Chapter 1 - Studying Life

• What is the scientific study of living things called?

  Biology
• What is the common origin of life on Earth estimated to have occurred?

  Almost 4 billion years ago
• What are the characteristics of living organisms?

  • Made of a common set of chemical components: carbohydrates, fatty acids, nucleic acids, amino acids
  • Most are made of cells enclosed by plasma membranes
  • Convert molecules from their environment into new biological molecules
  • Extract energy from the environment for biological work
  • Contain genetic information using a universal code for proteins
  • Share similarities among a fundamental set of genes
  • Replicate genetic information during reproduction
  • Exist in populations that evolve over time
  • Self-regulate their internal environment
• How long ago did Earth form?

  1. 6 to 4.5 billion years ago
• What type of cells dominated life for 2 billion years?

  Prokaryotes
• What are the two main groups of prokaryotes?

  Bacteria and Archaea
• What major lineage of life emerged from early prokaryotes?

  Eukaryotes
• What do eukaryotic cells contain that prokaryotic cells do not?


  Internal membranes enclosing specialized organelles
• What process changed the nature of life on Earth about 2.5 billion years ago?

  Photosynthesis
• What do photosynthetic organisms transform sunlight energy into?

  Biological energy
• What were early photosynthetic cells likely similar to?

  Cyanobacteria
• What did the increase of O₂ in the atmosphere allow for?

  Life to move onto land
• What is the ozone layer's role in relation to UV radiation?

  It absorbs damaging UV radiation
• What is a genome?

  The sum total of all the DNA in a cell
• What are the repeating subunits of DNA called?

  Nucleotides
• What is a gene?


  A specific segment of DNA that contains information for making a protein
• What is the major unifying principle of biology?

  Evolution
• Who compiled factual evidence for evolution?

  Charles Darwin
• What does natural selection lead to?

  Adaptations
• What is a binomial scientific name composed of?

  • Genus name
  • Species name

  Example: Homo sapiens
• How has our understanding of evolutionary relationships been enhanced?

  By molecular techniques such as genome sequencing
• What are the three domains of life?

  • Bacteria (prokaryotes)
  • Archaea (prokaryotes)
  • Eukarya (eukaryotes)
• What type of organisms evolved from protists?

  Multicellular Eukarya (plants, animals, and fungi)
• What is the biological hierarchy in multicellular organisms?

  • Differentiated cells organized into tissues
  • Different tissue types form organs
  • Organs are grouped into organ systems
• What are examples of cellular work?

  • Movement of molecules or the whole organism
  • Synthesis of new complex molecules
  • Electrical work of information processing in nervous systems
• What is homeostasis?


  Maintenance of the narrow range of conditions that support survival
• What are the five steps of the hypothesis-prediction approach?

  1. Making observations
  2. Asking questions
  3. Forming hypotheses
  4. Making predictions based on hypotheses
  5. Testing the predictions
• What do controlled experiments manipulate?

  One or more of the factors being tested
• What is the independent variable in an experiment?


  The variable being manipulated
• What is the dependent variable in an experiment?


  The response that is measured
• What do statistical methods help scientists determine?

  If differences between groups are significant
• What does a null hypothesis state?

  That no differences exist
• Why are religious or spiritual explanations not considered science?


  They are not testable using scientific methods
• What are the implications of biology in modern agriculture?

  • Increased food production
  • Development of new crop strains resistant to pests or drought
• How does biology relate to medical practice?

  • Explains how organisms work
  • Helps understand problems and diseases
  • Some diseases result from genetic variations
• How can biology inform public policy?

  • Raises ethical and policy issues
  • Biologists advise on issues like overfishing
• Why is biology crucial for understanding ecosystems?

  • Human activities cause unprecedented changes in Earth systems
  • Increasing atmospheric CO₂ contributes to climate warming and species extinctions
• What is an important aspect of science regarding results?

  Replication of results
• What have many investigators tested regarding atrazine?


  The feminizing effects of atrazine on amphibian and vertebrate species
• What is similar in the molecular mechanisms of atrazine's effects?

  They are similar in amphibians, fish, reptiles, and human cell cultures