Chapter Summary

• Biology is the scientific study of organisms, including their characteristics, evolution, functions, and interactions.

• All living organisms are related to one another through common descent. Shared features among organisms support the concept of a common ancestry for all life on Earth. These features include: a common set of chemical building blocks, a nearly universal genetic code, sequence similarities across fundamental genes, and similarities in cellular structure and function.

• Cells evolved early in the history of life. Cellular specialization allowed multicellular organisms to increase in size and diversity. Review Figure 1.2

• Photosynthesis provided a means of capturing energy directly from sunlight, and over time changed Earth’s atmosphere.

• The instructions for a cell are contained in its genome, which consists of DNA molecules made up of sequences of nucleotides. Specific segments of DNA called genes contain the information the cell uses to make proteins through processes of transcription and translation. Review Figure 1.6.

• Evolution—change in the genetic makeup of biological populations through time—is a fundamental principle of life. Populations evolve by means of several different processes, including natural selection, which is responsible for the diversity of adaptations found in living organisms.

• Biologists use fossils, anatomical similarities and differences, and molecular comparisons of genomes to reconstruct the history of life. Life is divided into two major lineages—Bacteria, Archaea. One lineage of Archaea became specialized as Eukarya, which includes all multicellular organisms. Review Figure 1.9

• Life can be studied at different levels of organization within a biological hierarchy. The specialized cells of multicellular organisms are organized into tissues, organs, and organ systems.

• Living organisms, whether unicellular or multicellular, must regulate their internal environment to maintain homeostasis, the range of physical conditions necessary for their survival and function.

• Individual organisms form populations and interact with other organisms of their own and other species. The populations that live and interact in a defined area form a community, and communities together with their abiotic (nonliving) environment constitute an ecosystem. Review Figure 1.10, Activity 1.1

• Scientific methods combine observation, the gathering of information (data), experimentation, and the application of logic to study the natural world. Many scientific investigations involve five steps: making observations, asking questions, forming hypotheses, making predictions, and testing those predictions. Review Figure 1.12

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• Hypotheses are tentative explanations of observations or answers to questions. Predictions made on the basis of a hypothesis are tested with additional observations and experiments. The two general types of experiments are comparative and controlled. Review Investigating Life: Corals in Hot Water, Animation 1.1

• Quantifiable data are critical in evaluating hypotheses. Statistical methods are applied to quantitative data to establish whether the differences observed could be the result of chance. These methods start with the null hypothesis that there are no differences apart from random variation. See Appendix B

• Biological knowledge obtained from a model system may be generalized to other species.

• Application of biological knowledge is responsible for vastly increased agricultural production.

• Understanding and treating human disease requires integrating a wide range of biological principles, from molecular biology to cell biology, physiology, evolution, and ecology.

• Biologists are often called on to advise government agencies on the solutions to important problems that have a biological component.

• Biology is increasingly important for understanding how organisms interact in a rapidly changing world.

• Biology helps us understand, appreciate, and enjoy the diverse living world.