What is biology?  Bio means “life”  logy mean “study”  Life” emerges at the level of cells  Nature has levels of organization properties emerge at successively higher levels  Life properties  Organization More next slide!  Metabolism Chemical process total (more later)  Growth Increase in size or number  Adaptability Adjust to changes (more later)  Evolve Better fit the environment  Irritability Respond to stimuli

How organisms are organized?  Atoms  organized into molecules  multicelled species,  cells organized into tissues, organs, and organ systems  organisms  consist of one or more cells  emergent properties  life emerges at cellular level We study the world of life at different levels of organization, from atoms and molecules to the biosphere

Organisms then group as:  Population individuals species in specific area  Community populations in specific area  Ecosystem community interacting with its environment  Biosphere All regions of Earth that hold life Land, water, and atmosphere

What does life requires?  Organisms require energy and materials to sustain their organization and activities Nutrients are required for growth and survival Producers make their own food Consumers eat other organisms  Energy Flow and Material Cycling

Some more features of living organisms!  Organisms sense change Receptors respond to stimulation Responses keep internal conditions within ranges that cells can tolerate (homeostasis)

Organization is a must!  Organisms grow and reproduce Based on information encoded in DNA Inheritance transmits DNA from parents to offspring through reproduction mechanisms Development transforms first cell into an adult

So much unity, so many species  The world of life, past and present, shows great diversity  Classification systems organize species in ever more inclusive groups  Species: One kind of organism  Each species has a two-part name First part: Genus name Combined with the second part, it designates one particular species

What are domains?  Current classification groups all species into three domains Bacteria (single-celled prokaryotes) Archaea (single-celled prokaryotes) Eukarya (protists, plants, fungi, and animals) Bacteria Eukarya Archaea

What is critical thinking and science?  Critical thinking is a self-directed act of judging the quality of information as one learns  Science is a way of looking at the natural world Helps minimize bias in judgments Focuses on testable ideas about observable aspects of nature  Researchers generally Observe something in nature Form hypotheses (testable assumptions) about it Make predictions about what might occur if the hypothesis is not wrong Test their predictions by observations, experiments, or both

What are experiments ?  Tests used to support or falsify a prediction Variable characteristic is measured and changed In the control group, variables do not change  Biological systems have many variables  Experiments simplify observations of nature Focus on cause, effect, or function of one variable at a time  Researchers design experiments to minimize potential bias in interpreting results

What is a scientific theory?  A well-tested hypothesis Explains a broad range of observations Can be used to make useful predictions about other phenomena  Opinion and belief are not scientific theory