked. Refrigeration preserves food by slowing down the growth and reproduction of micro-organisms and the action of enzymes which cause food to rot. The introduction of refrigerators improved the diets of many by allowing foods to be stored safely for longer periods, particularly during warm weathers. Freezing is one of the most commonly used processes for preserving a very wide range of food including prepared food stuffs which would not have required freezing in their unprepared state. For example, potato waffles must be kept in the freezer, but potatoes themselves require only a cool dark place. In domestic freezers the temperature is around 10 degrees below zero. At this level the action of micro-organisms is stopped almost completely. Industrial ways of preservation All traditional ways of preservation are also used in industry; but these processes are not apt for all kinds of foods, like milk, a substance that should be consumed inmediatelly. As a result of this, industry has developed more sofisticated ways of preserving foods: Food additives are substances added to food to preserve flavor, enhance its taste and make it last longer, like with preservatives. Some additives have been used for centuries; for example, preserving food by pickling (with vinegar) or using sulfur dioxide as in some wines. Sterilization techniques are used in the food industry to eliminate all the micro-organisms. There are different ways of sterilization, being pasteurization the most widely-used. This technique, mostly applied to milk, consists of heating it at 80 degrees for 30 seconds. This process kills 99.5% of all the germs contained in milk. Illnesses of the digestive system Ulcers: An ulcer is small wound that appears on the stomach walls. This illness is normally related to stress and it causes severe pain when food is ingested. Gastritis: An inflammation of the stomach walls, which causes a burning sensation and makes digestion difficult. Gastroenteritis: It is due to infections caused by viruses, bacteria or food poisoning. It causes discomfort, pain, fever, vomiting and diarrhea. Cavities: The progressive destruction of teeth caused by the bacteria which live in the mouth. Illnesses of the respiratory system Besides the “common cold” bronchitis and asthma are the most common. Bronchitis: An inflammation of the bronchia caused by a bacterium. An antibiotic treatment is required. Asthma: An allergic reaction which causes sudden muscular contractions of the bronchioles, making breathing particularly difficult. Illnesses of the circulatory system Normally, due to the obstruction of the blood vessels as a result of bad nutritional habits, alcohol and stress. Arteriosclerosis: A serious illness caused by the accumulation of fats in the arteries. Thrombosis: Due to the forming of blood clots. The clot circulates until it reaches a narrow blood vessel, where it gets stuck. Heart attacks or angina: Severe conditions caused by the obstruction of the coronary arteries which take the blood to the cardiac muscles. Illnesses of the excretory system They mostly affect the urinary tract, the kidneys and the bladder; some of them may become very serious if not treated properly and on time. Kidney infection: Characterized by the presence of blood in the urine and backache. Kidney stones: Caused by the accumulation of renal calcium in the kidney. It is very painful. 1. Interaction We may define interaction as the capacity that organisms and systems have of making contact, interacting and communicating with their environments, habitats or other organisms and systems. Interaction among organisms is diverse, for it includes a variety of actions such as looking for and finding food, protection from danger or courting the females of the species. We may also say that interaction refers to a sequence of complex actions divided in three steps: Obtain information from the external or internal environment (Done with the organs of sense). Process information that is received and decide on a response. This only occurs in animals. (Done by the nervous system). Respond to the information that is received. (Done by the responsive organs like muscles, bones and tendons). The information that an organism receives is called “the stimulus, which provokes a response. When this response involves movement, we may classify it into two different types: Positive responses: The organism responds by moving towards the stimulus. Negative responses: The organism responds by moving away from the stimulus. In the case of plants, the functions on interaction and co-ordination are different because they do not have a nervous system. However, plats do receive stimuli and respond.