Summary

1.1 The Characteristics of Life

Evolution accounts for both the diversity and the unity of life we see about us. All organisms share the following characteristics of life:

  • Organization: The levels of biological organization become larger as follows: atoms and molecules → cells → tissues → organs → organ systems → organisms → species → populations → communities → ecosystems → biosphere.

  • Require materials and energy: Living organisms need an outside source of materials and energy. Metabolism is the term used to summarize these chemical reactions in the cell. Photosynthesis is an example of a metabolic process.

  • Reproduce and develop: Organisms reproduce to pass on their genetic information, included in the genes of their DNA, to the next generation. Mutations introduce variation into the DNA. Development is the series of steps that an organism proceeds through to become an adult.

  • Respond to stimuli: Organisms detect and react to internal and external events.

  • Maintain homeostasis: Homeostasis is the ability to maintain a stable internal environment.

  • Adaptations: Adaptations allow an organism to exist in a particular environment. Evolution is the accumulation of these changes over multiple generations and the resulting adaptation to the organism’s environment.

1.2 The Classification of Life

  • In taxonomy, organisms are assigned an italicized binomial name that consists of the genus and the specific epithet. From the least inclusive to the most inclusive category, each species belongs to a genus, family, order, class, phylum, kingdom, supergroup, and, finally, domain. Systematics is the study of evolutionary relationships between species.

  • The three domains of life are Archaea, Bacteria, and Eukarya. Domain Archaea and domain Bacteria contain prokaryotic organisms that are structurally simple but metabolically complex. Domain Eukarya contains the eukaryotic protists, fungi, plants, and animals. Protists range from single-celled to multicellular organisms and include the protozoans and most algae. Among the fungi are the familiar molds and mushrooms. Plants are well known as photosynthetic multicellular organisms, whereas animals are multicellular and ingest their food. This domain is being reorganized into supergroups to reflect their evolutionary relationships.

  • Each species has a Latin scientific name that consists of the genus and species name. Both names are italicized, but only the genus is capitalized, as in Homo sapiens.

1.3 The Process of Science

When studying the natural world, scientists use a process called the scientific method.

  • Observations, along with previous data, are used to formulate a hypothesis. Inductive reasoning allows a scientist to combine facts into a hypothesis.

  • New observations and/or experiments are carried out in order to test the hypothesis. Deductive reasoning allows for the development of a prediction of what may occur as a result of the experiment. A good experimental design includes an experimental variable and a control group. Scientists may use models and model organisms in their experimental design.

  • The data from the experimental and observational results are analyzed, often using statistical methods. The results are often presented in tables or graphs for ease of interpretation.

  • A conclusion is made as to whether the results support the hypothesis or do not support the hypothesis.

  • The results may be submitted to a scientific publication for review by the scientific community.

  • Over time, multiple conclusions in a particular area may allow scientists to arrive at a theory (or principle or law), such as the cell theory or the theory of evolution. The theory of evolution is a unifying concept of biology.

1.4 Science and the Challenges Facing Society

Whereas science investigates the principles of the natural world, technology applies this knowledge to the needs of society. Some challenges that scientists are investigating include:

  • The impact of climate change and global warming.

  • The loss of biodiversity and habitats such as coral reefs and rain forests. This often results in the extinction of species.

  • Emerging diseases, such as avian influenza and SARS, and reemerging diseases, such as Ebola.