Chapter 1-3.docx - 1. LearningOutcomes ,youshouldbeableto 1...

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1.1 The Characteristics of Life Learning Outcomes Upon completion of this section, you should be able to 1. Distinguish among the levels of biological organization. 2. Identify the basic characteristics of life.   Biology  is the scientific study of life. Life on Earth takes on a staggering variety of forms, often functioning and  behaving in ways strange to humans. For example, gastric-brooding frogs swallow their embryos and give birth to  them later by throwing them up! Some species of puffballs, a type of fungus, are capable of producing trillions of  spores when they reproduce. Fetal sand sharks kill and eat their siblings while still inside their mother.  Some  Ophrys  orchids look so much like female bees that male bees try to mate with them. Octopuses and squid  have remarkable problem-solving abilities despite a small brain. Some bacteria live their entire life in 15 minutes,  while bristlecone pine trees outlive 10 generations of humans. Simply put, from the deepest oceanic trenches to the  upper reaches of the atmosphere, life is plentiful and diverse. Figure 1.1 illustrates the major groups of living organisms. From left to right, bacteria are widely distributed,  microscopic organisms with a very simple structure. A  Paramecium  is an example of a microscopic protist. Protists  are larger in size and more complex than bacteria. The other organisms in Figure 1.1 are easily seen with the naked  eye. They can be distinguished by how they get their food. A morel is a fungus that digests its food externally. A  sunflower is a photosynthetic plant that makes its own food, and an octopus is an aquatic animal that ingests its food. Figure 1.1 Diversity of life.  Biology is the scientific study of life. This is a sample of the many diverse forms of life  that are found on planet Earth. Although life is tremendously diverse, it may be defined by several basic characteristics that are shared by all  organisms. Like nonliving things, organisms are composed of chemical elements. Also, organisms obey the same  laws of chemistry and physics that govern everything within the universe. The characteristics of life, however, provide  insight into the unique nature of life, and help to distinguish living organisms from nonliving things. Life Is Organized The complex organization of life (Fig. 1.2) begins with  atoms , the basic units of matter. Atoms combine to form  small  molecules , which join to form larger molecules within a  cell , the smallest, most basic unit of life. Although a cell is alive, it is made from nonliving molecules. Some cells, such as single-celled  Paramecium,  live independently. In 
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