CHAPTER OUTLINE 1.1 The Characteristics of Life The diversity of life seems overwhelming, and yet all living things have certain characteristics in common. Organisms Are Organized Organisms can be organized in a hierarchy of levels. A cell is the smallest unit of life. Organisms Acquire Materials and Energy Organisms need an outside source of materials and energy to maintain their organization or carry on life’s other activities. Organisms Reproduce Life comes only from life. Organisms Respond to Stimuli Organisms respond to external stimuli, often by moving toward or away from a stimulus. Organisms Are Homeostatic Homeostasis means “staying the same.” The internal environment of an organism stays relatively constant. Organisms Grow and Develop Growth, recognized by an increase in the size of an organism and often in the number of cells, is a part of development. Organisms Have the Capacity to Adapt Natural selection results when adaptations, which are certain features that make organisms better suited to an environment, allow those individuals of a species to be able to reproduce and pass on those characteristics. Evolution explains both the unity and diversity of life. 1.2 The Classification of Organisms Because life is so diverse, it is helpful to have a classification system to group organisms based upon their similarities. Domains Domains are the largest classification category. There are three domains: Archaea, Bacteria, and Eukarya. Archaea and Bacteria are unicellular prokaryotes, which lack the membrane-bounded nucleus found in the cells of eukaryotes, which make up the Eukarya. Kingdoms Systematists are in the process of deciding how to categorize archaea and bacteria into kingdoms. The eukaryotes are currently classified into four kingdoms: protists, fungi, plants, and animals. Other Categories The other classification categories are phylum, class, order, family, genus, and species. Scientific Names Taxonomy is the assignment of a binomial, or two-part name, to each species, where the first word is the genus to which the species belongs and the second word is the species. Scientific names are in a common language—Latin. 1.3 The Organization of the Biosphere The organization of life extends beyond the individual to the population, community, ecosystem, and finally the biosphere, which is the zone of air, land, and water on Earth where living organisms are found. The Human Species The human species tends to modify existing ecosystems for its own purposes. Humans depend on healthy ecosystems for food, medicines, and various raw materials. Biodiversity 1 Biodiversity encompasses the total number of species, the variability of their genes, and the ecosystems in which they live. 1.4 The Process of Science Biology is the scientific study of life. Observation Natural phenomena can be understood more fully by observing and studying them. Hypothesis After making observations and gathering knowledge about a phenomenon, a scientist uses inductive reasoning to come up with a hypothesis, a tentative explanation for the natural event. Experiment/Further Observations Testing a hypothesis involves either conducting an experiment or making further observations. Data The results of an experiment are referred to as the data. Data should be observable and objective, rather than subjective or based on opinion. Conclusion Scientists must analyze the data to reach a conclusion to determine if the hypothesis can be supported or not. Scientific Theory The ultimate goal of science is to understand the natural world in terms of scientific theories, concepts that join together well-supported and related hypotheses. A Controlled Study Most investigators perform controlled studies in which the experimental group receives a treatment and the control group receives no treatment. The Experiment The pigeon pea plant is a legume with a high rate of atmospheric nitrogen conversion. A hypothesis was outlined involving winter wheat and nitrogen fertilizer. The Results The results lead to the conclusion that the hypothesis is not supported. Continuing the Experiment The researchers modified the hypothesis to involve sustained effects. The Results The results lead to the conclusion that the hypothesis was supported. Ecological Importance of This Study This study showed that the use of a legume improved the soil to produce a better yield than the use of a nitrogen fertilizer over the long haul. 1.5 Science and Social Responsibility The application of scientific knowledge for a practical purpose is called technology. Most technologies have benefits but also drawbacks. Making value judgments is not a part of science. Ethical and moral decisions about technology must be made by all people. 2