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Careers, hobbies and element of personal culturePeople studying life sciences can choose from many careers. For example, marine biologist. Some marine biologists consider the affects of air and water pollution on the ocean and its life. Others study fish populations for better fishing control. A marine biologist collects samples of water with help of different equipment and then studies them in laboratory. Bird curator. A curator of birds takes charge of the bird collection. The job may involve traveling to the jungles of South America or Africa to collect more exotic birds. Commercial fisher. These people catch fish and other sea products to sell to people and industry enterprises. Each fisherman uses different tools as well as methods. Many commercial fishermen are experienced in finding the best places to fish. Veterinarian. A veterinarian works at animal hospital, ranch, farm, animal shelter or zoo. Veterinarians must enjoy working with all types of animals. They also must be prepared to work long hours when necessary. Beekeeper. A beekeeper raises bees to pollinate crops and to make honey. They use special tools to remove honey and beeswax. The beekeeper must wear netting for protection. Entomologist. These scientists understand and study the value of insects. They examine the affect of insects on other organisms. Some entomologists even develop ways to use insects for food. Fish culturist. These people raise young fish for streams and lakes, sell alive fish as a bait and fresh fish to restaurants and stores. They make sure the water moves at the right speed and its depth and temperature are correct and know habits and diseases of fish. Science illustrator. Medical and biological illustrators create diagrams, paintings and charts, make life-size models that you may find in classrooms, medical offices and museums. They need good hands, artistic talent and some scientific background. Their drawings must be exact. Medical record technician. A medical record technician is responsible for maintaining complete medical records on every patient. He performs such tasks as filing and typing, code and review records for completeness and accuracy. Optician. An optician fits glasses to a person’s face. He measures different distances on person’s face and then chooses correct lenses. These specialists also use tools. Recreation leader. These people plan and manage games, sport and art activities, work for after-school sports programs, day camps, businesses, schools and hospitals. They work with people of all ages. Science writer. Science writers take material for their books in nature. They are interested in complex subjects for writing easy-to-read stories. Living Organisms and the Main Processes of Life Life may be difficult to define but it is usually easy to recognize. Each living thing is known as organism. All organisms carry out life processes. They grow and develop, respond, use energy and reproduce, they are highly organized, and have a life span, adjust to their environment. One of the main aims organisms use food is for their growth. An organism grows by using materials from its surroundings to become larger in size. In addition, the growth of organisms does not occur at a constant rate. The growth takes place during certain periods of an organism’s life. For example, a baby generally doubles weight during the first five months of life. Then the rate of growth slows down. Most organisms do not become adults just by growing larger. The growth always takes place in a specific way which is different for each kind of organism. Different plants grow at different rates. Sometimes new structures appear and old ones take on new functions. In short, organisms do not simply grow in size - they develop. The development of a living thing includes all the changes it undergoes as it is maturing. Taking on special functions by different groups of cells during embryo’s formation is an important part of development. Development does not stop when an organism reaches its adult form. Even after the growth has stopped, repair, rebuilding and replacement go on continuously throughout an organism life span. No organism, however, can keep renewing itself forever. In time repair processes become less efficient. As a result, the organism deteriorates and eventually dies. Most organisms have a fixed length of life. The average length of life of an organism is its life span. Every living cell is a highly complex structural and chemical system. It consists of thousands of substances, many of which have never been made in the laboratory. Organisms make these substances from simpler substances in their surroundings. In fact, all organisms consist of the same chemical raw materials as nonliving things. The only difference lies in the way in which these raw materials are organized into more complex substances. Inside a living cell there are many complex structures that the cell uses to stay alive. These structures perform many functions. Each cell is, in fact, a complete chemical factory. A cell conducts all its own repairs and even generates its own power. In short, a cell controls and regulates all its own activities. No work of any kind can be done without some form of energy. This energy is provided by the food we eat. In the cells of our body, foods are chemically «burned» to release their energy. Cells use the energy to carry out their activities. All living things need energy and need it constantly. An organism will die if it goes without food for very long because it must do a great deal of work just to stay alive. Even when we sleep our organism works. Every living thing is constantly building the substances that it needs. Generally, such chemical building requires energy. However, cells are also constantly breaking down other substances and this process releases energy. The sum of all this chemical building up and breaking down is metabolism. The metabolism can also be considered as the sum of all the ways in which an organism gets and uses energy. One of the most vital activities of living things is the reproduction of an offspring. The process of producing offsprings or new individuals, is called reproduction. Since no organism lives forever, reproduction is necessary for the continued existence of a species or kind of living thing. New individuals are always like their parents in kind but different in detail. All organisms respond to conditions in their surroundings. Any condition to which an organism can react is called a stimulus. What the organism does as a result of the stimulus is a response. The ability to respond to stimuli is typical of all living organisms. Biologists call this property irritability. Human beings and other higher organisms detect stimuli through senses that include sight, hearing and smell. What organisms detect affects their behavior. To survive, an organism must adjust to changes in its environment. An environment includes everything in an organism’s surroundings that affects it in any way. Any environment can support only a limited number of each type of organism. The survivors will be the individuals best adjusted to their environment. Environmental conditions change, however. To survive, organisms must adjust or adapt to such changes. Any change in an organism, that makes it better suited to its environment, is called an adaptation. Individual organisms can adapt to many short-term changes in their environments. They can cope with changes in the weather or with the passage of the seasons. Any response that increases an individual’s chances of surviving is called an adaptive response. Groups of organisms can also adapt to long-term changes. This process occurs over many generations and does not depend on changes by individual organisms during their lifetimes. It depends entirely on the traits or characteristics received by new individuals from their parents. These traits are inherited or passed from generation to generation. Some variation or set of differences generally exist among individuals in a group of organisms. Many such differences are inherited. If the environment changes, certain traits may take on special importance. They may give the individual that has them an edge in competition with others of its kind. If the environmental conditions change and become less favorable, some individuals adapt to new conditions. Such animals may at first be few in number. In each generation, however, a high proportion of unprotected animals will die before they have a chance for reproduction. Many of protected individuals will survive and pass their traits on to their offspring. In this offspring, the number of unprotected individuals will be very few. Thus, the valuable trait will become more common in each new generation. Eventually it will be the rule rather than the exception. Over a long period, the group of organisms will have adapted to the new, less favorable conditions. The Scientific Method Is A Way Of Knowing Scientific discoveries are made in a variety of ways using many approaches. The chart shows some of the important procedures many life scientists pass through in testing new ideas. Over time, these procedures have come to be called the scientific method (Chart 1.1). Scientists first identify and state a problem. Then they collect information about the problem and create an idea that attempts to explain the problem. This idea is the hypothesis. At this point, scientists gather and record facts - data by observing or experiments. Scientists then analyze data and draw conclusions. Finally, scientists keep their hypothesis or begin to look for another explanation of the problem. If their hypothesis stands the test of new data, it can become a theory. A theory is an explanation supported by data that makes the most sense of a problem. Theories may change as new evidence becomes available. Chart 0.1 The scientific method 1.State and
Experiments
When we plan an experiment, we need to use control and variable groups. These groups must have the same conditions, such as: age, sex, temperature, food, seasons of year etc. Also we can use only one control group and few variable groups. After the experiment, the conclusion is made. If this hypothesis was tested many times it could contribute to a scientific theory. Metric System and Measuring Life scientists must often measure the height, width, mass, volume and temperature of an organism or its surroundings. Measurements give people exact descriptions of some features of living things. Throughout the world, many scientists use the metric system for their measurements. The metric system is based on units and prefixes (Table 1.1). The metric unit of length is the meter. It is often used to measure the heights of organisms. For convenience, we can use km, cm, mm, microns. The gram is the metric unit used to measure mass. As you see, the mass of an organism is usually measured in kg, gm, mg. Volumes in life science are measured in liters and milliliters. A milliliter is also known as a cubic centimeter. Thermometers are used to measure temperature. Life scientists measure temperatures in degrees Celsius. The speed of an organism is measured in km or cm per hour, minute or second. The cheetah runs as fast as 71 km per hour.
Table 0.1. Metric System
Date: 2014-12-22; view: 989
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identify problem Observation
Hypothesis Gather and Conclusions
analyze data
2.Collect information